Electronic properties of the 2D-hole accumulation layer on hydrogen terminated diamond

Hydrogen-tenninated diamond films have been investigated by Contact Potential Difference Measurements (CPD or Kelvin force), Hall effect experiments and theoretical calculations where the Schrodinger and Poisson equations have been solved to calculate the density of state (DOS) distribution at the surface of hydrogen-terminated diamond. From CPD experiments, we detect the Fermi energy to be about 700-meV deep in the valence band. This is in agreement with results from numerical calculations, where Fermi energies in the range 240-880 meV below the valence band maximum at the surface are deduced. The calculations show that a two-dimensional (2D) density of state is present at the surface. Temperature-dependent hole sheet densities and mobilities are used to discuss the properties of the 2D-DOS. From this data, we conclude that the 2D-DOS is distorted by disorder arising from nonperfect hydrogen termination of the surface, by surface roughness, and/or by ionic molecules, which are part of the adsorbate layer. (C) 2004 Elsevier B.V. All rights reserved.