Growth of<i>c</i>-oriented MgB₂thin films by pulsed laser deposition: structural characterization and electronic anisotropy

Abstract

MgB2 thin films were deposited using Pulsed Laser Deposition (PLD) and\nex-situ annealing in Mg atmosphere. The films presented critical temperatures\nup to 36K and turned out to be preferentially c-oriented both on Al2O3 (r-cut)\nand MgO(100) substrates. Synchrotron analyses gave also some indications of in\nplane texturing. The films exhibit very fine grain size (1200angstromin the\nbasal plane and 100angstrom along c-axis) but the general resistivity behavior\nand the remarkable extension of the irreversible region confirm that the grains\nboundaries are not barriers for supercurrents. Upper critical field\nmeasurements with the magnetic field perpendicular and parallel with respect to\nthe film surface evidenced a field anisotropy ratio of 1.8. The Hc2 values are\nconsiderably higher with respect to the bulk ones, namely when the field lies\nin the basal plane, and the field-temperature phase diagram for the two\nmagnetic field orientations suggest the possibility of strongly enhancing the\npinning region by means of texturing.\n