STM Study of C_2H_2 Adsorption on Si(100)(STM-Si(001))

概要

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The adsorption of C_2H_2 on Si(100)2x1 has been studied for the first time using STM. Upon exposure of the sample at room temperature to 0.2L C_2H_2 (approximately 20% coverage) adsorption of the molecule on alternate dimer pairs is observed, leading to either a local 2x2 or c(2x4) structure. In the filled state image, a local minimum is observed in the center of the reacted dimer pairs, while the unreacted dimer pairs maintain the normal bean shaped contour of the clean surface. Upon annealing the substrate at 775K, the surface becomes disordered and the steps are no longer visible. After further annealing at 875K, SiC clusters are formed and the 2x1 structure is again seen between the clusters. Annealing to higher temperatures around 1100K leads to pinning of the step movement by the SiC clusters. We find that at saturation coverage, the molecule forms a well-ordered 2x2 overlayer on the surface. Annealing to intermediate temperatures below 900K leads to results similar to that seen for lower coverages. However, annealing at 1100K results in facetting of the surface. Annealing at 1275K creates anisotropic facets which are oriented along the 110 direction with a typical aspect ratio of approximately four to five. These facets act as nucleation sites for subsequent carbonization and SiC growth.STMC_2H_2acetyleneSi(100)SiCepitaxythin film
東北大学の論文
1997-03-28