The microwave plasma enhanced chemical vapor deposition technique has been employed to grow polycrystalline diamond films on p-doped Si (100) substrates starting from highly diluted (1% CH 4 in H 2) gas mixtures. Coplanar interdigitated Cr/Au contacts have been thermally evaporated on two samples about 8 μm thick having different grain size. Dark current-voltage (I-V) measurements and impedance characterization have been found to be dependent on the grain size and on the quality of the examined samples
