Superconductivity of thin films lead, indium, and thin prepared in the presence of oxygen

We have studied the influence of oxygen on the superconducting properties of thin films of lead, indium, and tin deposited on glass or sapphire substrates. In addition, the morphological microstructure was investigated by scanning electron microscopy. The film thickness was 1.0 μm, and the partial pressure of O2 during the film deposition was raised up to 1 x 10-4 Torr. In all three materials the development of a granular structure and a strong increase in the residual electric resistivity was observed due to the O2-treatment. Whereas in the Pb films no change of the critical temperature was found, the In films deposited on glass substrates showed a slight increase of Tsub(c) due to the oxygen. The strongest increase of Tsub(c) (up to 8%) was observed in the O2-treated Sn films. These results are discussed in terms of the McMillan theory. From our measurements of the critical current density jsub(c) we conclude that edge pinning is dominant in the undoped films. All three materials showed a strong increase of jsub(c) due to the O2-treatment which must be interpreted in terms of bulk pinning. (orig.)