Negative ion resonances and vibrational mode selectivity in inelastic electron scattering studies of hydrogen and diethylsilane adsorbed on Si(100)

High-resolution electron energy loss spectroscopy and theoretical calculations of related isolated molecules have been used to identify and assign negative ion resonances (NIR) in the vibrational excitation functions of hydrogen and diethylsilane adsorbed on Si(100)-(2×1). For H/Si(100) the NIR at ∼3 eV leads to mode selective enhancement of Si–H stretching vibrations. For diethylsilane adsorbed on Si(100), a strong resonance is identified at ∼8 eV and mode selective excitation is again observed, with only vibrations associated with the ethyl groups of the adsorbed molecule enhanced by this mechanism.