Phase-change materials: Vibrational softening upon crystallization and its impact on thermal properties

Toshiyuki Matsunaga, Noboru Yamada, Rie Kojima, Shinichi Shamoto, Masugu Sato, Hajime Tanida, Tomoya Uruga, Shinji Kohara, Masaki Takata, Peter Zalden, Gunnar Bruns, Ilya Sergueev, Hans Christian Wille, Raphaël Pierre Hermann, Matthias Wuttig

Research output: Contribution to journalArticlepeer-review

95 Citations (Scopus)

Abstract

Crystallization of an amorphous solid is usually accompanied by a significant change of transport properties, such as an increase in thermal and electrical conductivity. This fact underlines the importance of crystalline order for the transport of charge and heat. Phase-change materials, however, reveal a remarkably low thermal conductivity in the crystalline state. The small change in this conductivity upon crystallization points to unique lattice properties. The present investigation reveals that the thermal properties of the amorphous and crystalline state of phase-change materials show remarkable differences such as higher thermal displacements and a more pronounced anharmonic behavior in the crystalline phase. These findings are related to the change of bonding upon crystallization, which leads to an increase of the sound velocity and a softening of the optical phonon modes at the same time. Crystallization of amorphous solids is usually accompanied by significant changes of transport properties, such as an increase in thermal conductivity. Phase-change materials, however, reveal a remarkably low thermal conductivity in the crystalline state. This phenomenon is caused by the change of bonding upon crystallization which leads to an increase of the sound velocity and a softening of the optical modes.

Original languageEnglish
Pages (from-to)2232-2239
Number of pages8
JournalAdvanced Functional Materials
Volume21
Issue number12
DOIs
Publication statusPublished - 2011 Jun 21
Externally publishedYes

Keywords

  • anharmonic lattice modes
  • condensed matter
  • gamma-ray spectroscopy
  • phase-change materials
  • phonon measurements
  • thermal conduction

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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