Collective modes of misfit dislocations in lattice-mismatched thin films

L. B. Hovakimian, Shun ichiro Tanaka

Research output: Contribution to journalConference articlepeer-review

Abstract

We study the nature and spectrum of fundamental vibrational excitations in the assembly of misfit accommodating dislocations. The physical system considered is a Lomer array of equispaced dislocations in a lattice-mismatched interface between a substrate and a thin film with similar elastic properties. Within the framework of the isotropic elasticity theory we calculate the effective force constants of harmonic springs that establish the dynamical correlations between the oscillating dislocations. Our interest is concentrated on the case where the thickness of the overlayer is much less than the separation between the nearest-neighbor dislocations. We show how in this situation the free surface of the film exerts a profound screening influence on the dislocation-dislocation correlations; it is demonstrated that the force constants exhibit sensitive dependence not only on the lattice mismatch, but also on the film thickness. We then deduce the dispersion of collective dislocation excitations and find that the latter propagate along the interface much more slowly than the ordinary sound waves. Our results reveal the manner in which the thickness of the film controls the magnitude of the vibrational quantum that characterizes the natural oscillations of arrayed dislocations. It is shown that this anomalous energy quantum manifests itself in the low-temperature heat capacity of the misfit array.

Original languageEnglish
Pages (from-to)143-148
Number of pages6
JournalMaterials Research Society Symposium - Proceedings
Volume472
Publication statusPublished - 1997 Dec 1
Externally publishedYes
EventProceedings of the 1997 MRS Spring Symposium - San Francisco, CA, USA
Duration: 1997 Apr 11997 Apr 4

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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