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Direct Evidence for a Systematic Evolution of Optical Band Gap and Local Disorder in Ag, In Doped Sb 2 Te Phase Change Material
Author(s) -
Shukla Krishna Dayal,
Sahu Smriti,
Manivannan Anbarasu,
Deshpande Uday Prabhakarrao
Publication year - 2017
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201700273
Subject(s) - amorphous solid , materials science , doping , crystallization , band gap , 3d optical data storage , phase (matter) , phase transition , spectroscopy , phase change material , order (exchange) , analytical chemistry (journal) , phase change , condensed matter physics , crystallography , optoelectronics , chemistry , physics , thermodynamics , organic chemistry , chromatography , quantum mechanics , finance , economics
Rapid and reversible switching properties of Ag, In doped Sb 2 Te (AIST) phase change material is widely used in re‐writable optical data storage applications. We report here a systematic evolution of optical band gap ( E g ), local disorder (Tauc parameter, β ), and Urbach energy ( E U ) of AIST material during amorphous to crystalline transition using in situ UV–Vis–NIR spectroscopy. Unlike GeTe‐Sb 2 Te 3 (GST) family, AIST material is found to show unique characteristics as evidenced by the presence of direct forbidden transitions. Crystallization is accompanied by a systematic reduction in E g from 0.50 eV (as‐deposited amorphous at 300 K) to 0.18 eV (crystalline at 300 K). Moreover, decrease in E U (from 272 to 212 meV) and β is also observed during increasing the temperature in the amorphous phase, revealing direct observation of enhancement of the medium‐range order and distortion in short range order, respectively. These findings of optical transition would be helpful for distinguishing the unique behavior of AIST material from GST family.