The formation and properties of diamond-like carbon (DLC) films prepared on silicon substrates at room temperature, using C2H2-Ar plasma immersion ion processing, are investigated with respect to him deposition parameters. Decreases in the reactive gas-flow ratios of C2H2 to Ar(F-C2H2/F-Ar) or the gas pressure were found to decrease the hydrogen content, increase the density and hardness, and improve the surface finish of the DLC films, all of which led to enhanced tribological properties. Decreasing the friction coefficient requires increasing the hardness of the film and smoothing its surface, whereas increasing the wear resistance correlates with reducing both the hydrogen content and residual stress in DLC films. High hardness and optimum tribological properties were reached as the growth of DLC films was subjected to low-energy ion impingement, which was induced by a - 150 V pulsed bias from the C2H2-Ar plasma produced at low reactive gas pressures with low F-C2H2/F-Ar ratios. [S0734-2101(99)02305-2].