Local adsorption geometry of acetylene on Si(100)(2x1): Multiple sites and the role of substrate temperature

Article

关键词: X-RAY PHOTOELECTRON;    SI(001) SURFACE;    SI(100)-(2X1) SURFACE;    FIRST-PRINCIPLES;    THERMAL-DECOMPOSITION;    MOLECULAR ADSORPTION;    ETHYLENE ADSORPTION;    C2H2 ADSORPTION;    DIFFRACTION;    SPECTROSCOPY;   

DOI  :  10.1103/PhysRevB.66.085333

来源: SCIE

【 摘 要 】

Using C 1s scanned-energy mode photoelectron diffraction the local adsorption geometry of acetylene on the Si(100)(2x1) surface has been investigated at both low and room temperatures. Clear differences in the data at the two sample temperatures are attributed to the co-occupation of at least two distinct local sites. Quantitative modeling based on a two-site model indicates that the majority state at low temperature is bridge site adsorption with the C-C axis of the acetylene directly above, and parallel to, Si-Si surface dimers. At room temperature a second state accounts for more than 50% of the adsorbed acetylene molecules, and the favored model places these acetylene molecules midway between pairs of Si dimers, although the azimuthal orientation of the C-C axes is ambiguous. One possible geometry for this second species is the pedestal site tetra-sigma species previously proposed by Xu [Phys. Rev. Lett. 84, 939 (2000)], although the specific geometry proposed by this group can be excluded. An alternative rotated pedestal site is comparably probable. There is no direct evidence for any occupation of a rotated bridge site across the ends of two adjacent Si dimers, but partial occupation of this site cannot be excluded.

【 授权许可】

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