Surface Processes Occurring during Breakdown of High-Voltage Devices

In order to understand the breakdown phenomena on insulators, we create in the amorphous SiO2 sample a permanent localized charge which is either negative (implanted electrons) by electron bombardment, or positive (implanted holes), by bombardment with helium metastable atoms and photons. The implanted negative charge is destroyed when another part of the sample is bombarded. This remote neutralization of the charge is tentatively explained in the frame of electronic structure of SiO2: holes and electrons could recombine through the localized levels in the forbidden band gap after a conduction mechanism in the glass. The surface breakdown could hence be explained as a band effect rather than an electron produced by an electron source on the cathode in the vacuum region.