The effects of 600 eV electron irradiation on adsorbed layers of trimethylamine (TMA) on a Si(100) surface at 100 K were studied using high-resolution electron energy loss spectroscopy (HREELS), temperature programmed desorption (TPD), electron-stimulated desorption (ESD) and x-ray photoelectron spectroscopy (XPS). Experiments were performed at monolayer and higher coverages. The ESD results obtained on physisorbed TMA indicate electron-induced decomposition of the parent molecule. The HREELS data also show cleavage of N-C bonds on the chemisorbed layer of TMA and deposition of CH x groups on the surface, which is also supported by a dramatic enhancement of hydrogen desorption at 960 K following electron irradiation. This multiple-step process is supported by ESD signal decay curves obtained during electron irradiation. Following electron irradiation of TMA/Si(100), the intensity of low temperature TPD peaks corresponding to TMA fragments decreases; however, the intensity of the mass 2 peak increases dramatically compared with the un-irradiated surface. This is indicative of electron-induced associative desorption of molecular hydrogen. The HREELS data from monolayer coverage of TMA on Si(100) after electron irradiation suggests the removal of CH x groups from the adsorbate layer and deposition of carbon and hydrogen on the surface. In the absence of physisorbed layers there is no indication of electron-induced desorption of TMA fragments.

The effect of low-energy electron irradiation on adsorbed layers of diethylsilane (DES) on the Si(100) surface at 100 K were studied using temperature programmed desorption (TPD) and electron stimulated desorption (ESD). As has been observed previously, TPD studies of adsorbed DES have shown desorption of both molecular hydrogen and ethylene. Adsorption of DES at 100 K also results in a loosely bound layer that desorbs molecularly at a temperature of ∼140 K. Strong evidence exists for thermal removal of ethylene from the surface during programmed heating via a b-hydride elimination process. Irradiation of the dosed surface with electrons results in a number of interesting effects. Electron-induced enhancement of both hydrogen and ethylene desorption from Si(100) is observed. In addition, both neutral and ionic desorption of surface species was observed, induced by electron irradiation. Desorption of neutral species having masses of 2, 15 and 28 indicate electron-induced removal of hydrogen and ethylene, with a methyl group appearing as a result of ethylene dissociation. Hydrogen removal occurs from two distinct states, as identified by the decay of neutral hydrogen from the surface, characterized by two decay constants. Analysis of the energy of desorbing H + species suggests two distinct kinetic energy distributions at 1.8 and 4.1 eV, which contribute to the desorption signal.