Statistical study of dc breakdown in a nanometer electrode gap and evidence of elementary mechanisms

Breakdown in Argon at nanoscale interelectrode gaps is studied to highlight the deviation from Paschen's law prediction. The discharge occurs between gold-plated electrodes in a setup similar to a planar configuration. A fast cutoff system allows the measurement of up to one hundred breakdowns for each experimental condition. A statistical study is then conducted on the probability distribution of breakdown voltages. The presence of two peaks in the breakdown distribution shows a competition between two different elementary discharge processes. One of it always occurs around a field value of 7.7×10^{8}V/m and does not seem to be affected by the pressure: this is the field emission breakdown mechanism. The other pressure-dependent mechanism is present only when the electrode gap is sufficiently large: this is the Townsend avalanche breakdown mechanism. The statistical method introduced in this work allows for a better interpretation of the processes involved in breakdown in submicrometer interelectrode spaces.