TRIBOLOGICAL PROPERTIES OF DIAMOND-LIKE CARBON-FILMS DEPOSITED BY NEGATIVE CARBON ION-BEAM

Excellent antiwear diamond-like carbon (DLC) films were prepared on si licon wafers by a novel negative carbon ion beam deposition system. Th is system does not need any gas in the chamber; deposition occurs unde r high vacuum. The ion source has good control of the C- beam energy ( from 50 to 150 eV) and produces a 0.5-in.-diam ion beam for. DLC coati ng. All coatings showed ultrasmooth surfaces (Ra similar to 1nm) and g ood adhesion. The results of infrared and Raman spectroscopy show that the degree of diamond-like character in the films, the sp(3) fraction , increases as a function of deposition energy in this particular ener gy range. The nanoindentation hardness of the films also increases fro m 15 to;50 GPa as deposition energy increases. The wear rates and fric tion coefficients against a M-50 steel bearing ball were measured in a pin-on-disk tribometer with a normal load of 9.8 N, calculated nomina l Hertzian stress of 0.8-1.8GPa. The measured wear rates of the DLC fi lms were of the order of 10(-7) and 10(-8) mm(3)/Nm depending on the d eposition energy of the carbon beam. The friction coefficients in the steady state were found to be around 0.1. These results indicate excel lent applications for abrasion resistant DLC coatings. We are developi ng a rectilinear negative carbon ion beam deposition system (up to 8 i n.) for large area application, and many of the process scale-up issue s have been solved. (C) 1998 American Vacuum Society. [S0734-2101(98)0 3406-X].