ELECTRONIC-STRUCTURE OF WURTZITE II-VI COMPOUND SEMICONDUCTOR CLEAVAGE SURFACES STUDIED BY SCANNING-TUNNELING-MICROSCOPY

We report atomically resolved scanning tunneling microscopy (STM) imag es of cleavage surfaces of wurtzite II-VI compound semiconductors. CdS e(<11(2)over bar 0>), CdSe(<10(1)over bar 0>), and CdS(<10(1)over bar 0>) were investigated The STM images confirm a 1x1 reconstruction for all surfaces. At negative and positive sample voltages the occupied an d empty dangling-bond states above anions and cations, respectively, d ominate the contrast of the STM images. No states in the band gap were found. The electronic structure of the surface permits the observatio n of dopant atoms in subsurface layers and thus also cross-sectional s canning tunneling microscopy studies of point defects and heterostruct ures.