Synthesis of diamondlike carbon films with superlow friction and wear properties

In this study, we introduce a new diamondlike carbon (DLC) film providing a friction coefficient of 0.001 and wear rates of 10(-9)-10(-10) mm(3)/N m i n inert-gas environments (e.g., dry nitrogen and argon). The him was grown on steel and sapphire substrates in a plasma enhanced chemical vapor deposi tion system that uses a hydrogen-rich plasma. Employing a combination of su rface and structure analytical techniques, we explored the structural chemi stry of the resultant DLC films and correlated these findings with the fric tion and wear mechanisms of the films. The results of tribological tests un der a 10 N load (creating initial peak Hertz pressures of 1 and 2.2 GPa on steel and sapphire test pairs, respectively) and at 0.2 to 0.5 m/s sliding velocities indicated that a close correlation exists between the friction a nd wear coefficients of DLC films and the source gas chemistry. Specificall y, films grown in source gases with higher hydrogen-to-carbon ratios had th e lowest friction coefficients and the highest wear resistance. The lowest friction coefficient (0.001) was achieved with a film on sapphire substrate s produced in a gas discharge plasma consisting of 25% methane and 75% hydr ogen. (C) 2000 American Vacuum Society. [S0734-2101(00)14204-6].