The adsorption of C2H2 on Si(100) 2×1 has been studied for the first time using STM. Upon exposure of the sample at room temperature to 0.2 L C2H2 (approximately 20% coverage) adsorption of the molecule on alternate dimer pairs is observed, leading to either a local 2×2 or c(2×4) 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 775 K, the surface becomes disordered and the steps are no longer visible. After further annealing at 875 K, SiC clusters are formed and the 2×1 structure is again seen between the clusters. Annealing to higher temperatures around 1100 K leads to pinning of the step movement by the SiC clusters. We find that at saturation coverage, the molecule forms a well-ordered 2×2 overlayer on the surface. Annealing to intermediate temperatures below 900 K leads to results similar to that seen for lower coverages. However, annealing at 1100 K results in facetting of the surface. Annealing at 1275 K creates anisotropic facets which are oriented along the  direction with a typical aspect ratio of approximately four to five. These facets act as nucleation sites for subsequent carbonization and SiC growth.
|Journal||Journal of the Korean Physical Society|
|Issue number||SUPPL. PART 1|
|Publication status||Published - 1997 Dec 1|
ASJC Scopus subject areas
- Physics and Astronomy(all)