Self-consistent modeling of microwave activated N₂/CH₄/H₂ (and N₂/H₂) plasmas relevant to diamond chemical vapor deposition

Abstract

The growth rate of diamond by chemical vapour deposition (CVD) from microwave (MW) plasma activated CH4/H2 gas mixtures can be significantly enhanced by adding trace quantities of N2 to the process gas mixture. Reasons for this increase remain unclear. The present article reports new, self-consistent two-dimensional modelling of MW activated N2/H2 and N2/CH4/H2 plasmas operating at pressures and powers relevant to contemporary diamond CVD, the results of which are compared and tensioned against available experimental data. The enhanced N/C/H plasma chemical modelling reveals the very limited reactivity of N2 under typical processing conditions and the dominance of N atoms amongst the dilute ‘soup’ of potentially reactive N-containing species incident on the growing diamond surface. Ways in which these various N-containing species may enhance growth rates are also discussed.

Diaphite: diamond-graphene hybrid nanostructures grown in CH4/H2/N2 chemistry

“…This underscores the importance of the interconversion of radicals and their diffusion onto the growing diamond surface, as it significantly impacts the activation barrier for the transition from graphite to diamond and the quality of the resulting diamond formation. It is important to note that plasma chemistry involving nitrogen, carbon, and hydrogen encompasses a total of 535 possible reactions 50 . The introduction of low levels of nitrogen in the plasma-assisted growth reaction promotes the growth of small islands that act as active sites for the diffusion of CH 2 groups, eventually migrating to the diamond surface, resulting in a higher growth rate 25,[51][52][53] .…”

Fast, Efficient Tailoring Growth of Nanocrystalline Diamond Films by Fine-Tuning of Gas-Phase Composition Using Microwave Plasma Chemical Vapor Deposition

“…On the other hand, in present case, the addition of a small amount of N 2 and O 2 into the gas phase may result in the creation of more minor species such as CN, CO, N, O, NO, NH, and OH, which are also participating in the diamond growing process and competing with the major growth species, namely CHx (x = 1,2,3) radicals [ 43 , 44 , 45 ], and thus can drastically influence diamond growth. However, so far, we could not answer the following questions: how are these minor species involved in the growth process, and why MCD grows instead of NCD when the amount of O 2 exceeds that of N 2 up to a critical point?…”