Electronic structure of wurtzite II-VI compound semiconductor cleavage surfaces studied by scanning tunneling microscopy

We report atomically resolved scanning tunneling microscopy (STM) images of cleavage surfaces of wurtzite II-VI compound semiconductors. CdSe(112¯0), CdSe(101¯0), and CdS(101¯0) were investigated. The STM images confirm a $1\times 1$ reconstruction for all surfaces. At negative and positive sample voltages the occupied and empty dangling-bond states above anions and cations, respectively, dominate the contrast of the STM images. No states in the band gap were found. The electronic structure of the surface permits the observation of dopant atoms in subsurface layers and thus also cross-sectional scanning tunneling microscopy studies of point defects and heterostructures.