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SUMMARY:The impurity levels of lanthanide ions in silica
DTSTART;VALUE=DATE-TIME:20110714T093000Z
DTEND;VALUE=DATE-TIME:20110714T094500Z
DTSTAMP;VALUE=DATE-TIME:20260418T165621Z
UID:indico-contribution-4859@events.saip.org.za
DESCRIPTION:Speakers: R.E. Kroon (Physics Dept\, University of the Free St
 ate)\nSilica is a basic material of technological importance for optics\, 
 microelectronics\, photonics and fibre optics.  Its high absorption edge e
 nergy makes its particularly useful for UV applications and it has been us
 ed as a host material for a variety of luminescent lanthanide ions due to 
 its chemical stability and non-hygroscopic nature. For lanthanide ions the
  4f electron energy levels are shielded from the host environment by the f
 illed outer 5s and 5p orbitals\, so that the transitions between these sta
 tes and therefore the luminescent wavelengths are relatively insensitive t
 o the host.  For this reason little attention has been paid until recently
  to the location of the impurity levels of the lanthanide ions within the 
 energy gaps of their hosts.  However\, luminescence from some lanthanide i
 ons\, e.g. cerium\, occurs due to f-d transitions from the unshielded 5d s
 tate of which the energy relative to the f-states is therefore host depend
 ent.   The absolute positions of the 4f and 5d states relative to the ener
 gy gap of the host also affect quenching and charge trapping phenomena and
  so they are required for proper modeling of phosphor performance.  Recent
 ly Dorenbos has suggested that the energy levels of any of the 13 divalent
  lanthanides relative to the band edges of the host can be found using onl
 y three parameters. However\, obtaining this data for a particular host is
  not always straightforward e.g. use can be made of the f-d transition ene
 rgy of cerium\, but different values for this parameter in silica have bee
 n reported.  In this paper a scheme for the energy levels of both the diva
 lent and trivalent lanthanide ions in silica is proposed and compared to t
 he experimental data.\n\nhttps://events.saip.org.za/event/7/contributions/
 4859/
LOCATION: Acro1
URL:https://events.saip.org.za/event/7/contributions/4859/
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