Atom abstraction and gas phase dissociation in the interaction of XeF2 with Si(100)

Xenon difluoride reacts with Si(100)2x1 by single atom abstraction whereby a dangling bond abstracts a F atom from XeF2, scattering the complementary XeF product molecule into the gas phase, as observed in a molecular beam surface scattering experiment. Partitioning of the available reaction energy produces sufficient rovibrational excitation in XeF for dissociation of most of the XeF to occur. The resulting F and Xe atoms are shown to arise from the dissociation of gas phase XeF by demonstrating that the angle-resolved velocity distributions of F, Xe, and XeF conserve momentum, energy, and mass. Dissociation occurs within 2 A of the surface and within a vibrational period of the excited XeF molecule. Approximately an equal amount of the incident XeF2 is observed to react by two atom abstraction, resulting in adsorption of a second F atom and scattering of a gas phase Xe atom. Two atom abstraction occurs for those XeF product molecules whose bond axes at the transition state are oriented within +/- 60 degrees of the normal and with the F end pointed toward the surface.