Excess modes and enhanced scattering in rare-earth-doped amorphous silicon thin films

B. L. Zink, R. Islam, David Smith, F. Hellman

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

We report specific heat and thermal conductivity of gadolinium- and yttrium-doped amorphous silicon thin films measured using silicon-nitride membrane-based microcalorimeters. Addition of gadolinium or yttrium to the amorphous silicon network reduces the thermal conductivity over a wide temperature range while significantly increasing the specific heat. This result indicates that a large number of nonpropagating states are added to the vibrational spectrum that are most likely caused either by localized vibration of the dopant atom in a Si cage or softening of the material forming the cage structures. High-resolution cross-sectional electron micrographs reveal columnar features in Gd-doped material which do not appear in pure amorphous silicon. Scattering from both the nanoscaled columns and the filled-cage structures play a role in the reduced thermal conductivity in the rare-earth-doped amorphous semiconductor. The overall result is an amorphous solid with a large bump in C/T3 and no plateau in thermal conductivity.

Original languageEnglish (US)
Article number205209
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume74
Issue number20
DOIs
StatePublished - 2006

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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