EXAFS Studies of Ge-Sb-Te Alloys for Phase-Change Applications

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Title: EXAFS Studies of Ge-Sb-Te Alloys for Phase-Change Applications
Author: Baker, David Andrew
Advisors: David Aspnes, Committee Member
Michael A. Paesler, Committee Co-Chair
Gerald Lucovsky, Committee Co-Chair
Gerald Iafrate, Committee Member
Abstract: Studies of amorphous (a-) semiconductors have been driven by technological advances as well as fundamental theories. Observation of electrical switching, for example, fueled early interest in a-chalcogenides. More recently a-chalcogenide switching has been applied successfully to programmable memory devices as well as DVD technology where the quest for the discovery of better-suited materials continues. Thus, switching grants researchers today with an active arena of technological as well as fundamental study. Bond constraint theory (BCT) and rigidity theory provide a powerful framework for understanding the structure and properties of a-materials. Application of these theories to switching in a-chalcogenides holds the promise of finding the best composition suited for switching applications. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy is an ideally suited technique to investigate the switching properties of these materials. Films of amorphous Ge2Sb2Te4, Ge2Sb2Te5, and Ge2Sb2Te7 exhibit differing bonding structures and bond statistics, which result in different electronic and optical properties. Results of new EXAFS experiments on these three critical compositions in the Ge-Sb-Te system are presented in light of BCT and rigidity theory.
Date: 2007-12-07
Degree: PhD
Discipline: Physics
URI: http://www.lib.ncsu.edu/resolver/1840.16/3418

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