The distribution of elements in sequentially prepared MgB2 on SiC buffered Si substrate and possible pinning mechanisms

Applied Surface Science, Volume 269, 15 March 2013, Pages 29-32.
S. Chromik, A. Nishida, V. Strbik, M. Gregor, J.P. Espinós, J. Liday, R. Durný.

 

Institute of Electrical Engineering, Slovak Academy of Sciences, 841 04 Bratislava, Slovak Republic &

Department of Applied Physics, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan &

Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, 84248 Bratislava, Slovak Republic &

Instituto de Ciencia de Materiales de Sevilla, Avda Américo Vespucio 49, 41092 Sevilla, Spain &

Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovičova 3, 812 19 Bratislava, Slovak Republic

 

Abstract

 

MgB₂ thin films are prepared by sequential evaporation of boron and magnesium bilayers on SiC buffered Si substrates followed by an in situ annealing. Precursor Mg–B bilayers are deposited by electron beam evaporation at room temperature. The amount of B is varied so as to result in different thickness (15 nm and 50 nm) of stoichiometric MgB₂ final film after an in situ reaction with the excess Mg top layer in the vacuum. We show the distribution of the elements through the film.

X-ray photoelectron spectroscopy analyses have shown that carbon is not free in the films (except the surface of the film) and silicon is in the compound form, too. In the case of the 15 nm thick films we see a strong interdiffusion of the elements (C, B) and we observe a suppression of T_C of the film to 20 K. We register different slope of the HC₂(T) dependence – the lowest temperature value of HC₂ for the 15 nm thick film exceeds the one for the 50 nm thick film in spite of lower T_C. We suppose that {Delta}l pinning mechanism is dominant for the 15 nm thick film.

 

 

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