Electric field-dependent conductivity of polycrystalline diamond thin films

Abstract

The dc electrical conductivity of polycrystalline diamond films with submicron grain sizes has been studied as a function of the applied electric field up to the point of electrical breakdown. For electric fields below approximately 105 V/cm, the films exhibited predominantly ohmic behavior. For higher electric fields, however, the conductivity was field activated according to Poole’s Law. The data is consistent with a Poole–Frenkel reduction of the ionization energy associated with Coulombic potentials surrounding ionizable centers, where the Coulombic potentials overlap. Consequently, the dielectric strength of the films in this study are lower than that reported for single-crystalline diamond.