Transport properties of CVD diamond elucidated by DC and AC conductivity measurements

Detailed comprehensive study was carried out on diamond thin films to understand the charge carrier transport with respect to temperature and frequency domain of AC conductivity. Metal-Diamond-Metal structures were used to study the bulk transport and surface conductivity of freestanding films. Large differences were observed between the surface and bulk admittance values of as grown films. Bulk transport resulted in thermally activated behavior both in AC and DC measurements with activation energies of 0.65 eV for thermionic emission of trapped charge. Normalized Cole-Cole plots can be explained on the basis of a superposition of four Voigt elements representing an effective medium constituted by a distribution of grains, elongated in the growth direction, and temperature dependent leakage paths. A simple model of the grain boundary is introduced to discuss and justify the observed results. (C) 2003 Elsevier B.V. All rights reserved.