YBa/sub 2/Cu/sub 3/O/sub 7/(-/spl delta/) a-axis films and planar junctions

In order to prepare planar junctions, multilayers were sputtered, using YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// as superconductor and PrBa/sub 2/Cu/sub 3/O/sub 7/(-/spl delta/) as barrier material. The sandwiches are a-axis oriented. Out of these, single junctions were etched, planarized with CeO/sub 2/. Finally gold contacts were sputtered. The junctions are squares of size 20/spl times/20 to 100/spl times/100 /spl mu/m/sup 2/. A prerequisite for successful preparation of junctions from a-axis oriented multilayers is a study of such films. Films deposited by RF off-axis sputtering were characterized electrically, Their morphology was investigated by XRD, AFM and TEM. The films are very smooth and have a grain size of below 100/spl times/100 nm/sup 2/. To improve T/sub c/ and crystal quality, template layers were used. The T/sub c/ of a single film is about 62 K; by using a template layer up to 78 K can be reached. For a-axis oriented growth not only a reduction of the deposition temperature is important, but also the growth rate must be high enough. Best results were obtained at rates higher than 150 nm/h. The first planar junctions show a supercurrent, but otherwise rounded I-V curves.<>