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Scanning tunneling microscopy (STM) and spectroscopy (STS) in combination with density functional theory (DFT) calculations are employed to study the surface and subsurface properties of the metastable phase of the phase-change material Ge 2 Sb 2 Te 5 as grown by molecular beam epitaxy. The (111) surface is covered by an intact Te layer, which nevertheless permits the detection of the more disordered subsurface layer made of Ge and Sb atoms. Centrally, we find that the subsurface layer is significantly more ordered than expected for metastable Ge 2 Sb 2 Te 5. First, we show that vacancies are nearly absent within the subsurface layer. Secondly, the potential fluctuation, tracked by the spatial variation of the valence band onset, is significantly less than expected for a random distribution of atoms and vacancies in the subsurface layer. The strength of the fluctuation is compatible with the potential …
American Physical Society
Publication date: 
11 Dec 2017

J Kellner, G Bihlmayer, VL Deringer, M Liebmann, C Pauly, A Giussani, JE Boschker, R Calarco, R Dronskowski, M Morgenstern

Biblio References: 
Volume: 96 Issue: 24 Pages: 245408
Physical Review B