Effect of negative rf bias on electrophotographic properties of hard diamond-like carbon films deposited on organic photoconductors

Hard diamond-like carbon (DLC) films were prepared on organic photoconductor (OPC) and PMMA (polymethyl methacrylate) samples by electron cyclotron resonance (ECR) CH4-Ar plasma deposition with low substrate bias. The films exhibited a specific electrical resistivity above 1 x 10(14) Omega cm and very high transmittance for the visible spectrum of 370-800 nm. The hardness of the OPC samples was increased at least fourfold after deposition of DLC films. The acceptance voltage, photodischarge rate and dark decay rate of the DLC-coated OPC samples were all improved, and reached optimal values for rf biases around -90 V. The results indicated that the deposition of hard DLC films on OPC is a very promising technique to lengthen the working lifetimes of the OPC materials.