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Publication - Professor Mike Ashfold

    Spatially Resolved Optical Emission and Modelling Studies of Microwave-Activated H2 Plasmas Operating under Conditions Relevant for Diamond Chemical Vapor Deposition

    Citation

    Mahoney, EJD, Truscott, BS, Mushtaq, S, Ashfold, MNR & Mankelevich, YA, 2018, ‘Spatially Resolved Optical Emission and Modelling Studies of Microwave-Activated H2 Plasmas Operating under Conditions Relevant for Diamond Chemical Vapor Deposition’. Journal of Physical Chemistry A, vol 122., pp. 8286-8300

    Abstract

    A microwave (MW) activated hydrogen plasma operating under conditions
    relevant to contemporary diamond chemical vapor deposition reactors has
    been investigated using a combination of experiment and self-consistent
    2-D modeling. The experimental study returns spatially and wavelength
    resolved optical emission spectra of the d → a (Fulcher), G → B, and e →
    a emissions of molecular hydrogen and of the Balmer-α emission of
    atomic hydrogen as functions of pressure, applied MW power, and
    substrate diameter. The modeling contains specific blocks devoted to
    calculating (i) the MW electromagnetic fields (using Maxwell’s
    equations) self-consistently with (ii) the plasma chemistry and electron
    kinetics, (iii) heat and species transfer, and (iv) gas–surface
    interactions. Comparing the experimental and model outputs allows
    characterization of the dominant plasma (and plasma emission) generation
    mechanisms, identifies important coupling reactions between hydrogen
    atoms and molecules (e.g., the quenching of H(n > 2) atoms and electronically excited H2 molecules (H2*) by the alternate ground-state species and H3+ ion formation by the associative ionization reaction of H(n = 2) atoms with H2), and illustrates how spatially resolved H2* (and Hα)
    emission measurements offer a detailed and sensitive probe of the
    hyperthermal component of the electron energy distribution function.

    Full details in the University publications repository