Crystal structure of carbon-implanted Group 4 transition metals

The dose dependence of the crystal structures and lattice parameters of carbon-implanted titanium, zirconium and hafnium has been investigated by X-ray diffraction (XRD) measurements. Implantations of C-12(+)-ions were performed at doses between 1 x 10(17) and 1.5 x 10(18) ions cm(-2) at 100 keV. The beam current density was limited to around 10 mu A cm(-2) and the specimen was mounted on a water-cooled holder. XRD patterns showed that only one carbide phase with the B1 (NaCl) type structure was characterized for all metals over the whole implant dose range, and its lattice parameter was mostly in agreement with that of monocarbide at doses over 1 x 10(18) ions cm(-2). A solid solution was observed at doses less than 5 x 10(17) ions cm(-2). For zirconium and hafnium, the crystallized Cl (CaF2) type oxide other than the B1-type carbide and solid solution was found. These results will be discussed from the viewpoint of composition and crystal structure.