Preparation and properties of W-containing diamond-like carbon films by magnetron plasma source ion implantation

Abstract

W-containing diamond-like carbon (DLC) films were prepared on silicon wafers by a process combining reactive magnetron sputtering with plasma source ion implantation (PSII). A tungsten disc was used as a target for the sputter source. Ar/C 2H 2 mixed gas was introduced into the discharge chamber. Superposed negative high voltage pulses (− 10 kV, 100 Hz, 100 μs and DC − 0.5 kV) were applied to the substrate holder. The chemical composition of the films was determined using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Surface morphology was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The film structure was characterized by Raman spectroscopy, X-ray diffractometry and high resolution transmission electron microscopy (HREM). Sheet resistivity of the films was measured by a four-point probe method. Furthermore, a ball-on-disc test was employed to obtain information about the frictional properties and sliding wear resistance of the films. The structure of the films changed from metal-containing DLC to a composite of metal-containing DLC and metal carbides with increasing metal content in the films. WC 1− X carbides were observed for films composed of higher amounts of W than 20 at.%. Around 10 nm diameter nanocrystallites of WC 1− X were observed by HREM. The sheet resistivity of the films decreased drastically with increasing metal content in the films. The tribological properties of the films were improved by metal element doping. A low friction coefficient 0.09 was derived for 0.5 at.% W-containing DLC film.