A comparison of Mo films bias sputtered in Ar/N₂ with related high energy ion implantation experiments

Mo films were prepared by bias sputtering in a dc-triode system using an Ar/N2 mixture as sputter gas. The substrates were held at -180°C. The resulting changes of the residual resistivity ρ0 and transition temperature to superconductivity Tc were measured as a function of the nitrogen concentration within the films cN. Large Tc increases up to 7.6 K have been found for highly disordered films (ρ0=100 μΩ cm, cN =10 at. %). For still higher cN values, Tc decreased to about 5 K, while the resistivity increased up to 500 μΩ cm, exhibiting a negative temperature dependence typical for amorphous materials. Our results will be compared to an implantation experiment, where N+ ions have been implanted into preexisting Mo films.