Study of Ar/N$_{\mathrm{2}}$ microplasma sources for the production of atomic nitrogen for nitride deposition

A ns-pulsed Micro-Hollow Cathode Discharge (MHCD) array reactor running in Ar/N$_{\mathrm{2}}$ has been studied and developed, the objective being the production of high densities of atomic nitrogen for material deposition. MHCDs are a type of microplasmas in which a set of holes of several hundreds of micrometers in diameter is drilled through an electrode-dielectric-electrode sandwich structure. MHCDs generate high electron densities (up to 10$^{\mathrm{16}}$ cm$^{\mathrm{-3}})$, potentially allowing a high dissociation degree of nitrogen molecules, which is particularly suited for nitride deposition. The microplasma reactor is composed of two chambers at different pressure levels, with the MHCD array located at their junction. The high-pressure chamber (50 mbar) favors the production of high-density plasmas and, consequently, the nitrogen dissociation, while the low-pressure chamber (1 mbar) limits the nitrogen recombination. 1 and 7 MHCDs operating in different Ar/N$_{\mathrm{2}}$ gas mixtures have been experimentally characterized by using different diagnostics (electrical measurements, optical emission spectroscopy and fast imaging) to better understand the physics of the discharge. This has been done by varying the repetition frequency rate (10 to 40 kHz) and the Ar to N$_{\mathrm{2}}$ ratio in the gas mixture.