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

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 (15nm and 50nm) 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 15nm thick films we see a strong interdiffusion of the elements (C, B) and we observe a suppression of TC of the film to 20K. We register different slope of the HC2(T) dependence – the lowest temperature value of HC2 for the 15nm thick film exceeds the one for the 50nm thick film in spite of lower TC. We suppose that δl pinning mechanism is dominant for the 15nm thick film.