Microstructure modification of amorphous carbon films by ion-implantation techniques

Abstract

Microstructure modification of amorphous carbon films containing about 30 at.% hydrogen (a-CHx) and nonhydrogenated amorphous carbon (a-C) films was accomplished with a vacuum arc metal plasma implanter and a cathodic arc plasma system, respectively. The films were implanted with Si, Ti, Hf, W, and Al of ion doses approximately equal to 1 and 3 × 1016 ions/cm2 and mean ion kinetic energies in the range of 3–70 keV, depending on the implantation method. Simulation results demonstrated a profound effect of the size of implant species, ion dose, mean ion kinetic energy, and implantation processes on the implant spatial distributions. Statistical roughness results showed a negligible effect of ion implantation on the film surface topography. Elastic recoil spectroscopy revealed a decrease in the hydrogen content of the a-CHx films due to the ion bombardment. A monotonic decrease in the Raman scattering intensities and a downward shift of the carbon peak position occurred with increasing ion dose for both types of films and implantation techniques. Nanoindentation experiments demonstrated an effect of ion implantation on the apparent film hardness, depending on the flux and kinetic energy of implanted species. Changes in the hardness characteristics of the implanted films are interpreted in terms of the chemical reactivity of implant elements and microstructure modifications caused by irradiation damage, dehydrogenation, and higher contents of tetrahedral (s p3) carbon hybridization due to carbide bond formation.