Amorphous System and Theory
Xi’an Jiaotong University
Xianning West Road No. 28, Xi’an, Shanxi
Wei Zhang is a professor at School of Materials Science and Engineering, Xi’an Jiaotong University. He received his Bachelor’s and Master’s degrees in Physics from Zhejiang University. He obtained his Ph.D. degree from RWTH Aachen University, Germany in 2014. After his postdoc work at RWTH Aachen University, he joined Xi’an Jiaotong University in 2015. His research interest includes phase-change memory, neuro-inspired computing, and first-principles materials design. He has published 70 academic papers on high-profile journals, including Science (3), Nat. Mater. (3), Nat. Rev. Mater., Adv. Mater. (3), Mater. Today, Sci. Bull., ACS Nano and others. The citation of these articles is ~2900 (H-index 28). His awards include the IFAM Young Scientist Award and the K.C. Wong Education Foundation Lecturer Award.
Abstract for Presentation
Crystallization simulations of amorphous Ge-Sb-Te alloys
Ge–Sb–Te (“GST”) alloys are leading phase-change materials for non-volatile memory and neuro-inspired computing. Upon fast crystallization, these materials form rocksalt-like phases with large structural and vacancy disorder, leading to an insulating phase at low temperature. Here, a comprehensive description of crystallization, structural disorder, and electronic properties of GeSb2Te4 based on realistic, quantum-mechanically based (“ab initio”) computer simulations with system sizes of more than 1000 atoms is provided. It is shown how an analysis of the crystallization mechanism based on the smooth overlap of atomic positions (SOAP) kernel reveals the evolution of both geometrical and chemical order. The connection between structural and electronic properties of the disordered, as-crystallized models, which are relevant to the transport properties of GST, is then studied. Furthermore, it is shown how antisite defects and extended Sb-rich motifs can lead to Anderson localization in the conduction band. Beyond memory applications, these findings are therefore more generally relevant to disordered rocksalt-like chalcogenides that exhibit self-doping, since they can explain the origin of Anderson insulating behavior in both p- and n-doped chalcogenide materials.
Figure 1. The SOAP-based characterization of the crystallization process for GeSb2Te4.
 W. Zhang*, R. Mazzarello, M. Wuttig, E. Ma, Nat. Rev. Mater. 4 (2019) 150.
 Y. Xu, Y. Zhou, X. Wang, W. Zhang*, E. Ma, V.L. Deringer, R. Mazzarello*, Adv. Mater. 34 (2022) 2109139.
 W. Zhang, A. Thiess, P. Zalden, R. Zeller, P.H. Dederichs, J.Y. Raty, M. Wuttig*, S. Blügel, R. Mazzarello*, Nat. Mater. 11 (2012) 952.
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