High power impulse magnetron sputtering of diamond-like carbon coatings

High power impulse magnetron sputtering (HiPIMS) of diamond-like carbon coatings is reviewed. Three variations of HiPIMS were used to deposit diamond-like carbon coatings: use of neon as compared to argon for sputtering, very high discharge peak current density in an Ar atmosphere, and the use of bursts of short sputtering pulses. All three variations were able to provide sufficient ion-to-neutral ratios to effectively control the coating quality using substrate bias. The resulting coatings are typically smooth, amorphous, hard (up to 25 GPa), and dense but have low stress (below 2.5 GPa). The coatings exhibit an increased stability at higher temperature (up to 500 degrees C) compared to the coatings prepared using standard magnetron sputtering. The resulting coatings also exhibited low wear rates in ambient ball-on-disc tests (2.1 x 10(-8 )mm(3 )N(-1 )m(-1)). These improvements are explained in terms of the rate of sputtered carbon atom ionization in the plasma and material transport to the substrate. However, the chemical bonding in the films is not yet well understood as relatively low sp(3) bond content has been observed.