SmBaCuO films grown at low temperature and pressure

Abstract

We have fabricated SmBaCuO thin films at 550–850°C and at oxygen pressures of 1.2–6.0×10 −5 mbar in the presence of ozone. Various groups have reported on the existence of a solid solubility region in bulk Sm 1+ x Ba 2- x Cu 3O y made at atmospheric oxygen pressure and 975°C. For these conditions, the superconducting transition temperature, T c, is known to drop to zero as x is increased from 0 to 0.5. In contrast, we find hardly any decreases of T c in our films in the range 0< x<1 and 750°C< T growth<800°C, with T c' s about 90 K, from which we conclude that the solid solubility is strongly reduced or absent at low oxygen/ozone pressure in this growth temperature range. For this range of composition and growth temperature, we also observe no change in the c-axis lattice constant. The growth temperature that is needed to obtain a film with T c,0 above 80 K equals 750°C, which is roughly 100°C higher than in the case of YBaCuO films grown under comparable conditions. These results are discussed using thermodynamic equilibrium data of RE 1+ x Ba 2- x Cu 3O y (REY, Sm, La). At low temperature on a SrTiO 3 substrate we observe an I-centered cubic phase.