The differential reactivity of octahydridosilsesquioxane on Si(1 0 0)-2×1 and Si(1 1 1)-7×7: a comparative experimental study

Scanning tunneling microscopy (STM), in conjunction with X-ray photoemission (XPS) and reflection-absorption infrared (RAIRS) spectroscopy, has been used to investigate the reaction of octahydridosilsesquioxane clusters (H8Si8O12) on the Si(1 0 0)-2×1 and Si(1 1 1)-7×7 surfaces. The clusters exhibit a markedly different reactivity upon exposure to the two clean silicon surfaces. STM data is presented that, in conjunction with XPS and RAIRS data, provides numerous constraints upon possible geometries for the chemisorbed clusters. The sum of the data is consistent with a dissociative reaction mechanism on Si(1 0 0)-2×1, resulting in cluster attachment to the surface via a single vertex. Conversely, data of Si(1 1 1)-7×7 subject to a saturation exposure of H8Si8O12 is presented that is highly suggestive of cluster decomposition on the surface.