TEM study of the structural similarity between NaCl and rhombohedral phase of Te-based ternary chalcogenide materials

Title
TEM study of the structural similarity between NaCl and rhombohedral phase of Te-based ternary chalcogenide materials
Authors
선창우이정용김용태
Issue Date
2009-01
Publisher
Physica status solidi. A, Applied research
Citation
VOL 206, NO 1, 50-53
Abstract
A well-known Te-based ternary chalcogenide, Ge–Sb–Te (GST; especially Ge2Sb2Te5), undergoes a two-crystalline phase change – involving metastable NaCl and stable rhombohedral phases – during crystallization [1]. Since the phase-change mechanism is related to the speed of operation of the phase-change memory, many research groups have tried to understand the transition behaviours between NaCl and rhombohedral structures [2–10]. Most studies report that the quick phase change is due to vacancies that exist in the 4(b) site of the NaCl structure. The Ge–Bi–Te (GBT) alloy GeTe–Bi2Te3, which is known to be a thermoelectric material [11–13], is a pseudo-binary alloy resembling GST. Yusu et al. propose that in this GeTe–Sb2Te3 pseudobinary system, the crystallization speed can be improved when some of the Sb is replaced by Bi [14]. Thus, GBT is expected to show a crystallization mechanism similar to that of GST. Recently, the report of Matsunaga et al. of metastable NaCl-structured Ge2Bi2Te5 at room temperature [15] has supported this expectation; however, highresolution transmission electron microscopy (HR-TEM) studies of NaCl-structured GBT are somewhat uncommon. Moreover, microstructural characterizations of the general relationship between NaCl and rhombohedral structures are also insufficient. In this report, we show not only the existence of general high-symmetry atomic figures in rhombohedral- structured ternary chalcogenide, which belongs to the P3m1 or R3m space group, but also suggest explanations for the lattice-distortion-driven phase transformation mechanism between NaCl and rhombohedral structures.
URI
http://pubs.kist.re.kr/handle/201004/34304
ISSN
0031-8965
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KIST Publication > Article
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