The in situ annealing conditions of pulsed laser deposited MgB2 films were studied. The precursor films were deposited at 250C from a stoichiometric MgB2 target in a 120mTorr Ar atmosphere. The films were then in situ annealed at 450C to 800C, using annealing times of 60s to 600s. It was found that the superconducting properties depended in a crucial way on the annealing conditions: temperature, heating rate and time. The best film with a thickness of about 600nm was obtained under the following annealing conditions: Tanneal = 680–690C , tanneal = 60s, heating rate = 38C/min. The TC,onset of the film was 28K with a transition width of about 10K. The hysteresis loop of the magnetic moment of the film indicates weak field dependence in high fields. Magneto-optical imaging of the film showed quite homogeneous magnetic flux penetration, indicating structural homogeneity. The films without annealing exhibited no superconductivity.

In situ Annealing of Superconducting MgB2 Films Prepared by Pulsed Laser Deposition. Y.Zhao, M.Ionescu, A.V.Pan, S.X.Dou, E.W.Collings: Superconductor Science and Technology, 2003, 16, 1487-92