Structure and tribo-mechanical properties of Si- and W-containing amorphous carbon based multilayers
Wolfgang Tillmann, Nelson Filipe Lopes Dias, Dominic Stangier, Serguei Matveev, Carl Arne Thomann, J. Debus
Abstract
Designing the film architecture of amorphous carbon based systems is effective in tailoring the tribo-mechanical properties. For this purpose, alternating a-C and a-C:X layers, with X = Si or W, were grown with a layer ratio of 1, a bilayer period of ~200 nm, and a bilayers number of 5 in a magnetron sputtering process. By comparing with a-C(:X) monolayers, the structure and tribo-mechanical properties of alternating a-C/a-C:X films were evaluated. Although the bonding state of the a-C network of a-C:X in a-C/a-C:X is comparable to monolayered a-C:X, the multilayer design significantly affects the tribo-mechanical properties. The a-C/a-C:X multilayers exhibit a higher hardness compared to a-C:X. With a coefficient of friction of 0.12 ± 0.01, a-C/a-C:Si shows a low friction as a-C:Si with 0.09 ± 0.01, but the wear rate is significantly lower for a-C/a-C:Si with (3.4 ± 0.7) × 10-7 mm³/Nm than a-C:Si with (8.3 ± 1.0) × 10-7 mm³/Nm. Contrarily, a-C/a-C:W and a-C:W provide similar wear rates of 1.2 to 1.4 × 10-7 mm³/Nm, but the coefficient of friction is lower for a-C/a-C:W with 0.29 ± 0.02 than a-C:W with 0.36 ± 0.01. Hence, the multilayer design is efficient in improving the tribo-mechanical properties of a-C:X based films.