Study of the superconducting MgB2 films by ion beam analysis methods

Abstract Superconducting MgB 2 films were prepared by sequential e-beam evaporation of boron and magnesium on randomly oriented sapphire, glassy carbon and silicon substrates followed by an in-situ annealing. Ion beam analysis (IBA) methods using a 2530 keV 3 He + beam were applied to obtain the Mg and B film profiles by Rutherford backscattering (RBS) and nuclear reaction analysis (NRA). It was found that Mg and B diffuse rather deeply into the substrates due to the annealing process. A presence of O and C in the MgB 2 films was detected, apparently as formation of MgO and eventually B 2 O 3 . The zero resistance critical temperatures T co values were 28 K for MgB 2 /Al 2 O 3 and 25 K for MgB 2 /C samples. Because of a rather high annealing temperature of 700 °C, we obtained T co =8 K only in the case of MgB 2 /Si(111) sample.