ESR Study on Diamond-Like Carbon Thin Films Prepared by r.f. Plasma Pulsed Deposition Method

Abstract

Diamond-like carbon (DLC) thin films were deposited by the plasma CVD method in which the substrate electrode was powered by radio frequency (13.56MHz). The deposition temperature was controlled by the “plasma pulsed deposition technique”: repeated cycles of alternating 5s deposition with 3min cooling. The deposited DLC films were studied using Electron Spin Resonance (ESR) to determine the influence of both deposition and post-deposition annealing conditions. ESR spectral variations obtained in this study with spin density and linewidth are consistent with the microstructural changes observed during work reported previously, in which the film deposition conditions and the effect of post-deposition DLC film annealing were examined. When the films were deposited using more than 100W r.f. power, further progress of carbon radical reaction was observed with increase in deposition temperature. When the films were annealed, an increase in the film hardness was observed when the annealing temperature was held below about 300°C, as reported previously. The ESR study supports the hypothesis that carbon radicals remaining in the DLC films react with each other to further increase the densication of the film structural network. When the films were annealed at temperatures >300°C, the film structure was deteriorated by oxidation reactions. The ESR spectral variations obtained during annealing procedures are consistent with these conclusions. Furthermore, variations in the linewidth in ESR spectra have been discussed mainly in terms of exchange narrowing related to microstructural changes of the DLC films.