Implantation and diffusion of carbon into niobium carbide single crystals

Single crystals of NbCsub(0.89) with a superconducting transition temperature Tsub(c) of 3.7 K were implanted with carbon ions and subsequently annealed at high temperatures. After annealing between 1000 and 11000C a maximum Tsub(c) of 11.5 K was obtained. Diffused samples were produced by evaporation of carbon layers onto NbCsub(0.89) single crystals followed by a high temperature treatment. In the diffusion experiments a maximum Tsub(c) of 11.1 K was obtained with a diffusion temperature of 14500C. The difference in the maximum Tsub(c) values between the implanted and the diffused samples is shown to be due to a carbon content closer to stoichiometry in the implanted samples. (author)