Development of hydrogenated amorphous carbon thin film with high electrical resistance for use in embedded sensors in abrasive environment

In this study, a hydrogenated amorphous carbon (a-C:H) film with a high electrical resistance is developed for use in embedded sensors in an abrasive environment. The a-C:H and a-C:H:Si films were deposited by magnetron sputtering. Graphite targets were sputtered by means of bipolar pulsed-direct current power supply and addition of acetylene, argon, and krypton. The a-C:H:Si films were deposited using graphite targets with small silicon inserts. To optimize the adhesion, a chromium nitride interlayer was deposited prior to the carbon layer. The influence of bias voltage, acetylene flow, deposition pressure, and silicon doping on the electric resistance was investigated. Hardness, hydrogen content, and bonding status of the coating were also determined. It was found that the resistance of the film increases with decreasing negative bias voltage and increasing acetylene flow and deposition pressure. With increasing resistivity of the film, the hardness decreases. This was attributed to higher hydrogen contents in these films. The silicon doping of the films has no significant effect on the electrical resistance.