Angle-resolved inverse photoelectron spectroscopy studies of CdTe(110), CdS(112¯0), and CdSe(112¯0)

Abstract

The conduction-band structures of CdTe(110), CdS(112¯0), and CdSe(112¯0) have been studied using angle-resolved inverse photoelectron spectroscopy. With normally incident electrons substantial parts of the conduction bands have been observed and several critical points determined. The energy positions of these are compared with theoretical predictions. Clear discrepancies are found, especially for the wurtzite crystals CdS and CdSe. Unoccupied surface resonances have been observed on CdTe(110) and on CdS(112¯0). Those associated with the broken bonds on the surfaces are found 1.4 and 1.2 eV above the conduction-band minimum (CBM), respectively. On CdS(112¯0) a second surface resonance is found 3.2 eV above the CBM, being split off from the $M_1$ point in the Brillouin zone. A fluorescence process involving the Cd 4d level has been observed in all three materials. This yields information on the partial density of p states in the valence band.