Pronounced magnetic-field- and bias-sensitive features of the transport properties of a Fe/SiO₂/p-Si hybrid structure in planar geometry at temperature variation are investigated. Comparative analysis of two Fe/SiO₂/p-Si samples, one with a continuous Fe film and the other with two electrodes formed from a Fe layer and separated by a micron gap, shows that these features are due to the metal-insulator-semiconductor (MIS) transition with a Schottky barrier near the interface between SiO₂ and p-Si. Resistance of such a MIS transition depends exponentially on temperature and bias. In the structure with a continuous ferromagnetic film, the competition between conductivities of the MIS transition and the Fe layer results in the effect of current channel switching between the Fe layer and a semiconductor substrate. Within certain limits, this process can be controlled by a bias current and a magnetic field. Positive magnetoresistance of the structures at high temperatures is determined, most likely, by disorder-induced weak localization. In the structure with the gap, negative magnetoresistance is observed at certain temperature and bias. Its occurrence should be attributed to an inversion layer formed in the semiconductor near the SiO₂/p-Si interface when MIS transition is in the inversion regime.

The results of the structural and magnetic studies of the epitaxial structure prepared during the simultaneous evaporation from two iron and silicon sources on an atomically pure Si(111)7 × 7 surface...

We use the Vienna ab initio simulation package (vasp) for evaluation of the quasiparticle spectra and their spectral weights within Hedin's $\text{GW}$ approximation (GWA) for ${\text{Fe}}_3\text{Si}$ and $\alpha {\text{-FeSi}}_2$ within the non-self-consistent one-shot approximation ${\text{G}}_0{\text{W}}_0$ and self-consistent $\text{scGWA}$ with the vertex corrections in the particle-hole channel, taken in the form of two-point kernel. As input for ${\text{G}}_0{\text{W}}_0$, the band structure and wave functions evaluated within the generalized gradient corrected local-density approximation to density functional theory (GGA) have been used. The spectral weights of quasiparticles in these compounds deviate from unity everywhere and show nonmonotonic behavior in those parts of bands where the delocalized states contribute to their formation. The ${\text{G}}_0{\text{W}}_0$ and scGWA spectral weights are the same within 2%–5%. The scGWA shows a general tendency to return ${\text{G}}_0{\text{W}}_0$ bands to their GGA positions for the delocalized states, while in the flat bands it flattens even more. Variable angle spectroscopic ellipsometry measurements at $T=296$ K on grown single-crystalline $\sim 50$-nm-thick films of ${\text{Fe}}_3\text{Si}$ on $n$-Si(111) wafer have been performed in the interval of energies $\omega \sim (1.3–5)$ eV. The comparison of ${\text{G}}_0{\text{W}}_0$ and $\text{scGW}$ theory with experimental real and imaginary parts of permittivity, refractive index, extinction and absorption coefficients, reflectivity, and electron energy loss function shows that both ${\text{G}}_0{\text{W}}_0$ and $\text{scGW}$ qualitatively describe experiment correctly, the position of the low-energy peaks is described better by the $\text{scGW}$ theory, however, its detailed structure is not observed in the experimental curves. We suggest that the angle-resolved photoemission spectroscopy experiments, which can reveal the fine details of the quasiparticle band structure and spectral weights, could help to understand (i) if the scGWA with this type of vertex correction is sufficiently good for description of these iron silicides and, possibly, (ii) why some features of calculated permittivity are not seen in optical experiments.