We have designed photodetectors based on a combination of nanocrystalline diamond (NCD) and bilayer metallic layers in a metal-semiconductor-metal (MSM) structure. The NCD films were deposited on silicon substrates which nucleated by different metallic layers (tungsten, molybdenum) and nanodiamond suspension. We found that the metallic layers not only significantly improve the nucleation density of the substrates but also reduce the surface roughness of the fabricated NCD films from 8.3 nm to 4.7 nm. Furthermore, the one-step fabrication of MSM photodetectors adopts metallic interlayers consisting of two functions (diamond nucleation site and back electrodes), which shows high detection efficiency and rapid response to UV irradiation in air ambient. The W/NCD/W structure exhibits good Ohmic contact characteristics and significant changes (similar to 3 orders of magnitude) in photocurrent and stable reproducibility. The achievement of this research indeed demonstrates great prospects of photodetector applications of NCD films in the future. (C) 2018 Published by Elsevier B.V.