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Disorder in order: A study of local and global order in Ge‐rich GeSbTe alloys
Author(s) -
Fons P.,
Matsunaga T.,
Kolobov A. V.,
Krbal M.,
Tominaga J.,
Yamada N.
Publication year - 2012
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201200497
Subject(s) - condensed matter physics , curie temperature , scattering , order (exchange) , amorphous solid , materials science , diffraction , phase transition , phase (matter) , crystallography , physics , chemistry , optics , quantum mechanics , finance , ferromagnetism , economics
Disorder in the amorphous state of phase‐change alloys has been a focus of much research, however, more recently it has become clear that there is significant temperature activated disorder in the crystalline phases that may have important implications for electrical transport. We explore order on different length scales using a variety of techniques. Bragg diffraction (BD) to determine average order, X‐ray absorption to analyze order on nearest neighbor length scales, and total scattering to investigate structure on intermediate length scales. We find that Ge‐rich phase‐change alloys lying along the technological important (GeTe) x –(Sb 2 Te 3 ) 1 − x pseudobinary tie line exhibit a ferroelectric transition at a Curie temperature T c from rhombohedral to cubic symmetry using BD while short‐range order probes such as X‐ray absorption spectroscopy indicate that local rhombohedral symmetry is maintained. Using total X‐ray scattering, we demonstrate that this apparent discrepancy can be resolved by the introduction of disorder on intermediate length scales using a simple model.