Comparison of carbon films between dc glow discharge and dc magnetron sputtering processes

Abstract

Diamondlike hard carbon coatings were deposited on germanium in a dc plasma discharge vacuum chamber using a hydrogenated hexane fluid. Vapors from the hexane fluid were mixed with argon gases, keeping a 0.1-molar ratio of hexane to argon ions. The dc cathode voltage of 1.0 kV and the gas pressure of 50–100 mTorr were maintained for 30 min for the hard carbon coatings. The deposition process was reproducible and accurately controlled by the two independent parameters: dc cathode voltage V and gas pressure P. On the other hand, amorphous hard carbon films were prepared by dc plasma magnetron sputtering of a graphite target in ultrapure argon gas at a pressure of 5-10 mTorr at a substrate temperature of 100°C. The dc power range was 300-500 W. Both techniques of deposition of carbon films show extreme hardness, chemical inertness, high electrical resistivity, and optical transparency in the IR 8-12-μm region. The carbon films generated with the dc plasma of hydrocarbon gases result in high transmittance values compared with those of films generated by dc magnetron sputtering of graphite targets.