Transport properties of hydrogen-terminated nanocrystalline diamond films

Hydrogen-terminated nanocrystalline diamond films of different granularity are investigated by van der Pauw measurement of the resistivity and Hall effect depending on the grain size. In agreement with the observation on the hydrogenated diamond single crystals, the measured transport quantities are surface related. The room temperature resistivity strongly increases when the mean grain size at surface varies from about 400 nm down to 40 nm while the Hall concentration is only weakly dependent on the granularity and exhibits values comparable with those found in hydrogenated single crystals. Using a two-dimensional geometrical model, we show that effective resistivity is controlled by the transversal resistance of the grain boundaries. Based on the mobility-concentration relation obtained by the surface adsorbate desorption. microscopic origin of the boundary resistance is discussed. (C) 2011 Elsevier B.V. All rights reserved,