Effects of bias and inert gas on properties of diamond-like carbon deposited by d.c. PACVD

Diamond-like carbon films were deposited by d.c. plasma-assisted CVD from acetylene or cyclohexane at substrate biases of -400 V to -800 V and pressures of 100 mTorr and 200 mTorr. The films were characterized for index of refraction, IR absorption, hydrogen content, and wear resistance. The thermal stability in vacuum was also characterized. It was found that the properties of the films are dependent on the precursor and the substrate bias. The properties of the films deposited from acetylene are only slightly dependent on the substrate bias and diamond-like properties were obtained for the whole range of investigated bias. In contrast, the properties of the films deposited from cyclohexane are strongly affected by the bias and an absolute bias higher than 500 V was required to obtain diamond-like properties at the used discharge pressures. Dilution of cyclohexane with an inert gas enhanced the diamond-like properties of the films deposited at -400 V and a sufficiently large dilution ( [C6H12] [Ar]= 1 4) produced films having properties similar to those of the films deposited at higher bias. © 1994.