YBaCuO multilayer structures using CeO/sub 2/ insulating films

We have fabricated YBaCuO crossover using CeO/sub 2/ insulating film as high-T/sub c/ multilayer structure. The bottom YBaCuO bridges showed good critical temperature T/sub c/ of 87 K and critical current density J/sub c/ of 1.0/spl times/10/sup 5/ A/cm/sup 2/. The top YBaCuO bridges, however, showed lower J/sub c/ than the bottom YBaCuO, since the grain boundaries were formed at the step edges of the bottom bridge. The crossover structures have a resistivity of more than 1/spl times/10/sup 8/ /spl Omega//spl middot/2 cm below 80 K, indicating superior insulating properties of the CeO/sub 2/ layer. In order to improve J/sub c/ of the top YBaCuO bridges, we have also studied the properties of YBaCuO bridges on CeO/sub 2/ film bank. It is found that J/sub c/ of the top bridges was not only dependent on the step height, but also depends on the YBaCuO thickness. In order to improve J/sub c/ of the top bridges, lower step height and thicker YBaCuO films are required.