A Comparison of DLC Films of Single and Multilayer Structure Prepared by the Cathodic Arc and RF Plasma Deposition and Implantation

Single and multilayer Diamond-like carbon films, total thickness approximately 300nm, were deposited on to silicon (100 oriented and 3I2 nm thick) using a plasma ion immersion and impIantation (PIII) process with two different implementations: a) Filtered cathodic arc PVD and b) RF plasma CVD deposition and implantation. The multilayer structure consists of alternatively high and low density of carbon layers, deposited by varying the bias voltage applied to the substrate. In addition, we have obtained DLC compressive stress data as a function of both DC bias up to 3 kV and Pulse bias up to 30 kV for the two methods of deposition.

The motivation for this study was to establish a coating methodology for DLC that yields the highest sp³:sp² ratio consistent with good adhesion strength. Such a coating is expected to be hard but not easily delaminated and would be useful when coated on to steel substrates such as industrial cutting tools, to enhance life performance and cost savings. By means of Raman spectroscopy, TEM, fracture SEM and Rockwell indentation tests, the deposition parameters for the high speed cutting steel coating process were optimized. It was found that the intrinsic stress of carbon was a major factor that influences adhesion and limits thick DLC films. However, the incorporation of a lower stress, graphitic layer or a silicon layer reduces the overall level of intrinsic stress. This paper discusses the mechanical and tribological properties of the singIe and multilayer structure and presents a comparison between the two methods of deposition.