New physical picture for surface diffusion at high temperatures

I. I. Suni, E. G. Seebauer

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Surface diffusion of In and Sb on Ge(111) has been measured by optical second harmonic microscopy. This technique employs surface second harmonic generation to directly image submonolayer surface concentration profiles. At low coverage, the activation energy Ediff and pre-exponential factor D0 are extraordinarily large for both systems and cannot be explained by theories based on simple site-to-site hopping. Molecular dynamics simulations of a Lennard-Jones(111) surface has revealed a new mechanism for high-temperature diffusion which is probably operative on Ge(111). At low coverages and high temperatures, adatom-vacancy pairs. This process is characterized by a high enthalpy of pair formation and a high entropy of activation due to lattice relaxation near the vacancy. At high coverages, the behaviour of Sb and In are quite different. As the In coverage increases, a larger fraction of In resides in the adlayer, so the diffusion parameters slowly approach those for site-to-site hopping. For Sb there is evidence for immobile islands at higher coverages. This does not effect Ediff but decreases D0 due to the smaller number of diffusion paths around the island. The gradual change of In diffusion parameters with coverage is interrupted by an apparent phase transition at θ=0.16, where both Ediff and D0 peak sharply.

Original languageEnglish (US)
Title of host publicationMechanisms of Thin Film Evolution
EditorsSeshu B. Desu, David B. Beach, Bruce W. Wessels, Suleyman Gokoglu
PublisherPubl by Materials Research Society
Pages21-26
Number of pages6
ISBN (Print)1558992162
StatePublished - Jan 1 1994
Externally publishedYes
EventProceedings of the 1993 Fall Meeting of the Materials Research Society - Boston, MA, USA
Duration: Nov 29 1993Dec 3 1993

Publication series

NameMaterials Research Society Symposium Proceedings
Volume317
ISSN (Print)0272-9172

Other

OtherProceedings of the 1993 Fall Meeting of the Materials Research Society
CityBoston, MA, USA
Period11/29/9312/3/93

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ASJC Scopus subject areas

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

Cite this

Suni, I. I., & Seebauer, E. G. (1994). New physical picture for surface diffusion at high temperatures. In S. B. Desu, D. B. Beach, B. W. Wessels, & S. Gokoglu (Eds.), Mechanisms of Thin Film Evolution (pp. 21-26). (Materials Research Society Symposium Proceedings; Vol. 317). Publ by Materials Research Society.