Low-energy electron beam induced dissociation of methyl groups chemisorbed on semiconductor surfaces: (CH3)3Al adsorbed on GaAs and InSb

It is shown that the incident electron beam in high-resolution electron energy loss spectroscopy (HREELS) studies of (CH3)3Al chemisorbed on the (100) surfaces of GaAs and InSb leads to electron beam induced dissociation of adsorbed CH3 groups. Vibrational modes associated with surface CH2 species appear in spectra recorded at high electron beam energies with a threshold of 10 eV. Dissociation cross-sections for CH2 production have been calculated and found to be very large, varying between 2×10−16 cm2 at 30 eV and 7×10−17 cm2 at 20 eV. It is suggested that an electron impact mechanism is responsible for dissociation and the high cross-sections reflect a relatively long lifetime for the excited states which are not quenched efficiently for adsorption on semiconductor surfaces.