Surface Fermi Level Position of Diamond Treated with Plasma

Abstract

ABSTRACTThe surface Fermi level position of undoped epitaxial diamond layers is estimated from contact potential difference between Au reference and diamond measured by Kelvin probe method. The surface Fermi level position of the as-grown layer is located at the energy of 0.75 eV above the valence band edge. O2 plasma treatment leads to an upward shift of the surface Fermi level position to an energy of 1.89 eV from the valence band edge. The surface Fermi level is located at an energy of 0.97 eV above the valence band edge after H2 plasma treatment. Reversible change in the surface Fermi level position is found between O2 and H2plasma treatments. A change in the band bending is observed at the surface of polycrystalline diamond films treated with various ways by X-ray photoclcctron spectroscopy (XPS) analysis. A variation in the current-voltage characteristics of epitaxial and polycrystalline diamonds treated with O2 and H2 plasmas can be qualitatively explained in terms of a change in the band bending due to the shift of the surface Fermi level position.