MgB/sub 2/ superconducting films for bolometer applications

Thin superconducting films of MgB/sub 2/ has been prepared on r-plane sapphire and silicon nitride (SiN) by ex-situ technique and co-deposition of B and Mg at several substrate temperatures with the aim to fabricate superconducting bolometers. MgB/sub 2/ films on r-plane sapphire, realized by annealing of a B film at 890(degree)C, show a T/sub c/=38 K and RRR=2 while no transition has been observed for MgB/sub 2/ films on SiN above 5 K treated in the same way. A reliable process of MgB/sub 2/ growth on SiN with T/sub c/ between 27 K and 30 K and transition width of 0.5 K has been performed by codeposition Mg and B and following annealing to 600(degree)C.