Effect of substrate bias on microstructure and tribological performance of GLC films using hybrid HIPIMS technique

The Cr-doped hydrogen-GLC films were prepared by a hybrid magnetron sputtering system composed of a direct current magnetron sputtering (DC-MS) source of carbon and a high power impulse magnetron sputtering (HIPIMS) source of Cr with reactive gas of C2H2. The hydrogen-free GLC and Cr-doped GLC films were also prepared for comparison. The influence of substrate bias on the Cr-doped hydrogen-GLC films was investigated. With the increase of substrate bias from −100 V to −250 V, the re-sputtering of weak bonding sp2 firstly occurred and induced an increased sp3 bonding. However, the following sp3 to sp2 transformation resulted in a decreased sp3 bonding. The change trends of surface roughness and friction coefficient with the increased bias voltages were the same as those of sp3 bond. The lowest surface roughness and lowest friction coefficient corresponded to the highest sp3 with the Cr-GLC-H films at the bias voltage of −100 V.