Electron irradiation effects on DES/Ge(1 0 0) at 90 K

The effects of electron irradiation of diethylsilane-covered Ge(1 0 0) surfaces at 90 K was studied by temperature programmed desorption (TPD), electron stimulated desorption (ESD), and Auger electron spectroscopy (AES). Adsorption of diethylsilane (DES) at 90 Kon Ge(1 0 0) results in thermal desorption of hydrogen at 570 K from the substrate and at 635 K a b-hydride elimination process which results in the removal of carbon species from the surface. The b-hydride elimination process leads to desorption of ethylene (mass 28) at 635 K. A low temperature peak due to desorption of physisorbed DES is observed at 150 K. After electron irradiation, two new high temperature hydrogen TPD peaks at 725 and 800 K appear. In the case of ethylene, a new TPD peak is observed at 800 K following electron irradiation of DES/Ge(1 0 0). ESD decay curves and kinetic energy distribution data show that hydrogen desorbs from at least two surface states while ethylene electronically desorbs from one state. Thermal desorption of DES from Ge(1 0 0) leads to accumulation of silicon on the surface up to a saturation level of 40% (atomic concentration). This result indicates that it is not possible to epitaxially grow silicon on germanium, due to diffusion of silicon into the germanium substrate. Electron irradiation of DES/Ge(1 0 0) leads to increasing amounts of carbon on the surface and no detectable changes in the surface concentration of silicon. This suggests that electron induced removal of ligands from silicon facilitates the migration of silicon into germanium.