Tribological properties of bias voltage modulated a-C:H nanoscaled multilayers

Abstract

Nanoscaled multilayer coatings consisting of alternating layers of hard and soft amorphous hydrogenated carbon (a-C:H) films have been deposited by modulation of the substrate bias voltage in a plasma activated chemical vapor deposition (PACVD) process. Alternating hard/ soft a-C:H nanolayers is a model system to investigate the correlation of the different layers and interfaces with the final tribological and mechanical properties. The substrate bias voltage determines the ratio of sp 2/sp 2 bonded carbon, the internal stress and the hydrogen content in the different a-C:H layers, all of which contribute to the mechanical properties. Different bias voltage functions (sinusoidal, triangular, rectangular, etc.) were used to obtain soft, graded or sharp interfaces between the layers. The mechanical and tribological behavior of the multilayer structures have been characterized by tribological tests.