| Summary: | 碩士 === 國立中正大學 === 物理學系暨研究所 === 100 === Reconstructions introduced by depositing Au and Co on clean Si(111) surface have been studied by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). By depositing a small amount of Au (Au coverage < 0.5 monolayers) onto a clean Si(111)-(7×7) surface, a coexistence of (7×7) and (5×2)/Au structures has been found on the surface. The areal ratio between the two structures can be controlled by Au coverage. After a sub-monolayer Co deposition, CoSi2 islands emerge on the (5×2)/Au domain whereas the (7×7) domain transforms into a (√7×√7) structure without the presence of CoSi2 islands, which would only appear at higher Co coverage, demonstrating a selective growth of islands on a surface. By investigating the size distribution of CoSi2 islands on a wide (5×2)/Au terrace or a collection of neighboring (5×2)/Au terraces, we are able to estimate the diffusion length of Co atoms under a simple diffusion model.
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