The spatially anisotropic kinetics involved in the chemical reaction between highly ordered pyrolytic graphite (HOPG) and a beam containing hyperthermal (approximately 8 km s(-1)) O((3)P) atomic oxygen and molecular oxygen yields unique surface morphologies. Upon exposure at moderate sample temperatures (298-423 K), numerous multilayer circular pits embedded in the reacted areas have been observed with the use of atomic force microscopy and scanning tunneling microscopy. These pits have diameters spanning nanometers to micrometers and depths from a few to tens of nanometers. The most striking characteristic of these pits is the convex curvature of the pit bottoms, where the highest point on the pit bottom is at the center and the lowest point occurs around the peripheral edge. Such structure arises by the interplay between kinetics of pit nucleation, the spatially anisotropic kinetics involved in the lateral and downward reactivity of HOPG, and the fluence of atomic oxygen. These kinetics, which are also influenced by the high reactivity of the translationally hot impinging oxygen atoms, govern the overall morphological evolution of the surface.

No abstract

The formation of monolayers of alkylsilanes on a gold surface is characterized by X-ray photoelectron and reflection-absorption infrared spectroscopies. The reaction occurs through the activation of multiple Si-H bonds. Reactivity of the newly synthesized systems to oxygen and water is reported.

Single and multicomponent mixed layers of silsesquioxane clusters on freshly evaporated gold surfaces have been investigated by X-ray photoelectron spectroscopy and reflection-absorption infrared spectroscopy. Approximately 5-10% of the cluster layers (e.g., H8Si8O12 and H10Si10O15) on gold desorb upon evacuation of the adsorbate from the reaction chamber. These open adsorption sites are an avenue for cluster displacement reactions that yield mixed monolayers (e.g., H8Si8O12/D8Si8O12 and H8Si8O12/C6H13-H7Si8O12) of several compositions on gold. This dynamic behavior is not observed for the C6H13-H7Si8O12 cluster layer on gold. Rather, this molecule acts as a poison to these reported displacement processes at the gold surface.