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 °C for 1 min in a 760 Torr Ar atmosphere. Despite the short annealing time, an x-ray θ–2θ 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 nm in a 5 × 5 µm2 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 Hc 2–T curves when parallel and perpendicular fields were applied. The slope of the Hc 2–T curves in the low field regime is 1 T K−1, which is among the highest reported values.