Electron affinity of undoped and boron-doped polycrystalline diamond films

Abstract

The electron affinity of polycrystalline undoped and boron-doped diamond films was investigated by means of X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. It was demonstrated that both as-grown and hydrogenated polycrystalline diamond films exhibited true negative electron affinity (NEA). Positive electron affinity (PEA) was observed after diamond surface oxidation in plasma. NEA reduction was observed after hydrogenation of the polycrystalline film surface in plasma. This effect was related to depolarization of the surface dipoles, an increase in the density of surface defects, and an increase in contaminations on the surface. Boron doping of the diamond film had a negligible effect on electron affinity. Downward surface band bending was found for all the samples that were studied, and there was larger band bending for polycrystalline diamond surfaces modified in plasma than for as-grown polycrystalline diamond surfaces.