Ion Beam Assisted Deposition of Si-Diamond-Like Carbon Coatings on Large Area Substrates

Hard, low-friction silicon-containing diamond-like carbon coatings (Si-DLC), were formed by Ar+ ion beam assisted deposition (IBAD), on 5 in. diameter silicon wafers. The diffusion pump oil precursor (tetraphenyl-tetramethyl-trisiloxane: (C6H5)4(CH3)4Si3O2) was evaporated through seven, 3 mm diameter, closely packed apertures (multinozzle/multi-aperture container) arranged in a hexagonal pattern, approximately 5 mm apart according to mathematical model [1[ developed at ARL describing the spatial distribution of film deposition from nozzles and apertures onto inclined substrates.The ion energy was kept at 40 keV whereas the ion current density and the oil evaporation temperature were varied to produce hard, lubricious and adherent films. The multinozzle array allowed the relatively uniform (± 20%) coverage of the entire 5 in. substrate. The thickness and the microhardness of the films were measured along the rectilinear surface coordinates of the substrate area. Depending on the deposition parameters the standard deviation of the coating thicknesses and Knoop micro-hardness varied from 14 to 30 percent respectively over the substrate. This is a significant improvement from the previously used single nozzle set up where the standard deviation of the coating thickness was 50 to 100 percent for 2 in. diameter substrates. The Knoop microhardness and the sliding friction coefficient of these coatings ranged from 10,000 to 20,000 MPa and 0.04 to 0.2 respectively. These values are in agreement with our previously reported single nozzle results [2].