YBCOのマルチ-プルーム・マルチ-ターンPLD成膜

抄録

We have investigated the high-speed deposition of YBa₂Cu₃O_7-x (YBCO) using PLD on a CeO₂-capped IBAD buffer layer. In order to speed up the coated conductor process, we introduced a continuous PLD system mainly consisting of high-power laser equipment and a vacuum chamber with a reel-to-reel substrate transfer system. The laser system was designed so that the laser beam scans YBCO targets during deposition and raises plural and discrete plumes (multi-plume). The aim of this is to perform high-speed production of YBCO layers. Although high laser pulse frequency deposition makes high-speed deposition possible, it causes roughening of the surface morphology and lowers the J_c. The multi-plume gave us a high J_c during low laser pulse frequency deposition and high-speed deposition at a higher frequency. The substrates were turned three times to enlarge the deposition area (multi-turn). Within 15 degrees aslant to a plume center, we obtained a high J_c for all turns. Using this multi-plume and multi-turn PLD equipment, we have succeeded in deposition of a 21m-long YBCO layer with a high end-to-end critical current (I_c) of 85 A and high J_c exceeding 1 MA/cm². I_c data measured in 1.4m intervals showed good uniformity, with a standard deviation of 3.43%. This layer also showed high in-plane alignment, attaining 5.2 degrees of full-width-at-half-maximum as observed by X-ray phi scans. These results indicate the availability of utilizing multi-plume and multi-turn PLD for YBCO-coated conductor preparation.