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

Abstract

Highly smooth and c-axisoriented superconducting MgB2 thin films were prepared by pulsed laser deposition (PLD) with off-axis geometry. The films were depositedon Al2O3–C substrates perpendicularly aligned to a stoichiometricMgB2 target in a 120 mTorr high purity Ar background gas. An in situ annealing was carried out at650 °C for 1 min in a 760 Torr Ar atmosphere. Despite the short annealing time, an x-rayθ–2θ scan shows fairly good crystallization, according to the clearc-axis oriented peaks for the films. Both atomic force microscopy and the x-ray diffractionresults indicate that the crystallite size is less than 50 nm. The root mean square roughnessof 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 noanisotropy in Hc 2–T curves when parallel and perpendicular fields were applied. The slope of theHc 2–T curves in the lowfield regime is 1 T K−1, which is among the highest reported values.