Collective and vibrational excitations on then-doped GaAs(110) surface

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Abstract
A detailed high-resolution electron-energy-loss-spectroscopy study of the surface collective and vibrational excitations of the clean n-doped GaAs(110) cleaved surface is presented. Measurements were taken exploiting a wide range of primary-beam energy and at two different dopant concentrations. Due to their coupling in the sample with higher doping, both the free-carrier plasmon and the Fuchs-Kliewer mode show dispersion. The phonon intensity behavior, when the primary-beam energy is changed, is opposite to that of the plasmon. The intensity behavior of the latter mode, in particular, suggests its spatial confinement beneath the surface.