Cross-comparison of diagnostic and 0D modeling of a micro-hollow cathode discharge in the stationary regime in an Ar/N2 gas mixture

A micro-hollow cathode discharge (MHCD) operated in Ar/N-2 gas mixture, working in the normal regime, was studied both experimentally and with a 0D (volume-averaged) model in this work. This source provides high electron densities (up to 10(15) cm(-3)) at low injected power (1 W). To understand the mechanisms leading to the production of N atoms, the densities of electrons, N atoms and argon metastable atoms (Ar*) were monitored over a wide range of experimental conditions. Electrons, N atoms and Ar* densities were probed by means of optical emission spectroscopy, vacuum ultra violet Fourier transform spectroscopy and tunable diode laser absorption spectroscopy, respectively. Measurements showed that using a smaller hole diameter enables to work with less injected power, while increasing the power density inside the hole and, subsequently, increasing the densities of excited species. Varying the percentage of N-2 in the gas mixture highlighted that, up to 80%, the density of N atoms increases although the dissociation rate drops. Looking at the processes involved in the production of N atoms with the help of the 0D model, we found that at very low N-2 fraction, N atoms are mostly produced through dissociative electron-ion recombination. However, adding more N-2 decreases drastically the electron density. The density of N atoms does not drop thanks to the contribution of Ar* atoms, which are the main species dissociating N-2 between 5% and 55% of N-2 in the gas mixture. A reasonable agreement is found between the experiments and the model results. This study shows that, with this MHCD, it is possible to significantly modify the production of N atoms when modifying the physical parameters, making it particularly relevant for applications requiring a N atoms source, such as nitride deposition.

Automated summary

This study investigates the micro-hollow cathode discharge operated in Ar/N-2 gas mixture and provides insights into the mechanisms and control of N atom production. The results show that the physical parameters, such as hole diameter and N-2 percentage, greatly affect the density of N atoms.