Photoemission study of CdTe surfaces after low-energy ion treatments

We present a study of low-energy ion surface cleaning treatments and their impact on the surface electronic structure of an air-exposed CdTe thin film treated with CdCl₂. In order to determine the electronic structure using surface-sensitive photoemission, surfaces need to be free of contaminants. This is achieved by subsequent low-energy ion treatment steps, carefully monitoring the chemical and electronic surface structure. We present data on the valence band maximum (VBM), and core-level binding energies, that suggest that neither preferential sputtering occurs nor metallic states are formed using our cleaning procedure. For a clean CdTe surface, the VBM is determined to be (0.8 ± 0.1) eV below the Fermi energy.