(305) SrTiO3 as substrate for coherently tilted epitaxial YBa2Cu3Ox thin films

Abstract

High T, superconductingYBazCusO, (YBCO) thin films have been prepared on (305) SrTiOs (STO) substrates. X-ray diffraction analysis and Rutherford backscattering experiments reveal that the c-axis of the layers is directed along the [OOl] ST0 axis. Bragg reflection measurements from YBCO lattice planes with high h, k, and I indices confirm that the film growth is epitaxial and almost single domain. For the critical current density j,(77 K) values of 2>( lo6 and 1 x lo3 A/cm2 have been found in the [OlO] and [SO]] YBCO directions, respectively.The question of the superconducting properties anisotropy in the case of the high T, superconductors (HTS) is of great importance now. Recent experiments show strong anisotropy in coherence length c,;' critical current density j, and resistivity p above the critical transition temperature T," between the directions parallel and perpendicular to the Cu02 planes in the YBazCu30, (YBCO). The origin of such behavior may be in the quasi-two-dimensional nature of high T, superconductivity.5Measurements of the anisotropy of the transport properties on YBCO single crystals are difficult because of the well pronounced layered nature that inhibits the preparation of monocrystalline structures with dimensions in the c-direction large enough for j, measurements. Requirements of YBCO thin films are also exceptionally high. One should use epitaxial films which are single domain, properly oriented and free from twins.The aim of this work is to study the possibility of the growth of coherently tilted epitaxial YBCO thin films on specially oriented (305) SrTiO, (STQ) substrates and apply these for the study of the anisotropy in the YBCO transport properties. Jia et al. showed that YBCO can cover steps on the (001) ST0 substrates. If the angle a between the normal to the (macroscopic) step surface and the (001) ST0 direction is below ~:40", the YBCO on the step is c-axis oriented.6 The surface of our (305) ST0 substrates is similar to that of a step with a = 30.96". Therefore, we expect YBCO to grow on (305) ST0 substrates with the c-axis tilted with an angle of 31" relative to the substrate surface normal, and directed along the [OOl] ST0 axis, see Fig. 1. If epitaxial and single domain films can be made, they allow us to study the anisotropy in the electrical properties of YBCO thin films for the first time, then also anisotropic behavior of many other physical properties of YBCO can be studied on these films.We have studied single and double layers of YBCO and PrBa,Cu30, (PBCO), grown on (305) ST0 (Akzo International Research SCT) using off-axis rf magnetron sputtering as a deposition technique. The deposition setup and typical sputter parameters are described elsewhere.7 X-ray diffraction analysis (XRD) and 2 MeV 4Hef Rutherford backscattering spectrometry (RBS) were used to determine the orientation of the (double) layers. The XRD experiments were performed on a Philips Materials Research Diffractometer (MRD) equipped with parallel beam x-ray optics.* The RBS data were analyzed using th...

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Magnetization-induced resistance-switching effects inLa0.67Sr0.33MnO3/YBaZalk1, Veldhorst2, Brinkman3 et al. 2009Phys. Rev. B351240View full textAdd to dashboardCite

“…A disadvantage of these structures is the weak coupling between the superconductor and the ferromagnet, due to the strongly anisotropic nature of superconductivity in YBCO. In order to achieve coupling that is ͑partly͒ in the ab plane, we will exploit coherently tilted epitaxial growth 25 of YBCO on STO ͑305͒ substrates. On these substrates, YBCO grows with the c axis making a 31°a ngle with respect to the sample surface, as indicated in Fig.…”

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