Dynamic observation of gold adsorption on Si(111)7×7 surface by high-resolution reflection electron microscopy

Abstract

Dynamic processes of gold adsorption on Si(111)7×7 surface are observed in-situ by high-resolution reflection electron microscopy (HR-REM); the 5-fold superlattice fringes of the 5×2 structure of 1.7 nm spacing are resolved in addition to the superlattice fringes of the 7×7 structure of 2.3 nm spacing. On a substrate held at 650°C, a domain of the 5×2 structure is nucleated at the higher side of a step on the 7×7 surface and grows along the 2-fold, in preference to the 5-fold, directions to expand towards the lower and higher sides of the step. After the 5×2 structure transforms into the √3×√3 structure by further deposition, the steps change their configurations and move in an oscillatory manner. The implication for models of gold adsorption, and the influence of defects and superlattice registry on the kinetics, are discussed.