Large-area pulsed laser deposition of YBCO thin films: homogeneity and surface

Abstract.

YBCO thin films and buffer layers are deposited by a special PLD setup with an 8-cm line focus on cylindrical targets and substrate scanning perpendicular to it. Different kinds of substrates (SrTiO₃, MgO, LaAlO₃, Y-ZrO₂and sapphire) as large as 7×20 cm² were coated with YBCO. Two important aspects of the presented PLD setup will be discussed in detail: the method of substrate heating and the variation of the angle between the incident laser beam and the target surface (“wobbling”). The surface of the target material has been investigated by SEM. The influence of target “wobbling” on the time stability of the plasma will be discussed. The homogeneity of the deposited YBCO films with respect to structural and electrical properties has been investigated by XRD, RBS/channeling, and spatially resolved inductive measurements of T_c and j_c. The values of j_c on 7×20 cm²in situ buffered sapphire substrates are 2.0 MA/cm² at (77 K, 0 T) with a j_c variation of less than ±20%.