LOW-ENERGY-ELECTRON BEAM-INDUCED DISSOCIATION OF METHYL-GROUPS CHEMISORBED ON SEMICONDUCTOR SURFACES - (CH3)(3)AL ADSORBED ON GAAS AND INSB

It is shown that the incident electron beam in high-resolution electro n energy loss spectroscopy (HREELS) studies of (CH3)(3)Al chemisorbed on the (100) surfaces of GaAs and InSb leads to electron beam induced dissociation of adsorbed CH, groups. Vibrational modes associated with Surface CH, species appear in spectra recorded at high electron beam energies with a threshold of 10 eV. Dissociation cross-sections for CH 2 production have been calculated and found to be very large, varying between 2 x 10(-16) cm at 30 ev and 7 x 10(-17) cm(2) at 20 eV. It is suggested that an electron impact mechanism is responsible for dissoci ation and the high cross-sections reflect a relatively long lifetime f or the excited states which are not quenched efficiently for adsorptio n on semiconductor surfaces. (C) 1998 Elsevier Science B.V. All rights reserved.