Fabrication and properties of a-C:H/boron-doped diamond structure

The fundamental regions of photovoltaic conversion from each band gap are considered ultraviolet light on diamond and visible light on amorphous carbon. This difference suggests that the cell that forms electric junctions using both materials shows photovoltaic efficiency under ultraviolet light and visible light. A photovoltaic cell with a hydrogenated amorphous carbon (a-C:H) film deposited on a boron-doped diamond layer was fabricated to confirm this suggestion. The a-C:H film was deposited by radio-frequency plasma-enhanced chemical vapor deposition (R-F-CVD) on heavily boron-doped diamond, which was homoepitaxially grown by microwave plasma CVD on single-crystal diamond. The photovoltaic characteristics of the cell were obtained using xenon lamp irradiation and a UV filter. The open-circuit voltage and short-circuit current of the cell without the UV filter were -62 mV and 17.7 nA, respectively. The opencircuit voltage and short-circuit current decreased with insertion of the UV filter between the cell and the lamp. These results indicate that the photovoltaic effect of an a-C:H/boron-doped diamond cell can produce not only visible light but also UV light.