Au adsorption on Si(5 5 12) surfaces and facet formation studied by high resolution in situ REM

Adsorption processes of Au on a high index Si(5 5 12) surface were studied in situ by high resolution reflection electron microscopy with subunit cell resolution. Growth of new phases is quite anisotropic and rapid along the [1 1̄ 0] direction reflecting quite anisotropic substrate surface structure. At around 715°C, successive changes from (5 5 12) to two-fold (3 3 7), (5 5 11) and (2 2 5) facet were noted as an increase of Au deposit. (7 7 17) surface units are locally formed before formation of the two-fold (3 3 7) surfaces. At higher temperature 780°C (above roughening temperature 750°C of (5 5 11)-Au surface), a disordered surface is formed after formation of the two-fold (3 3 7) facet. The disordered surface is a higher temperature phase of the (5 5 11) surface. Above changes are discussed in terms of characteristics of these high index surface structures.