Coexistence of grains with differing orthorhombicity in high quality YBa2Cu3O7minus;dgr;thin films

摘要

High quality films of YBa2Cu3O7minus;dgr;on LaAlO3have been grown by pulsedhyphen;laser deposition at oxygen pressures of 3.4ndash;54 Pa (25ndash;400 mTorr). Xhyphen;ray diffraction reveals the coexistence of grains that align with the substrate axes (axialgrains) and grains that are rotated by 0.4deg; from the substrate axes (diagonalgrains). The axial grains are tetragonal while the diagonal grains achieve lattice parameters close to bulk YBa2Cu3O7. The relative proportion of axial grains accounts for the measured variations of normalhyphen;state conductance and superconducting critical current density from film to film, based on a simple twohyphen;dimensional model of randomly positioned, insulating axial grains. copy;1994 American Institute of Physics.