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On the atomic structure of thin amorphous Ge–Sb–Te films
Author(s) -
Frumar Miloslav,
Kohoutek Tomas,
Prikryl Jan,
Orava Jiri,
Wagner Tomas
Publication year - 2009
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.200982021
Subject(s) - amorphous solid , crystallite , high resolution transmission electron microscopy , nucleation , materials science , thin film , crystallization , transmission electron microscopy , crystallography , electron diffraction , germanium , analytical chemistry (journal) , diffraction , nanotechnology , chemical engineering , optoelectronics , optics , chemistry , metallurgy , silicon , physics , organic chemistry , chromatography , engineering
The structure of thin films of Ge 2 Sb 2 Te 5 was studied by high‐resolution transmission electron microscopy (HRTEM) and by X‐ray diffraction (XRD). The as‐evaporated films prepared by flash evaporation were amorphous. Nearly, all the atoms were randomly distributed but even in as‐evaporated films small areas with some ordering were noticeable. The number and size of the ordered areas increased with thermal treatment of films to temperatures ∼80 °C, i.e., ∼70 °C below the crystallization temperature of amorphous Ge 2 Sb 2 Te 5 . After thermal treatment, small embryos of nucleation centers (size <8 nm) were formed. According to XRD measurements the films as a whole were still fully amorphous. The crystallite model of the structure of amorphous solids is then partly valid, at least for Ge 2 Sb 2 Te 5 . We expect that it can be applied also for other Ge–Sb–Te‐based films, as well as for the other amorphous chalcogenides. The possible impact of the formation of nucleation “embryos” on storage time of data in optical and electrical phase‐change memory materials and devices is discussed.