Photoelectron diffraction and photoelectron holography study of a Ge(111) high-temperature surface phase transition

T. T. Tran, S. Thevuthasan, Y. J. Kim, D. J. Friedman, A. P. Kaduwela, G. S. Herman, C. S. Fadley

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    Abstract

    Further evidence for a reversible high-temperature surface-disordering phase transition at ∼1060 K on Ge(111) has been found using Ge 3p X-ray photoelectron diffraction (a short-range order probe of surface structure that is sensitive to the first 3-5 spheres of neighbors) and photoelectron holography (a recently suggested direct 3D imaging technique). Azimuthal diffraction data at takeoff angles of θ = 19° (including nearest-neighbor forward-scattering directions and yielding high surface sensitivity) and θ = 55° (for which second-nearest-neighbor forward-scattering directions and more bulk sensitivity are involved) show abrupt drops in intensity of ∼30%-40% over the temperature interval of 900-1200 K. Photoelectron holographic near-neighbor images at temperatures both below and above the transition region furthermore indicate an identical near-neighbor structure for all atoms present in ordered sites. These combined diffraction and holography data show that by 1200 K, the Ge(111) surface is covered by a completely disordered overlayer of 2.0-2.5 Ge monolayers in thickness. The rate of growth of this overlayer with increasing temperature is also in excellent agreement with recent medium-energy ion scattering results, although the thicknesses we find for the overlayer are 1.5-2.0 times larger. A more detailed analysis of the θ = 19° and the θ = 55° data also suggests the possible presence of a partially disordered interface between the liquid-like overlayer and the bulk, also of 2 Ge monolayers in thickness and consisting of laterally strained domains.

    Original languageEnglish
    Pages (from-to)270-284
    Number of pages15
    JournalSurface Science
    Volume281
    Issue number3
    DOIs
    Publication statusPublished - 1 Feb 1993

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    ASJC Scopus subject areas

    • Condensed Matter Physics
    • Surfaces and Interfaces
    • Surfaces, Coatings and Films
    • Materials Chemistry

    Cite this

    Tran, T. T., Thevuthasan, S., Kim, Y. J., Friedman, D. J., Kaduwela, A. P., Herman, G. S., & Fadley, C. S. (1993). Photoelectron diffraction and photoelectron holography study of a Ge(111) high-temperature surface phase transition. Surface Science, 281(3), 270-284. https://doi.org/10.1016/0039-6028(93)90640-6