INFLUENCE OF SURFACE QUALITY ON TUNNELING AND ELECTRICAL-PROPERTIES OF NDCECUO THIN-FILMS

Thin films of Nd1.85Ce.15CuO4-y were prepared by laser ablation on heated SrTiO3 substrates in 150 mTorr o2. After deposition, the films were annealed in vacuum at 820C. This step is necessary in order to achieve bulk superconductivity in the samples, but has a deleterious influence on their surface properties. Tunneling characteristics measured on such samples show very broad features, making a determination of the gap very difficult. A very high contact resistance resulted in difficulties with Hall and magnetoresistance measurements. To remedy these problems, we studied the influence of different etches and surface treatments. The contact resistance and the tunneling characteristics are used to evalueate the merits of these different methods.