High-quality MgB2 thin films in situ grown by dc magnetron sputtering

Thin films of the recently discovered magnesium diboride (MgB 2 ) intermetallic superconducting compound have been grown using a magnetron sputtering deposition technique followed by in situ annealing at 830 °C. High-quality films were obtained on both sapphire and MgO substrates. The best films showed a maximum T c of 35 K (onset), a transition width of 0.5 K, a residual resisitivity ratio up to 1.6, a low-temperature critical current density J c > 10 6 A cm −2 and an anisotropic critical field with γ ≃ 2.5 close to the values obtained for single crystals. The preparation technique can be easily scaled to produce large-area in situ films.