ELECTRICAL-PROPERTIES OF THE INTERFACE BETWEEN YBA2CU3OX FILMS AND VARIOUS SUBSTRATES

The electrical properties of the interfacial layers between YBCO films and various substrates were studied using in situ resistivity measurements. It was found that this method is sensitive to even a 10-Å-thick interface layer. Moreover, it yields the resistivity of the interfacial layer and the YBCO film during deposition. For yttria-stabilized zirconia, the interface has a very low resistivity. For MgO and sapphire the interface has a high resistivity; SrTiO3 falls between these two cases. Sapphire shows a large reaction layer and evidence for nucleated growth, which are probably responsible for its relatively poor superconducting properties.