Effects of H-2 and/or O-2 plasma treatments on photoconductivity of freestanding polycrystalline diamond films

Thick (ca. 700 mu m) freestanding polycrystalline diamond films, 10 X 10 mm , were obtained using a high power (4 kW) microwave plasma-enhanced chemica l vapor deposition system. Prior to fabricating the photoconductors, we tre ated the growth side (as-grown surface of the film) and the substrate side (the interfacial surface of the film detached from the Mo substrate) using H-2 and/or O-2 plasma. Using these films, we fabricated parallel-type ohmic -contacted diamond photoconductors. At as-grown states, the growth side sho wed noticeable photoconductivity, while the substrate side showed little ph otoconductivity. O-2 plasma treatment of these sides led to the extinction of the photoconductivity. After exposing these sides again to H-2 plasma, w e observed not only distinct photoconductivity at the substrate side but al so the reappearance of photoconductivity at the growth side. Based on these results, we suggest the primary factor for the photoconductivity of these films. (C) 2000 The Electrochemical Society. S0013-4651(00)01-057-0. All ri ghts reserved.