Superconducting magnesium diboride films with Tc ≈ 24 K grown by pulsed laser deposition with in situ anneal

Thin superconducting films of magnesium diboride (MgB2) with T-c approximate to 24 K were prepared on various oxide substrates by pulsed laser deposition followed by an in situ anneal. A systematic study of the influence of various in situ annealing parameters shows an optimum temperature of about 600 degreesC in a background of 0.7 atm of Ar/4%H-2 for layers consisting of a mixture of magnesium and boron. Contrary to ex situ approaches (e.g. reacting boron films with magnesium vapor at approximate to 900 degreesC), these films are processed at a temperature at which MgB2 does not decompose rapidly even in vacuum. This may prove enabling in the formation of multilayers, junctions, and epitaxial films in future work. Issues related to the improvement of these films and to the possible in situ growth of MgB2 at elevated temperature are discussed. (C) 2001 Published by Elsevier Science B.V.