MgB2 superconducting films for bolometer applications

Thin superconducting films of MgB₂ 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. MgB₂ films on r-plane sapphire, realized by annealing of a B film at 890°C, show a T_c=38 K and RRR=2 while no transition has been observed for MgB₂ films on SiN above 5 K treated in the same way. A reliable process of MgB₂ growth on SiN with T_c between 27 K and 30 K and transition width of 0.5 K has been performed by co-deposition Mg and B and following annealing to 600°C.