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Title: Intrinsic evolutions of dielectric function and electronic transition in tungsten doping Ge{sub 2}Sb{sub 2}Te{sub 5} phase change films discovered by ellipsometry at elevated temperatures

Tungsten (W) doping effects on Ge{sub 2}Sb{sub 2}Te{sub 5} (GSTW) phase change films with different concentrations (3.2, 7.1, and 10.8%) have been investigated by variable-temperature spectroscopic ellipsometry. The dielectric functions from 210 K to 660 K have been evaluated with the aid of Tauc-Lorentz and Drude dispersion models. The analysis of Tauc gap energy (E{sub g}) and partial spectral weight integral reveal the correlation between optical properties and local structural change. The order degree increment and chemical bond change from covalent to resonant should be responsible for band gap narrowing and electronic transition enhancement during the phase change process. It is found that the elevated crystalline temperature for GSTW can be related to improved disorder degree. Furthermore, the shrinkage of E{sub g} for GSTW should be attributed to the enhanced metallicity compared with undoped GST.
Authors:
; ; ; ;  [1] ; ; ;  [2]
  1. Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China)
  2. State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)
Publication Date:
OSTI Identifier:
22420252
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CHEMICAL BONDS; DOPED MATERIALS; ELLIPSOMETRY; FILMS; GERMANIUM COMPOUNDS; OPTICAL PROPERTIES; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; TIN TELLURIDES; TUNGSTEN