Growth of c-oriented MgB2 thin films by pulsed laser deposition:: structural characterization and electronic anisotropy

MgB2 thin films were deposited using pulsed laser deposition (PLD) and ew situ annealing in Mg atmosphere. The films presented critical temperatures up to 36 K and turned out to be preferentially c-oriented both on Al2O3 (r-cut) and MgO(100) substrates. Synchrotron analyses also gave some indications of in-plane texturing. The films exhibit very fine grain size (1200 Angstrom in the basal plane and 100 Angstrom along the c-axis) but the general resistivity behaviour and the remark-able extension of the irreversible region confirm that the grains' boundaries are not barriers for supercurrents. Upper critical field measurements with the magnetic field perpendicular and parallel with respect to the film surface evidenced a field anisotropy ratio of 1.8. The H-c2 values are considerably higher with respect to the bulk ones, namely when the field lies in the basal plane, and the field-temperature phase diagram for the two magnetic field orientations suggest the possibility of strongly enhancing the pinning region by means of texturing.