Off axis RF magnetron sputtering system has been assembled for the deposition of the superconducting thin film. The target with the cation ratio (Y:Ba:Cu) being 1:2.6:5.6 has been prepared by calcining and by sintering the powder. The larger amount of the powder, the worst homogeniety of the powder during calcining for the target. Because the huge powder should be needed to make the target, it's good to part the powder to small batchs and to heat-treat them respectively.
The $YBa_2Cu_3O_X$ superconducting thin films have been deposited on MgO (100) single crystal substrates by the sputtering system. Thicknesses of the films are 1/2μm or so. Atmosphere, deposition temperature, substrate, and displacement from the plasma were taken to be parameters and the related results of cation ratio, lattice parameter, degree of aligning, $T_c$, and $J_c$ were investigated.
Two atmospheres have been used for the deposition. The one is 70 O2 30 Ar and the other is 50 $O_2$ 50 Ar. Oxygen-rich-atmosphere would get highly textured film, yet the cation ratio was very different from that of target for the large resputtering effect.
The deposition temperature was set in the step of 10℃ from 700℃ to 800℃. Deposition temperature has severely effected on the cation ratio, the lattice parameter, and the degree of texturing. As the temperature increased, cation ratio converged to Y:Ba:Cu=1:2:3. At about 730℃, drastically increased was the fraction of the grains with their a-axis normal to the substrate plane to the grains with their c-axis normal. In addition, the cation ratio(Cu/Y) was minimized at this temperature.
Displacement from the plasma increased the cation ratio(Cu/Y) by diminishing resputtering effect. $T_c$ of the films grown on MgO and $SrTiO_3$ was 72K and 88K respectively. $J_c$ was measured to record about $10^4$A/㎠ for the film on MgO. The lattice parameters of a and c tended to shrink as deposition temperature increased.
From the above, it is thought that the most important parameter is deposition temperature of this sputtering system. More thorough investigation out of this results would give more definite conditions to get the superconducting epitaxial films with reproducibility.
