THERMALLY-INDUCED AND ELECTRON-INDUCED CHEMISTRY OF CF3I ON NI(100)

We have investigated the thermally-induced and electron-impact-induced chemistry of CF3I on Ni(100) following adsorption at 100 K. The data support a model for the thermally-induced chemistry, in which CF3I dissociates to CF3 and I, either upon adsorption or at slightly-elevated temperatures. Most CF3 decomposes to adsorbed C and F. Above 75% saturation of the first layer, the availability of surface sites for decomposition decreases to a level where some adsorbed CF3 remains intact and desorbs as such. Bombardment of multilayer CF3I by low-energy electrons introduces new chemistry. Electron-induced decomposition (EID) of the parent molecule occurs through both C-I and C-F bond scission, with a measured cross section of 1.5 x 10(-16) cm(2) (upper limit). Thermally-induced desorption from the electron-bombarded surface indicates a number of EID fragment reactions, most notably carbon-carbon bond formation, as evidenced by C2F3I+, C2F4+, C2F5+, C3F5+, and C4F7+. To our knowledge, this is the first report of C-C bond formation in small. fluorocarbons adsorbed on metal surfaces.