Off-axis MgB2 films using an in situ annealing pulsed laser deposition method

Highly smooth and c-axis oriented superconducting MgB2 thin films were prepared by pulsed laser deposition (PLD) with off-axis geometry. The films were deposited on Al2O3-C substrates perpendicularly aligned to a stoichiometric MgB2 target in a 120 mTorr high purity Ar background gas. An in situ annealing was carried out at 650 degrees C for 1 min in a 760 Torr Ar atmosphere. Despite the short annealing time, an x-ray theta-2 theta scan shows fairly good crystallization, according to the clear c-axis oriented peaks for the films. Both atomic force microscopy and the x-ray diffraction results indicate that the crystallite size is less than 50 nm. The root mean square roughness of our off-axis film is similar to 4 nm in a 5 x 5 mu m(2) area. The T-c onset value of the best off-axis film reaches 33.1 K with a narrow transition width of 0.9 K. The films showed no anisotropy in H-c2-T curves when parallel and perpendicular fields were applied. The slope of the H-c2-T curves in the low field regime is 1 T K-1, which is among the highest reported values.