Atomic and electronic structures of amorphous Ge2Sb2Te5; melt-quenched versus ideal glasses

• Published in: Journal of physics. Condensed matter 2010-05, Vol.22 (20), p.205504-205504
• Main Authors: Cho, E, Im, J, Park, C, Son, W J, Kim, D H, Horii, H, Ihm, J, Han, S
• Format: Article
• Language: English
• Subjects: Amorphous semiconductors, metallic glasses, glasses; Amorphous semiconductors, metals, and alloys; Amorphous structure; Atomic structure; Bonding; Condensed matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Covalence; Disordered solids; Electron states; Electronic structure; Electronic structure of disordered solids; Exact sciences and technology; Germanium; Glass; Physics; Structure of solids and liquids; crystallography
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/22/20/205504

To investigate an amorphous structure of Ge2Sb2Te5 that satisfies the 8-N rule (so-called 'ideal glass'), we perform alternative melt-quench simulations on Si2As2Se5 and replace atoms in the final structure with Ge--Sb--Te. The resulting structures have salient features of the 8-N rule such as the tetrahedral configuration for all Ge atoms and the localized Te lone pairs at the valence top. In addition, the average Ge--Te and Sb--Te distances are in good agreement with experiment. The energetic stability of the ideal glass supports the existence of this amorphous structure that is distinct from the melt-quenched glass. From the analysis of electronic structures and optical dielectric constants, it is concluded that the electronic character of the melt-quenched amorphous Ge2Sb2Te5 lies in between the resonant p-bonding of the crystalline phase and the covalent bonding of the ideal glass.