OBSERVATIONS OF THE AU/SI(111) SYSTEM WITH A HIGH-RESOLUTION ULTRAHIGH-VACUUM SCANNING ELECTRON-MICROSCOPE

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 5x2-Au or, square-root 3 x square-root 3-Au structure partially covering a Si(111)-7 x 7 surface are clearly observed. Domains of 5x2-Au formed by Au deposition onto a substrate held at approximately 870 K show threefold elongation corresponding to three equivalent kinds of domains rotated 120-degrees to each other. On the other hand, 5x2-Au regions formed by partial Au desorption by heating at approximately 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.