Impact of bias on the graphite-like carbon films grown by high power impulse magnetron sputtering

The graphite-like carbon (GLC) films were deposited by high power impulse magnetron sputtering (HPPMS) on Si substrates. The impacts of the synthesis conditions, such as the substrate bias, ion energy and pressure, on the properties of the GLC films were evaluated. The GLC films were characterized with X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM), and conventional mechanical probes. The results show that the substrate bias voltage strongly affects the microstructures and mechanical properties. For instance, as the bias increased, the surface became increasingly smooth, accompanied by an increased hardness and internal compressive stress; the sp2 density changed in a decrease-increase mode, minimized at -100 V. at -300 V, the GLC films display excellent tribological performance, possibly because of the increased sp2 density and surface hardness, and a decreased surface roughness.