We have investigated the early stage of Ag island growth at 2 monolayer (ML) coverage on the hydrogen-terminated Si(111)-(1 × 1) surface using low-energy electron-diffraction (LEED) and scanning tunneling microscopy (STM) at room temperature. First, it is found that the Ag(10) LEED pattern varies from arc-like spots to three spots by changing the Ag deposition rate from 1.0×10-1 (a fast deposition rate) to 1.1×10-4 (a slow deposition rate) ML/s. Second, STM observation reveals that adsorbed Ag atoms grow into dome-like three dimensional (3D) clusters at the fast deposition rate and flat-top two dimensional (2D) islands at the slow deposition rate. Third, most abundant 2D islands show the 8 atomic layer height, which coincides with that obtained from the quantum size effect. The side structures of 2D islands agree well with those calculated from Wulff theory. We will discuss the exact nature of 3D clusters and 2D islands of Ag grown on the hydrogen-terminated Si(111)-(1 × 1) surface and these results indicate the possibility of using kinetic controlled growth to investigate the physics of crystal growth.
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