The effect of carbon ion implantation on the nucleation of diamond on Ti-6Al-4V alloy

Abstract

The heterogeneous nucleation of diamond particles during the early stages of diamond film formation on non-diamond substrates is not well understood. In this work, we used ion implantation as a pretreatment process, to control the nucleation of diamond particles. The well known surgical alloy Ti-6Al-4V (“mirror” polished) was used as the substrate. Carbon ions at 30 keV energy were implanted at room temperature into masked regions on the samples, up to doses of 1×10 16-7×1 17 ions cm -2. At the high doses, carbon concentrations up to 80 at.% were generated as shown by Rutherford backscattering spectrometry (RBS). After ion implantation, diamond depositions were conducted at MRL utilizing a Toshiba microwave chemical vapour deposition (CVD) system. Operating conditions were 12 kPa total system pressure, 1% methane in hydrogen at a total flow of 100 standard cm 3 min -1, substrate temperature of 1000 °C, deposition time 5 h. The deposited films were studied by scanning electron microscopy, microfocus Raman scattering and RBS. The results indicate (a) a reduction in nucleation density up to 8 times with increasing ion dose, (b) near perfect diamond particles (Raman scattering) and (c) large internal stresses leading to partial flaking when the film becomes continuous. The role of a possible “carbided layer” formed by ion implantation is discussed.