Microstructure and wear resistance of doped diamondlike carbon prepared by pulsed laser deposition

We have investigated the microstructure and tribological properties (wear resistance) of diamondlike carbon (DLC), DLC doped with Cu and DLC doped with Ti deposited by a sequential pulsed laser ablation of two targets onto Si(100) substrates. The composition of these films was determined by Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy(XPS). Raman spectroscopy and detailed analysis of the electron diffraction pattern of the films showed typical features of DLC with a structure dominated by sp(3) bonded carbon. Wear resistance measurements made on these samples by means of the "crater grinding method" showed that DLC + 2.75%Ti has the highest wear resistance, while that of undoped DLC has the lowest among the samples. The improvement of wear behavior of the doped films was attributed to the reduction of internal compressive stress due to the presence of more compliant atoms, as indicated by the G-peak position shift to smaller Raman shift. The XPS studies showed the evidence for the formation of TiC bonding in the Ti doped films. Thus we expect metal-doped DLC coatings can have better tribological properties than the undoped, highly stressed DLC coatings.