M.F. Rocha

Ion beam analysis of copper selenide thin films prepared by chemical bath deposition

Abstract Analyses of Rutherford back scattered (RBS) 4 He + -particle spectra of copper selenide thin films deposited on glass slides by chemical bath were carried out to determine the changes brought about in the thin film by annealing processes. The atomic density per unit area and composition of the films were obtained from these measurements. This analysis shows that annealing in a nitrogen atmosphere at 400°C leads to the conversion of CuxSe thin film to Cu2Se. Results of X-ray diffraction, optical, and electrical characteristics on the films are presented to supplement the RBS results.

Study of the superconducting MgB2 films by ion beam analysis methods

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.