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Title: Ge L{sub 3}-edge x-ray absorption near-edge structure study of structural changes accompanying conductivity drift in the amorphous phase of Ge{sub 2}Sb{sub 2}Te{sub 5}

A gradual uncontrollable increase in the resistivity of the amorphous phase of phase-change alloys, such as Ge{sub 2}Sb{sub 2}Te{sub 5}, known as drift, is a serious technological issue for application of phase-change memory. While it has been proposed that drift is related to structural relaxation, no direct structural results have been reported so far. Here, we report the results of Ge L{sub 3}-edge x-ray absorption measurements that suggest that the drift in electrical conductivity is associated with the gradual conversion of tetrahedrally coordinated Ge sites into pyramidal sites, while the system still remains in the amorphous phase. Based on electronic configuration arguments, we propose that during this process, which is governed by the existence of lone-pair electrons, the concentration of free carriers in the system decreases resulting in an increase in resistance despite the structural relaxation towards the crystalline phase.
Authors:
 [1] ; ;  [2] ; ;  [3] ; ;  [4] ; ;  [5]
  1. Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562 (Japan)
  2. Nanoelectronics Research Institute and Green Nanoelectronics Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562, Japan and Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1, Kouto, Sayo, Hyogo 679-5198 (Japan)
  3. Nanoelectronics Research Institute and Green Nanoelectronics Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562 (Japan)
  4. Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1, Kouto, Sayo, Hyogo 679-5198 (Japan)
  5. DEIB - Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy)
Publication Date:
OSTI Identifier:
22273955
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 17; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION; AMORPHOUS STATE; ANTIMONIDES; CONCENTRATION RATIO; ELECTRIC CONDUCTIVITY; ELECTRONIC STRUCTURE; ELECTRONS; GERMANIUM TELLURIDES; PHASE CHANGE MATERIALS; RELAXATION; X RADIATION