Speaker
Ms
Mmapula Baloi
(University of the Witwatersrand)
Description
Ge2Sb2Te5 (GST225) is a chalcogenide phase change alloy widely used in optical storage media and electronic memory devices. It has been studied in the past two decades due to its optical and electrical properties driven by fast and reversible structural phase transformation. However, its elastic properties have not been thoroughly investigated. Since thermal energy can be stored in vibrational modes, surface Brillouin scattering (SBS) has been used to determine the elastic properties and correlate them with thermal properties. RF-magnetron sputtering was used to deposit films of thickness varying from 50-500 nm on a Si/Si1O2 substrate. The crystalline (c) phase was obtained by annealing the samples at a temperature of 150 ֯C for one hour. Since the transition between the amorphous (a) and crystalline phases is associated with a volume change, we studied this by measuring the densities of the two phases using x-ray reflectivity. Rutherford Backscattering was used to investigate the films chemical composition and atomic density, which was found to be n~3.05×〖10〗^22 and 3.01×〖10〗^22 atoms cm^(-3) for a-GST225 and c-GST-225. The elastic constants for the amorphous (a) and crystalline (c) phases obtained are C11=37.9/37.0 GPa, C12=17.6/13.1 GPa and C44=10.2/12.0 GPa respectively. The corresponding longitudinal and transverse velocities are vl=2558/2499 m/s and vt=1325/1421 m/s. Lastly the calculated minimum lattice thermal conductivities of a- and c-GST225 were found as κmin=0.283 and 0.287 Wm^(-1) K^(-1). Such low thermal conductivities are desirable for improving thermal management in memory devices during programming.
Supervisor details<br><b>If not a student, type N/A.</b><br>Student abstract submision<br>requires supervisor permission:<br>please give their name,<br> institution and email address.
Daniel Wamwangi
University of the Witwatersrand
daniel.wamwangi@wits.ac.za
| Consideration for<br>student awards<br><b>Choose one option<br>from those below.</b><br>N/A<br>Hons<br>MSc<br>PhD | MSc |
|---|---|
| Please confirm that you<br>have carefully read the<br>abstract submission instructions<br>under the menu item<br>"Call for Abstracts"<br><b>(Yes / No)</b> | Yes |
Primary authors
Dr
Bhekumusa Mathe
(University of the Witwatersrand)
Mr
Christoph Persch
(RWTH Aachen University)
Dr
Daniel Wamwangi
(wits university)
Prof.
David Billing
(University of the Witwatersrand)
Prof.
Matthias Wuttig
(RWTH Aachen University)
Ms
Mmapula Baloi
(University of the Witwatersrand)
Morgan Madhuku
(iThemba LABS)
