Breakdown mechanism in hydrogen microdischarges from direct-current to 13.56 MHz

Abstract

This paper contains the results of experimental studies of the breakdown phenomena in hydrogen microdischarges from direct current to very high radio frequencies. Measurements were performed for two types of electrode configurations, glass melting electrodes and electrodes with Bruce profiles, by varying the gap size from to , with the pressure ranging between and . The breakdown voltage curves and waveforms of the discharge voltage and current are presented and discussed. In the low-frequency region, the breakdown voltage values are comparable to the dc breakdown voltage data. The breakdown voltages recorded for high frequencies are similar to and lower than those obtained for the low-frequency region. For the gap size of , the breakdown voltage does not depend on the frequency since the strong electric field formed in microgaps overcomes the electron work function, enhancing secondary-electron production. The current-generating mechanism before breakdown is field emission, as verified by a linear Fowler–Nordheim plot with a negative slope. With increasing gap size, the breakdown voltage increases since the contribution of the field emission is progressively reduced. The breakdown voltages that correspond to the glass melting electrodes are lower since such electrodes have edge issues and an inability to achieve a homogeneous field, unlike electrodes with Bruce profiles. The results presented here could be useful both for a better understanding of the non-equilibrium processes which occur in radio-frequency microdischarges during breakdown and for determining the minimum ignition voltages in microplasma sources as well as the maximum safe operating voltage and critical dimensions in other microdevices.