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 s itu annealing in Mg atmosphere. The films presented critical temperatures u p to 36 K and turned out to be preferentially c-oriented both on Al2O3 (r-c ut) and MgO(100) substrates. Synchrotron analyses also gave some indication s of in-plane texturing. The films exhibit very fine grain size (1200 Angst rom in the basal plane and 100 Angstrom along the c-axis) but the general r esistivity behaviour and the remark-able extension of the irreversible regi on 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 rat io 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-tempera ture phase diagram for the two magnetic field orientations suggest the poss ibility of strongly enhancing the pinning region by means of texturing.