Deposition of nitrogen doped amorphous carbon film using high power impulse magnetron sputtering

A thin film having electrical conductivity and corrosion resistance is required for a separator of a polymer electrolyte fuel cell or an electrode of lithium ion battery. An amorphous carbon (a-C) thin film shows good adhesion to the substrate and high corrosion resistance, and exhibits an electrical conductivity by doping nitrogen. The a-C film deposited by high power impulse magnetron sputtering (HiPIMS) shows high film density and good adhesion due to high plasma density. In this study, the effect of nitrogen doping to a-C film ​​deposited by HiPIMS was investigated.

A negative pulse voltage with a frequency of 400 Hz was applied to the carbon target. The pulse duration was 10 µs and the peak power density was 1.2 kW/cm². The flow rate ratio of N₂ gas to Ar gas was varied from 0 to 20% at the pressure of 0.5 Pa and the total flow rate of 10 sccm.

I_D/I_G ratio, which is due to disorder and graphite band, was evaluated by Raman scattering spectroscopy. I_D/I_G ratio increased and the G peak position shifted to the higher wavenumber with increasing the nitrogen gas flow rate ratio. These results indicate that the incorporation of nitrogen induces an increase and clustering of sp2 bond.