Mechanical properties of DLC films prepared by bipolar pulsed DC PACVD

The most common method for the deposition of DLC films is radio frequency PACVD (rf, 13.56 MHz), which is technically difficult and expensive to scale up to industrial dimensions. Alternative methods are direct current (DC) or medium frequency (mf) plasma excitation which are easier and cheaper to scale up. The deposition of DLC coatings by bipolar-pulsed direct current PACVD (bp DC PACVD) will be discussed. The experiments were carried out in a commercially available plasma nitriding plant. Adhesion was improved by an intermediate Si-C:H layer using tetramethylsilane (Si(CH3)4) as a precursor. Methane (CH4) was used for depositing the DLC films. The mechanical properties of the films such as hardness, Young's modulus, and wear resistance were studied as a function of the process parameters such as bias current, pressure and methane flow and could be correlated to the reduced parameter J/p0.5. The properties thus obtained are comparable with those by rf PACVD.