Local structural environments of Ge doped in eutectic Sb-Te film before and after crystallization

Title
Local structural environments of Ge doped in eutectic Sb-Te film before and after crystallization
Authors
정병기신상열최용규
Keywords
amorphous chalcogenide film; EXAFS spectroscopy; Phase change material; Crystallization properties
Issue Date
2018-06
Publisher
The Journal of physics and chemistry of solids
Citation
VOL 117-85
Abstract
Electrical phase change device using the Ge-doped eutectic Sb-Te (e.g., Ge1Sb8Te2) film is known to exhibit improved energy efficiency thanks to lowered threshold voltage as well as decreased power consumption for the reset operation, as compared with Ge2Sb2Te5 film. Ge K-edge EXAFS analysis is employed in this study in an effort to elucidate such merits of Ge1Sb8Te2 film in connection with its local atomic arrangements. It is then verified that a Ge atom is four-fold coordinated in its nearest-neighboring shell both in the as-deposited and in the annealed films. It needs to be highlighted that approximately two Sb atoms constitute the Ge tetrahedral units in its amorphous state; however, after being crystallized, heteropolar Ge-Sb bonds hardly exist in this Ge1Sb8Te2 film. It has been known that crystallization temperature and activation energy for crystallization of this Ge1Sb8Te2 composition are greater than those of Ge2Sb2Te5 composition. In addition, these two phase change materials exhibit distinctly different crystallization mechanisms, i.e., nucleation-dominant for Ge2Sb2Te5 film but growthdominant for Ge1Sb8Te2 film. These discrepancies in the crystallization-related properties are delineated in terms of the local structural changes verified from the present EXAFS analysis.
URI
http://pubs.kist.re.kr/handle/201004/67352
ISSN
0022-3697
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KIST Publication > Article
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