ELECTRONIC-PROPERTIES OF SB MONOLAYERS ON III-V(110) SURFACES DETERMINED BY RESONANCE RAMAN-SCATTERING

Resonance Raman scattering (RRS) experiments have been performed to ex plore the electronic states via the vibrational modes of highly ordere d (1 x 1) monolayers of Sb on InP (110) and GaAs(I 10) prepared by the rmal annealing. In accordance to the Cs symmetry of the two-atom unit cell of the monolayers three modes of A' and one of A'' symmetry are o bserved by Raman scattering. The scattering intensities show pronounce d resonances which are related to electronic transitions between the t wo-dimensional electronic surface bands. The resonances are found to b e characteristic for each vibrational mode. This can be understood in terms of different electronic bands being involved in the scattering p rocess. For Sb on GaAs (110), the resonance of the A'' mode yields a m aximum between 2.2 and 2.3 eV. On InP(110), resonances at 2.55 eV for the 1A', 2.3-2.6 eV for the 2A', 1.9 eV for the IA'' and greater-than- or-equal-to 3.0 eV for the 3A' modes occur. For both Sb on GaAs and In P the transition energies observed by RRS coincide with features repor ted by several other techniques. The resonance behavior of the ideal m onolayers can be understood as a fingerprint of the joint density of s tates at the interface. In contrast, resonance Raman spectra taken aft er deposition of 1.5 ML Sb without annealing reveal a different resona nce behavior. In this case, where the monolayer is not ideally ordered , the resonances are smeared out over an energy range between 2.3 and 2.7 eV revealing the influence of imperfections on the electronic band structure.