Optical Emission from C2− Anions in Microwave-Activated CH4/H2 Plasmas for Chemical Vapour Deposition of Diamondстатья
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Дата последнего поиска статьи во внешних источниках: 23 июня 2017 г.
Аннотация:Visible emission from C2−(B2Σu+) anions has been identified underlying the much stronger Swan 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 vapor 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 modeling, identifies dissociative electron attachment(DEA) to C2H radicals in the hot plasma as the dominant source of
the observed C2−* emission. Modeling not only 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.