$CoSi2$ surface phase separation into self-assembled lateral multilayers

$CoSi2$ was grown on the Si(001) surface by solid-phase reaction. Its transformation from elemental Co/Si(001) was complete after a 700 °C anneal, as followed from the reflection high-energy electron diffraction analysis. Scanning tunneling microscopy observations of the resulting surface revealed a variety of atomic reconstructions, some apparent only under bias-dependent imaging conditions. Particularly striking was the appearance of alternating $(3√2×2√2)-R45°$ and $(4√2×2√2)-R45°$ surface domains arranged in long parallel stripes. Plausible reasons for such a phase separation are discussed.