Electronic structure and phase composition of dielectric interlayers in multilayer amorphous nanostructure [(CoFeB)$_{60}$C$_{40}$/SiO$_{2}$]$_{200}$

The multilayer amorphous nanostructure [(CoFeB)$_{60}$C$_{40}$/SiO$_{2}$]$_{200}$ of alternating composite and dielectric layers was obtained by ion-beam sputtering on a rotating pyroceramic substrate of two targets, one of which was a Co$_{40}$Fe$_{40}$B$_{20}$ metal alloy plate with graphite inserts. The dielectric interlayers of SiO$_2$ were sputtered from a quartz plate (second target). The thicknesses of bilayers of the multilayered nanostructure (MNS) (6 nm), consisting of metal–carbon composite layers (CoFeB)$_{60}$C$_{40}$ approximately 4 nm in thickness and a silicon oxide dielectric interlayers with a thickness of approximately 2 nm, were determined by small-angle diffraction. The results of experimental layer-by-layer study without destroying the MNS by ultrasoft X-ray spectroscopy (USXES) showed a significant deviation of the stoichiometric composition of the dielectric interlayers from stoichiometry sputtered quartz towards decreasing oxygen concentration with the formation of SiO$_{1.3}$ suboxide. As a result of simulation of the Si $L_{2,3}$ spectra of silicon using reference spectra of known phases, the concentration of the silicon suboxide phase in the amorphous dielectric interlayers reaches about half of the interlayer content, the second half of which is accounted for SiO$_2$ dioxide. A “shielding” effect of carbon in the metal layers is manifested in the absence of silicide formation at the interfaces of the multilayer structure under study and should help to increase the anisotropy of their electromagnetic properties.