Reconstruction and growth of Ag on the Si(111)-√3 × √3 -Ag surface at low temperature

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Abstract
Surface reconstruction structures and epitaxial growth of Ag on the Si(111)-√3 × √3 -Ag structure at low temperature (160-K order) have been investigated by reflection high-energy electron diffraction (RHEED). When Ag was deposited on a √3 × √3 -Ag surface at 160 K, reconstruction structures √21 × √21 and 6×6 were observed in addition to the √3 × √3 structures. The √3 × √3 and √21 × √21 structures were observed for a thickness range between 0.19 and 2.6 ML, and the 6×6 structures appeared and coexisted with the √3 × √3 and √21 × √21 structure between 0.7 and 1.7 ML. From RHEED patterns analysis, a 6×6 model was proposed. Beyond Ag growth of 3 ML, three-dimensional (3D) Ag islands were formed at the temperature range from 160 K to RT. These results imply that the mean free path of Ag atoms on the √3 × √3 -Ag surface is large enough even at 160 K that 2D nuclei cannot be formed on the terrace in spite of decreasing substrate temperature.