Time resolved microwave conductivity (TRMC) measurements have been used for the analysis of the charge carrier dynamics in hetero-structures, formed by the deposition of nano-crystalline diamond (NCD) films on top of crystalline silicon substrates. It is found that the NCD film deposition results in all cases in an increase of the crystalline silicon surface recombination. Nevertheless, we could demonstrate the successful realization of diamond film/Silicon hetero-diodes when depositing intrinsic or slightly boron-doped diamond films. In a coplanar contact geometry based device a strong sensitivity to UV light irradiation has been found. In this case a fast small positive light induced current signal is followed by a much slower negative signal giving rise to persistent negative photoconductivity.