Grain boundary effects on carrier transport in undoped polycrystalline chemical‐vapor‐deposited diamond

A quantitative measure of grain‐boundary effects on the carrier transport properties in polycrystalline chemical‐vapor‐deposited diamond has been obtained using a 10‐ns hard x‐ray excitation source. Two device geometries were used to gain insight into the extent of grain‐boundary effects: one having the applied electric field normal and the other parallel to the grain orientation. The applied electric field intensity was varied to adjust the mean‐free carrier drift distance. The degradation in the carrier transport properties at an electric field intensity of 10 kV/cm by the grain‐boundary appears to be approximately a factor of two in comparison to the intragrain carrier transport.