Resonant vibrational excitation of H-GaAs(0 0 1) in HREELS

High resolution electron energy loss spectroscopy (HREELS) has been used to study the adsorption of hydrogen on the Ga-rich GaAs(0 0 1)-c(8×2) surface. Particular attention is focused on the inelastic electron scattering processes associated with this adsorbate system and the characteristics of each spectral feature. Extensive HREELS measurements, and comparison with theoretical predictions based on pure dipole scattering, provide clear evidence for the involvement of a negative ion resonance at 8 eV in the excitation of the Ga–H stretching vibration at 1900 cm−1. High frequency features at ∼2120 cm−1 are shown to be predominantly the combination of a coupled plasmon–phonon mode and the Ga–H stretch. At low hydrogen coverages, a contribution to this loss feature can be assigned to an As–H stretching mode.