A. K. Fedotov

Negative capacitance in (FeCoZr)–(PZT) nanocomposite films

In this work, attention was focused on the inductive contribution to the real part of admittance G(T, f) in (Fe0.45Co0.45Zr0.10)x(PZT)(1−x) nanocomposite films deposited in a mixed argon‐oxygen atmosphere. The observed G(x, f, T ) dependences for the films on the dielectric side of the insulator‐metal transition demonstrated the negative capacitance (NC) effect that was maximal for the nanocomposites with 0.40 <x< 0.60, where the metallic FeCoZr nanoparticles were totally oxidized. The NC effect was explained by a specially developed model for the ac hopping conductance of the electrons between the fully oxidized nanoparticles embedded in the PZT matrix. In accordance with the model, under the determined conditions the observed structure of nanocomposites led to an increase in the hopping electron mean lifetime on nanoparticles and hence to the possibility of positive angles of the phase shifts θ and a proper NC (inductive-like contribution) effect. (Some figures may appear in colour only in the online journal)

Temperature and frequency dependences of real part of impedance in the FeCoZr-doped PZT nanogranular composites

The study of carrier transport in granular nanocomposite films consisting of ferromagnetic Fe45Co45Zr10 alloy nanoparticles embedded in a low-conductive Pb81Sr4(Na5Bi5)15(Zr57.5Ti42.5)O3 matrix has been performed. Real part of the impedance of the nanocomposites was studied as a function of composition, temperature and frequency, for the samples with 25 ≤ x ≤ 80 at.%, deposited by ion-beam sputtering in Ar + O2 gas mixture at the oxygen pressures of

The influence of charge states and elastic stresses on the diffusion of point defects in silicon

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Electrical activity of grain boundaries in silicon bicrystals and its modification by hydrogen plasma treatment

= 2.4·10−3 and 3.7·10−3 Pa. It has been proved that approaching the threshold concentration, xC in the FeCoZr alloy resulted in the transition from high-ohmic to low-ohmic state with the x increase, without the change of hopping mechanism of carrier transport.

TRANSFORMATION OF ELECTRICAL ACTIVITY OF EXTENDED DEFECTS IN SILICON POLYCRYSTALS UNDER ANNEALING AND HYDROGEN PLASMA TREATMENT

The properties of nanostructures such as ultrathin layers 50 nanometers in thickness or smaller are strongly dependent on the state of a defect subsystem in the layers. The objective of this paper is to study the influence of charge states and internal elastic stress on the transport of point defects in silicon. The equation for the diffusion of point defects taking into account the contributions of different charge states of defects to the transport process is reduced to the form convenient for numerical solution. For this purpose, the effective diffusivity of point defects was obtained as a function of the dopant concentration and empirical parameters. The effective coefficient of the absorption of point defects by immobile sinks was also obtained in a similar convenient form. Using the modified equation for the diffusion of point defects, we have simulated the transport processes of diffusing species for different charge states of defects and nonuniform dopant distributions. The cases of zero and nonzero elastic stress were investigated.

Low-Temperature DC Carrier Transport in (Fe0.45Co0.45Zr0.10)x(Al2O3)1−x Nanocomposites Manufactured by Sputtering in Pure Ar Gas Atmosphere

Electrical activity of grain boundaries (GBs) and its transformation under the influence of low-energy hydrogen plasma treatment in p-type silicon bicrystalline samples cut from EFG silicon polycrystals were investigated. Comprehensive studies have enabled one to investigate the electrical activity of GBs relative to the minority (MIC) and majority (MAC) carriers and to demonstrate the possibility of controlling this activity by different processing methods. These studies allowed for establishing the correlation between the type, structure and individual electrical activity of GBs and also thermal pre-history of samples. Among the tested modes, hydrogenation was found to be the most radical method of electrical activity modification for all types of GBs. In the process, results on hydrogenation of GBs in EFG silicon crystals depend essentially on three factors: type of GBs, state of ribbons (as-grown or annealed) and concurrence of grain boundary dangling bonds and boron passivation effects.

Photoemission electron microscopy of arrays of submicron nickel rods in a silicon dioxide matrix

A possibility to control the electrical activity of extended defects (grain boundaries, dislocations) under annealing and hydrogen plasma treatment by different regimes of silicon ribbons grown with the edge-defined film-fed growth technique was studied. It is shown that the results of hydrogenation of grain boundaries (GBs) significantly depend on two factors: the type of GBs (deviated or general) and the state of ribbons (as-grown or annealed). Heat treatment of polysilicon in different ambients results in a considerable decrease of the electrical activity of dislocation, and special and weakly-deviated GBs too. On the contrary, the activity of general and highly-deviated GBs is enhanced after annealing. Our investigation has revealed that the electrical activity of general GBs is defined significantly by the cooling rate after annealing.

Charge states and distribution of iron ions in polycrystalline cubic boron nitride

This presented work investigates the structure and temperature relationship/dependence of the DC conductivity in the (Fe0.45Co0.45Zr0.10)x(Al2O3)1−x nanocomposites deposited in Ar atmosphere with composition (  at.%) and temperature (  K). It is shown that VRH displayed crossover from Mott-like to Shklovskii-Efros regimes which occurred at temperatures of 100–120 K. It is also noted that the observed shift of the percolation threshold to higher concentrations of metallic fraction can be attributed to the disordering of the metallic nanoparticles due to the incorporation of the residual oxygen in the vacuum chamber during the deposition procedure.

Electrical characterization of interfaces in unitype directly bonded silicon wafers

Arrays of Ni rods (∼500 nm diameter) formed by the ion-track technology in combination with electrochemical deposition into a SiO2 matrix on the surface of single-crystal silicon plates have been investigated using photoemission electron microscopy with high-intensity synchrotron (undulator) radiation. An analysis of the Ni L2,3 X-ray absorption near-edge structure (XANES) spectra has demonstrated that rod-like structures in pores and connecting bridges between the rods are formed by a metallic nickel phase, which is stable to oxidation by atmospheric oxygen. No formation of intermediate compound phases (nickel silicides and oxides) is observed at the Ni/SiO2 heterojunction, whereas oxidized nickel(II) species are identified on the surface of the SiO2 matrix, which presumably can be attributed to nickel silicate and hydroxide compounds formed upon nickel(II) chemisorption in electrochemical deposition electrolytes.

Evaluation of market needs in Belarus for improvement of master-level education in the field of physical sciences

Abstract The local electronic states and distribution of 57 Fe ions in cubic boron nitride (c-BN) polycrystals as a function of technological processing were investigated. The study has been performed on c-BN samples prepared by catalytic synthesis and by direct phase transformation. It was established that in catalytically synthesised c-BN iron ions are predominantly incorporated into the grain bulk in Fe 3+ charge state. In the contrary, in c-BN manufactured by direct phase transformation Fe ions are distributed mainly along the grain boundaries in Fe 2+ state probably due to the enhanced grain boundary diffusion of iron. Suppression of grain boundary diffusion of Fe ions (and their predominant incorporation into the grain bulk) under catalytic synthesis was ascribed to interlocking of Fe ions movement by precipitation of nitrides and borides of catalytic impurities (Al and Si) nucleated at the grain boundaries during c-BN synthesis.