Structure and optical properties of diamondlike carbon synthesized by plasma immersion ion processing

Hard and transparent diamondlike carbon (DLC) films have been prepared on room-temperature substrates by using a C2H2-Ar plasma immersion ion processing (PIIP) method. The optical properties of the DLC films with different thicknesses deposited on PMMA (polymethyl methacrylate), silicon wafers, and glass plates were systematically examined. It was found that careful control of substrate bias voltage was needed for favorable growth of DLC films with low atomic hydrogen content, high hardness and wear resistance, and excellent optical properties. The resultant DLC films exhibited a low friction coefficient, high optical gap energy, and very high optical transmittance both in infrared and visible light ranges. The study confirmed that C2H2-Ar PIIP with low negative bias voltages and suitable C2H2/Ar gas ratios can produce optically transparent and hard DLC films on optical materials.