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Phase-change memory materials under high pressure (2015-12)

来源：admin 发布时间：2016-05-17

Time: 12/30/2015-10:00
Location: M255
Reporter: Ming Xu
Abstract:
The binary phase change memories, which take advantage of the resistive contrast between the amorphous and the crystalline phases, will eventually give way to the high-capacity multi-state memories, in which both phases can reach various resistive states. Recent studies demonstrated that these multiple resistive states can be achieved in crystalline phase change materials (PCMs), by manipulating the vacancies in Ge-Sb-Te (GST) system and controlling the disorder with different annealing temperatures. In lieu of the heat treatment, our large-scale ab initio molecular dynamics (AIMD) simulations show that pressure can also tune the disorder in crystalline PCMs. Our models contain 1008 atoms of rocksalt-like GeSb2Te4 with random distribution of vacancies, and the AIMD simulations were performed at various temperatures and pressures for about 100 ps. We observed that, by lowering the migration energy for the anti-site hopping (e.g., Te ions jump to the Ge/Sb layers and Sb ions hop to the Te layers), the high pressure increases the compositional disorder due to the accumulation of these anti-site ions, resulting in some localized electronic states near the bottom of the conduction band. On the other hand, the disorder leads to the unoriented displacement of the anti-site ions, distorting and destabilizing the lattice near them. The disorder-induced electron localization triggered by pressure will pave the way for the understanding and development of the multi-state memory devices. And the random distortion of lattices due to the compositional disorder offers a new mechanism that may contribute to the amorphization of crystalline PCMs at high pressure.
Reporter’s introduction
Xu , RWTH Aachen, Germany postdoctoral researchers Humboldt . He has obtained BS and MS degrees in Fudan University and received a doctorate at Johns Hopkins University . He has worked under the famous scientist Professor material Man, the famous Professor Matthias Wuttig phase change memory authority phase change material for many years in-depth study . For the first time using first principles to determine the exact structure of the phase change material glassy structure and properties for the first time using the pressure of glassy and crystalline state of the phase change material can be adjusted. Results published in Physical Review Letters, PNAS, Advanced Science and other journals .
Contact Person:Dashan Shang(9088)