J/sub c/ enhancement in YBa/sub 2/Cu/sub 3/O/sub x/ thin films by introduction of one-dimensional artificial pinning centers

A novel technology to introduce artificial pinning centers (APCs) into YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thin films prepared by pulsed laser deposition (PLD) was investigated for a drastic improvement of J/sub c/ in the films. Linear-like defects (one-dimensional APCs) were introduced perpendicular to the surface of the c-axis oriented films during the deposition process by using distributed Y/sub 2/O/sub 3/ nano-islands on substrates. The density of nano-islands was varied within 0.8-1.2/spl times/10/sup 10//cm/sup 2/ by PLD. A normalized resistivity as a function of temperature in magnetic fields shows a sharper resistivity drop for the film with APC, compared to pure YBCO film. J/sub c/ of the film with APC was also increased to 0.12 MA/cm/sup 2/ (77 K, B//c, 5 T), which was about two times higher than that of the pure YBCO film. The film had a very large J/sub c/ peak when the field was applied close to the c-axis. The peak J/sub c/ increased with the number density of Y/sub 2/O/sub 3/ nano-islands. This indicates that strong APCs parallel to the c-axis were incorporated into the YBCO film.