Diamond like carbon films deposited from graphite target by asymmetric bipolar pulsed-DC magnetron sputtering

Diamond like carbon (DLC) thin films have been deposited at room temperature from a graphite target by asymmetric bipolar pulsed-DC reactive magnetron sputtering. DC bias was applied to the substrate holder between 0 and − 300 V. Pulsed-DC power density and pressure were fixed at 4.4 W/cm 2 and 1.3 Pa. Pulse frequency was kept constant at 150 kHz. The results have been discussed in terms of the effects induced by substrate bias voltage. Pulsed-DC power increases the ionization of the plasma compared to processes using RF power. The conditions during the process can be described by a higher ion and electron density, the existence of more energetic species and an intense ion bombardment of substrate during the negative pulse. The substrate bias voltage induces considerable effects on deposition rate, intrinsic compressive stress and abrasive wear of the films, but it has no appreciable effect on the surface water contact angle of DLC films. Intrinsic compressive stress is limited by the carbon surface ion implantation, which in turn is controlled by the bias voltage applied to the substrate. The Davis model fitting indicates an increase in the averaged growth rate to ion flux ratio which could justify the decrease of compressive stress of the studied samples.