Optical Emission from C2 Anions in Microwave-Activated CH4/H2 Plasmas for Chemical Vapor Deposition of Diamond

Edward J D Mahoney, Benjamin S Truscott, Michael N R Ashfold, Yuri A Mankelevich

Research output: Contribution to journalArticle (Academic Journal)

11 Citations (Scopus)
428 Downloads (Pure)

Abstract

Visible emission from C2(B2Σu+) anions has been identified underlying the much strongerSwan band emission from neutral C2(d3Πg) radicals (henceforth C2* and C2*, respectively) in MW-activated C/H/(Ar) plasmas operating under conditions appropriate for the chemical vapour deposition (CVD) of diamond. Spatially resolved measurements of the C2* and C2* emissions as functions of the C/H/(Ar) ratio in the input gas mixture, the total pressure, and the applied MW power, together with complementary 2-D(r, z) plasma modelling, identifies dissociative electron attachment (DEA) to C2H radicals in the hot plasma as the dominant source of the observed C2* emission. Modelling indicates substantially higher concentrations of C2H anions (from analogous DEA to C2H2) in the near-substrate region, but also suggests that the anion number densities will typically be 3–4 orders of magnitude lower than those of the electrons and partner cations, i.e. mainly C2H2+ and C2H3+. The identification of negatively charged carbon-containing species in diamond CVD plasmas offers a possible rationale for previous reports that nucleation densities and growth rates can be enhanced by applying a positive bias to the substrate.
Original languageEnglish
Pages (from-to)2760−2772
Number of pages13
JournalJournal of Physical Chemistry A
Volume121
Issue number14
Early online date20 Mar 2017
DOIs
Publication statusPublished - 13 Apr 2017

Fingerprint Dive into the research topics of 'Optical Emission from C<sub>2</sub><sup>–</sup> Anions in Microwave-Activated CH<sub>4</sub>/H<sub>2</sub> Plasmas for Chemical Vapor Deposition of Diamond'. Together they form a unique fingerprint.

  • Projects

    Student Theses

    Alternative Excitation Mechanisms Occurring within Microwave-activated Plasmas under Conditions Relevant to the Chemical Vapour Deposition of Diamond

    Author: Mahoney, E. J. D., 1 Oct 2019

    Supervisor: Ashfold, M. (Supervisor) & Western, C. (Supervisor)

    Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

    File

    Datasets

    Cite this