  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 650C 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 50nm. The root mean square roughness of our
off-axis film is ~4 nm in a 5x5 square micron area. The Tc 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 Hc2-T curves when parallel and perpendicular
fields were applied. The slope of Hc2-T curves in low field regime is 1 T/K,
which is among the highest reported values.
