Pulsed voltage pre-breakdown observations on silicon in vacuum

The flashover process consists of three phases: phase i is characterized by the presence of displacement, ohmic, or space-charge-limited (SCL) current; phase ii represents partial collapse in the applied voltage accompanied by luminosity and an increase in current; and phase iii, or flashover, consists of complete voltage collapse, rapid rise in current, and intense luminosity. The existence of low-level emission in the ultraviolet-visible range during phase i in the presence of well-established SCL current is shown. The luminosity exhibits an increase in intensity just prior to the initiation of phase ii, thus indicating the onset of device failure as evidenced by partial voltage collapse. The inception voltage for phase i luminosity shows a correlation with the onset of phase ii and iii processes, but no correlation with the conditioned flashover voltage is observed. Sample preparation can significantly increase the luminosity inception voltage