Surface reconstructions and morphological modifications: restructuring of W(111) induced by sulfur overlayers

C. H. Nien, T. E. Madey

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11 Scopus citations

Abstract

The restructuring of S/W(111) surfaces has been studied using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and scanning tunneling microscopy (STM). Dosing W(111) with a saturation coverage of H2S followed by annealing to > 800 K causes a substrate reconstruction with (4 × 4) periodicity. After the formation of the (4 × 4) structure over the entire surface, and upon further annealing, the terrace-step configurations also restructure and form triangular terraces. Upon heating to T > 1000 K, the triangular terraces coalesce and enlarge, in addition to forming multiple steps. A size-mismatch mechanism, based on charge transfer between S and W atoms, is proposed to explain the formation of (4 × 4) structures: strain introduced at the surface by adsorption of large sulfur anions is relieved by the (4 × 4) reconstruction. We have explored the consequences of a terrace growth mechanism for S(4 × 4)/W(111) that is based on local step structures, coupled with domain mismatch.

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