Surface flashover characteristics of polished-polycrystalline diamond thin films in vacuum

Diamond is known to be an excellent electrical insulator and also an exceptional thermal conductor material. Because of these properties of diamond, polycrystalline diamond thin films are becoming attractive candidates for protective coatings, and, as insulating material for high voltage systems. They are also being examined for use in the construction of spacecraft components. In this work, experimental results of surface flashover of polycrystalline diamond thin films operated in space vacuum conditions are presented. The polycrystalline diamond samples used in the experiments were produced by a microwave plasma CVD deposition technique, and the diamond films were polished to optical quality before the experiments. The electrode material was copper, and a DC voltage was applied between the electrodes. Two copper electrodes were placed on the diamond film surface at a discrete distance from one another. The sample/electrode assembly was placed in a high vacuum chamber and the surface flashover occurred between the electrodes but on the surface of the diamond surface in vacuum. Surface flashover voltage characteristics and breakdown voltage-wave forms of polished diamond thin film samples were determined. These results were compared with the surface flashover characteristics of quartz and optical quality diamond-like carbon (DLC) thin film samples.