Structural and mechanical properties of amorphous-carbon films produced by high-fluence metallic ion implantation into polyimide

Metal-doped amorphous-carbon layers were fabricated by high-dose tungsten ion implantation into polyimide (C22H10N2O5) films, and the chemical states, structure and friction properties were investigated. The tungsten ion implantation was performed with an acceleration voltage of 70 kV using a MEVVA-type ion implanter. The dose of the implantation ranged from 1×1015 to 5×1017 cm−2. The X-ray photoelectron spectroscopy (XPS) study showed the formation of WC bonds in the implanted layer and tungsten atoms exposed on the surface due to sputtering, along with the formation of WO bonds in the specimen implanted at 5×1017 cm−2. The cross-sectional transmission electron spectroscopy (TEM) observation shows neither metallic particles nor domains of compounds formed in the specimens implanted with tungsten ions. The friction coefficient measurement with a pin-on-disk tribometer at an applied load of 5 N under atmospheric room temperature showed a large effect due to tungsten implantation. The friction coefficient decreased with an increase in fluence, the minimum value being 0.14 for a specimen implanted at 1×1016 cm−2. In this specimen, the wear volume was also minimized.