Observations of the Au/Si(111) System with a High-Resolution Ultrahigh-Vacuum Scanning Electron Microscope

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Abstract
Secondary electron (SE) imaging with a high-resolution ultrahigh-vacuum scanning electron microscope (UHV-SEM) has been applied to the observation of the Au/Si(111) system. Domains of the 5×2-Au or √3×√3-Au structure partially covering a Si(111)-7×7 surface are clearly observed. Domains of 5×2-Au formed by Au deposition onto a substrate held at ∼870 K show threefold elongation corresponding to three equivalent kinds of domains rotated 120° to each other. On the other hand, 5×2-Au regions formed by partial Au desorption by heating at ∼1270 K from an entirely covered surface display larger size without such elongation. Granular clusters, a few nm in size, of Au formed by deposition approximately at room temperature, and large three-dimensional islands formed in the Stranski-Krastanov growth mode are also clearly imaged.