Field-emission-driven direct current hydrogen discharges in microgaps

This letter contains results of the experimental and theoretical studies of the direct current hydrogen discharges generated between two plane-parallel tungsten electrodes separated from 1 μm to 100 μm. Breakdown voltage curves and volt-ampere characteristics of the discharges are presented and discussed in order to investigate fundamental processes leading to the breakdown in microgaps. Our experimental results are in accordance with the theoretical predictions which state that Townsend phenomenology breaks down when field emission becomes the key mechanism affecting the breakdown and deforming the left-hand side of the breakdown voltage curves. Based on the measured breakdown voltage curves, the dependence of the effective yield on the electric field in microgaps has been determined. Space charge effects are also estimated and distinction between Fowler-Nordheim field emission and space charge limited current density is considered.