Diagnostics and modelling of hollow cathode arc plasma used for deposition of metal–carbon films

Abstract

In the present study a characterisation is presented of a hollow LaB₆ cathode arc plasma used for the deposition of graded Me–a-C:H layer systems. An argon–methane plasma (flowrates 150 and 10 smL min ^–1 respectively) with a power of about 1 k Wand a pressure of 1 Pa is analysed. A numerical model for calculating spatially resolved density profiles is achieved by solving the diffusion equations with a continuum regime approach using a control volume method. It appears that in a plasma without magnetic confinement the densities of the most relevant CH₄⁺ and CH₃⁺ species are of the order of 10⁹ cm^–3. From these densities expected deposition rates of the order of 500–1000 nm h^–1 are calculated. Langmuir probe measurements, energy resolved mass spectroscopy, and deposition trials have been performed experimentally. Electron densities were of the order of 10¹¹ cm^–3 and temperatures were 5–8 eV. Mass spectra also indicate CH₃⁺ as the predominant hydrocarbon ion in the deposition plasma. Both densities and growth rates are shown to be of the same order as the calculated values.