Microwave Plasma-Activated Chemical Vapor Deposition of Nitrogen-Doped Diamond. I. N2/H2 and NH3/H2 Plasmas

Ben S Truscott, Mark W Kelly, Katie J Potter, MacK H Johnson, Michael N R Ashfold*, Yuri A Mankelevich

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

16 Citations (Scopus)
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Abstract

We report a combined experimental/modeling study of microwave activated dilute N2/H2 and NH3/H2 plasmas as a precursor to diagnosis of the CH4/N2/H2 plasmas used for the chemical vapor deposition (CVD) of N-doped diamond. Absolute column densities of H(n = 2) atoms and NH(X3Σ, v = 0) radicals have been determined by cavity ring down spectroscopy, as a function of height (z) above a molybdenum substrate and of the plasma process conditions, i.e., total gas pressure p, input power P, and the nitrogen/hydrogen atom ratio in the source gas. Optical emission spectroscopy has been used to investigate variations in the relative number densities of H(n = 3) atoms, NH(A3Π) radicals, and N2(C3Πu) molecules as functions of the same process conditions. These experimental data are complemented by 2-D (r, z) coupled kinetic and transport modeling for the same process conditions, which consider variations in both the overall chemistry and plasma parameters, including the electron (Te) and gas (T) temperatures, the electron density (ne), and the plasma power density (Q). Comparisons between experiment and theory allow refinement of prior understanding of N/H plasma-chemical reactivity, and its variation with process conditions and with location within the CVD reactor, and serve to highlight the essential role of metastable N2(A3Σ+u) molecules (formed by electron impact excitation) and their hitherto underappreciated reactivity with H atoms, in converting N2 process gas into reactive NHx (x = 0–3) radical species.
Original languageEnglish
Pages (from-to)12962-12976
Number of pages15
JournalJournal of Physical Chemistry A
Volume119
Issue number52
Early online date23 Nov 2015
DOIs
Publication statusPublished - 31 Dec 2015

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