Disorder control of Tc in thin film molybdenum

We have looked at the dependence of the superconducting transition temperature on the deposition parameters of magnetron sputtered Mo on Si3N4 coated Si substrates. From the measurements we can conclude that impurity inclusion/disorder and strain have an influence on the transition temperature, where under certain conditions a transition temperature as high as 2.4 K could be reached. This is significantly above the 900 mK measured for bulk Mo. The impurity content and strain in the film are influenced by the deposition rate, substrate bias, working gas pressure, substrate structure and system pre-conditioning. A model based on the change of the Coulomb interaction potential due to defect/disorder generation, without a significant change in the density of states, was shown to best explain the results observed.