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An approach to form planar structures based on ferromagnetic Fe1 − xSix films is presented. Epitaxial Fe1 − xSix iron-silicon alloy films with different silicon content (x = 0-0.4) were grown on Si(111) substrates. Structural in situ and ex situ characterization of the films obtained was made by X-ray diffraction, reflective high-energy electron diffraction, Rutherford backscattering spectrometry and transmission electron microscopy, which confirmed single crystallinity and interface abruptness for all films. Etching rates in the wet etchant (HF: HNO3: H2O = 1: 2: 400) for the films with various chemical composition were obtained. A nonmonotonic dependence of the etching rate on silicon content with a maximum for the composition Fe0.92Si0.08 was discovered. Moreover, the etching process is vertical and selective in the etching solution, i.e., the etching process takes place only in silicide film and does not affect substrate. As an example, a four-terminal planar structure was made of Fe0.75Si0.25/Si(111) structure using the etching rate obtained for this silicon content. Magneto-optical Kerr effect (MOKE) microscopy and transport properties characterization indicated successful etching process.

1.Currently, ferromagnetic iron silicide Fe 3 Si turns out to be a promising material for such applications as spin transistors, magnetoresistive memory, and mag neto optical devices [1][2][3][4] owing to its high Curie temperature (about 840 K), relatively high magnetic permeability, low magnetic and crystallographic anisotropy, high electrical resistivity, and high spin polarization (as high as 43%). During the last decade, thin films of this material have been widely studied. A lot of papers deal with the interplay of their structural and magnetic characteristics [5,6], as well as with the transport properties and developments of prototypes of spintronic devices [7,8]. However, the electronic structure and optical properties of Fe 3 Si are still rather poorly studied. In particular, the energy dependence of its relative permittivity is treated only in one theo retical paper [9], the results of which have not been verified by experiment. The main aims of our work are to study the optical characteristics of an epitaxial Fe 3 Si/Si(111) iron silicide film and to determine the dispersion of the relative permittivity ε using the spec troscopic ellipsometry technique. 2.The Fe 3 Si film was obtained by the thermal evap oration technique in ultrahigh vacuum at the recon structed Si(111)7 × 7 surface. The formation of the film structure was controlled by an LEF 751M high speed laser ellipsometer [10]. The technique used for the preparation of the atomically clean Si(111)7 × 7 surface, the process of growth of Fe 3 Si/Si(111)7 × 7 film, and the data on the structure of this film and its magnetic properties were described in [11].The data obtained by single wavelength ellipsome try for the synthesized Fe 3 Si/Si(111) film (Fig. 1) were analyzed by the method described in [12]. This analy sis was based on the optical model involving a homo geneous isotropic film at a semi infinite isotropic sub strate. The value obtained for the thickness of the formed film agrees well with the data provided by transmission electron microscopy. It equals 27 nm.In Fig. 1, we can see that the behavior of the thick ness at the initial stages of the film growth is not phys ical. The calculated refractive index n and the coeffi cient of absorption k vary drastically beginning from values close to the optical parameters of silicon (n = 3.93 and k = 0.54) to those characteristic of conduct ing materials (n = 3.43 and k = 3.54). We attribute such behavior at the initial stage of the film formation to the epitaxial island growth mechanism, rather than to layer by layer growth. After 45 min of film growth, the thickness begins growing monotonically and n and k achieve values remaining unchanged in the course of further growth. Thus, when the effective thickness achieves 5 nm, the Fe 3 Si film forms as a continuous layer. The values of the real and imaginary parts of the relative permittivity determined by the laser ellipsom etry (λ = 632.8 nm) at a temperature of 150° are ε' = -0.97 and ε'' = 24.07, respectively.3. In the present work, the energy ...

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We report on abrupt changes in dc resistance and impedance of a diode with the Schottky barrier based on the Mn/SiO2/p-Si structure in a magnetic field. It was observed that at low temperatures the dc and ac resistances of the device change by a factor of more than 106 with an increase in a magnetic field to 200 mT. The strong effect of the magnetic field is observed only above the threshold forward bias across the diode. The ratios between ac and dc magnetoresistances can be tuned from almost zero to 108% by varying the bias. To explain the diversity of magnetotransport phenomena observed in the Mn/SiO2/p-Si structure, it is necessary to attract several mechanisms, which possibly work in different regions of the structure. The anomalously strong magnetotransport effects are attributed to the magnetic-field-dependent impact ionization in the bulk of a Si substrate. At the same time, the conditions for this process are specified by structure composition, which, in turn, affects the current through each structure region. The effect of magnetic field attributed to suppression of impact ionization via two mechanisms leads to an increase in the carrier energy required for initiation of impact ionization. The first mechanism is related to displacement of acceptor levels toward higher energies relative to the top of the valence band and the other mechanism is associated with the Lorentz forces affecting carrier trajectories between scatterings events. The estimated contributions of these two mechanisms are similar. The proposed structure is a good candidate for application in CMOS technology-compatible magnetic- and electric-field sensors and switching devices.

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