Local bonding arrangements in amorphous Ge2Sb2Te5 : the importance of Ge and Te bonding

Issue Title: Proceedings of the International Conference on Optical and Optoelectronic Properties of Materials and Applications (ICOOPMA 2006) Guest Editors: Jai Singh, Takeshi Aoki, Koichi Shimakawa and Harry Ruda Extended X-ray absorption fine structure (EXAFS) studies of as-deposited Ge^sub 2^Sb^...

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Bibliographic Details
Published in:Journal of materials science. Materials in electronics 2007-10, Vol.18 (S1), p.399-403
Main Authors: BAKER, D. A, PAESLER, M. A, LUCOVSKY, G
Format: Article
Language:English
Subjects:
Applied sciences
Electronics
Exact sciences and technology
Magnetic and optical mass memories
Materials
Storage and reproduction of information
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Summary:Issue Title: Proceedings of the International Conference on Optical and Optoelectronic Properties of Materials and Applications (ICOOPMA 2006) Guest Editors: Jai Singh, Takeshi Aoki, Koichi Shimakawa and Harry Ruda Extended X-ray absorption fine structure (EXAFS) studies of as-deposited Ge^sub 2^Sb^sub 2^Te^sub 5^ films yield Ge K edge spectra essentially the same as previously reported; however, these earlier studies assumed only Te nearest neighbors, but the comprehensive analysis of this paper indicates significant concentrations of both Ge-Ge and Ge-Te bonds. Average bond coordination and number of valence bonding constraints/atom have been determined from an extension of bond-constraint theory that includes broken bond-bending constraints for Ge-Ge bonds, and optical memory alloys on the Sb^sub 2^Te^sub 3^-GeTe tie-line 3.05 ± 0.05 bonding constraints/atom, consistent with formation of an intermediate phase. The fraction of threefold or over-coordinated Te increases from 7.1 to 25% along this tie-line, and the amorphous to crystalline optical transmissivity transition occurs over a narrow temperature range,
ISSN:0957-4522
1573-482X
DOI:10.1007/s10854-007-9233-5