Tribological and mechanical properties of diamond-like carbon prepared by high-density plasma

Diamond-like carbon films (DLC) have been deposited by plasma-enhanced chem ical vapor deposition using a commercial r.f. high-density plasma (HDP). Th e hardness and elastic modulus have been determined from force-displacement curves using a nanoindentation instrument. The friction coefficients and w ear rates have been measured using a pin-on-flat tribometer in ambient air and UHV at maximum Hertzian contact pressure of 1.09 GPa. It was found that the hardness, Young's modulus, and wear resistance of the films increased with decreasing hydrogen content of the films. A viscoplastic behavior has been observed for films with hydrogen content higher than 30% indicating th at these films have a softer 'polymer-like' structure. The unbound hydrogen present in the HDP films contributes to the enhancement of the viscoplasti c behavior of the him and to the decrease of the friction in UHV. The corre lation between viscoplastic properties, him structure and tribological beha vior of the HDP films is presented and compared to those obtained with samp les prepared by d.c. PECVD. (C) 2001 Elsevier Science B.V. All rights reser ved.