Surface breakdown characteristics of polycrystalline diamond thinfilms in vacuum

摘要

Design and development of high voltage devices operated in vacuumenvironment requires a sound understanding of surface flashoverphenomena across solid insulators supporting the “highvoltage” electrodes. It is widely accepted that the surfaceflashover phenomenon is due to the field emission of electrons at thecathode “triple junction” (electrode/insulator/vacuuminterface) when the applied field exceeds some threshold value. Besidethe main cause of the surface breakdown, other contributing factors maybe listed as (1) surface condition of the dielectric (2) type ofdielectric material, (3) material type and surface condition ofelectrodes and (4) the operating environment. In this work we willpresent experimental results of surface flashover characteristics ofpolycrystalline diamond and other dielectric thin films as well as bulkdielectric materials in vacuum. We have concentrated our investigationson the effects of outgassing species from the dielectric material on thesurface flashover phenomena. Mass spectroscopy techniques are employedto determine the outgassing species before and after the surfaceflashover, and the effects of these species on the initiation of thebreakdown