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SUMMARY:Systematic Study of Up-Conversion Luminescence in NaYF4:Yb3+\,R3+
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3851@events.saip.org.za
DESCRIPTION:Speakers: Tero Laihinen (University of Turku\, Department of C
hemistry\, Turku\, Finland)\nIn up-conversion luminescence\, the absorptio
n of two or more low energy photons is followed by the emission of a high
energy photon. NaYF4:Yb3+\,R3+ (R: Pr\, Nd\, Sm\, Eu\, Tb\, Dy\, Ho\, Er o
r Tm) materials were prepared to study up-conversion luminescence. The mat
erials were studied with TG-DSC\, FTIR and XPD methods. Up-conversion lumi
nescence was studied with NIR laser excitation at 976 nm. The DSC curves s
howed an exothermic signal at 400-500 oC due to the cubic-to-hexagonal pha
se transition of NaRF4. The TG curves showed only small mass losses (ca. 2
-4 %) during heating to 500 °C. The FTIR spectra did not reveal other imp
urities apart from water absorbed in the KBr discs. The XPD patterns confi
rmed the hexagonal structure of the annealed materials. The up-conversion
luminescence was observed of Pr3+\, Nd3+\, Eu3+\, Tb3+\, Ho3+\, Er3+ and T
m3+. The up-conversion luminescence was not obtained of Sm3+ and Dy3+.\n\n
https://events.saip.org.za/event/39/contributions/3851/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3851/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rare earth doped lanthanum strontium borate (La2Sr3(BO3)4: xTb3+)
polycrystalline green phosphors
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3852@events.saip.org.za
DESCRIPTION:Speakers: Roz Madihlaba (University of the Western Cape)\nRece
ntly\, great efforts have been made to develop efficient phosphor systems.
Among these\, a number of works have been carried out on investigations o
f the luminescent properties for borates\, aluminates and gannets [1\, 2].
Since the first white light emitting diodes(W-LED’s) became commercial
ly available\, it have attracted great attention for their obvious advanta
ges such as long lifetime\, high luminescence efficiency\, low power consu
mption and environmental friendliness\, consequently they are expected to
replace incandescent and fluorescent lamps for general lighting applicatio
n in the future. Good glass host is very important for efficient luminesce
nce of rare-earth ions. Borate glass is a suitable optical material with h
igh transparency\, low melting point\, high thermal stability and good rar
e-earth ions solubility. Among them\, La2Sr3(BO3)4\, is one of the best ca
ndidates for the desired host materials of phosphors\, and La2Sr3(BO3)4:xT
b3+\, as a green phosphor could be possible used extensively in future in
plasma display panels. Tb3+ -doped phosphors are considered more important
due to their efficiency in the display of sharp and intense green emissio
n at 544 nm due to an electronic transition of 5D4-7F5. In this paper\, we
report combustion synthesis of some important\, borate based\, PL phospho
rs using commonly available fuels and oxidizers.\n\nhttps://events.saip.or
g.za/event/39/contributions/3852/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3852/
END:VEVENT
BEGIN:VEVENT
SUMMARY:A study of the interface kinetics affecting cylindrical phase sepa
ration in PS-b-PMMA copolymer thin films
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3859@events.saip.org.za
DESCRIPTION:Speakers: Zelalem N. URGESSA (NMMU)\nIn this study a controlle
d examination was undertaken in order to confirm and compare the parameter
s affecting PS-b-PMMA copolymer thin film nano-masks. A PS-b-PMMA copolyme
r with a molecular weight of 67 100 g.mol-1 (70:30) was used to produce th
in film nano-masks on treated and untreated Si substrates. By simultaneous
ly annealing samples of differing thin film thicknesses on the two types o
f treated silicon substrate in the same ambient (vacuum of 6 ×〖10〗^(-
2) mbar) a direct comparison is made between the samples. It is shown tha
t the average domain spacing’s for perpendicular-to substrate morphology
is approximately 40 nm. Additionally\, the effect of thin film thickness
on the formation of a perpendicular morphology is clearly demonstrated\, w
ith a thickness repeat period of approximately 32 nm. Importantly\, interf
ace effects are seen between the thin film and both the substrate and vacu
um interfaces\, and a minimum vacuum quality is shown to be a necessary re
quirement for producing uniform perpendicular morphologies across the thin
film.\n\nhttps://events.saip.org.za/event/39/contributions/3859/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3859/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luminescence investigation of dual mode emitting Ho3+ doped tellur
ite glass
DTSTART;VALUE=DATE-TIME:20150507T121000Z
DTEND;VALUE=DATE-TIME:20150507T123000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3853@events.saip.org.za
DESCRIPTION:Speakers: Anurag Pandey (University of the Free State)\n1. Int
roduction \n\nLanthanides activated luminescent materials having increasin
g interest among researchers owing to its broad area of applications in ph
otonic\, sensing\, security and biomedical fields [1]. Rare earth doped gl
asses are one of the best luminescent solids because of their multifunctio
nal uses from daily live to scientific applications. Tellurite glasses are
a better choice for preparing luminescent glasses rather than other oxide
s due to its low phonon frequency characteristics [2]. Triply ionized holm
ium is a good candidate for an activator due to its strong emission in the
green region and dual mode emitting properties [3]. Several glass synthes
is techniques are in used but the melt-quenching technique is the simplest
and cheapest method for the preparing of glasses [2].The present work is
focused upon luminescence emission from the Ho3+ doped TeO2-ZnO glass prep
ared by a melting and quenching method.\n\n2. Results\n\nThe amorphous nat
ure of the prepared glass was checked by X-ray diffraction patterns of the
prepared glass while the thermal behavior was discussed on the basis of t
hermogravimetric analyses. The luminescence property of the glass was dete
rmined via absorption and photoluminescence emission spectra. Fig. 1 shows
the photoluminescence emission spectra of the prepared glass upon 980 and
488 nm excitations. The results suggest a tunable two photon upconversion
emission and intense green emitting downconversion emission from the samp
le which is also explained via a suitable energy level structure diagram.
Thus dual mode emission (up and down-conversion) observed from the prepare
d glass is useful in lighting and enhancing the efficiency of solar panels
. \n \nFig.1: Schematic diagram of dual mode emission from the Ho3+ doped
TeO2-ZnO glass.\n\n3. References\n\n[1]A. Pandey\, S. Som\, V. Kumar\, V.
Kumar\, K. Kumar\, V. K. Rai\, and H. C. Swart. Sens. Actuators B 202 (201
4) 1305. \n[2] D. K. Mohanty\, V. K. Rai\, Y. Dwivedi and S. B. Rai. Appl.
Phys. B 104 (2011) 233.\n[3] A. Pandey\, V. K. Rai. Dalton Trans. 42 (201
3) 11005.\n\nAcknowledgements\n\nThis research is supported by the South A
frican Research Chairs Initiative of the Department of Science and Technol
ogy (84415) and National Research Foundation of South Africa. The financia
l support from the University of the Free State is also acknowledged.\n\nh
ttps://events.saip.org.za/event/39/contributions/3853/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3853/
END:VEVENT
BEGIN:VEVENT
SUMMARY:TOF SIMS Analysis\, Structure and Photoluminescence Properties of
Pulsed Laser Deposited CaS:Eu2+ thin films
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3854@events.saip.org.za
DESCRIPTION:Speakers: Raphael Nyenge (University of the Free State and Ken
yatta University)\n1. Introduction \n\nRed-emitting alkali earth sulfide p
hosphor such as divalent europium (Eu2+) doped calcium sulfide (CaS: Eu2+
) is a good material for blue pumped three-band phosphor-converted white L
EDs since it has strong absorption in the blue region [1]. CaS: Eu2+ thin
films were deposited on Si (100) substrates using the pulsed laser deposit
ion technique to investigate the effect of Argon (Ar)\, Oxygen (O2)\, and
vacuum deposition atmospheres on the structural\, morphological and photol
uminescence (PL) properties of the thin films. The phosphor target was abl
ated using a 266 nm Nd: YAG laser. X-ray diffraction\, Atomic force micros
copy\, scanning electron microscopy\, energy dispersive X-ray\, fluorescen
ce spectrophotometry\, and time-of-flight secondary ion mass spectrometry
(TOF-SIMS) were used to characterize the thin films. \n \n2. Results\n\
nThe PL results for CaS: Eu2+ thin films deposited using different atmosph
eres are shown in Fig.1. Films prepared in Ar atmosphere showed better PL
intensity than the films deposited in an O2\, while the least intensity wa
s observed from the films prepared in vacuum. The emission observed at aro
und 650 nm for all the films is attributed to the transitions from the exc
ited state to the ground state of the Eu2+ [2] ions. The emission at 6
18 nm\, which is more prominent in the film prepared in O2\, is ascribed t
o transitions in Eu3+ [3]\, suggesting that Eu2+ was unintentionally oxid
ized to Eu3+. TOF-SIMS images indicated that Eu2+ ions were evenly distrib
uted in the CaS host and that the thicknesses of the prepared thin films d
epend on the atmosphere in which the films were grown. The overlay of Fig.
2 shows Eu in the +3 state\, observed as EuO+ (m/z = 168. 8992) in the fi
lms prepared in an oxygen atmosphere. It is speculated that less oxidation
of Eu2+ occurred during deposition in argon and vacuum atmospheres\, sinc
e insignificant PL emission due to Eu3+ was observed.\n\n
\n\n\n\n\n3. References\n\n[1] Jia\, X. Wang. Opt. Mater. 30 (2007) 375.\
n[2] H. K. Yang\, K. S. Shim\, B. K. Moon\, B. C. Choi\, J. H. Jeong\, S.
S. Yi and J. H. Kim. Thin Solid Films 516 (2008) 5577.\n[3] P. Dorenbos. J
. Lumin. 104 (2003) 239.\n\nhttps://events.saip.org.za/event/39/contributi
ons/3854/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3854/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Transport characteristics of n-ZnO/p-Si heterojunction as determin
ed from temperature dependent current-voltage measurements
DTSTART;VALUE=DATE-TIME:20150505T124000Z
DTEND;VALUE=DATE-TIME:20150505T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3855@events.saip.org.za
DESCRIPTION:Speakers: Stive Roussel Tankio Djiokap (Nelson Mandela Metropo
litan University)\nhttps://events.saip.org.za/event/39/contributions/3855/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3855/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Non-rare earth doped persistent luminescence materials
DTSTART;VALUE=DATE-TIME:20150507T113000Z
DTEND;VALUE=DATE-TIME:20150507T115000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3856@events.saip.org.za
DESCRIPTION:Speakers: Jorma Hölsä (University of Turku)\n1. Introduction
\n\n Both the commercial markets as well as research and development of
persistent luminescence phosphors have been dominated by materials doped
with Eu2+. The domination of Eu2+ over other rare earths (R\; e.g. Ce3+\,
Pr3+\, Tb3+) is due to e.g. the strong and easily tunable emission (Fig. 1
) as well as the favourable energy level scheme of Eu2+ vs. the host band
structure [1]. For many reasons this situation may soon change: i) europiu
m is needed for many other phosphor applications\, ii) the recovery and re
cycling of europium from persistent luminescence materials is nearly impos
sible and iii) e.g. the biotechnical applications require strongly red emi
tting biomarkers. The economic pressure due to both aggressive and wildly
fluctuating pricing policy of rare earths is probably the most important d
riving force to the change.\n\n2. Results\n\nThe pursuit for cheaper persi
stent luminescence materials has already resulted in the adoption of such
inexpensive host materials as the alkaline earth aluminates\, MAl2O4 (M: C
a\, Sr)\, Sr2MgSi2O7 or Sr4Al14O25 [1]. The replacement of Eu2+ (and R3+ c
o-) dopants with non-rare earths is ensuing at a much slower pace despite
many outstanding possibilities. For example\, the first persistent lumines
cence material\, the famous Bologna Stone from the beginning of the 17th c
entury\, uses doping with Cu+ in BaS [2]. The 3d elements such as Ti3+\, C
r3+ and Mn2+ have been shown to give strong persistent luminescence\, too
[1\,3]. Many main group metal ions such as Pb2+ and Bi3+ can also be used
as dopants. To improve either the absorption of incident radiation\, the e
fficiency of emission or its tunability\, combinations with conventional d
opants (e.g. Eu2+- Mn2+ or Cr3+-Pr3+) or with non-rare earth ones (e.g. Cr
3+-Bi3+ or Mn2+-Bi3+) may be used [3]. As for the mechanism of persistent
luminescence\, it is necessary to consider first the redox behaviour of th
e dopants. It is noted at once that each dopant has an oxidized counterpar
t: Eu2+/3+\, Ce3+/IV\, Pr3+/IV\, Tb3+/IV\, Ti3+/IV\, Cr3+/IV\, Cu+/2+\, Pb
2+/IV and Bi3+/V. However\, this does not necessarily mean that this count
erpart is easily observed experimentally. The mechanism should thus be sim
ilar to the very efficient Eu2+ based persistent luminescence and the elec
trons act as charge carriers [1].\nEventually\, the properties of a Eu2+-M
n2+ dopant combination is described (Fig. 2) [4]. Efficient persistent lum
inescence and also tuning of emission from red to blue via e.g. magenta ca
n be achieved. System’s efficiency depends now not only on the individua
l dopants but also on the persistent energy transfer between them.\n\nhttp
s://events.saip.org.za/event/39/contributions/3856/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3856/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Low-Temperature Alpha-Particle Irradiation of Pd/4H-SiC Schottky b
arrier diodes
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3857@events.saip.org.za
DESCRIPTION:Speakers: Ezekiel Omotoso (University of Pretoria)\nThe effect
of low-temperature alpha-particle irradiation on Pd/4H-SiC Schottky barri
er diodes has been investigated. The motivation is to study the radiation
damage of the sample after bombarded with 1.6 MeV a-particles [(He)^(2+)]
at 20 K and the annealing of the radiation-induced defects taking place wi
th increasing in temperature. The of fluence alpha-particles amounted to 3
× (10)^(13) (cm)^(–2). Thermal admittance and photo-capacitance spectr
oscopy were employed to characterize the diodes. The shallow donors D1 and
D2 were detected in the as-grown as well as in the a-bombarded samples. T
he defects TαAnn was stable to both irradiation and annealing at room tem
perature.\n\nhttps://events.saip.org.za/event/39/contributions/3857/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3857/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chloride-based SiC growth on a-axis 4H-SiC substrates
DTSTART;VALUE=DATE-TIME:20150505T120000Z
DTEND;VALUE=DATE-TIME:20150505T122000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3860@events.saip.org.za
DESCRIPTION:Speakers: Erik Janzen (Semiconductor Materials (IFM)\, Linkopi
ng University)\nSiC has during the last few years become increasingly impo
rtant as a power-device material for high voltages. The thick low-doped vo
ltage-supporting epitaxial layer is normally grown by CVD on 4˚ off-cut 4
H-SiC substrates at a growth rate of 5-10 µm/h using silane and propane (
or ethylene) as precursors. The concentrations of epitaxial defects and di
slocations depend to a large extent on the underlying substrate but can al
so be influenced by the actual epitaxial growth process. Here we will pres
ent a study on the properties of the epitaxial layers grown by a Cl-based
technique on an a-axis (90˚ off-cut from the c direction) 4H-SiC substrat
e\n\nhttps://events.saip.org.za/event/39/contributions/3860/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3860/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Synthesis and characterisation of copper sulphide quantum dots for
photovoltaic cell applications
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3861@events.saip.org.za
DESCRIPTION:Speakers: Leandre' Brandt (University of the Western Cape)\nht
tps://events.saip.org.za/event/39/contributions/3861/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3861/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The influence of oxygen partial pressure on material properties of
Eu3+- doped Y2O2S thin films deposited by Pulsed Laser Deposition method.
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3862@events.saip.org.za
DESCRIPTION:Speakers: ABDUB ALI (UNIVERSITY OF THE FREE STATE)\n1. Introdu
ction\n\nEu3+- doping has been of interest to improve the luminescent char
acteristics of thin-film phosphors. Europium-doped Y2O2S exhibits strong
UV and cathode ray-excited luminescence\, so it is widely used as red phos
phors for low-pressure fluorescent lamps\, cathode-ray tubes and plasma di
splay panels [1]. Also\, the hexagonal Y2O2S is a good host material for r
are earth ions. In recent years\, the Y2O2S: Eu has received much attentio
n for its tremendous potential applications in optical display and lightin
g materials and basic science research on special luminescent spectra. Nan
oscale and thin film Y2O2S: Eu has remarkably different luminescent proper
ties from those of bulk samples: such as emission line broadens\, lifetime
changes and its spectra shift [2]. In this study Y2O2S: Eu thin films hav
e been deposited with the pulsed laser deposition technique in an O2 envir
onment. The oxygen pressure was changed from 0 to 140 mtorr.\n2. Results\
nThe X-ray diffraction patterns (Fig.1) show mixed phases of cubic and hex
agonal crystal structures. As the oxygen partial pressure increased\, the
crystallinity of the films improved. Further increase of the O2 pressure t
o 140 mtorr reduced the crystallinity of the film. Similarly\, both scanni
ng electron microscopy and atomic force microscopy confirmed that an incre
ase in O2 pressure affected the morphology of the films. The average band
gap of the films calculated from diffuse reflectance spectra using the Kub
elka-Munk function was about 4.75 eV. The photoluminescence measurements (
Fig.2) indicate red emission of Eu3+ doped Y2O2S thin films with the most
intense peak appearing at 619 nm\, which is assigned to the 5D0-7F2 transi
tion of Eu3+. This most intense peak is totally quenched at higher O2 pres
sures. This phosphor may be good promising material for applications in th
e flat panel displays.\n\nhttps://events.saip.org.za/event/39/contribution
s/3862/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3862/
END:VEVENT
BEGIN:VEVENT
SUMMARY:CHARACTERIZATION OF CRYSTALLITE MORPHOLOGY FOR DOPED STRONTIUM FLU
ORIDE NANOPHOSPHORS BY TEM AND XRD
DTSTART;VALUE=DATE-TIME:20150505T100000Z
DTEND;VALUE=DATE-TIME:20150505T102000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3863@events.saip.org.za
DESCRIPTION:Speakers: Mike Lee (NMMU)\nM.E. Lee1\, J.H. O’Connell1\, M.Y
.A. Yagoub2\, H.C. Swart2 and E. Coetsee2\n\n 1Centre for HRTEM\, Nelson M
andela Metropolitan University\, Port Elizabeth\, 2Department of Physics\
, University of the Free State\, Bloemfontein\, South Africa \n\nCorrespon
ding author e-mail address: michael.lee@nmmu.ac.za\n\n1. Introduction\nStr
ontium fluoride (SrF2) is one of the most widely used optical materials du
e to its optical properties (wide bandgap and low phonon energy) as well a
s physical properties (low refraction index\, high radiation resistance\,
mechanical strength and low hygroscopicity)[1\,2]. Europium doped (optimal
ly ~2%) strontium fluoride (Eu:SrF2) nanophosphors have been shown to poss
ess improved scintillation properties [3]. Previous work on the characteri
zation of the material by X-ray diffraction (XRD) has produced results on
the average dimensions for the nanoparticles [4]. However\, analysis of ex
act morphology and orientation for the nanocrystallites will require alter
native techniques such as high resolution transmission electron microscopy
(HRTEM). In this paper\, complimentary results obtained by HRTEM will be
compared to results obtained from XRD.\nDoped and undoped SrF2 samples wer
e prepared by a hydrothermal process described in the literature [5]. The
reaction product consists of spherical SrF2 particles having dimensions in
the range 0.8-2.0 μm as measured by scanning electron microscopy seconda
ry electron (SEM-SE) imaging. The FIB lamellae produced from the nanophosp
hor particles were imaged in a TEM. XRD analysis showed the structure of t
he material to agree with the expected space group Fm3m. The micron-sized
particles were assumed to consist of nanocrystallites which are unimodal a
nd single phased. Application of the Scherrer's equation to calculate the
crystallite size produced dimensions in the range of 6-8 nm. The accuracy
of the Scherrer equation will however depend on a number of factors such a
s grain size distribution\, crystal defects and lattice strain.\n \n2.
Results\nThe high angle annular dark field (HAADF) STEM imaging of the FIB
lamella\, clearly demonstrate the nanocrystalline composition of the part
icles shown in figure 1. The selected area diffraction patterns (SAD) cle
arly shows the presence of numerous\, relatively randomly oriented crystal
lites. The hollow cone technique is used to produce dark field (DF) microg
raphs obtained by precessing the indicated diffraction ring through the ob
jective aperture by applying hollow cone precession of the incident beam a
s shown in figure 2. Exposure time was an integer multiple of the precessi
on period. The hollow cone DF TEM images have demonstrated evidence for a
bimodal distribution of crystallite sizes. Firstly\, a 5-10 nm size distri
bution which is in reasonable agreement with the XRD Scherrer calculation
was measured. A second distribution of crystallite sizes in the range of 5
0-80 nm was also observed\, as shown in figure 2. Data from the hollow con
e TEM technique has therefore shown the crystallite size distribution to b
e bimodal which was not possible to determine by the XRD Scherrer equation
.\n\n \n\n\n\n3. References\n[1] K.V. Ivanovskikh\, V.A. P
ustovarov\, M. Kirm\, B.V. Shulgin. J. Appl. Spectrosc. 72 (2005) 564.\n[2
] B.M. Van der Ende\, L. Aarts and A. Meijerink. Adv. Mater. 21(2009) 307
3.\n[3] S.Kurosawa\, Y. Yokota\, T. Yanagida\, A. Yoshikawa Phys. Status S
olidi C 9 (2012) 2275.\n[4] M.Y.A. Yagoub\, H.C. Swart\, L.L. Noto\, J.H.
O’Connel\, M.E. Lee\, E. Coetsee. J. Lumin. 156 (2014) 150.\n[5] J. J. P
eng\, S. Hou\, X. Liu\, J. Feng\, X. Yu\, Y. Xing\, Z. Su. Mater. Res. Bul
l. 47 (2012) 328.\n\nhttps://events.saip.org.za/event/39/contributions/386
3/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3863/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effective doping of ZnO quantum dots with Rare Earth ions for opto
-electronic applications
DTSTART;VALUE=DATE-TIME:20150505T071000Z
DTEND;VALUE=DATE-TIME:20150505T073000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3865@events.saip.org.za
DESCRIPTION:Speakers: GUY LEBA KABONGO (University of South Africa)\nhttps
://events.saip.org.za/event/39/contributions/3865/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3865/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Interplay between phase transitions and thermoluminescence in BaAl
2O4
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3867@events.saip.org.za
DESCRIPTION:Speakers: Jorma Hölsä (University of Turku)\n1. Introduction
\n\n The Eu2+ and R3+ doped alkaline earth aluminates (MAl2O4\; M: Ca\,
Sr\, Ba) are among the best persistent luminescence materials [1]. The mo
st efficient is\, however\, SrAl2O4:Eu2+\,Dy3 – partly due to its emissi
on in green to which the human eye is sensitive. Also the blue emitting Ca
Al2O4:Eu2+\,Nd3+ is more efficient than the barium one. All three material
s should have similar properties since they have the stuffed tridymite (Si
O2) type structure. However\, SiO2 is known for polymorphism and MAl2O4 de
rived from this do not behave dissimilarly. Although CaAl2O4 seems to have
only one form and SrAl2O4 two\, for BaAl2O4 one knows two hexagonal [2] a
nd one orthorhombic forms. These polymorphs are found at high temperatures
quite far from the usual operating range (<200 °C) of persistent lumines
cent materials. Nevertheless\, the role of possible low temperature phase
transitions should not be excluded as a reason for the less good persisten
t luminescence performance of BaAl2O4:Eu2+(\,R3+) [3\,4]. Further studies
were carried out by using the high-temperature X-Ray Powder Diffraction (H
T-XPD)\, Differential Scanning Calorimetry (DSC) and thermoluminescence (T
L) methods.\n\n2. Results\n\nThe HT-XPD patterns of BaAl2O4 (Fig. 1) at ro
om temperature (RT) correspond to the hexagonal P63 form. Additional weak
reflections may indicate symmetry decrease to e.g. orthorhombic but this n
eeds further proof. The RT structure is not stable for more than some 50
°C before significant changes occur in the intensity of all reflections.
Characteristic to these changes is that they occur over a wide temperature
range and smooth changes seem to be the rule rather than the exception. T
he intensity variation suggests displacement of atoms away from the reflec
tion planes and changes may thus occur just in the space group. The DSC me
asurements were inconclusive since only a few broad signals and strong bac
kground variation were found instead of sharp signals. These features are
in agreement with the slow and gradual nature of the changes in the XPD pa
tterns.\nBoth the HT-XPD and DSC results correlate well with the bands obs
erved in the TL glow curves. When compared to the very simple (1 or 2 TL b
ands) glow curves of CaAl2O4:Eu2+ or SrAl2O4:Eu2+ (without R3+ co-doping)\
, the five broad TL bands for BaAl2O4:Eu2+ between 100 and 400 °C (Fig. 2
) indicate a more complex trap structure with energies from 0.8 to 1.4 eV.
Thus a reason for the inferiority of the BaAl2O4 host vs. CaAl2O4 and SrA
l2O4 is clear: the close to continuous distribution of traps does not allo
w long term storage of input energy but the bleaching of the traps occurs
too rapidly. The persistent luminescence is then of short duration.\n\nhtt
ps://events.saip.org.za/event/39/contributions/3867/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3867/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Wavelength-modulated photocurrent spectroscopy of GaSb/GaAs quant
um ring solar cells
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3868@events.saip.org.za
DESCRIPTION:Speakers: Nambinintsoa Romeoh HASINJATOVO MANDANIRINA (Nelson
Mandela Metropolitan University)\n1. Introduction\nIn recent years\, many
studies have been reported on the optical response characterization of typ
e-II GaSb/GaAs quantum dot solar cells [1-2]. It has been shown that incor
porating quantum structures into the junction can considerably extend the
near band-edge response of the solar cell [2]. Unlike with conventional re
sponse measurements\, where the intensity of the light source is typically
modulated\, differential spectroscopy is performed by modulating the wave
length of the pseudo-monochromatic excitation source [3-4]. However\, due
to the spectral dependence of most excitation sources\, the optical inten
sity is inherently also modulated. As an example\, in order to obtain the
correct differential quantum efficiency (QE) spectrum of the solar cell\,
the photon flux of the excitation source would need to be measured separa
tely and subtracted ...\n\nhttps://events.saip.org.za/event/39/contributio
ns/3868/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3868/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Self-Assembled Nanotubular Mesoporous Layered Double Hydroxides wi
th Tunable Photoluminescence
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3869@events.saip.org.za
DESCRIPTION:Speakers: Danilo Mustafa (University of São Paulo)\nSelf-asse
mbled luminescent LDH nanotubes (Ø 20nm) combine the potential of RE3+ co
ntaining LDH with a high surface area and easily accessible mesopores (±1
75 m2/g\; 0.75 cm3/g) suitable for hosting large sensitizing dyes and othe
r interesting photonic species such as luminescent nanodots.\n\nhttps://ev
ents.saip.org.za/event/39/contributions/3869/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3869/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Response of Ni/4H-SiC Schottky barrier diodes to alpha-particle ir
radiation at different fluences
DTSTART;VALUE=DATE-TIME:20150505T122000Z
DTEND;VALUE=DATE-TIME:20150505T124000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3870@events.saip.org.za
DESCRIPTION:Speakers: Ezekiel Omotoso (University of Pretoria)\nWe have in
vestigated the effect of 251-Am alpha-particle irradiation of energy 5.4 M
eV on 1.9 × 10^(16) cm^(–3) N-doped 4H-SiC SBDs at different fluences.
Prior to bombardment\, we observed four defects with energies 0.10\, 0.12\
, 0.16 and 0.65 eV below the conduction band. Alpha-particle irradiation i
ntroduced one additional defect with a very broad peak after receiving a 2
.8 × 10^11 cm^(–2) fluence\, and the peak became conspicuous after seve
ral irradiations. The signature in term of energy and apparent capture cro
ss section was estimated to be 0.37 eV and 5.5 × 10^(–16) cm^2\, respec
tively. The introduction rate of this defect was determined to be 6500 cm^
(–1).\n\nhttps://events.saip.org.za/event/39/contributions/3870/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3870/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Electrical Characterisation of Electron Beam Exposure Induced Defe
cts in Silicon
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3871@events.saip.org.za
DESCRIPTION:Speakers: Helga Danga (University of Pretoria)\nSilicon (Si) i
s one of the most important semiconductor materials and it has been studie
d extensively. This is mainly due to its low cost\, thermal stability\, an
d good durability. It is because of these properties that Si is a suitabl
e candidate for exploring the electron beam exposure (EBE) technique. The
main aim of developing the EBE technique was to see if electron beam depos
ition (EBD) induced defects could be introduced in a controlled manner.Dee
p level transient spectroscopy (DLTS) and high resolution Laplace-DLTS wer
e used to characterise the defects introduced in epitaxially grown p-type
Si during electron beam exposure. In this process\, Si samples were first
exposed to the conditions of EBD without metal deposition (EBE). After EB
E\, Aluminium and Nickel Schottky contacts were fabricated using the resis
tive deposition method. For the Aluminium contacts\, the defect level H(0.
33) was identified as the interstitial carbon (C_i ) related defect. It wa
s a result of induced damage and could only be explained by the presence o
f donor-like traps. The capture cross-section was calculated to be 1.6×
〖10〗^(-19) 〖cm〗^(-2) from the Arrhenius plot shown in figure 1.The
defect level observed using the Nickel contacts had an activation energy
of H(0.55) with a capture cross-section of 6.6×〖10〗^(-14) 〖c
m〗^2. This defect has an activation energy similar to the I-defect. Pint
ilie et al observed a similar energy level\, 0.545eV\, with a capture cros
s-section of 1.7×〖10〗^(-15) 〖cm〗^2 and 9.0×〖10〗^(-14) 〖cm
〗^2 after exposing their samples to high irradiation fluences. The defec
t level was detected using thermally stimulated current (TSC).\n\nhttps://
events.saip.org.za/event/39/contributions/3871/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3871/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Spectroscopic properties of Pr3+ ions embedded in lithium borate g
lasses
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3872@events.saip.org.za
DESCRIPTION:Speakers: Durgaprasad Ramteke (Department of Physics\, Univers
ity of the Free State)\nhttps://events.saip.org.za/event/39/contributions/
3872/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3872/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Zn2SiO4:Mn2+ co-doped with Tm3+ and other Re ions (Re = Rare-earth
): Synthesis\, Structure and Optical Properties
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3873@events.saip.org.za
DESCRIPTION:Speakers: Pontsho Mbule (University of South Africa)\nZinc sil
icate (Zn2SiO4) is a good host lattice for luminescence centers such as ra
re-earth ions and transition metals (TM) to prepare light emitting materia
ls (phosphors) that can emit blue\, green and red light upon excitation wi
th high energy electrons or photons. In this work\, combustion method was
used to prepare undoped and manganese (Mn2+) and thulium (Tm3+)–co-activ
ated zinc silicate (Zn2SiO4:Mn2+\,Tm3+) nanoparticulate powder phosphors.
In addition\, a selection of Re ions (rare-earth ions) were used for co-do
ping to tune the emission colour. The structure\, morphology and luminesce
nce properties were investigated by X-ray diffractometer (XRD) and Field-E
mission Scanning Electron Microscopy (FE-SEM) respectively \, while the op
tical and luminescent properties were examined by Fourier Transform Infrar
ed Spectroscopy (FTIR)\, ultraviolet visible (UV-vis) spectroscopy\, Varia
n Cary-eclipse fluorescence spectrophotometer and 325 He-Cd laser equipped
photoluminescence system.\n\nThe XRD patterns matching with the willemite
structure of Zn2SiO4 were observed. However\, there was additional second
ary peak assigned to (101) diffraction of the hexagonal wurtzite structure
of ZnO\, suggesting that our material was an admixture of ZnO and Zn2SiO4
. ZnO was either formed from the reaction of Zn2+ and O2- during the combu
stion reaction in air or resulted from the incomplete decomposition of the
precursors. A network of spherical (but faceted) agglomerated nanopartic
les were observed from undoped\, Mn2+-doped and Mn2+/Tm3+-codoped Zn2SiO4
powders. The PL spectra recorded from Zn2SiO4:Mn2+ nanophosphors with dopa
nt concentration of Mn2+ ions ranging from 0.045 – 0.09 mol% show strong
green-orange emission band at ~ 562 nm and a shoulder at ~523 nm and as t
he Mn2+ concentration increases the emission peak slightly shifted to the
higher wavelength. This is a typical emission of Mn2+ in α-Zn2SiO4 and m
ay be assigned to the electronic transition 4T1(4G) →6A1(6S). Tuning of
the emission colour by Tm3+ co-doping and other selected Re ions is demons
trated and will be discussed in detail. These nanophosphors have potential
applications in nanoelectronics and optoelectronics.\n\nhttps://events.sa
ip.org.za/event/39/contributions/3873/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3873/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effect of Ag doping on the luminescence of ZnO and ZnO:Tb
DTSTART;VALUE=DATE-TIME:20150507T115000Z
DTEND;VALUE=DATE-TIME:20150507T121000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3874@events.saip.org.za
DESCRIPTION:Speakers: Abd Ellateef Abbass (Sudanese)\nZnO has attracted co
nsiderable attention as a photonic material and ZnO:Tb is a promising mate
rial for phosphor converted white light emitting diodes. It has been repor
ted that metallic Ag nanoparticles will precipitate if an excessive amount
of Ag is doped into ZnO and localized surface plasmon resonance effects a
ssociated with metallic nanoparticles are of great interest because they h
ave the potential to significantly enhance the luminescence properties of
phosphors. In this study we investigated the effect of doping ZnO and ZnO:
Tb with Ag on their luminescence properties. The addition of Ag caused mor
e than a twofold increase the near band edge recombination peak of ZnO nea
r 390 nm. However\, the addition of Ag to ZnO:Tb reduced the characteristi
c green luminescence from the Tb ions. Possible mechanisms for this and th
e influence of intrinsic defects in the ZnO are discussed.\n\nhttps://even
ts.saip.org.za/event/39/contributions/3874/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3874/
END:VEVENT
BEGIN:VEVENT
SUMMARY:n-WO3|p-Si tandem layer solar cells as new candidates on the Shock
ley-Queisser chart of photovoltaic efficiency
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3875@events.saip.org.za
DESCRIPTION:Speakers: Funda Mpanza (Heriot-Watt University)\nhttps://event
s.saip.org.za/event/39/contributions/3875/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3875/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The influence of reaction times on structural\, optical and lumine
scence properties of CdTe nanoparticles prepared by wet-chemical process.
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3876@events.saip.org.za
DESCRIPTION:Speakers: Sharon Kiprotich (University of the Free State)\nThe
title of the abstract is “The influence of reaction times on structural
\, optical and luminescence properties of CdTe nanoparticles prepared by w
et-chemical process”\nIn introduction\, the abstract reports the study o
f CdTe nanoparticles made by a simple green synthesis using L-cystein as a
capping agent\, potassium tellurite and sodium selenosulphate as stable t
ellurium and selenium sources. The synthesis parameters have considerable
influence on the particle size and photoluminescence quantum yield of the
CdTe nanoparticles.\nThe results part of the abstract\, discusses briefly
the properties of CdTe as characterised using PL\, TEM\, UV-vis and XRD. S
pectra on a representative TEM micrographs of CdTe nanoaprticles and PL em
ission of CdTe QDs prepared at various reaction emitting at different wave
length when excited by a single excitation wavelength were attached. Final
ly\, three references were appended at the foot of the abstract.\n\nhttps:
//events.saip.org.za/event/39/contributions/3876/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3876/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The effect of the Optical System on the Electrical Performance of
III-V Concentrator Triple Junction Solar Cells
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3877@events.saip.org.za
DESCRIPTION:Speakers: Ernest van Dyk (NMMU)\nThe progression of the develo
pment of High Concentrated Photovoltaic (H-CPV) technology promises lower
costs and higher cell and module efficiencies. However\, development is li
mited by various materials and device aspects. One of these\, the power pr
oduction limiting effects of the optical system on a Concentrator Triple J
unction (CTJ) cell in an H-CPV module\, is the focus of this paper. With c
arefully designed experiments\, which included spectral measurements\, top
ographic intensity profiles in the cell plane and the analysis of I-V curv
es of the CTJ cell/H-CPV module\, one can fully characterise loss mechanis
ms associated with the optical system and their effect on the electrical p
erformance of the CTJ cell.\n\nhttps://events.saip.org.za/event/39/contrib
utions/3877/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3877/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Advances in phosphors based on purely organic materials for solid
state lighting applications
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3878@events.saip.org.za
DESCRIPTION:Speakers: Kashma Sharma (Department of Physics\, University of
the Free State\, P.O. Box 339\, Bloemfontein 9300\, Republic of South Af
rica)\nhttps://events.saip.org.za/event/39/contributions/3878/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3878/
END:VEVENT
BEGIN:VEVENT
SUMMARY:XPS investigation of the photon degradation of Znq2 green organic
phosphor.
DTSTART;VALUE=DATE-TIME:20150507T134000Z
DTEND;VALUE=DATE-TIME:20150507T140000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3879@events.saip.org.za
DESCRIPTION:Speakers: Mart-Mari Duvenhage (University of the Free State)\n
Although tris-(8-hydroxyquinoline) aluminium (Alq3) is used as a green emi
ssive layer in organic light emitting diodes (OLED) it tends to degrade wi
th time leading to a decrease in device performance and efficiency. It has
been reported that by substituting Al with Zn to form bis-(8-hydroxyquino
line) zinc (Znq2)\, the Znq2 shows advantages over the Alq3 in electron tr
ansport and higher quantum yields in device performance which would result
in lower operating voltages. \n\nThere is a two fold increase in the phot
oluminescence intensity of Znq2 compared to that of Alq3. Znq2 powder was
irradiated with an UV source for 400 hours and the intensity vs time was m
onitored. From the N1s and O1s high resolution XPS peaks\, it can be seen
that the pyridyl ring stayed intact during degradation\, but that the phen
oxide ring ruptured and formed new bonds like C=O and C-OH.\n\nhttps://eve
nts.saip.org.za/event/39/contributions/3879/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3879/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effect of doping concentration on the conductivity and optical pro
perties of p-type ZnO thin films
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3880@events.saip.org.za
DESCRIPTION:Speakers: Trilok Pathak (Gurukula Kangri University\, Haridwar
\, India)\, Vinod Kumar (Department of Physics\, University of the Free st
ate\, Bloemfontein\, ZA-9300)\nZinc oxide (ZnO) is a multifunctional mater
ial with unique physical and chemical properties as well as good photo sta
bility.In present work we study the nitrogen doping effect on conductivity
and optical properties.\n\nhttps://events.saip.org.za/event/39/contributi
ons/3880/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3880/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ab initio studies of Split<110> and Tetrahedral Di-interstitials o
f Germanium (Ge) using Hybrid functional HSE06
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3881@events.saip.org.za
DESCRIPTION:Speakers: Emmanuel Igumbor (University of Pretoria)\nAs a resu
lt of its narrow band gap\, high carrier mobility and low voltage operati
on the application of Germanium (Ge) as a promising material for complemen
tary metal-oxide semiconductors (CMOS) technology is attracting attention
recently [1]. Studies on Several defects including self-interstitials\, in
terstitials\, vacancies and vacancy complexes [2-3] have been carried out.
For Silicon\, various interstitials and vacancies including mono-\, di-
and tri- has been studied[2]\, Ge mono-interstitials using local density a
pproximation(LDA)\, generalized gradient approximation (GGA) was reported[
3]\, but none have been studied on mono- and di-interstitials of Ge using
HSE[4]. In this work we present ab-initio calculations results of Ge Tetr
ahedral (TT) split<110> (SP10) and split<110>/Tetrahedral (SPT) di-interst
itials configurations in the frame work of density functional theory(DFT)
using hybrid functional (HSE06)[4] exchange correlation functional. The fo
rmation and transition level energies of defected configurations charge
states of -2\, -1\, 0\, +1 and +2 were obtained. Depending on the Fermi le
vel\, the formation energies shows that the SP10 is less favourable than T
while the combination of SPT forms the most stable defect. We find (+1/+2
) transition charges states level of TT to be 0.76 eV above valence band
maximum (VBM) and (+1/+2) for (SPT) configurations to be 0.72 eV above VBM
. These di-interstitials exhibited the properties of shallow and deep don
or at (+1/+2) above the Fermi level depending on the configurations. We co
mpare this result with calculation of di-interstitials in silicon and avai
lable experimental data.\n\nhttps://events.saip.org.za/event/39/contributi
ons/3881/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3881/
END:VEVENT
BEGIN:VEVENT
SUMMARY:An Ab-initio Study into possible metastability of the Antimony-vac
ancy (Sb - V) complex in Germanium.
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3882@events.saip.org.za
DESCRIPTION:Speakers: Geoffrey Webb (University of Pretoria)\nWe are inves
tigating the possibility of the Antimony-Vacancy complex (E-center) using
the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional within density funct
ional theory (DFT). The results are then compared the predictions we obtai
ned to experimental observations. We have in the past observed interesting
results for the similar case of metastability in the Boron – Vacancy co
mplex in silicon and wish to extend this research further to the Antimony-
Vacancy complex in Germanium. We investigate the dependencies of the form
ation energy of the complex to the position of the Germanium vacancy to re
spect to the substitutional Antimony within the supercell. We examine the
ability of the HSE06 functional to accurately predict the thermodynamic ch
arge transition levels and whether or not charge-state controlled metastab
ility exists in that of the Sb-V complex. The nearest neighbor and next ne
arest neighbor configurations of the Sb-V complex were also examined to gi
ve a greater understanding of the nature of this defect.\n\nhttps://events
.saip.org.za/event/39/contributions/3882/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3882/
END:VEVENT
BEGIN:VEVENT
SUMMARY:ANOTHER METHOD TO DETERMINE THE REFRACTIVE INDEX OF AlXGa1-XN
DTSTART;VALUE=DATE-TIME:20150507T092000Z
DTEND;VALUE=DATE-TIME:20150507T094000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3883@events.saip.org.za
DESCRIPTION:Speakers: JAA Engelbrecht (NMMU)\n1. Introduction \n\nAlGaN al
loys continue to be of great interest due to the application of these allo
ys in high-power\, high-temperature and high-frequency devices such as fie
ld-effect transistors\, UV-light emitting LED’s and laser diodes1-3. A
range of different electrical and optical properties can be obtained by va
rying the alloy composition of AlxGa1-xN by changing the amount of Al in t
he alloy. The characterization of these alloys to determine the various p
hysical properties as a function of Al content is therefore necessary. Opt
ical characterization is preferred as this technique has the advantage of
being non-contact and non-destructive. \n\nIn this work\, the use of infr
ared reflection spectroscopy to evaluate AlxGa1-xN epilayers grown with va
rying Al content by metalorganic vapour phase deposition (MOCVD) on sapphi
re substrates was investigated. The layer thickness was readily determine
d using interference fringes in the reflectance spectra of the samples4.
However\, this requires knowledge of the refractive index n as function of
the wavelength. Determination of the refractive index of AlxGa1-xN is ch
allenging\, since the refractive index is a function of wavelength and the
aluminium content of an AlxGa1-xN sample\, as well as the temperature of
the sample5. A number of techniques have been reported for the determinat
ion of the refractive index for AlxGa1-xN\, including from the refractive
indexes of AlN and GaN\, ellipsometry measurements or Sellmeier type equat
ions6. \n\nThe present investigation aims to provide an alternative metho
d to determine the refractive index of AlxGa1-xN at room temperature. The
method is based on the manipulation of earlier published experimental res
ults6 (Fig.1) and relations from the slope and y-intercept of straight lin
e graphs. The new formulation was then employed to obtain the thickness o
f the measured AlxGa1-xN epilayers\, using the observed interference fring
es (Fig. 2).\n \n2. Results\n\n \n Fig. 1
Examples of straight-line fits of previous results Fig. 2 Int
erference spectra of two AlxGa1-xN epilayers \n3. References\n\n1. N
. Maeda\, T. Saitoh\, K. Tsubaki\, T. Nishida and N. Kobayashi\, Jpn. J. A
ppl. Physics 38 (1999) L987-L989.\n2. T. Takano\, Y. Narita\, A. Horiuc
hi and H. Kawanishi\, Appl. Phys. Lett. 84 (2004) 3567-3569.\n3. J. Han
\, M.H. Crawford\, R.J. Shul\, J.J. Figiel\, M. Banas\, L. Zhang\, Y.K. So
ng\, H. Zhou and A.V. Nurmikko\, Appl. Phys. Lett. 73 (1998) 1688-1690.\n4
. F. Reizman\, J. Appl. Phys. 36 (1965) 3804\n5. U. Tisch\, B. Meyle
r\, O. Katz\, E. Finkman and J. Salzman\, J. Appl. Phys. 89 (2001) 2676-26
85.\n6. N.A. Sanford\, L.H. Robins\, A.V. Davydov\, A. Shapiro\, D.V. T
svetkov\, A.V. Dmitriev\, S. Keller\, U.K. Mishra and S.P. DenBaars\, J. A
ppl. Phys. 94 (2003) 2980-2991.\n\nhttps://events.saip.org.za/event/39/con
tributions/3883/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3883/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Optoelectronic properties and structural dependence of carbon nano
materials-based hybrid organic photovoltaic devices
DTSTART;VALUE=DATE-TIME:20150507T094000Z
DTEND;VALUE=DATE-TIME:20150507T100000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3884@events.saip.org.za
DESCRIPTION:Speakers: Brahim Aissa (QEERI-QF)\nWe report on the incorporat
ion of carbon nanomaterials (CNMs) such as single-walled carbon nanotubes
(SWCNTs) into organic PV (OPV) cells for efficiency optimization. Although
CNMs have been used before in OPVs\, the focus is put here to elucidate t
he effect of the structural properties of the CNMs on OPV performance\, wh
ich is poorly understood. More specifically\, we address the issue of impr
oving the performance of a new hybrid OPV device by combining the physical
and chemical characteristics of light-sensitive conjugated polymers (CP)\
, with the high electrical conductivity of SWCNTs by blending the both in
a composite photoactive layer. The focus is put on exploring in depth the
electronic and optoelectronic properties of the composite material in an O
PV scheme and exploring its corresponding photo-conversion capability. The
root-mean-square roughness\, photoluminescence and optical absorption wer
e found to increase with increasing SWCNTs content and a non linear correl
ation between the nanotubes loads and the open circuit voltage VOC was cle
arly pointed-out.\n\nhttps://events.saip.org.za/event/39/contributions/388
4/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3884/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Structural and luminescence properties of SrAl2O4:Eu2+\, Dy3+/Nd3+
phosphor thin films grown by pulsed laser deposition
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3885@events.saip.org.za
DESCRIPTION:Speakers: ALI HALAKE WAKO (University of the Freestate)\n1. I
ntroduction \n\nLong afterglow or persistent phosphors have the ability of
absorbing energy from UV or sunlight and then release it slowly in the da
rk [1\,2]. Inorganic phosphors doped with rare earth elements show broad b
and emission from blue to red which makes them suitable for a variety of i
ndustrial applications\, such as luminescent pigments\, fluorescent lamps\
, color display\, plasma display panels (PDP)\, radiation dosimetry and X-
ray imaging [3]. The type and duration of emission from a phosphor is aff
ected by a number of parameters such as the type and amount of activators
or dopants\, the structure of the host lattice\, the method of preparation
or growth conditions and other post-treatments. These parameters play a s
ignificant role in inducing a crystal field effect within the host matrix
which in turn influences the emission wavelength\, its intensity and lifet
ime. The main task would therefore be to optimize these factors to obtain
a phosphor that gives the best performance for the desired application. In
this study thin films of SrAl2O4:Eu2+\, Dy3+ /Nd3+ were prepared using Pu
lsed Laser Deposition (PLD). The effect of varying argon gas pressure and
substrate temperatures on the structure and photoluminescent (PL) properti
es of the SrAl2O4:Eu2+\, Dy3+ /Nd3+ thin films were investigated. \n\n2. R
esults\n\nX-ray diffraction (XRD) patterns of the SrAl2O4:Eu2+\, Dy3+ /Nd3
+ phosphor thin films deposited on Si(100) in vacuum\, 10\, 20 and 30 mTor
r argon partial pressure as compared with that of the as-prepared powder a
re shown in figure 1. The peaks fitted well with the powder and the JCPDS
card number 74-0794 for the monoclinic SrAl2O4 of space group P1211 (4). I
t can be seen that with increasing the argon pressure the peaks in the (22
0) direction shifted to the lower 2-theta angles from 29.1o in vacuum to 2
7.9o in 30 mTorr argon partial pressure. Ar has a higher mass density and
therefore tends to reflect lighter atoms in the plume more and these resul
ts in a film with big particles [4] which results in lattice expansion ind
ucing crystal field effect in host lattice causing the XRD peak shift to l
ower angles. Figure 2 shows PL emission spectra recorded with He-Cd laser
at excitation of 325 nm from SrAl2O4:Eu2+\, Dy3+/Nd3+ thin films deposited
under different argon atmospheres whereby emission peaks are observed to
shift towards the higher wavelength side. Larger particles will cause latt
ice expansion and increase the crystal-field interaction of Eu2+ resulting
in red shift.\n\nhttps://events.saip.org.za/event/39/contributions/3885/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3885/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Influence of varying Cr3+ mol% in MgAl2O4:0.1% Eu3+\, x% Cr3+ na
nophosphor synthesized by sol-gel process
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3886@events.saip.org.za
DESCRIPTION:Speakers: Setumo Victor Motloung (University of the Free State
(Qwaqwa Campus))\nThe XRD data revealed that all annealed samples consist
of the pure cubic MgAl2O4 structure. The estimated crystallites size were
in the range of 12.1 – 11.0 nm in diameter. SEM results showed that the
dopant type and varying the Cr3+ concentration in the co-activated sample
s influences the surface morphology of the phosphor. The PL results showe
d that the host\, 0.1% Cr3+ and Eu3+ activated nanophosphor emits at diffe
rent wavelengths. Emission peak at 390 nm is attributed to the band-gap de
fects in the host material. Emission at 405 is attributed to arise from bo
th the contribution from the host and Cr3+ (4T1 → 4A2 transition) emissi
ons. The green emission peak at 565 nm is attributed to arise from either
the host or Cr3+ (4T2 → 4A2 transition). An emission peak at 574 nm is a
ttributed to the well-known orange emission from 5D0 → 7F1 transition in
Eu3+ ion\, while the emission peak at 619 nm is assigned to the Eu3+ elec
tric dipole from 5D0 → 7F2 transition. An emission at 694 nm is attribu
ted to the Cr3+ from 2E → 4A2 transition. Co-activating the host with Cr
3+ ion quenches the host emission at 390 nm. The CIE color coordinates (se
e Fig. 2) shows that the emission color can be turned by varying the co-ac
tivator concentration.\n\nhttps://events.saip.org.za/event/39/contribution
s/3886/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3886/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The effect of high temperatures on the electrical characteristics
of Au/n-GaAs Schottky diodes
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3888@events.saip.org.za
DESCRIPTION:Speakers: Shandirai Tunhuma (University of Pretoria)\nWe inves
tigated the rectification properties of Gold Schottky contacts fabricated
on epitaxial n-type GaAs.The study was carried out using Laplace deep leve
l transient spectroscopy together with the current-voltage characteristics
and the capacitance voltage characteristics in the 80-480K range.\n\nhttp
s://events.saip.org.za/event/39/contributions/3888/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3888/
END:VEVENT
BEGIN:VEVENT
SUMMARY:AZO as a transparent conductive oxide for inversion-layer silicon
solar cells
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3889@events.saip.org.za
DESCRIPTION:Speakers: Fred Joe Nambala (University of Pretoria)\n1. Introd
uction\nZinc Oxide (ZnO) has been attracting much attention in research ac
tivities for applications in light emitting diodes\, spintronic devices\,
solar cells\, etc. [1]. Doping the ZnO changes its properties especially i
n increasing its electrical conductivity [2]. This work focuses on the dev
elopment of Aluminium doped Zinc Oxide (AZO) which has property-integrity
to allow a research-in-progress hybrid inversion layer silicon solar cell
to give maximum efficiency. The effects of thermal post-annealing in contr
olled air (N and O mixtures) on the electrical\, structural and optical pr
operties of undoped and aluminium-doped (i.e.\, 0%\, 2% and 5%) AZO thin f
ilms deposited on glass and silicon substrates by the sol-gel method are i
nvestigated.\n \n2. Results\nAZO was prepared using the sol-gel method
with 0%\, 2% and 5% Al. Thin films were then deposited on glass as well as
crystalline silicon (c-Si) immediately after preparation\, after 1 day\,
after 2 days\, and after 3 days\, pre-heating at 200˚C between layers. Af
ter a number of days\, they were post-annealed at 400˚C\, 450˚C\, 500˚C
\, 550˚C\, 600˚C and 650˚C. Various characterization techniques includi
ng four-point probe\, PL\, UV-Vis\, Raman spectroscopy\, AFM\, SEM and XRD
measurements were conducted on the prepared samples. The energy bandgaps
for 0%\, 2% and 5% of Al in ZnO were determined as 3.48 eV\, 3.37 eV and 2
.95 eV respectively for samples deposited on microscope glass slides after
1 day (‘Day 1’\, see Fig. 1) from the time of the sol-gel preparation
. The determined Eg results for AZO depositions on Day 0\, Day 2 and Day 3
after the preparation of the sol-gel are consistent with the trend of red
ucing bandgap as the concentration of Al increases from 0% through 2% to 5
% in the AlxZn1-xO polycrystalline material configuration. XRD measurement
s indicate that (002) is the most preferred orientation of the material.
Peaks for (010)\, (011) and (110) orientations were also observed in the X
RD pattern. Fig. 2 shows the de-convolution of peaks for AZO on glass Rama
n spectra\, re-sulting in significant attribution of measured peaks. The r
esults are being analyzed to understand the structural characterization of
the AZO. The measurements from the other techniques will also be discusse
d.\n\nhttps://events.saip.org.za/event/39/contributions/3889/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3889/
END:VEVENT
BEGIN:VEVENT
SUMMARY:VO2 nanorod as a new candidate for near infrared light harvesting
DTSTART;VALUE=DATE-TIME:20150506T092000Z
DTEND;VALUE=DATE-TIME:20150506T094000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3890@events.saip.org.za
DESCRIPTION:Speakers: Amos Akande (Dept. of Physics\, University of Limpop
o\, DST/CSIR National Centre for Nano-Structured Materials\, P O Box 395\,
Pretoria 0001\, South Africa)\nVanadium dioxide (VO2) thermocromic proper
ties have been widely applied in many devices in an attempt to solving the
world energy crises. One of such devices is thermochromic/switchable/smar
t window\, an energy saving window which is transparent to infrared light
with high refractive index above 70 degree C (the transition temperature o
f VO2) and refracts infrared light with low refractive index below this te
mperature. In this current attempt\, we have investigated the potentials o
f VO2 nanorod structure for near infrared light harvesting by coating the
material on p-type Si wafers using a simple doctor blading method. The n-V
O2|p-Si solar cell was annealed at 70 degree C and tested with a SF 150 sm
all beam simulator by SCIENCETECH Inc. from Ontario Canada. \nPhoton powe
r conversion efficiency (PCE) was calculated form the values of the open-c
ircuit voltage (Voc)\, fill factor (FF)\, and short-circuit current densit
y (Jsc)\, and a decreasing trend of PCE was observed with the photon power
.\n\nhttps://events.saip.org.za/event/39/contributions/3890/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3890/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The effect of urea ratio on structural and luminescence properties
of YVO4:Dy phosphor
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3891@events.saip.org.za
DESCRIPTION:Speakers: Kewele Emily Foka (University of the Fee Stae)\nThe
effect of urea ratio on structural and luminescence properties of YVO4:Dy
phosphor\n\n\n\n1. Introduction \n\nAlthough the luminescence characterist
ics of vanadates phosphors have been reported\, yttrium vanadates (YVO4) a
re good host materials for luminescence efficiency. Like Eu\, Tm and other
rare earth ions\, Dy can also act as a useful activator. Many researchers
have reported that YVO4 can be modified by Eu to be used as red phosphor
in colour television and cathode because of its high luminescence [1]. Be
sides europium\, Dy ions is a good activator for YVO4: Dy3+. Synthesis of
YVO4 has previously been prepared by various methods. Here YVO4:Dy was pre
pared by combustion method at initiation temperature of 600 oC. Combustion
method is one of an ideal technique\, because exothermic reaction was ini
tiated at the ignition temperature and it generates heat which was manifes
ted in a maximum temperature of 100-1650 K.\n \n2. Results\n\nFigure 1
shows the XRD patterns of the YVO4:Dy powders synthesized by combustion me
thod at initiation temperature of 600 o C with different mole ratios of ur
ea. The phosphor powder showed that the peaks were due to YVO4 tetragonal
phase (JCPDS 17-0341). No other crystalline phase was detected on XRD spec
tra. Scanning electron microscopy results showed when increasing ratio of
urea the agglomeration of particles decreases and the nanorod-like shape s
tructure starts to form. Figure 2 shows the emission spectra obtained from
excitation of 282 nm. The emission spectra consist of two main peaks\, ye
llow band at 573 nm corresponding to 4F9/2→6H13/2 and the blue band (482
nm) corresponds to the 4F9/2→6H15/2 transition. There is a very week ba
nd at 663 nm which correspond to 4F9/2→6H11/2 transition. The intensity
of the yellow emission is stronger than that of blue emission\, this is be
cause when the Dy3+ ions is located at low symmetry local sites with no in
version centers\, the 4F9/2→6H13/2 transition is prominent in its emissi
on spectrum.\n\n \n\n\n\n\n3. References\n\n[1] J. Wang\,
Y. Xu\, M. Hojamberdiev\, Y. Cui\, H. Liu and G. Zhu\, J. of Alloys and C
ompounds. 479 (2009)\, 772-776.\n[2] H. Zhang\, X. Fu\, S. Niu and Q. Xin\
, J. of Alloys and Compounds. 457 (2008) 61-65.\n\nhttps://events.saip.org
.za/event/39/contributions/3891/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3891/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lattice location of dopants in group-III nitrides and ZnO
DTSTART;VALUE=DATE-TIME:20150505T064000Z
DTEND;VALUE=DATE-TIME:20150505T071000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3892@events.saip.org.za
DESCRIPTION:Speakers: André Vantomme (KU Leuven\, Leuven\, Belgium)\nThe
properties (electric\, optic\, and magnetic) of impurities and dopants in
semiconductors are strongly dependent on the lattice sites which they occu
py. Although the main occupied site\, for a given impurity-host combinatio
n\, can often be predicted based on chemical similarities between impurity
and host elements\, such expectations fail in many cases. Furthermore\, m
inority sites (in case of multiple-site occupancy) are even more difficult
to predict\, detect and identify. In this talk\, we give an overview of r
ecent lattice location studies for impurities and dopants in ZnO and GaN\,
as representative wide-gap semiconductors. These experiments are based on
the emission channeling (EC) technique\, using radioactive isotopes produ
ced at the ISOLDE facility at CERN. EC makes use of the charged particles
emitted by a radioactive isotope upon decay. The screened Coulomb potentia
l of atomic rows and planes determines the anisotropic scattering of the p
articles emitted isotropically during the radioactive decay. Along low-ind
ex directions of single crystals and epitaxial films\, this anisotropic sc
attering results in well defined channeling or blocking effects. Because
these effects strongly depend on the initial position of the emitted par
ticles\, they result in emission patterns which are characteristic of the
lattice site(s) occupied by the probe atoms. In this talk\, we present som
e particular cases that illustrate the strengths of emission channeling wh
en studying systems exhibiting multiple-site occupancy.\n\nhttps://events.
saip.org.za/event/39/contributions/3892/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3892/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Microwave assisted synthesis of ZnO nanoparticles for lighting and
dye removal application
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3893@events.saip.org.za
DESCRIPTION:Speakers: Vijay Kumar (Department of Physics\, University of t
he Free State\, P.O. Box 339\, Bloemfontein 9300\, Republic of South Afri
ca)\nhttps://events.saip.org.za/event/39/contributions/3893/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3893/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The Quantum Design of Photosynthesis
DTSTART;VALUE=DATE-TIME:20150506T064000Z
DTEND;VALUE=DATE-TIME:20150506T071000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3894@events.saip.org.za
DESCRIPTION:Speakers: Rienk van Grondelle (VU University Amsterdam)\nPhoto
synthesis has found an ultrafast and highly efficient way of converting th
e energy of the sun into electrochemical energy. The solar energy is colle
cted by Light-Harvesting complexes (LHC) and then transferred to the React
ion Center (RC) where the excitation energy is converted into a charge sep
arated state with almost 100% efficiency. That separation of charges creat
es an electrochemical gradient across the photosynthetic membrane which ul
timately powers the photosynthetic organism. The understanding of the mole
cular mechanisms of light harvesting and charge separation will provide a
template for the design of efficient artificial solar energy conversion sy
stems.\n\nUpon excitation of the photosynthetic system the energy is deloc
alized over several cofactors creating collective excited states (excitons
) that provide efficient and ultrafast paths for energy transfer using the
principles of quantum mechanics. In the reaction center the excitons beco
me mixed with charge transfer (CT) character (exciton-CT states)\, which p
rovide ultrafast channels for charge transfer. However\, both the LHC and
the RC have to cope with a counter effect: disorder. The slow protein moti
ons (static disorder) produce slightly different conformations which\, in
turn\, modulate the energy of the exciton-CT states. In this scenario\, in
some of the LHC/RC complexes within the sample ensemble the energy could
be trapped in some unproductive states leading to unacceptable energy loss
es.\n\nHere I will show that LHCs and RCs have found a unique solution for
overcoming this barrier: they use the principles of quantum mechanics to
probe many possible pathways at the same time and to select the most effic
ient one that fits their realization of the disorder. They use electronic
coherence for ultrafast energy and electron transfer and have selected spe
cific vibrations to sustain those coherences. In this way photosynthetic e
nergy transfer and charge separation have achieved their amazing efficienc
y. At the same time these same interactions are used to photoprotect the s
ystem against unwanted byproducts of light harvesting and charge separatio
n at high light intensities.\n\nhttps://events.saip.org.za/event/39/contri
butions/3894/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3894/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Plasmonic systems and their Interaction with Moleucles
DTSTART;VALUE=DATE-TIME:20150505T091000Z
DTEND;VALUE=DATE-TIME:20150505T094000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3895@events.saip.org.za
DESCRIPTION:Speakers: Adi Salomon (Chemistry department\, BINA nanocenter\
, Bar Ilan University)\nWe look on interaction between molecules and light
at the nanoscale\, by fabrication of metallic nanostructures (plasmonic s
ystems). The interaction (coupling) is interesting both in the effect the
molecules have on the plasmons and in the effect the plasmons have on the
molecular transitions. Thus\, molecules which are immeressed is the plasm
onic field\, may undergo photochemical processes which otherwise suppresse
d.\nWe further discussed the coupling between localized plasmonic modes of
metallic nano structures and their nonlinear properties\, such as second
harmonic generation (SHG) . We show that when strongly coupled the equilat
eral triangular nanocavities lose their individual three-fold symmetry to
adopt a lower symmetry of the coupled system. The coupled system then resp
onds like a single dipolar entity\, and the SHG signal is either enhanced
or suppressed depending on the incoming beam polarization. \n\nReferences\
n[1] From Individual to coupled metallic nanocavities. Salomon\, A.\;Prior
\, Y.\; Kolkowski\, R.\; Zyss\, J. \; Journal of optics 2014\n[2] Role of
mode degeneracy in molecule-surface plasmon strong coupling. Salomon A. Wa
ng\, S. Hutchison\, J.A.\, Genet\, C. Ebbesen\, T.W. J. Phys. Chem. C\, 20
13\, 117 (43)\, pp 22377–22382 \n[3] Collective Plasmonic-Molecular Mode
s in the Strong Coupling Regime. Salomon\, A et al. .\; Phys. Rev. Le
tt 109\, 073002\, 2012 \n[4] Molecule – light complex: dynamics of hybr
id molecule – surface plasmon states. Salomon\, A. Genet\, C. and Ebbese
n\, TW. Angewandte Chemie\, 48\, Pages: 8749-8751\, 2009.\n\nhttps://even
ts.saip.org.za/event/39/contributions/3895/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3895/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Electrical characterization of Au/Ni/AlGaN Schottky barrier diodes
DTSTART;VALUE=DATE-TIME:20150505T081000Z
DTEND;VALUE=DATE-TIME:20150505T083000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3896@events.saip.org.za
DESCRIPTION:Speakers: Mmantsae Diale (University of Pretoria)\nIn this stu
dy\, Au/Ni Schottky barrier contacts have been fabricated on AlGaN grown b
y hydride vapor-phase epitaxy (HVPE). After ohmic and Schottky contacts f
abrication\, the contacts were annealed at 500°C. The electrical characte
ristics of the diodes were investigated by using current-voltage measureme
nts. The results show that the diodes characteristics improved after annea
ling\, with reverse leakage current dropping to less than 10-8 A. Furtherm
ore\, the analysis of the temperature dependent electrical characteristics
shows that the reverse current of the diodes increases with increasing te
mperature. The barrier height and ideality factors increased and decreased
with increasing temperature respectively.\n\nhttps://events.saip.org.za/e
vent/39/contributions/3896/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3896/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Analysis of deep level emission bands in solution grown ZnO nanoro
ds
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3897@events.saip.org.za
DESCRIPTION:Speakers: Crispin Munyelele Mbulanga (Nelson Mandela Metropoli
tan University)\nhttps://events.saip.org.za/event/39/contributions/3897/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3897/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Evolution of stress in thin hard films by surface Brillouin scatte
ring
DTSTART;VALUE=DATE-TIME:20150506T094000Z
DTEND;VALUE=DATE-TIME:20150506T100000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3898@events.saip.org.za
DESCRIPTION:Speakers: Daniel Wamwangi (wits university)\n1. Introduction \
n\nTransition metal based thin films continue to attract tremendous resear
ch interest due to their excellent properties. As such they are widely use
d as protective coatings in optics and cutting tools due to their chemical
properties\, low wear and tear under extreme environments [1]. However de
lamination and intrinsic stress remain a great challenge especially in mul
tilayer thin films. The mechanisms of thin film growth and intrinsic stres
s can be understood by investigating stress evolution through modification
of elastic constants after insitu Ar+ incorporation during film growth. I
n this work\, we present an alternative approach to investigate stress evo
lution of either crystalline or amorphous thin hard films using the compon
ents of the elastic constant tensor. Thin films of transitional metal carb
ide on etched (100) Si substrates have been grown by RF magnetron sputteri
ng at 0 and - 60V bias to observe stress evolution by surface Brillouin sc
attering. A RF power of 175W and Ar2 working gas pressure of 1.0 x10-3mbar
were used for film synthesis. X-ray Reflectometry has been used extract t
he film growth rate from measurements of film thickness\, interfacial roug
hness and density. The density values were used to extract and simulate ve
locity dispersion curves obtained from surface Brillouin scattering spectr
a. A low surface roughness has been determined by X-ray Reflectometry for
all films to 1.5 nm. Surface Brillouin studies on the - 60V biased
and pristine samples have shown the propagation of Rayleigh surface acoust
ic wave and higher frequency peaks. The presence of the high frequency shi
ft indicates a high film quality. The velocity dispersion curves show an i
ncrease in surface acoustic phonon velocity corresponding to an increase i
n elastic constants upon biasing. It is observed that Ar+ incorporation ch
anges the C33 elastic constant by 38% with a resulting columnar thin film
growth from the C11/C33 <1 values. \n\n\n \n2. Results\n\nFig 1 shows
the typical surface Brillouin scattering spectra of transitional metal car
bide. The true surface acoustic wave and the higher frequency peaks (Sezaw
a waves). The evidence of stress evolution is presented in Fig 2 which dep
icts an increase in the surface acoustic phonon velocity of the irradiated
samples. \n\n \n\n\n\n\n3. References\n\n[1] A. Palmero\
, E.D. van Hattum\, W.M. Arnoldbik\, F.H.P.M. Habraken\, Surface & Coating
s Technology 188-189\, 392 (2004).\n\nhttps://events.saip.org.za/event/39/
contributions/3898/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3898/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pd doped ZnO nanostructures: Structural\, luminescence and gas sen
sing properties
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3899@events.saip.org.za
DESCRIPTION:Speakers: Gugu Mhlongo (CSIR)\nUndoped and Pd (0.5 and 0.75 mo
l%) doped ZnO nanostructures were synthesized by a sol-gel method and anne
aled at 350 oC. An increase in the particle size with Pd doping was observ
ed. Room-temperature PL measurements showed that both oxygen and zinc rela
ted defects played a role in the defect emission process. PL and sensing a
nalyses revealed that there is a correlation between the sensing propertie
s and the relative concentration of the oxygen vacancies\, zinc vacancies
and zinc interstitials present on the surface of the ZnO- nanostructures.\
n\nhttps://events.saip.org.za/event/39/contributions/3899/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3899/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Structure and Spectroscopic Properties of M(Qn)3 complexes
DTSTART;VALUE=DATE-TIME:20150507T132000Z
DTEND;VALUE=DATE-TIME:20150507T134000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3900@events.saip.org.za
DESCRIPTION:Speakers: Hendrik Vissser (University of the Free State)\nMeta
l quinolinates are known as key materials in the design of organic light e
mission diodes (OLEDs). The aluminium complex\, tris-(8-hydroxyquinoline
) aluminium(III)\, is the most well-known molecule of this family\, althou
gh its gallium analogue has also been considered for use in OLEDs [1\,2].
Factors that govern the efficacy these metal complexes for potential use
in OLEDs include the type of isomer (mer versus fac)\, inter-molecular in
teractions (like π-π stacking) and solvento species “trapped” in the
crystal lattice. Furthermore it was shown that the emission spectra of t
hese complexes can be red or blue shifted by using derivatives of 8-hydrox
yquinoline on the 5 and 7 positions of the ligand backbone with electron w
ithdrawing or donating properties (as in 5\,7dichloro-8-hydroxyquinoline (
5\,7-Cl2Qn) or 5\,7 dimethyl-8-hydroxyquinoline (5\,7-Me2Qn)) [3-5]. \n\n
In this work\, various complexes of M(Qn)3 (M = Al(III)\, Ga(III)\, In(III
) and Eu(III)\; Qn = 8-hydroxyquinoline / 5\,7dichloro-8-hydroxyquinoline
/ 5\,7 dimethyl-8-hydroxyquinoline) have been synthesized and characterize
d with 1H NMR\, single crystal X-ray spectroscopy and other means and thei
r photoluminescence properties evaluated [6\, 7]. A systematic evaluation
of the structural versus luminescence properties of nine M(Qn)3 complexes
plus interesting results of two Europium(III) metal complexes are reporte
d here.\n\n3. References\n[1] C.W. Tang and S.A. Vanslyke\, Appl. Phys. Le
tt. 51 (1987) 913-915.\n[2] P.E. Burrows\, L.S. Sapochak\, L.S. McCarthy\,
S.R. Forrest and M.E. Thompson\, Appl. Phys. Lett.\, 64 (1994) 2718.\n[3]
A. Irfan\, R. Cui\, J. Zhang and L. Hao\, Chem. Phys. 364 (2009) 39-45.\n
[4] Y. Qin\, I. Kiburu\, S. Shah and F. Jakle\, Org. Lett. 8 (2006) 5227-5
230.\n[5] Y.W. Shi\, M.M. Shi\, J.C. Haung\, H.Z. Chen\, M. Wang\, X.D. Li
u\, Y.G. Ma\, H. Xu and B. Yang\, Chem. Commun. (2006) 1941-1943.\n[6] M.
Duvenhage\, H.C. Swart\, O.M. Ntwaeaborwa and H.G. Visser\, Optical Materi
als\, 25 (2013) 2366-2371.\n[7] M. Duvenhage\, H.G. Visser\, O.M. Ntwaeabo
rwa and H.C. Swart\, Physica B\, 439 (2014) 46 - 49.\n\nhttps://events.sai
p.org.za/event/39/contributions/3900/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3900/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Defects in Zinc Oxide Grown By Pulsed Laser Deposition
DTSTART;VALUE=DATE-TIME:20150507T071000Z
DTEND;VALUE=DATE-TIME:20150507T074000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3901@events.saip.org.za
DESCRIPTION:Speakers: Francis Ling (The University of Hong Kong)\nZnO is a
wide band gap semiconductor having excellent properties for fabricating o
ptoelectronic devices operating at the wavelength of ultra-violet (UV).
The realization of fabricating UV optoelectronic devices with ZnO based te
chnology is hindered by the asymmetric p-type doping difficulty\, which is
related to the poor understanding of the defects\, defect compensation\,
and defect control in ZnO materials.\n Using pulsed laser deposition (P
LD)\, undoped ZnO films with (002) orientation are grown on c-plane sapphi
re with the systematic variation of the fabrication parameters including t
he substrate temperature and oxygen pressure during the growth\, as well a
s the post-growth annealing temperature [1]. Defects in the films were ch
aracterized by the positron annihilation spectroscopy (PAS)\, Raman spectr
oscopy\, secondary ion mass (SIMS) and photoluminescence (PL). The elect
ron concentration (~1018 cm-3) is similar to the hydrogen concentration me
asured by SIMS. SIMS study also reveals thermal induced Zn out-diffusion
into the sapphire substrate and leaves out the VZn related defects at the
ZnO film. Oxygen deficient defect related Raman lines 560 cm-1 and 584 cm
-1 are identified and with their origins being discussed. PAS reveals two
kinds of VZn related defects having different microstructures in the PLD
grown films\, which are different from those identified in the ZnO single
crystals.\n Green luminescence (GL) with more than one origin is found
in the films with annealing temperature lower than 900oC. At the annealin
g temperature of 900oC\, the defect emission spectra (measured at 10 K) of
all the films irrespective of the initial growth condition exhibit a GL p
eaked at 2.47 eV and originated from a single defect\, and simultaneously
the ~3.23 eV donor-to-acceptor-pair (DAP) emission is introduced. PAS stu
dy shows that the GL at 2.47 eV and the DAP are correlated to VZn defect h
aving the ionization levels at EV+0.15 eV and EV+0.97 eV [2]. The result
is compatible with the LDA+U calculation [3].\n\nReferences\n[1] Zilan Wan
g et al\, J. Appl. Phys. 116\, 033508 (2014).\n[2] ZIlan Wang et al\, subm
itted to Appl. Phys. Lett.\n[3] A. Janotti and C. G. Van de Walle\, Phys.
Rev. B 76\, 165202 (2007).\n\nhttps://events.saip.org.za/event/39/contribu
tions/3901/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3901/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Analysis of temperature-dependent current-voltage characteristics
and extraction of series resistance in Pd/ZnO Schottky diode
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3902@events.saip.org.za
DESCRIPTION:Speakers: Meehleketo Advice Mayimele (university of Pretoria)\
nWe report on the analysis of current voltage (I-V) measurements performed
on Pd/ZnO Schottky barrier diodes in the 30-350 K temperature range. Assu
ming thermionic emission (TE) theory\, the forward bias I-V characteristic
s were analysed to extract Pd/ZnO Schottky diode parameters. Comparing Che
ung’s method in the extraction of the series resistance with Ohm’s law
\, it was observed that at lower temperatures (T<180 K) the series resista
nce decreased with increasing temperature\, the absolute minimum was reach
ed near 180 K and increases linearly with temperature at high temperatures
(T>200 K). The barrier height and the ideality factor decreased and incre
ased\, respectively\, with decrease in temperature\, attributed to the exi
stence of barrier height inhomogeneity. Such inhomogeneity was explained b
ased on TE with the assumption of Gaussian distribution of barrier heights
with a mean barrier height of 0.986 eV and a standard deviation of 0.015
eV. A mean barrier height of 0.994 eV and Richardson constant value of 37.
48 A cm-2 K-2 were determined from the modified Richardson plot that consi
ders the Gaussian distribution of barrier heights.\n\nhttps://events.saip.
org.za/event/39/contributions/3902/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3902/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Proteins as opto-electronic materials?
DTSTART;VALUE=DATE-TIME:20150506T074000Z
DTEND;VALUE=DATE-TIME:20150506T081000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3903@events.saip.org.za
DESCRIPTION:Speakers: David Cahen (Weizmann Inst. of Science)\nWe have sho
wn that electron transport (ETp)\, i.e.\, conduction\, through protein mon
olay-ers in a solid state–like configuration is remarkably efficient\, c
ompared to most molecules\, including conjugated ones.1 Some proteins also
have a natural electron transfer (ET) function and ET and ETp are related
\, but while nature regulates ET via redox chemistry\, where control over
the process is achieved even at the expense of free energy and low rates (
and ubiquity)\, in ETp no redox process is needed. This allows study of op
tically active\, no-redox proteins\, such as the rhodopsins. We studied E
Tp in the dark and under illumination\, esp. in bacteriorohodopsin\, but a
lso in halorhodopsin and the light-oxygen-voltage (LOV) sensing domain pro
teins. The experimental data on ETp via proteins show poor fits with curre
nt ET models (pathway or average packing density)\, such as lack of distan
ce dependence. We will discuss progress towards understanding solid-state
ETp charge transport \,which will help to advance bio-opto-electronics.\n\
n1 N. Amdursky et al.\, Adv. Mater. 42\,7142-7161 (2014) Electronic Transp
ort via Proteins 10.1002/adma.201402304 (progress report).\n\nhttps://even
ts.saip.org.za/event/39/contributions/3903/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3903/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Preparation and measurements of MOVPE multiple InAs/GaAs/GaAsSb qu
antum dot structures for the telecom wavelength region emitted from 1.3 to
1.8 µm
DTSTART;VALUE=DATE-TIME:20150506T085000Z
DTEND;VALUE=DATE-TIME:20150506T092000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3904@events.saip.org.za
DESCRIPTION:Speakers: Eduard Hulicius (Institute of Physics\, AS CR\, v.v.
i.)\nAlthough the self-assembled InAs/GaAs quantum dots (QDs) are intensiv
ely studied during more than the last twenty years\, the mass production o
f QD lasers started only in 2010 and the production of telecommunication Q
D lasers was announced even last year [1]. The main problem is the complex
ity of QD preparation process which includes not only the epitaxial layer
growth but also Stranski-Krastanow formation\, subsequent dissolution of Q
Ds during capping\, diversity of QD size and shape or the surfactant behav
ior of In atoms. The situation is even more complicated when QDs are cover
ed by InGaAs or GaAsSb strain reducing layer (SRL) to shift the QD lumines
cence toward telecom wavelength. The GaAsSb SRL seems to be more suitable
for MOVPE grown QD structures [2]. However\, in these structures the surfa
cting behavior of In and Sb atoms is enhanced which complicates growth of
multiple QD (MQD) structures for semiconductor laser application.\n In
this talk I will present our results obtained on QD and MQD structures wit
h InAs/GaAs QDs covered by GaAsSb SRL. The growth of these structures was
studied in situ by reflectance anisotropy spectroscopy (RAS)\, which offer
direct observation of processes during the structure growth such as quant
um dot formation\, and dissolution or surfacting of In and Sb atoms. The s
urfacting of In atoms in structures where QDs are covered only by GaAs or
by GaAsSb SRL will be compared. Enhanced In surfacting was observed for st
ructures with GaAsSb SRL. Possible ways how to suppress surfacting of both
types of atoms and how to prevent their transport on epitaxial surface to
subsequent QD layer in MQD structures will be suggested. Different interr
uption and growth rates of the separation layer growth under varying tempe
rature or composition gradient of GaAsSb SRL will be discussed with respec
t to the suppression of undesired surfacting of In and Sb atoms. The concl
usions derived from RAS measurements will be supported by TEM\, AFM and ph
otoluminescence (PL) results.\nProperties of InAs/GaAs QDs prepared by the
MOVPE technology covered by GaAsSb SRL with extremely long emission wavel
ength at 1.8 μm will be presented. The prolongation of the emission wavel
ength was achieved by the introduction of GaAsSb SRL with Sb content of ab
out 30% in the solid phase. The high Sb concentration in the SRL causes th
e preservation of QD size\, which is about 15 nm wide at the base and 5 nm
high. Increased QD size prolongs the PL wavelength. Furthermore\, high co
ntent of antimony leads to a creation of type II heterostructure for which
a red shift of the PL wavelength and decrease of the PL intensity is typi
cal. Low PL intensity may complicate light emitting applications\; however
\, fast separation of carriers in the type II structure is an advantage fo
r detector or solar cell application\, especially with the long wavelength
. With respect to the perspective application of this structure\, the phot
ocurrent (PC) measurement was chosen as the complementary characterization
method. A depression of PC for quantum well wavelength region (900-1200 n
m) was observed for positive bias\, while the PC from QDs (over 1200 nm) i
s not sensitive to the electric field orientation at all. Explanation of t
his unexpected phenomenon will be suggested.\n\n[1] Semiconductor lasers:
Fundamentals and Applications\, edited by A Baranov\, E Tournie\, Elsev
ier 2013\, ISBN 0857096400. \n[2] A. Hospodková et al\, J. Cryst. Growth
370 (2013) 303. doi: 10.1016/j.jcrysgro.2012.08.007\n\nhttps://events.saip
.org.za/event/39/contributions/3904/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3904/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The Synthesis and Characterization of Magnetic/ Luminescent Fe¬3O
4-InP/ZnSe Core-Shell Nanocomposite
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3905@events.saip.org.za
DESCRIPTION:Speakers: Zuraan Paulsen (Unversity of the Western Cape)\n1. I
ntroduction\n\nMagnetic luminescent nanoparticles have shown great promise
in various biomedical applications namely: contrast agents for magnetic r
esonance imaging\, multifunctional drug carrier system\, magnetic separati
on of cells\, cell tracking\, immunoassay\, and magnetic bioseparation. Ho
wever most of these nanoparticles are cadmium- based. Indium- phosphide is
known to be less toxic than cadmium- based products. This experiment desc
ribes the synthesis of a core- shell nanocomposite material\, which is com
posed of an iron oxide superparamagnetic core and an InP/ZnSe quantum dot
shell. The magnetic nanoparticles (MNP’s) and quantum dots (QD’s) were
synthesized separately before conjugation could occur. The MNP’s were f
unctionalized with a thiol-group allowing the QD shell to bind to the sur
face of the MNP by the formation of a thiol-metal bond.\n\n2. Results\nThe
synthesized nanocomposite was characterized with high- resolution transmi
ssion electron microscopy (HR-TEM)\, energy-dispersive X-ray spectroscopy
(EDS)\, selective electron area diffraction (SAED)\, scanning electron mic
roscopy (SEM)\, UV- visible spectroscopy\, XRD and photoluminescence. Thes
e techniques yielded particle size\, morphology\, dispersion\, and chemica
l composition including luminescence and florescence properties of the as
prepared nanoparticles. The TEM micrograph showed crystalline nanoparticle
s which are monodispersed. These particles would be more useful in the in
vivo applications after their solubility is tuned to a desired property. T
his experiment will continue further by investigating how various capping
agents’ affects the particles solubility. All the peaks of XRD patterns
were analyzed and indexed using ICDD data base\, comparing with magnetite
standards. The lattice constant a was found to be 8.330 Å\, which was com
pared with the lattice\nparameter for the magnetite of 8.39 Å. Further re
sults will be reported including their applications.\n
\n\n\n\n3. References\n\n[1] Pedro Tartaj1\, Ma
r´ıa del Puerto Morales1\, Sabino Veintemillas-Verdaguer\, Teresita Gonz
´alez-Carre ˜no and Carlos J Serna. 2003.\n[2] Shen Wu\, Aizhi Sun\, Fuq
iang Zhai\, Jin Wang\, Wenhuan Xu\, Qian Zhang\, Alex A. Volinsky\n[3] Sh
ouheng Sun\, Hao Zeng\, David B. Robinson\, Simone Raoux\, Philip M. Rice\
, Shan X. Wang\, and Guanxiong Li\n\nhttps://events.saip.org.za/event/39/c
ontributions/3905/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3905/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effect of solvent medium on the material properties of ZnO nanopar
ticles synthesized by sol-gel method.
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3906@events.saip.org.za
DESCRIPTION:Speakers: Jatani Ungula (University of the Free State)\nThe ab
stract gives an overview of the content of my paper entitled\, “Effect o
f solvent medium on material properties of ZnO nanoparticles synthesized b
y sol-gel method.”\nThe issues on applications\, optical and luminescenc
e properties and the structure of ZnO were mentioned in introduction. In a
ddition\, the abstract reports that\, in the research\, high-quality zinc
oxide (ZnO) nanoparticles were synthesized by sol-gel method using zinc ac
etate and sodium hydroxide precursors. The effect of varying volume ratios
of water to ethanol solvent on zinc oxide (ZnO) nanoparticles prepared at
constant temperature of 35 oC was studied. The material properties of the
nanoparticles were examined using SEM\, EDS\,XRD\,Uv-Vis Spectroscopy and
PL systems. The abstract provides summary of the results and discussions.
Essentially\, reports on scanning electron microscopy\, optical absorptio
n\, transmittance and the band gap were covered briefly. XRD and PL spectr
a were included in the abstract also. Finally\, two items of references we
re captured.\n\nhttps://events.saip.org.za/event/39/contributions/3906/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3906/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Characteristics of amorphous transparent and conductive oxides gro
wn by combinatorial pulsed laser deposition
DTSTART;VALUE=DATE-TIME:20150505T113000Z
DTEND;VALUE=DATE-TIME:20150505T120000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3907@events.saip.org.za
DESCRIPTION:Speakers: Valentin Craciun (National Institute for Laser\, Pla
sma and Radiation Physics)\nAmorphous and transparent semiconductor oxides
are key components of new thin film transistors (TFTs)\, solar cells elec
trodes and displays. By controlling their stoichiometry\, they can be used
as TFT channel (semiconductive behavior) or as transparent electrode (con
ductive behavior). Recently\, room temperature deposited indium zinc oxide
(IZO) and indium gallium zinc oxide (IGZO) thin films were shown to exhib
it very good transparency in the visible range\, low resistivity\, and hig
h mobility. Since the optical and electrical properties of these films dep
end on the In/(In+Zn) and Ga/(In+Ga+Zn) values\, the accurate measurement
of these ratios is important for future developments and applications. \nI
n this presentation we focus on the relationship between composition and p
roperties of IZO and IGZO thin films synthesized using the Combinatorial P
ulsed Laser Deposition technique. An accurate monitoring of the thin films
elemental composition was performed by Laser-Induced Breakdown Spectrosco
py (LIBS) based on plasma modeling in view of further in-situ and real-tim
e technological developments and process control in case of ASOs fabricati
on. The cation fractions measured by LIBS were compared to values obtained
by complementary measurements using Rutherford backscattering spectrometr
y\, energy dispersive X-ray analysis and X-ray fluorescence.\nThe optical
properties (thickness profile and refractive index determination) of the t
hin films were inferred from spectroscopic ellipsometry data acquired in t
he visible range and optical reflectance measured from 30 cm-1 (4 meV) to
30 000 cm-1 (4 eV). Complementary investigations to obtain the thickness a
nd density of the deposited films as well as their surface and interface r
oughness have been performed by fitting the measured X-ray reflectivity an
d X-ray diffuse scattering curves with simulated ones using dedicated mode
ls. The room temperature electrical properties were investigated using typ
ical four-point probe geometry and Hall measurements and compared with the
values estimated from the optical reflectance data. X-ray photoelectron s
pectroscopy was used to measure the energy discontinuities in the valence
and conduction bands of various dielectric/IGZO and dielectric/IZO heteros
tructures. All these measurements helped design better transparent and con
ductive oxides containing lower amounts of In\, an element that is rather
scarce and therefore expensive.\n\nhttps://events.saip.org.za/event/39/con
tributions/3907/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3907/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Structure and optical properties of undoped and Mn-doped ZnO(1-x)S
x nano powders prepared by precipitation method
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3909@events.saip.org.za
DESCRIPTION:Speakers: Lehlohonolo Koao (UFS (Qwa Qwa Campus))\n1. Introduc
tion \n\nWith a wide band gap of 3.4 eV and a large exciton binding energy
of 60 meV at room temperature\, ZnO is attractive for blue and ultra-viol
et optoelectronic devices\, and transparent conducting oxide films for pho
tovoltaic applications. The large excitonic binding energies of ZnO and Zn
S could enable efficient excitonic emission at temperatures well above roo
m temperature and therefore lower threshold intensities for optoelectronic
devices based on these semiconductors can be expected. Alloying ZnO by in
corporating equivalent anions has not been extensively studied. Anion dopi
ng in ZnO\, i.e.\, replacing oxygen by sulphur e.g. ZnO(1-x)Sx (ZnOS)\, ha
s been reported recently [1\, 2]. Due to the large electronegativity diffe
rences between O and S it would be expected that the bowing parameters of
ZnOS are large. The change of anions in ZnO by isoelectronic impurities is
important from the viewpoint of band gap engineering. In this work\, high
-quality undoped and Mn-doped ZnOS nano powders were prepared by the preci
pitation method.\n \n2. Results\n\nFigure 1 shows the typical XRD patte
rn of the obtained product. All the strong peaks in this pattern can be re
adily indexed to hexagonal wurtzite ZnOS structures. ZnOS alloys with a wu
rtzite structure were achieved for small content of sulphur and no evident
phase separation was observed in the investigated composition range as de
termined by X-ray diffraction. Scanning electron microscopy observations s
howed the presence of nano-crystallites that decrease in size with Mn-dopi
ng. The optical absorption measurements show strong excitonic peak emissio
n without any defect emission in the visible spectrum. The absorption edge
s of the nano powders shift towards low-energy side with increasing the Mn
-dopant content. The presence of the Mn dopant diminishes the excitonic em
ission. The bandgap energies of the ZnOS nano particles were calculated an
d found to change from 4.0 to 4.2 eV\, showing a nonlinear variation with
a bowing behavior that was previously reported. The photoluminescence emis
sion spectra of ZnOS nanoparticles gives four bands centering at about 54
8 nm\, 614 nm\, 649 nm and 670 nm\, wavelengths. Similar to observations\,
It has been reported that the dopants of S\, Mn can shift the luminescenc
e position of ZnOS nanocrystals.\n\nhttps://events.saip.org.za/event/39/co
ntributions/3909/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3909/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luminescence properties of CaO:Bi3+ phosphor
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3910@events.saip.org.za
DESCRIPTION:Speakers: Abdelrhman Mohmmed (University of the Free State)\nI
n recent years\, there has been growing importance focused on research in
light emitting diodes (LEDs) because of their long operation lifetime\, en
ergy-saving feature and high material stability [1\, 2]. During the past f
ew years\, white LEDs fabricated using a near ultraviolet (n-UV) LED (380
–420 nm) coupled with red\, green\, and blue phosphors have attracted mu
ch attention [2]. Accordingly\, it is necessary to develop new blue phosph
ors that could be effectively excited in the near ultraviolet range especi
ally for wavelengths of 400 nm [1]. The spectroscopic properties of the Bi
3+ ion in different hosts have attracted much attention due to its emissio
n wavelength that varies from the ultraviolet to the red region depending
on the host matrix [3]. Therefore\, with the appropriate matrix\, the emis
sion of Bi3+ ions can be used as a candidate for n-UV for LED applications
. CaO:Bi3+ phosphor powder was successfully synthesized by the sol-gel com
bustion method. The structure\, morphology and luminescent properties of t
he phosphor were characterized by X-ray diffraction (XRD)\, Scanning elect
ron microscope (SEM)\, photoluminescence (PL) and cathodoluminescence (CL)
techniques.\n\nhttps://events.saip.org.za/event/39/contributions/3910/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3910/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effects of the copper content on the structural and electrical pro
perties of Cu2ZnSnSe4 bulks used in thin-film solar cells
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3911@events.saip.org.za
DESCRIPTION:Speakers: Moges Tsega Yihunie (University of the Free State)\n
We have investigated the concept of defect in CuxZnSnSe4 (x= 1.62.0) an
d Cuy(Zn0.9Sn1.1)Se4 (y= 1.6-2.0) bulks prepared by liquid-phase sintering
at 600 oC for 2 h with soluble sintering aids of Sb2S3 and Te. All CuxZnS
nSe4 pellets exhibited p-type conductivity regardless of Cu contents but C
uy(Zn0.9Sn1.1)Se4 pellets show p-type at y=1.6 and n-type at y= 1.8-2.0. S
EM surface images showed the sintered CZTSe bulk exhibited a smooth\, dens
ely packed and homogeneous surface at the nearly stoichiometric compositio
n. Increasing the copper excess also yields a rougher CZTSe morphology. Th
e non-stoichiometric composition of CZTSe under various Cu contents caused
the intrinsic defects\, and the structural and electrical properties of t
he bulks can be explained based on the point defect properties. The defici
ency of Cu content in CZTSe bulks easily leads to smaller unit cells.\n\nh
ttps://events.saip.org.za/event/39/contributions/3911/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3911/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Polarization Controlled Light Emitter based on Elongated Pyramidal
Quantum Dots
DTSTART;VALUE=DATE-TIME:20150505T075000Z
DTEND;VALUE=DATE-TIME:20150505T081000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3912@events.saip.org.za
DESCRIPTION:Speakers: Per Olof Holtz (Linköping University\, Sweden)\n1.I
ntroduction\nPolarized light is the basis for a manifold of optoelectronic
technologies ranging from telecommunication and LCD-displays to quantum c
ryptography. However\, it is challenging to efficiently attain a strong po
larization of spontaneously emitted light\, in particular for the generati
on of single photons. In solutions of today\, mainly filtering of unpolari
zed light is employed. In this process\, a higher light transmission rate
larger than 50 percent from the source can never be achieved. Such a loss
is particularly devastating for quantum information technologies\, in whic
h each single quantum of light\, i.e. each photon\, literally counts. \n\n
2. Results\nOur approach is based on the unique properties of the III-nitr
ide materials\, known to be efficient light emitters in the blue and UV pa
rt of the spectrum. We have employed μm-sized GaN pyramids with six facet
s\, formed in etched circular holes in a patterned substrate by Selective
Area Growth (SAG). The holes are made in a SiN film on top of the substrat
e by means of standard UV lithography and RIE etching. The tips of the pyr
amids are made slightly truncated\, as has been demonstrated to be advanta
geous for quantum dot (QD) formation. The pyramids are subsequently overgr
own by a thin optically active InGaN quantum well and finally capped with
a thin GaN layer. Due to the accumulated strain caused by the lattice mism
atch between the GaN and InGaN well\, InGaN QDs will evolve on the microsc
opic c-plane area in the apex of the pyramid. Well-defined single emission
lines with a sub-meV line width have been monitored by means of μ-photol
uminescence (μPL) from these deterministic QDs. So far\, emission wavelen
gths have been demonstrated in the blue range\, around 400 nm\, but can be
pre-defined by altering the growth conditions\, such as the growth temper
ature\, the well width and/or the In composition\, for the InGaN layers.\n
In a subsequent step\, the circular holes in the patterned substrate have
been replaced by elongated holes in a specified direction. As a result\, e
longated pyramids are formed with ridges characterized by typical dimensio
ns of 1.0 µm length and 100 nm width on top of these asymmetric pyramids.
The elongation directions 0o\, 60o\, and 120o are preferable due to the s
ix-fold symmetry of the wurtzite crystal structure. \nThe primary emission
lines monitored are originating from electron-hole pairs\, i.e. single ne
utral excitons\, but also biexcitons and charged excitons have been monito
red. Interestingly\, the excitonic emission from the extended InGaN QDs on
top of the elongated pyramids exhibit a strong degree of linear polarizat
ion\, with a typical polarization ratio of about 85% achieved for the case
of an elongation of the pyramid base by 1μm. \nFor investigations of the
exciton lifetime\, μ-PL with a high spatial resolution combined with a s
treak-camera detector for recording the time spectral evolution under puls
ed excitation with ps pulse duration was employed. The exciton lifetimes h
ave been demonstrated to vary between 100 ps to 1 ns\, with shortest lifet
imes measured for the negatively charged QDs.\nIn order to demonstrate the
single photon characteristics of the dots\, temporal photon correlation s
pectroscopy has been performed. These correlation measurements have been d
one in a setup of a Hanbury-Brown and Twiss interferometer equipped with s
ensitive single photon detectors. The excitonic single photon emission and
biexcitonic photon bunching from the pyramidal dots are reported\, confir
ming the sound single photon properties of these dots.\n\n3. References\n1
.C.W.Hsu\, A. Lundskog\, K. F. Karlsson\, U. Forsberg\, E. Janzén and P.O
.Holtz\, Nano Letters Volume 11\, 2415 (April 28\, 2011)\n2.A. Lundskog\,
C.W. Hsu\, D. Nilsson\, U.Forsberg\, K. F. Karlsson\, P.O. Holtz and E. J
anzén\, Nature: Light\, Science & Applications (2014) 3\, Article:139\; d
oi:10.1038/lsa.2014.20\n3.A. Lundskog\, J. Palisaitis\, C. W. Hsu\, M. Eri
ksson\, K. F. Karlsson\, L. Hultman\, P.O.Å. Persson\, U.Forsberg\, P. O.
Holtz\, E. Janzen\, Nanotechnology 23\, 305708 (2012)\n4.A.Lundskog\, C.W
. Hsu\, D. Nilsson\, U. Forsberg\, P.O. Holtz and E. Janzén\, Journal of
Crystal growth 363\, 287 (2013)\n5.A. Lundskog\, U. Forsberg\, P.O. Holtz
and Janzén\, Crystal growth and design 12\, 5491 (2012)\n6.S. Amloy\, K.
Fredrik Karlsson\, P. O Holtz arXiv: 1311.5731\n7.T. Jemsson\, H. Machhada
ni\, P.O. Holtz and K. F. Karlsson\, Nanotechnology 26\, 065702 (2015)\n\n
https://events.saip.org.za/event/39/contributions/3912/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3912/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chemical and electrical characteristics of annealed Ni/Ir/Au and N
i/Au contacts on AlGaN
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3913@events.saip.org.za
DESCRIPTION:Speakers: Phuti Ngoepe (University of Pretoria)\nAluminum gall
ium nitride (AlxGaxN) is a ternary wide direct bandgap semiconductor. The
Al to Ga ratio can be varied to achieve various bandgap ranging from 3.4 e
V for pure GaN to 6.2 eV for pure AlN. This property makes AlGaN based dev
ices suitable for light emitting and light detecting devices such as LED
’s and photodiodes. In fabricating a device such as a Schottky diode the
metals deposited on the semiconductor play an important role in the opera
tion of the device. This is because the metal-semiconductor contact of a S
chottky diode influences the transport mechanisms of the device. It theref
ore becomes significant to understand the interaction of metals with the s
emiconductor substrate. Annealing has been used as a method of studying th
e evolution of the optical and electrical properties of semiconductor base
d devices [1\,2]. In particular a study was performed on AlGaN Ni (20 Å)/
Au (50 Å) and Ni (20 Å)/ Ir (30 Å)/ Au (50 Å) Schottky photodiodes [3
]. The samples were subjected to isochronous annealing for 5 min. under an
Ar. ambient. The evolution of the chemical properties of these contacts w
ith temperature is studied by using two surface characterization methods n
amely Time of Flight Secondary Ion Mass Spectroscopy (TOF-SIMS) and X-ray
photo electron spectroscopy (XPS).\n\nhttps://events.saip.org.za/event/39/
contributions/3913/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3913/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Synthesis and characterization of structural and luminescence prop
erties of TiO2 nanoparticles for water treatment application
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3914@events.saip.org.za
DESCRIPTION:Speakers: Francis Dejene (University of the Free Stet)\nIntrod
uction\nSolar water treatment is a low-technology solution that works to c
apture the heat and energy from the sun to make water cleaner and healthie
r for human use and consumption. The oxide nanoparticles synthesized by se
veral methods appears more and more useful because these nanoparticles hav
e good electrical\, optical and magnetic properties that are different fro
m their bulk counterparts [1]. Titania nanoparticles have received much in
terest for applications such as optical devices\, sensors\, and photocatal
ysis [2]. There are several factors in determining important properties in
the performance of TiO2 such as particles\, crystallinity and the morphol
ogy. TiO2 nanoparticles were synthesized by a simple sol-gel method. The s
tructure and morphology of the synthesised nanocrystalline TiO2 were chara
cterized by XRD\, SEM\, UV and PL. The effect of some parameters such as h
ydrolysis rate\, concentration amount of the precursor constituents\, and
annealing temperature were investigated.\nResults\nA representative scanni
ng electron microscopy image of the TiO2 nanoparticles synthesized present
ed in Fig. 1\, indicates that the sample is composed of roughly spherical
surface aspects. The anatase to rutile structural phase change occurs whe
n annealed at a temperature greater than 500 °C when evaluated from X-ray
diffraction pattern intensities of (101) and (110) peaks\, respectively.
Annealing samples at high temperature improves crystallinity as confirmed
by both SEM and XRD measurements. It was observed that the band gap of TiO
2 varied from 2.49 and 3.26 eV while the crystallite sizes calculated usin
g the Scherrer equation obtained from each set of synthesis conditions cha
nged from 8 to 10 nm with variation of hydrolysis rate. The emmissions spe
ctra (λexc= 325 nm) of TiO2 nanoparticles for different hydrolysis rate d
isplay peaks at 336\, 381 and 486 nm and the broad emission peak at about
381 nm is attributed to band gap transition.\n\nhttps://events.saip.org.za
/event/39/contributions/3914/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3914/
END:VEVENT
BEGIN:VEVENT
SUMMARY:AB-INITIO CALCULATION OF THE ELECTRONIC STATES INDUCED BY Nb AND C
r DOPING OF RUTILE AND ANATASE TiO2 .
DTSTART;VALUE=DATE-TIME:20150507T140000Z
DTEND;VALUE=DATE-TIME:20150507T142000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3916@events.saip.org.za
DESCRIPTION:Speakers: WINFRED MULWA (University of the Free State-Qwaqwa c
ampus\, Department of physics\, Private Bag x13\, Phuthaditjhaba\, 9866\,
SOUTH AFRICA)\nIn this study\, plane wave self consistent field calculatio
ns have been performed on the electronic structure of rutile and anatase p
hases of titanium dioxide (TiO2). To this end ab-initio calculations have
been performed for a 48-atom rutile supercell and 96-atom anatase supercel
l using the plane wave code – Quantum Espresso. Density functional theor
y (DFT) with hybrid functionals have been used to obtain a more accurate
description of the electronic properties of titanium dioxide in addition t
o the standard exchange-correlation (XC) functionals namely\; the local de
nsity approximation (LDA) and the generalized gradient approximation (GGA)
. In this study\, the screened hybrid functional of Heyd-Scuseria-Erzehoff
(HSE06) has been used. HSE06 is known to overcome most of the shortcoming
s of both the LDA and GGA XC functionals. Both the titanium dioxide struct
ures were fully optimized by minimizing the local total energy and atomic
forces\, after which band structure and density of states were calculated.
Band gap energies 1.89 eV (rutile)\, 2.28 eV (anatase) and 2.25 eV (rutil
e)\, 2.65 eV (anatase) were obtained using GGA-PBE and HSE06 functionals r
espectively. Experimental value for band gap is 3.0 eV for rutile and 3.2
eV for anatase. In order to obtain the bulk equilibrium properties\, the e
nergy volume curves for the two structures were fitted to the Murnaghan eq
uation of state.\nSubstitutional chromium and Niobium at the titanium site
s was found to introduced new electronic states within the band gap. These
new states are discussed with respect to tuning doped titanium dioxide fo
r the application in photocatalysis.\n\nhttps://events.saip.org.za/event/3
9/contributions/3916/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3916/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Annealed Ce-doped ZnO nanoparticles synthesized by chemical bath d
eposition method
DTSTART;VALUE=DATE-TIME:20150505T094000Z
DTEND;VALUE=DATE-TIME:20150505T100000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3917@events.saip.org.za
DESCRIPTION:Speakers: Lehlohonolo Koao (UFS (Qwa Qwa))\nThe X-ray diffract
ion results showed that All the ZnO samples possess a typical wurtzite str
ucture for non-annealed and annealed. It was observed that the XRD diffrac
tion intensities decrease with annealing temperature as shown in Fig. 1. T
his behaviour may be due the estimated crystallite size that decreased wit
h annealing temperature. In Fig. 2 The XRD spectra of the annealed ZnO:Ce3
+ nanostructures correspond to the various planes of a single hexagonal Z
nO phase for the lower and higher Ce concentration samples. At higher Ce m
olar concentration there is secondary phase. The estimated average crystal
lite sizes decay exponential with an increase in the amount of Ce. Scannin
g electron microscopy observations showed the presence of flower-like for
non-annealed samples and spherical nanoparticles for annealed samples. Dop
ing the annealed samples with Ce it was observed that the nanoparticles in
crease in size with an increase in the amount of Ce. At higher molar conce
ntration of Ce there was a mixture of spherical and hexagonal particles. T
he UV-Vis spectra showed that the absorption edges red shift slightly with
an increase in the molar concentration of Ce. The photoluminescence resul
ts showed that the maximum intensity is obtained for udoped ZnO nanopartic
le and doping with Ce there was decrease in luminescence intensity.\n\nhtt
ps://events.saip.org.za/event/39/contributions/3917/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3917/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Synthesis and Characterization of luminescence magnetic nanocompos
ite for biomedicine application
DTSTART;VALUE=DATE-TIME:20150507T123000Z
DTEND;VALUE=DATE-TIME:20150507T125000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3918@events.saip.org.za
DESCRIPTION:Speakers: Kiplagat Ayabei (University of the western cape)\n1.
Introduction\nIn the recent past\, magnetic materials and semiconductor i
norganic materials have been developed and applied (as independent) in fie
lds including biomedicine\, especially biotechnological processes imaging\
, tracking\, and separating biological molecules or cells. Processes of bi
omedical diagnosis and therapy require nanometer scale particles featuring
characteristics such as magnetization and fluorescence [1-4]. In the last
two decades research has been focused on fabrication of QDs constituting
elements of groups II-IV owing to their potential application in lasers\,
light emitting diodes and biological studies. However\, biological applica
tions of the as-prepared QDs were limited by presence of highly toxic Cadm
ium core. Strategies have been employed to alleviate toxicity of Cd based
core coating it with less toxic materials such as a ZnS shell. However\, e
xposure to UV light or oxidation results in the release of cadmium via sur
face oxidation. In the current study new type of Indium based quantum dot
was synthesized and conjugated to the magnetic nanoparticles. The QD were
characterized by PL\, HRTEM\, XRD\, SQUID and FTIR.\n\n2. Results and Disc
ussion\nThe photoluminescence characteristics of the coupled and uncoupled
indium based quantum dots were investigated to determine whether the fluo
rescing property could be retained in the bifunctional system. Generally\,
the PL intensity of the QDs was observed to remain almost the same with s
light blue shift\, most probably due to quenching effects of magnetic nano
particles (MNPs). Equally the quenching effect of the QDs on the magnetic
nanomaterials was also investigated. The toxicity of the as prepared nanop
articles was investigated and results will be reported during the conferen
ce.\n\nhttps://events.saip.org.za/event/39/contributions/3918/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3918/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Surface morphology and structural properties of iron oxide thin fi
lm photoanode prepared by dip coating: effect of electrochemical oxidation
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3919@events.saip.org.za
DESCRIPTION:Speakers: Maabong Kelebogile (University of Pretoria)\nMetal o
xides have attracted a considerable attention as transparent electrodes\,
active layers and charge collectors in energy harvesting activities due to
their diverse properties [1]. Due to its a nearly ideal band gap (~ 2.1 e
V) for solar energy conversions\, low cost\, chemical stability\, natural
abundance\, n-type conductivity\, “rust”- iron oxide (α-Fe2O3) - is r
egarded as a promising semiconductor in photovoltaic (PV) solar cells and
photoelectrochemical (PEC) cells [2]. However\, despite the good character
istics α-Fe2O3 absorbs weakly and conducts poorly due to poor carrier tra
nsport and rapid recombination of photo-generated electrons and holes. Sur
face morphology and structural properties strongly influences photoactivit
y efficiency of nanostructured electrodes [3]. α-Fe2O3 thin films were pr
epared by dip-coating method on fluorinated tin oxide (FTO) conductive gla
ss substrates from Fe (NO3)3•9H2O (28.0 g) and oleic acid (17.0 g) precu
rsor. Four layers of hematite films were obtained after repeated dip coati
ng and annealing at 500 ᵒ C for 2 hours. The photoanodes were electroch
emically oxidized (anodized) in 1M KOH at a constant anodization potential
of 500 mV for 1 min in dark and light conditions. The structural properti
es of α-Fe2O3 nanoparticles were investigated.\n2. Results\nFig 1 shows t
op view images of high resolution FE-SEM of pristine and anodized α-fe2O3
thin film photoanodes. The nanoparticles were spherical in shape. The mic
rographs depicts a denser surface after electrochemical oxidation of photo
anodes in light. Fig 2 XRD diffractograms of the films. The results show d
ecrease in linewidth of the peaks in anodized samples which indicates incr
ease in crystallite sizes upon the treatment.\n\nhttps://events.saip.org.z
a/event/39/contributions/3919/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3919/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The defect passivation effect of hydrogen on the optical propertie
s of solution-grown ZnO nanorods
DTSTART;VALUE=DATE-TIME:20150506T100000Z
DTEND;VALUE=DATE-TIME:20150506T102000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3920@events.saip.org.za
DESCRIPTION:Speakers: Zelalem N. URGESSA (NMMU)\nhttps://events.saip.org.z
a/event/39/contributions/3920/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3920/
END:VEVENT
BEGIN:VEVENT
SUMMARY:The Role of Titanium Valence on the Luminescence of ZrO2 Materials
DTSTART;VALUE=DATE-TIME:20150505T073000Z
DTEND;VALUE=DATE-TIME:20150505T075000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3921@events.saip.org.za
DESCRIPTION:Speakers: Jose Carvalho (University of Sao Paulo)\n1. Introduc
tion\nThe optical properties of zirconia materials have received much atte
ntion though no outstanding applications have been established so far. The
advantage of combining the efficient luminescence of the trivalent rare e
arths (R3+) and the stable and versatile zirconia host has finally been ru
ined by the incompatibility of these two systems: the charge compensation
defects created by the aliovalent substitution of the tetravalent zirconiu
m with trivalent (or divalent) rare earths have jeopardized the luminescen
ce efficiency [1]. So far\, no efficient tetravalent luminescent rare eart
h has been found and\, undoubtedly\, will not be in the future either. The
room temperature UV excited luminescence of the non-doped ZrO2 or zircona
tes or even hafnates have been noted in several reports. In addition to Ti
impurity luminescence\, defects as oxygen vacancies and colour centers ha
ve been offered as origins to luminescence. The Ti impurities were mention
ed as the luminescence center and a mechanism to the persistent luminescen
ce was proposed recently [2]. Regarding the details of the luminescence me
chanism\, synchrotron radiation techniques such as X-ray absorption and va
cuum UV (VUV) spectroscopy can unveil more details on the elements’ vale
nces as well as energy transfer processes.\n \n2. Results\n\nThe monocl
inic ZrO2 nanomaterials were prepared using the sol-gel route followed wit
h annealing at 1000 oC for 5 h. The typical VUV excited luminescence was o
bserved as a broad band centred at 500 nm (Fig. 1\, left). Starting with o
pposite hypotheses to explain this emission\, the materials were doped eit
her with Ti3+ or Lu3+ (both 0.5 mole-%) supposed to enhance the Ti3+ or de
fect emission\, respectively. The emission spectra at room temperature sho
w clearly that the 500 nm luminescence is due to a Ti3+ impurity\, albeit
at a trace element level [2]. The analogy between Ti3+/IV and Tb3+/IV sugg
ests the dopant can exist in both oxidation states in ZrO2 depending on th
e post-preparation treatment of the material. The XANES measurements (Fig.
2) on the Ti K edge proved inconclusive due to complicated pre-edge struc
ture\, however. Low temperature emission spectra with VUV excitation agree
with the emission of both TiIV and Ti3+ species in the Lu3+ doped and non
-doped material. Lu3+ doping enhances slightly the Ti3+ emission. The TiIV
charge transfer emission centered at 390 nm agrees with the UV-vis absorp
tion edge of TiO2. The broad bands at 750 nm may be attributed to TiIV Ti3
+ polarons [3] supporting the presence of both ions. The Ti doped material
s reveal only the 520 nm transition due to the eg → t2g transition of Ti
3+ splitting when symmetry lowers from Oh. The UV-VUV excitation spectra (
Fig. 1\, right) show energy transfer from the ZrO2 host to Ti3+/IV with Eg
at 5.25 eV which decreases with increasing temperature as usual.\n\nhttps
://events.saip.org.za/event/39/contributions/3921/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3921/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Inductively coupled plasma induced defects in n-Si using low energ
y Ar ions
DTSTART;VALUE=DATE-TIME:20150507T074000Z
DTEND;VALUE=DATE-TIME:20150507T080000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3922@events.saip.org.za
DESCRIPTION:Speakers: Sergio Coelho (UP)\nhttps://events.saip.org.za/event
/39/contributions/3922/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3922/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Electrical characteristics of a nearly ideal Ni/4H-SiC interface s
tudied by I–V–T and Admittance techniques
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3924@events.saip.org.za
DESCRIPTION:Speakers: Matshisa Legodi (University of Pretoria)\nhttps://ev
ents.saip.org.za/event/39/contributions/3924/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3924/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Interaction mechanism for energy transfer from Ce to Tb ions in si
lica
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3925@events.saip.org.za
DESCRIPTION:Speakers: Ted Kroon (University of the Free State)\nEnergy tra
nsfer phenomena can play an important role in the development of luminesce
nce materials. For example\, in co-doped silica samples the Tb ions produc
ing green luminescence useful in a variety of lighting and display applica
tions can be excited indirectly by energy transfer from the Ce ions which
have a longer\, more acccessible excitation wavelength. As a result of ene
rgy tranfer away from the Ce ions\, their luminescnce intensity and lifeti
me decreases as the Tb concentration increases. In this work we have comp
ared experimental measurements of these effects with models developed by I
nokuti and Hirayama [J. Chem. Phys. 47 (1967) 3211] for various interactio
n mechanisms and conclude that the energy transfer is as a result of dipol
e-dipole interactions.\n\nhttps://events.saip.org.za/event/39/contribution
s/3925/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3925/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Magneto-optical investigation of the cyclic redox R2O2S ↔ R2O2SO
4 (R: Eu\, Tb) reactions
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3926@events.saip.org.za
DESCRIPTION:Speakers: Jorma Hölsä (University of Turku)\n1. Introduction
\n\n Impurities and dopants’ inappropriate valences may deteriorate t
he performance of luminescent materials\, cause waste of the high purity (
rare earth) material and then incur significant financial losses [1]. The
methods used to detect elements’ valence (XPS\, Mössbauer and XANES) ar
e not sensitive enough for low concentrations and EPR is not suitable for
powders. Obtaining quantitative data leaves a lot to hope for\, too. To ma
ke the things worse\, the two most common rare earth dopants in phosphors\
, Eu3+ and Tb3+\, may exist in different oxidation states\, Eu2+ and TbIV
[1]\, as well. For the Eu3+ or Tb3+ doped R2O2S:Eu3+ and R 2O2SO4\, the Eu
2+ or TbIV may be formed since the manufacture of these phosphors involve
reducing and/or oxidizing conditions. The qualitative observation of Eu2+
can usually be made based on its intense luminescence due to the parity-al
lowed electric dipole 4f6↔4f55d1 transitions. In contrast\, the Eu3+ lin
e emission is weaker despite the high quantum yield. TbIV does not lumines
ce\, but this species may absorb the emission of Tb3+ and\, in addition\,
may facilitate non-radiative processes reducing the efficiency of Tb3+ dop
ed phosphors even further [1].\n\n2. Results\n\nIn this work\, the compari
son between the experimental and calculated temperature-dependent paramagn
etic susceptibilities was used to obtain quantitatively the concentrations
of the valence impurity in Eu2O2S (Eu2+) and Tb2O2SO4 (TbIV)\, both conta
ining nominally only R3+. The wave functions for the calculations were obt
ained from the analysis (Fig. 1) of the Eu3+ luminescence spectra [2\,3].
Minute (ppm level) Eu2+ impurities could be defined due to the huge differ
ence in the paramagnetic susceptibility of Eu2+ and Eu3+. However\, temper
atures below 50 K are then needed (Fig. 2). In contrast\, the TbIV impurit
y in a Tb3+ host can be determined already at higher temperatures with sim
ilar susceptibility measurements. The latter method is based on comparing
the slopes of the Tb3+/TbIV paramagnetic susceptibility vs. temperature cu
rves. The results for the Tb3+/TbIV couple are less sensitive than for the
Eu2+/Eu3+ one\, however. Finally\, the host independent temperature evolu
tion of the paramagnetic susceptibility was calculated for Gd3+ (or Eu2+ o
r TbIV) to yield an analytical expression to be used universally.\n\n3. Re
ferences\n\n[1] W. M. Yen\, S. Shionoya and H. Yamamoto (Eds.). Phosphor H
andbook\, 2nd ed.\, (CRC Press\, 2007).\n[2] J. Sovers and T. Yoshioka. J.
Chem. Phys. 51 (1969) 5330.\n[3] P. Porcher\, D. R. Svoronos\, M. Leskel
ä and J. Hölsä. J. Solid State Chem. 46 (1983) 101.\n\nhttps://events.s
aip.org.za/event/39/contributions/3926/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3926/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Making every photon count: Optical nanoscopy and single molecule s
pectroscopy applied to natural light-harvesting materials
DTSTART;VALUE=DATE-TIME:20150506T071000Z
DTEND;VALUE=DATE-TIME:20150506T074000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3927@events.saip.org.za
DESCRIPTION:Speakers: Tjaart Krüger (University of Pretoria)\nArtificial
photosynthesis is envisioned by many to be an important component of manki
nd’s long-term energy solution. Bio-inspired photosystems appear most pr
omising\, but the first constructs over the past few years have clearly po
inted to the infancy of this field [1]. To make progress\, a very detailed
understanding of natural photosynthesis is required in order to wisely ex
tract the most important design principles. Here\, the primary steps of ph
otosynthesis – light harvesting and charge separation – are the most c
rucial to ensure that the energy of an absorbed photon is stored with a su
fficiently high probability\, which is commonly 90-100% under conditions o
f low solar radiation! The latter of the two – charge separation – is
understood sufficiently well for the purpose of designing artificial devic
es. However\, the former – light harvesting – has proven to be a very
complex process and further experimental and theoretical advances are bein
g awaited. One such promising technique is known as single molecule spectr
oscopy (SMS)\, where the averaging effect of an ensemble is overcome by in
vestigating dynamical processes of a single light-harvesting unit.\nSMS\,
in fact\, laid the foundation for optical nanoscopy\, also known as superr
esolution microscopy\, which has developed tremendously since the first ex
perimental results appeared less than 10 years ago [2]. The new set of tec
hniques enables optical imaging of structures down to the nanometer scale\
, a two orders of magnitude improvement over the diffraction limit. Applic
ation of the technique was found particularly useful in biology\, because
subcellular structures can now be unraveled using light. Optical nanoscopy
is widely regarded as one of the most important developments in biophysic
al chemistry and chemical physics during the past two decades. It may ther
efore not be surprising that the founders were awarded the 2014 Nobel Priz
e in Chemistry.\nThe first part of the presentation will highlight the pri
nciples of optical nanoscopy\, point out the limitations in applying the t
echniques to autofluorescent systems\, such as photosynthetic light-harves
ting complexes\, and encourage application to other areas of materials sci
ence research where optical imaging on the mesoscopic scale will be instru
ctive. The second part of the presentation will highlight three design pri
nciples of photosynthetic light harvesting that were revealed using SMS. \
n\n2. Results\nIn nature\, proteins strongly bind a high density of chromo
phores to form extended\, complex networks of light-harvesting antennae\,
operating at a remarkable speed and efficiency. Even more intriguing is th
e level of adaptability to environmental influences at the macromolecular
scale to maintain a constant energy throughput at the photochemical reacti
on centre where charge separation occurs. One important part of this regul
ation involves very efficient absorption of solar energy and thermal dissi
pation of any excess excitation energy\, leading to a finely tuned feedbac
k self-protection mechanism. This should be done despite (or rather: with
the help of) structural fluctuations of the protein on a wide range of tim
escales. By mimicking the natural conditions that would give rise to the s
elf-protection state under levels of intense sunlight\, we have shown that
the main light-harvesting complex of plants – LHCII – uses intrinsica
lly available thermal energy dissipation channels by finely controlling it
s structural disorder on timescales of ms to tens of seconds [3]. Furtherm
ore\, using a mutant of LHCII where the terminal emitter chromophore clust
er is disrupted\, it was demonstrated that the terminal emitter cluster in
wild-type LHCII is responsible for energy transfer robustness due to the
combination of the particular energy gaps of the lowest exciton states and
the strong excitonic coupling of the chromophores in this cluster [4]. Fi
nally\, based on the spectral dynamics of light-harvesting complexes from
plant photosystem I and II\, we can conclude that the particular protein m
icroenvironment of a chlorophyll dimer is responsible for considerable tun
ing of the extent of shade absorption of plants [5].\n\n3. References\n[1]
R. E. Blankenship et al. Science (2011) 805\; J. Barber and P. D. Tran. J
. R. Soc. Interface (2013) 20120984.\n[2] E. Betzig\, G. H. Patterson\, R.
Sougrat\, O. W. Lindwasser\, S. Olenych\, J. S. Bonifacino\, M. W. Davids
on\, J. Lippincott-Schwartz and H. F. Hess. Science (2006) 1642\; S. T. He
ss\, T. P. Giriajan and M. D. Mason. Biophys. J. (2006) 4258\; M. J. Rust\
, M. Bates and X. Zhuang. Nature Methods (2006) 793.\n[3] T. P. J Krüger\
, C. Ilioaia\, M. P. Johnson\, A. V. Ruban\, E. Papagiannakis\, P. Horton
and R. van Grondelle. Biophys. J. (2012) 2669.\n[4] C. Ramanan\, J. M. G
ruber\, P. Maly\, M. Negretti\, V. I. Novoderezhkin\, T. P. J. Krüger\, T
. Mancal\, R. Croce and R. van Grondelle. Biophys. J. (2015) 1047.\n[5] T.
P. J Krüger\, E. Wientjes\, R. Croce and R. van Grondelle. Proc. Natl. A
cad. Sci. USA (2011) 13516.\n\nhttps://events.saip.org.za/event/39/contrib
utions/3927/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3927/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Preparation of ZnO nanorods and their gas sensing properties
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3928@events.saip.org.za
DESCRIPTION:Speakers: Katekani Shingange (CSIR and UFS)\nIn this work\, lo
w dimensional ZnO nanorods with different sizes were successfully prepared
using a microwave-assisted hydrothermal method. The influence of the micr
owave reaction time on the structural\, and luminescence properties of the
ZnO nanorods was studied using X-ray diffraction (XRD)\, Scanning electro
n microscope (SEM)\, and photoluminescence (PL). XRD analysis showed that
all samples have the typical hexagonal wurtzite structure without any othe
r new phases. The size of the ZnO nanorods was found to vary with variatio
n of reaction time\, respectively. The possible sensing mechanism and the
relationship between the sensing response and the content of defects were
proposed.\n\nhttps://events.saip.org.za/event/39/contributions/3928/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3928/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Structural and Optical Properties of Group-III Nitride Nanorods
DTSTART;VALUE=DATE-TIME:20150507T085000Z
DTEND;VALUE=DATE-TIME:20150507T092000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3929@events.saip.org.za
DESCRIPTION:Speakers: Jens Birch (Linköping University)\nIntroduction\n\n
One-dimensional group-III Nitride nanorods (NR)\, have drawn a large inter
est during the past decade thanks to great prospects for improved optoelec
tronics by e.g.\, increased quantum efficiency\, higher sensitivity\, lowe
r heat generation\, etc. as compared to bulk and quantum well-based device
s. \nMagnetron Sputter Epitaxy (MSE) allows for epitaxial growth of Al1-xI
nxN NRs as well as GaN NRs.[1\,2] Moreover\, low temperature group-III N e
pilayer growth is possible by MSE[3] and it is easily scalable to large ar
eas\, which make it an industrially potent\, yet unexploited\, technique.\
n\nResults\n\nAl1-xInxN NRs grown on ZrTiN seed layers feature In-rich cor
es and Al-rich shells\, as observed by high resolution electron microscopy
(HREM) and quantitative valence electron energy loss spectroscopy using s
canning transmission electron microscopy. Such nanorods exhibit near band-
edge optical emission at ~5 eV\, as observed by cathode luminescence. An i
nternal composition gradient in Al1-xInxN nanorods leads to a curved-latti
ce epitaxial growth (CLEG) [4] which is utilized for high precision tailor
ing of nanorod morphologies\, such as spirals and zig-zag shapes which ope
ns the possibility to obtain new unique optical properties. For example\,
Al1-xInxN spirals with a pitch of ~200 nm can be designed to produce eithe
r fully right-handed or left-handed circularly polarized reflected light a
t specific wavelengths in the UV-regime (see Fig 1). \n\nHigh quality G
aN NRs were grown by MSE at 1000°C on Si(111)\, 4-H SiC(0001) and SiOx su
bstrates\, using a liquid Ga-target. NRs can be grown at a thickness ~35 n
m and lengths up to several µm without extended defects as seen in HREM.
Low-temperature micro photoluminescence (µPL) reveal intense and sharp ba
nd-edge emission\, characteristic of donor-bound exitons\, with a FWHM =
1.7 meV at 3.48 eV. (see Fig. 2)\n\nIn conclusion\, we show that reactive
Magnetron Sputter epitaxy (MSE) can be used to produce high quality group-
III Nitride NRs\, with optical properties comparable to e.g.\, MBE grown s
tructures\, as well as new tailored NRs by CLEG\, featuring unique polariz
ing properties.\n\nhttps://events.saip.org.za/event/39/contributions/3929/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3929/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Effect of Substrate temperature on the defect related emission of
ZnO thin films prepared by pulsed laser deposition
DTSTART;VALUE=DATE-TIME:20150507T080000Z
DTEND;VALUE=DATE-TIME:20150507T082000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3930@events.saip.org.za
DESCRIPTION:Speakers: Vinod Kumar (Department of Physics\, University of t
he Free state\, Bloemfontein\, ZA-9300)\n1. Introduction \n\nZinc Oxide (Z
nO) has attracted much attention in research activities with potential app
lications such as light emitting diode\, spintronic device\, transparent c
onductive electrodes\, laser and solar cells due to its wide band gap (~3.
37 eV) and large exciton binding energy (~60 meV) [1\,2]. There are severa
l deposition techniques used to grow ZnO thin films\, including chemical v
apour deposition (CVD) [3]\, magnetron sputtering [4]\, spray pyrolysis [5
]\, the sol-gel method [6] and pulsed laser deposition (PLD) [7]. In the c
ase of PLD prepared films\, the degree of orientation is influenced by the
deposition conditions such as temperature\, background gas composition an
d pressure\, and kinetic energy of the plume particles [7]. The trivalent
rare earth (RE3+) doped ZnO belong to one kind of novel optical materials
and have drawn an increasing amount of attention [8]. Terbium doped ZnO (
ZnO:Tb3+) thin films were prepared by PLD at different substrate temperatu
res. In the present work\, the effects of substrate temperature on the str
ucture\, optical and luminescence properties of ZnO:Tb3+ thin film were in
vestigated in detail. A correlation was found between the defects (confirm
ed by X-ray photoelectron spectroscopy) and the Photoluminescence (PL) res
ults.\n \n2. Results\n\nFigure 1 shows the XRD patterns of the ZnO thin
films deposited on Si substrates at different substrate temperatures rang
ing from room temperature (RT) to 400ºC. According to the XRD patterns\,
all ZnO films were oriented along the (002) plane. This is in line with th
e characteristics of the hexagonal ZnO wurtzite where the c-axis is perpen
dicular to the substrate plane [9]. The PL spectra of the ZnO films grown
at the different substrate temperatures are shown in figure 2. It is worth
noting that the films mainly exhibit emission in the UV region. The stron
g near-band edge emission at room temperature is due to free exciton recom
bination. Generally in ZnO\, the visible light emission is ascribed to the
structural defects [10] such as zinc vacancy (VZn)\, oxygen vacancy (Vo)\
, interstitial zinc (Zni)\, interstitial oxygen (Oi) and antisite oxygen d
efects (OZn) [10]. The PL spectra of the ZnO:Tb3+ thin films are character
ized by three different types of transitions\, the one is due to exciton r
ecombination emission\, the second is due to defect level emission and the
third is due to the Tb3+ f-f transitions. For the emission due to the Tb3
+ ions\, a green emission peak at 543 nm and a few minor peaks at 489 and
622 nm were detected. These peaks represent the 5D4-7F5\, 5D4-7F6\, and 5D
4-7F3 transitions of Tb3+\, respectively [10].\n
\n\n\n\n3. References\n\n[1] U. Ozgur\, Y.I. Alivov\, C. Liu\, A.
Teke\, M.A. Reshchikov\, S. Dogan\, V. Avrutin\, S.J. Cho\, et. al\, J. A
ppl. Phys. 98 (2005) 041301.\n[2] Vinod Kumar\, N. Singh\, V. Kumar\, A. K
apoor\, L.P. Purohit\, O.M. Ntwaeaborwa and H.C. Swart\, J. Appl. Phys. 11
4 (2013) 134506. \n[3] J. Hu and R.G. Gordon\, J. Appl. Phys. 71 (1992) 88
0.\n[4] Y. Igasaki and H. Saito\, J. Appl. Phys. 70 (1991) 3613.\n[5] A.F.
Aktaruzzaman\, G.L. Sharma and L.K. Malhotra\, Thin Solid Films 198 (1991
) 67.\n[6] Vinod Kumar\, R. G. Singh\, L. P. Purohit and Fouran Singh\, J.
Alloys & Comp. 544 (2012) 120.\n[7] A. Suzuki\, T. Matsushita\, N. Wa
da\, Y. Sakamoto and M. Okuda\, Jpn. J. Appl. Phys. 35 (1996) L56.\n[8] X.
Chen and Wenqin Luo\, J. Nanoscie. Nanotechn. 10 (2010) 1482.\n[9] S. Cho
opum\, R.D. Vispute\, W. Zoch\, A. Balsamo\, R.P. Sharma\, T. Venkatesan\,
et. al\, Appl. Phys. Lett. 75 (1991) 3947. \n[10] Vinod Kumar\, S. Som\,
V. Kumar\, V. Kumar\, E. Coetsee\, O.M. Ntwaeaborwa and H.C. Swart\, Chemi
cal Eng. J.\, 255 (2014) 54.\n\nhttps://events.saip.org.za/event/39/contri
butions/3930/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3930/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Synthesis and Characterization of a Novel Rare-Earth Oxyorthosilic
ates (R2SiO5) (R = La\, Gd\, Y) Doped Dy3+ Nanophosphors
DTSTART;VALUE=DATE-TIME:20150506T113000Z
DTEND;VALUE=DATE-TIME:20150506T130000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3931@events.saip.org.za
DESCRIPTION:Speakers: Simon. N Ogugua (UNIVERSITY OF THE FREE STATE)\n1. I
ntroduction \nNowadays\, phosphors have found applications in solid state
lighting\, phototherapy\, information display technologies\, and solar ce
lls\, among other things. Rare earth oxyorthosilicates of the form R2SiO5
(R = La\, Gd\, Y) doped with rare earth elements\, have been of interest
for the past decades due to their wide band gap\, fast decay times\, high
quantum efficiency\, high density and minimal self-absorption. Using urea-
assisted solution combustions method\, we prepared both single and mixed r
are-earth oxyorthosilicates doped with Dy3+ powder nanophosphors.\n2. Resu
lts\nThe structures of our phosphors analysed using X-ray diffraction (XRD
) confirmed that the phosphors crystalized in the pure monoclinic phases o
f La2SiO5\, Gd2SiO5 and Y2SiO5 or in the mixture of any of the three compo
unds. We also analysed the morphologies\, elemental composition\, and the
chemical and electronic states of our powders using field emission scannin
g electron spectroscopy (FE-SEM)\, energy dispersive X-ray spectroscopy (E
DS) and X-ray photoelectron spectroscopy (XPS) respectively. The photolumi
nescence (PL) (Fig. 1) measured when the samples were excited using a 325
nm He-Cd laser showed broad blue emission assigned to self-trapped exciton
s in SiO2 [1] (which were not observed in the PL spectra measured in phosp
horescence mode when the samples were excited using monochromatic xenon la
mp) and 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+ [2]. The col
our purity of the samples calculated using the CIE coordinate calculator c
onfirmed that the phosphors can emit tunable colours and white light. Furt
hermore\, there was even distribution of the atomic and molecular ionic sp
ecies on the surfaces of the samples as shown in the time-of-flight second
ary ion mass spectrometer images in Fig 2. \n\n3. References\n[1] C. Itoh
\, K. Tanimura\, N. Itoh. J. Phys. C. Solid State Phys. 21(1988) 4693.\n[2
] K.G. Sharma\, N.R. Singh. New J. Chem. 37 (2013) 2784.\n\nhttps://events
.saip.org.za/event/39/contributions/3931/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3931/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Characterisation of Defects in Photovoltaic modules using Electrol
uminescence and Large-Area Light Beam Induced Current (LA-LBIC) techniques
DTSTART;VALUE=DATE-TIME:20150507T100000Z
DTEND;VALUE=DATE-TIME:20150507T102000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3932@events.saip.org.za
DESCRIPTION:Speakers: Ernest van Dyk (NMMU)\n1. Introduction \nThe perform
ance and longevity of photovoltaic (PV) modules can be severely limited by
poor material\, manufacturing defects and physical cracks. Cell mismatch
can occur when a solar cell in a series-connected string produces a lower
current than the other cells in that string[1]. The current output of th
e entire string is limited by the weakest cell in the string so damage to
a single cell in a module can affect the entire module’s current output.
These material defects are not always identifiable in visual inspection s
o additional characterisation techniques are necessary.\nIn this study Ele
ctroluminescence (EL) imaging and Large-Area Light Beam Induced Current (L
A-LBIC) measurements were used. EL is an effective\, fast and non-destruc
tive characterisation technique for PV modules and is widely used in PV mo
dule manufacturing to assess the quality of the finished module[2\, 3]. T
he EL emitted under forward bias is related to the recombination\, optical
and resistive properties of the cell. LA-LBIC is also a non-destructive
spatial characterisation tool capable of measuring the photo-response of P
V modules[4]. The PV module is spot-illuminated using a light source moun
ted above the module on a motorised x-y scanning stage. At each point the
current output of the module is measured at a set voltage level. This pr
ovides a photo-response map of the PV module related to the wavelength of
the light source used. \n\n2. Results\nFigure 1 shows an EL image of a mon
o-crystalline silicon module with striation rings visible as a dark circle
in the centre of the cell. In this region of the cell the presence of ox
ygen precipitates results in the recombination of electron hole pairs. Th
is defect occurs during the wafer growth stage and affects the efficiency
of the cell and will lower the module efficiency. However\, it is not reg
arded as a module failure. The corresponding LA-LBIC photo-response map i
s shown in figure 2. The striation ring is visible in the centre of the c
ell as an area of decreased photo-response. LA-LBIC and EL measurements h
ave shown good agreement in measurement results and the two techniques hav
e proved complementarity in PV module characterisation.\n\nhttps://events.
saip.org.za/event/39/contributions/3932/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3932/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Characterization of TiO2 nanostructures prepared by mic
rowave method for gas sensing
DTSTART;VALUE=DATE-TIME:20150505T131500Z
DTEND;VALUE=DATE-TIME:20150505T150000Z
DTSTAMP;VALUE=DATE-TIME:20260615T104149Z
UID:indico-contribution-39-3933@events.saip.org.za
DESCRIPTION:Speakers: zamaswazi portia Tshabalala (DST/CSIR National Centr
e for Nano-Structured Materials\, Council for Scientific and Industrial Re
search\, Pretoria\, 0001\, South Africa)\n1. Introduction\nThe need for ga
s sensors to monitor and detect toxic\, explosive and combustible gases in
mines and in the environment has stimulated researchers to develop portab
le gas sensing devices that can detect at low concentration and at room te
mperature. Monitoring such gases can help to prevent occurrences of fatal
accidents such as fire and explosions [1]. \n\nAmongst the metal-oxides (M
OXs) semiconductors\, TiO2 appears to be the most attractive material beca
use of its diverse applications in various fields such as spintronics\, so
lar cells\, photocatalysis and gas sensors [2]. In addition\, it has a goo
d thermal stability and can operate in harsh environment. The structure an
d morphology of MOXs can be controlled by varying the synthesis procedure.
\n\nIn this study we report the synthesis of TiO2 nanostructures using a
simple hydrothermal method in NaOH solution at 220 °C for 15 minutes. The
influence of hydrochloric acid (HCl) aqueous solution as a washing agent
on the surface morphology\, structure and gas sensing properties of the Ti
O2 nanoparticles was investigated. Additionally\, the effect of calcinatio
n temperature on the properties of TiO2 nanoparticles was also studied in
detail. \n \n2. Results\nFig. 1 shows the XRD patterns of the as-prepar
ed TiO2 nanoparticles washed with distilled water and different concentrat
ions of HCl. Based on the results in Fig 1\, the structure of the starting
material\, P25 Degussa shows a mixture of both anatase and rutile phases.
The material washed with H2O and HCl aqueous solution after synthesis rev
eals only the anatase phase. Previous studies reported that pure anatase T
iO2 phase has comparatively good sensing properties. The SEM images of P25
Degussa compared with that washed with H2O and various concentrations of
HCl aqueous solution are shown in Fig. 2. The particle sizes of the as-pre
pared samples increased as the concentration of the HCl as washing agent w
as increased as depicted in Fig. 2(c-d). The insets of figure 2 show the p
article size distribution. The results revealed that when the grain size i
ncreases\, grain boundaries decrease providing a large surface area thus i
ncreasing the sensing capabilities.\n\nhttps://events.saip.org.za/event/39
/contributions/3933/
LOCATION:Mabula Game Lodge
URL:https://events.saip.org.za/event/39/contributions/3933/
END:VEVENT
END:VCALENDAR