The Auger electron spectroscopy method confirmed a high concentration of carbon atoms (~ 85 at.%) introduced into silicon by cold implantation of recoil atoms. Carbon atoms are concentrated in a thin (~ 5 nm) near-surface region of silicon. Annealing of such a structure did not reveal a noticeable diffusion of carbon, which prevents obtaining a layer of SiC with a thickness of more than a few nm. This problem was solved by using radiation-enhanced diffusion. This made it possible to control the distribution profiles of carbon atoms in a wide range. Annealing at 1150oC allowed obtaining layers of amorphous-crystalline SiC with a thickness of 50-150 nm. Higher annealing temperatures are required to obtain a single-crystal SiC film. Keywords: cold implantation, radiation-enhanced diffusion, silicon carbide, recoil atom, thin films.

The lattice dynamics of Ba 2 ZnTeO 6 double perovskite in three phases has been studied. Vibrational spectra and dynamic charges are calculated. In the rhomobohedral phase R3m, soft modes were found; after their condensation, the C2/m phase was obtained, which agrees with the experiment. An assessment was made of the dependence of the enthalpy of different phases on pressure; it showed that the monoclinic phase is more favorable at 0 pressure, but as the pressure increases to 2.9 GPa, the cubic phase Fm3m becomes advantageous. Keywords: Lattice dynamics, phase transitions, double perovskites.

The Auger electron spectroscopy method confirmed a high concentration of carbon atoms (~ 85 at. % ), introduced into silicon by cold implantation of recoil atoms. Carbon atoms are concentrated in a thin (~ 5 nm) near-surface region of silicon. Annealing of such a structure did not reveal a noticeable diffusion of carbon, which does not allow obtaining a layer of SiC with a thickness of more than a few nm. The solution to this problem was carried out by the use of radiation-stimulated diffusion. This made it possible to control the distribution profiles of carbon atoms in a wide range. Annealing at 1150 oC allowed to obtain layers of amorphous crystalline SiC with a thickness of 50-150 nm. Higher annealing temperatures are required to obtain a single-crystal SiC film.

The physical properties of the NiB4O7 and CoB4O7 tetraborate compounds in three structural modifications with the sp. gr. Pbca, Cmcm, and P6522 have been calculated using the density functional theory in the VASP software package. The pressure dependences of the enthalpy of the compounds in the investigated structural modifications have been calculated. The calculated electron densities of states and band structures showed that the compounds under study in all the considered modifications are dielectrics with a band gap of 3–4 eV. The calculation of the magnetic exchange constants in the Heisenberg model have shown qualitative agreement with the experiment.

The effect of low-energy proton irradiation on the pulse characteristics of silicon n+-p-p+ structures is analyzed. It is shown that irradiation with protons with an energy of 180 keV and a dose of 1015 cm−2 creates a region with an effective lifetime of 5.5·10−8 s in the space charge region of the n+-p junction. Such elements can be used to create high-speed photodiodes with an operating modulation frequency of 18 MHz.

Within a framework of the density functional theory using the VASP software package, physical properties of tetraborate compounds NiB4O7 and CoB4O7 in three structural modifications with space symmetry groups of Pbca, Cmcm and P6522 were calculated. The dependences of the enthalpy of compounds on pressure in studied structural modifications are calculated. The calculated electron densities of states and band structures showed that studied compounds in all considered modifications are dielectrics with a band gap of 3-4 eV. The calculation of the magnetic exchange constants was carried out in the Heisenberg model, which showed qualitative agreement with experiment.

Nanoparticle formation in silicon subsequently doped with Zn and О ions and annealed in vacuum is presented in this paper. Standard n-type Si plates with the (100) orientation, a thickness of 380 nm, and a diameter of 76 mm and grown by the Czochralski method are implanted with 64Zn+ ions with a dose of 5 × 1016 cm–2 and an energy of 50 keV and with 16О+ ions with a dose of 2 × 1017 cm–2 and an energy of 20 keV. The ion current does not exceed 0.5 µA/cm2 during implantation so that plate overheating in comparison to room temperature does not exceed 50°С. Then the plates were cut into samples with dimensions of 10 × 10 mm and annealed at a temperature of 400 to 900°С with a step of 100°С in vacuum for 30 min. It is discovered that, after implantation, an amorphized layer with a thickness of approximately 150 nm is formed in Si; amorphous Zn and O nanoparticles with dimensions of about 5 nm are formed in it. Radiation-induced defects are annealed during heat treatment, and the amorphized-layer thickness decreases. After annealing, a peak at a wavelength of 370 nm forms at 700°С in the photoluminescence spectrum; it is caused by the formation of ZnO-phase nanoparticles. This peak vanishes after annealing at 900°С, and a peak at a wavelength of 425 nm appears in the photoluminescence spectrum; it is due to the appearance of the Zn2SiO4 phase.

The surface layer of a SiO2/Si structure implanted with Zn+ and O+ ions and annealed in neutral and inert atmospheres is studied. At first, n-Si(100) silicon plates are oxidized in dry O2 to achieve an oxide-film thickness of 0.2 μm. Then, at room temperature, they are sequentially implanted with a dose of 5 × 1016 cm–2 of 70-keV 64Zn+ ions and with a dose of 6.1 × 1016 cm–2 of 40-keV $$^{{16}}{\text{O}}_{2}^{ + }$$ ions. Plate overheating, compared with room temperature, does not exceed 70°C. The samples are isochronously annealed for 1 h in N2 at a temperature from 400 to 600°C and then in Ar in the range of 700–1000°C with a step of 100°C. After implantation, the crystalline phase Zn(102) is found to form in the SiO2 film. After annealing at 700°C, Zn is oxidized to form the ZnO phase. Analysis of the diffraction patterns shows the β-Zn2SiO4 and Zn1.95SiO4 phases to be additionally formed in the samples after annealing at 800°C. After annealing at 900°C and above, the ZnO phase was not detected in the samples.

Vibrational, polarization, magnetic, and electronic properties of double perovskites CaMnTi2O6 and CaFeTi2O6 with a rare type of “column” ordering of divalent metal cations have been calculated based on the density functional theory. Analysis of the crystal lattice dynamics for paraelectric phase P42/nmc of both compounds has revealed that ferroelectric instability exists only in CaMnTi2O6. It is found that the structure distortion of the paraphrase of CaMnTi2O6 in the eigenvector of the unstable polar mode leads to a structure with the P42/nmc space group. The calculated spontaneous polarization for the ferroelectric phase of CaMnTi2O6 is Ps = 25 μC/cm2. The spin-polarization calculations have shown that the ground state is ferromagnetic in the CaFeTi2O6 crystal and antiferromagnetic in the CaMnTi2O6 crystal. The exchange interaction constants have been calculated using the Heisenberg model and the mean field approximation; the phase transition temperature for each compound has been estimated.

Ab initio calculations of the structural, electronic, and optical properties of the CdB 4 O 7 and HgB 4 O 7 tetraborate compounds in three structural modifications with the Pbca , Cmcm , and Pmn 2 1 symmetry have been performed in the framework of the density functional theory using the VASP package. The calculations of the electronic band structure showed that these compounds in all the investigated modifications are dielectrics with a band gap of 2–4 eV. The calculation of the structural properties of the tetraborates under pressure showed that the phase transition between the Pbca and Pmn 2 1 structures in cadmium and mercury tetraborates occurs under pressures of 4.8 and 4.7 GPa, respectively.

The magnetic, electronic, and polarization properties of the SrFeO3 and SrMnO3 compounds with a perovskite structure are calculated using the density functional theory in the bulk and thin-film states. A ferroelectric instability is found to be absent in the bulk state, and the polar mode is softened in the thin-film state of SrMnO3 in the presence of tensile stresses in the substrate. As a result, a polar phase with a polarization of 23 μC/cm2 appears, which agrees with experimental data. The study of the magnetic and electronic properties demonstrates the existence of G-type antiferromagnetic ordering in SrMnO3 and the appearance of a dielectric gap of about 1.5 eV in its thin film. A ferromagnetic phase with metallic conduction in both the bulk and thin-film states is detected in SrFeO3.

AbstractAb initio calculations of the structural, electronic, and optical properties of the CdB_4O_7 and HgB_4O_7 tetraborate compounds in three structural modifications with the Pbca , Cmcm , and Pmn 2_1 symmetry have been performed in the framework of the density functional theory using the VASP package. The calculations of the electronic band structure showed that these compounds in all the investigated modifications are dielectrics with a band gap of 2–4 eV. The calculation of the structural properties of the tetraborates under pressure showed that the phase transition between the Pbca and Pmn 2_1 structures in cadmium and mercury tetraborates occurs under pressures of 4.8 and 4.7 GPa, respectively.

The dynamics of the crystal lattice of RFe 3 (BO 3 ) 4 (R = Pr, Nd, Sm, Gd, Tb, Dy, and Ho) compounds in the high-symmetry R 32 phase has been calculated. Significant changes in spectra of compounds with various rare-earth ions have been obtained only near the edge Λ point of the Brillouin zone ( q Λ = 1/3(−2 b 1 + b 2 + b 3 , where b 1 , b 2 , and b 3 are the reciprocal lattice vectors) for acoustic oscillation branches. A decrease in the frequency of an acoustic mode at the point Λ has been revealed in all studied compounds. This frequency depends on the type of rare-earth ion and decreases from a compound with Pr to a compound with Ho down to imaginary values. Such a behavior of the frequency of the unstable acoustic mode is in good agreement with experimental data on the dependence of the temperature of the R 32 → P 3 1 21 structural phase transition on the type of rare-earth ion in ferroborates.

A novel method of silicon carbide growth on silicon substrates is proposed. The method makes use of carbon recoil atoms implantation from a layer of molecules of carbon-containing gas, adsorbed on a cooled silicon surface bombarded by argon ions. A silicon carbide film is formed on the surface of a Si(1 1 1) substrate after high-temperature annealing in vacuum. The film properties are studied by IR-spectroscopy, XRD, AFM and optical microscopy methods. The studies have shown that the proposed method enables the growth of single-crystalline SiC films on the Si crystal surface. (C) 2018 Elsevier B.V. All rights reserved.

Предложен новый способ введения углерода в металлические каталитические пленки для синтеза графена. Способ основан на явлении имплантации атомов отдачи углерода из слоя молекул метана, адсорбированных на металлической пленке, при облучении такой структуры ионами инертных газов. Для увеличения толщины адсорбированного слоя метана образцы охлаждались до температуры -190oC. Этот метод был реализован на поликристаллической пленке никеля. После отжига на поверхности никелевой пленки методом рамановской спектроскопии обнаружены многочисленные фрагменты многослойного графена. DOI: 10.21883/PJTF.2017.12.44708.16736

Within the first principles approach implemented in the VASP package, a correlation between magnetic, electronic, polarization, and optical properties, on the one hand, and the structural ordering of cations, on the other hand, is investigated in double perovskites LaPbTSbO 6 (T = Fe, Co, Ni). Two types of cation ordering are considered: simultaneous layered (LL) and checkerboard (RR) ordering of both cations. These two types of ordering are chosen due to their significance; namely, the ordering RR is one of the most implementable types of cation ordering in double perovskites, and compounds with layered ordering can be considered as a heterostructure consisting of periodically alternating metal–nonmagnetic metal layers, which is of interest for experimental synthesis and investigation. It is found that the type of cation ordering in compounds with T = Fe and Ni radically changes the magnetic and/or electronic properties of the compound. Moreover, it is found that low-symmetry stable phases are polar for both types of cation ordering, and the values of spontaneous polarization are evaluated.

A new method of introducing carbon into catalytic metal films for graphene synthesis is proposed. The method is based on the phenomenon of carbon recoil atoms from a layer of methane molecules that are adsorbed on a metal film being incorporated into this film under the action of bombardment with inert gas ions. To increase the thickness of adsorbed methane layer, the substrate is cooled down to −190°C. The proposed method has been implemented on a polycrystalline nickel film. After the final annealing, Raman spectroscopy showed the presence of numerous fragments of multilayer graphene on the film surface.