Interface formation between GaS and CVD diamond films

Thin GaS films were deposited on B-doped diamond (as-grown) and on oxygen-annealed B-doped diamond (O-ann.) films grown by plasma-assisted chemical vapor deposition on p+-type Si(001) substrate and the interface formation has been characterized by Auger electron spectroscopy (AES), low-energy electron-loss spectroscopy (LEELS) and X-ray photoelectron spectroscopy (XPS). The thermal evaporation of a GaS single crystal is used for the deposition. LEELS spectra taken at low EP (≤200 eV) indicate that the surface-related peaks are dominant for both as-grown and O-ann. films. Whereas, Surface- and bulk-plasmon peaks of diamond are dominant in the LEELS spectra taken at high EP for both as-grown and O-ann. films. After the deposition of GaS at 500–550°C, some new loss peaks consisting of superposition of the peaks due to GaS appear in the LEELS spectra for both as-grown and O-ann. films. XPS spectra indicate a downward band bending due to oxygen treatment. The downward band bending decreases as a result of GaS deposition and increases as a result of post-annealing at higher temperature. CS and CGa bonds are observed for GaS-deposited diamond films. Secondary electron emission spectra indicate that the S-terminated diamond films seem to possess a positive electron affinity surface.