A. Jelenak et al., THE INFLUENCE OF EXCITED-STATES ON THE KINETICS OF EXCITATION AND DISSOCIATION IN GAS-MIXTURES CONTAINING METHANE, DIAMOND AND RELATED MATERIALS, 4(9), 1995, pp. 1103-1112
In this paper, we extend the calculations for rare gas discharges, whi
ch aim to establish the influence of excited states on the kinetics of
electron-induced excitation, to rare gas-methane mixtures and pure me
thane which are often used in diamond-like film deposition. In particu
lar, we address the effect of non-thermal vibrational populations on t
he rate coefficients in methane-containing gas discharges using the pr
ocedure applied previously for pure silane. Furthermore, we investigat
e the kinetics of electronically excited levels of rare gases and meth
ane in the presence of a significant population of excited states. The
se states may contribute to the overall ionization, excitation and dis
sociation rates through stepwise processes, superelastic collisions an
d energy transfer processes. The influence of superelastic processes o
n the development of the negative differential conductivity (NDC) is d
iscussed on the basis of the momentum transfer theory, and it is shown
that the NDC is reduced when significant populations of excited state
s are present. This is of importance for calculations of the transport
coefficients for a.c. electric fields where NDC leads to a complex te
mporal dependence of the drift velocity and thus directly affects the
power deposition in the discharge. Finally, we present the rate and tr
ansport coefficients calculated for methane in r.f, fields based on th
e Monte Carlo simulation for time-dependent fields. A good agreement w
ith the effective field approximation and earlier Boltzmann calculatio
ns is found.