N2-H2 capacitively coupled radio-frequency discharges at low pressure. Part II. Modelling results: the relevance of plasma-surface interaction

TL;DR

This study models low-pressure N2-H2 RF discharges, emphasizing the critical role of plasma-surface interactions, especially surface ammonia production, in influencing discharge chemistry and electrical properties.

Contribution

It introduces a hybrid simulation approach that integrates plasma dynamics with detailed surface chemistry, highlighting the importance of plasma-surface interactions in low-pressure discharges.

Findings

Surface ammonia production significantly affects discharge chemistry.

Secondary electron emission impacts electrical parameters.

Plasma-surface interactions are crucial at low pressures.

Abstract

In this work, we present the results of simulations carried out for N2-H2 capacitively coupled radio-frequency discharges, running at low pressure (0.3-0.9 mbar), low power (5-20 W), and for amounts of H2 up to 5 pct. Simulations are performed using a hybrid code that couples a two-dimensional time-dependent fluid module, describing the dynamics of the charged particles in the discharge, to a zero-dimensional kinetic module, that solves the Boltzmann equation and describes the production and destruction of neutral species. The model accounts for the production of several vibrationally and electronic excited states, and contains a detailed surface chemistry that includes recombination processes and the production of NHx molecules. The results obtained highlight the relevance of the interactions between plasma and surface, given the role of the secondary electron emission in the electrical parameters of the discharge and the critical importance of the surface production of ammonia to the neutral and ionic chemistry of the discharge.