Local structure of the crystalline and amorphous states of Ga2Te3 phase-change alloy without resonant bonding: A combined x-ray absorption and ab initio study

A. V. Kolobov, P. Fons, M. Krbal, K. Mitrofanov, J. Tominaga, and T. Uruga
Phys. Rev. B 95, 054114 – Published 17 February 2017

Abstract

Phase-change memories are usually associated with GeTe-Sb2Te3 quasibinary alloys, where the large optical contrast between the crystalline and amorphous phases is attributed to the formation of resonant bonds in the crystalline phase, which has a rocksalt-like structure. The recent findings that tetrahedrally bonded Ga2Te3 possesses a similarly large property contrast and very low thermal conductivity in the crystalline phase and undergoes low-energy switching [H. Zhu et al., Appl. Phys. Lett. 97, 083504 (2010); K. Kurosaki et al., Appl. Phys. Lett. 93, 012101 (2008)] challenge the existing paradigm. In this work we report on the local structure of the crystalline and amorphous phases of Ga2Te3 obtained from x-ray absorption measurements and ab initio simulations. Based on the obtained results, a model of phase change in Ga2Te3 is proposed. We argue that efficient switching in Ga2Te3 is due to the presence of primary and secondary bonding in the crystalline phase originating from the high concentration of Ga vacancies, whereas the structural stability of both phases is ensured by polyvalency of Te atoms due to the presence of lone-pair electrons and the formation of like-atom bonds in the amorphous phase.

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  • Received 13 October 2016
  • Revised 23 January 2017

DOI:https://doi.org/10.1103/PhysRevB.95.054114

©2017 American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
Condensed Matter, Materials & Applied Physics

Authors & Affiliations

A. V. Kolobov* and P. Fons

  • Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan and Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Mikazuki, Hyogo 679-5198, Japan

M. Krbal

  • Center of Materials and Nanotechnologies (CEMNAT), Faculty of Chemical Technology, University of Pardubice, Legion's sq. 565, 53002 Pardubice, Czech Republic

K. Mitrofanov and J. Tominaga

  • Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan

T. Uruga

  • Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Mikazuki, Hyogo 679-5198, Japan

  • *a.kolobov@aist.go.jp

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Issue

Vol. 95, Iss. 5 — 1 February 2017

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