Study of the mechanical properties of tetrahedral amorphous carbon films by nanoindentation and nanowear measurements

Nanoindentation and nanowear measurements, along with the associated analys is suitable for the mechanical characterization of tetrahedral amorphous ca rbon (ta-C) films are discussed in this paper. Films of approximately 100-n m thick were deposited on silicon substrates at room temperature in a filte red cathodic vacuum are evaporation system with an improved S-bend filter t hat yields films with high values of mass density (3.2 g/cm(3)) and sp(3) c ontent (84-88%) when operating in a broad bias voltage range (-20 V to - 35 0 V). Nanoindentation measurements were carried out on the films with a Ber kovich diamond indenter applying loads in the 100 muN-2 mN range, leading t o maximum penetration depths between 10 and 60 nm. In this measurement rang e, the ta-C thin-films present a basically elastic behavior with high hardn ess (45 GPa) and high Young's modulus (340 GPa) values. Due to the low thic kness of the films and the shallow penetration depths involved in the measu rement, the substrate influence must be taken into account acid the area fu nction of the indenter should be accurately calibrated for determination of both hardness and Young's modulus. Moreover, nanowear measurements were pe rformed on the films with a sharp diamond tip using multiple scans over an area of 3 mum(2), producing a progressive wear crater with well-defined dep th which shows an increasing linear dependence with the number of scans. Th e wear resistance at nanometric scale is found to be a function of the film hardness. (C) 2001 Elsevier Science B.V. All rights reserved.