A special patented design is built up to produce homogeneous YBa2Cu3O7−x (YBCO) films by pulsed laser deposition (PLD) over areas as large as 7×20 cm2. The use of a line focus (8 cm) reduces the substrate movement to one dimension. The demands on plasma homogenization, substrate scanning and film temperature during the deposition process for large area PLD are discussed and their technical realization is presented. First results of 1×1 cm2 YBCO films at different positions on the substrate holder (11×28 cm2) show homogeneous deposition conditions. The transition temperatures of the deposited YBCO thin films on 1×1 cm2 SrTiO3 substrates are TC=89 K with critical currents of 4×106 A/cm2 at T=77 K. The structural properties of these films (χmin=4.5%) indicate also their high crystalline quality. The variation of film thickness perpendicular to the scanning direction is less than ±9% and along the scanning direction ±7%.
One of the most promising technologies for the fabrication of high-T c cables is the ion-beam-assisted deposition ͑IBAD͒ technique. The performance of the superconductors fabricated by IBAD, and the fabrication costs, are to a great extent determined by the critical current densities of the superconductors' grain boundaries. Since, in bicrystalline samples, overdoping has been found to improve the transport properties of grain boundaries in high-T c superconductors, we have explored whether overdoping also enhances the critical currents of IBAD samples. The measurements show that, depending on the critical current density of the superconducting film, J c ͑77 K͒ is increased by factors up to 2.2, also in applied magnetic fields of several tesla.
YB~,CLI,O,-~ thin films deposited by pulsed laser deposition were patterned by ion implantation. The pa~terning technique is based on the local disordering of the crystal structure due to elastic collisions of the imp1,mted 0'"-ions and thus . on a strong breakdown of superconductivity in the irradiated areas. With tkis patterning method circular and meandering structures with a size of 1 rnm were prepared for invesuga~ions regarding high current applications. Oi-ions with an energy of 180 keV were used to avoid a contamination of the film. The achieved structures were investigated concerning a dependence on the dose by means of RBS, XRD, A M and magneto-optical characterization. Using a fluence of 5 x 1 0 '~ O+/cm2 a fully planar and stable s~ructure can be obtained. The patterning depth can be adjusted by varying the implantation energy. So thjs technique was also used successfully on YBCO thin films covered already wi tll a 300 ntn Au lop layer. O 1998 Elsevier Science 8.V.
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