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Chemical vapor deposited nitrogen-doped graphene, transferred on SiO2/Si substrate was selectively patterned by femtosecond laser ablation for formation of the topology dedicated for charge carrier measurements. Ultrashort 1030 nm wavelength Yb:KGW fs-laser pulses of 22 μJ energy,14 mJ/cm2 fluence, 96% pulse overlap and scanning speed of 100 mm/s were found to be optimum regime for the high throughput microstructure ablation in graphene, without surface damage of the substrate in the employed fs-laser micromachining workstation. Optical scanning electron, atomic force microscopy as well as Raman spectroscopy were applied to clarify the intensive fs-laser light irradiation effects on graphene and substrate as well as to verify the quality of the graphene removal. Measurements of magnetotransport properties of the fs-laser ablated nitrogen-doped graphene microstructure in the Hall configuration enabled determination of the type as well as concentration of charge carriers in a wide temperature range.

We study the changes of Bi electronic structure near T and L points of the Brillouin zone caused by doping with Sn (concentrations 0.08 at.%). Hall coefficient and magnetoresistance measurements (under magnetic field up to 8 T) enabled calculation of magnetoconductivity tensor components. The usage of quantitative mobility spectrum analysis together with the isotropic approximation for band structure allowed the estimation of Fermi level position at temperatures 10–300 K. The results have shown that Sn doping shifts the Fermi level down on the energy scale at the L point (in all temperature range) and at the T point under (primarily at low temperatures), leading to the decrease of band overlap.

We present the results on low temperature current-voltage characteristics of noncompensated Si doped by Sb. In the temperature range 1.9–2.25 K and at electrical fields smaller than 1 V/cm, the negative differential resistance (NDR) was observed. The external magnetic field enhances the region of the NDR. We attribute this effect to the delocalization of the D− states in the upper Hubbard band due to the accumulation of the charge injected by current.

In our work, we studied zinc oxide ceramic samples doped with aluminum and gallium. Structure peculiarities of ceramics depending on their synthesis regime were investigated by the SEM, EDX, XRD, and Raman spectroscopy methods. It was demonstrated that at some technological conditions the formation of indesirable phases of zinc aluminate or gallate may occur preventing an uniform material doping and reducing quality of samples. Single-phase ZnO ceramics were produced when the nanostructured alumina powders were used as a dopant source. The correlations between the synthesis regimes of ZnO ceramics and their electrophysical parameters essential for thermoelectric figure-of-merit (electrical conductivity and Seebeck coefficient) have been established. The best electrophysical characteristics were obtained when the nanostructured alumina produced by combustion in isopropyl alcohol was used as a dopant. Conductivity and Seebeck coefficient of such ceramics are equal to 3·103 S/m and -0.27 mV/K, respectively, corresponding to the power factor of 2.2·10-4 W/(m·K2).

Seebeck coefficient values measured for textured polycrystalline Bi films have been compared with numerically computed ones. The proposed computation procedure requires crystallographic texture mapping and values of single-crystalline transport coefficients as input data. The comparison of computed and measured Seebeck coefficients allowed determining the factors affecting films' transport properties except of crystalline texture. Two particular cases are considered: when the film properties are affected only by texture and when they depend on texture and grain size simultaneously.

In the present paper we have studied the peculiarities of carrier transport properties of nanoheterostructures containing silicon substrate covered with porous silicon layer, where pores were either filled or non-filled with ferromagnetic Ni clusters.We have carried out DC conductivity experiments as a function of temperature (ranging from 2 to 300 K) and porosity of porous silicon layer (between 30% and 70%). Presence of a surface layer with high resistance on the porous silicon top and its role in nanoheterostructure formation was revealed. It was shown that specific electrochemical kinetics of Ni deposition into porous silicon significantly influences resultant nanostructure resistance and high temperature conductance activation energy.

It has been established that in the nanocomposite Cux(SiO2)(100 x) with the metallic phase content x = 27.27 at.% the following phenomena occur: hopping conductivity, additional polarity and coilless-like inductance. Coilless-like inductance phenomenon consists in the occurrence of positive values of phase shift in the high frequency area. Activation energy of the dielectric relaxation time for copper nanoparticles of unoxidized surface is of approx. 0.0003 eV, whereas surface oxidation causes a potential barrier occurrence and activation energy increase up to approx. 0.3360 eV. Comparative analysis of results obtained for the Cux(SiO2)(100 x) material and the measurements results obtained for the nanocomposites (FeCoZr)x(Al2O3)(100 x), (FeCoZr)x(CaF2)(100 x) and (FeCoZr)x(PZT)(100 x), which containing nanoparticles of ferromagnetic alloy, has been performed. It has shown that the type of magnetic properties of metallic phase, which is ferromagnetic ones for FeCoZr and diamagnetic ones for Cu, does not affect capacitive and inductive phenomena of the nanocomposites. The phenomena are related only to the nanogranular structure of the materials and the hopping mechanism of the charge transport between the metallic phase nanoparticles.

In this paper the results of investigations of electrical properties of metal dielectric nanocomposites (FeCoZr)x(CaF2)100􀀀x are presented. The samples with the metallic phase content x = 45:7 at.% were produced by ion-beam sputtering method in pure argon atmosphere, and subsequently annealed at 398 K for 15 min. The measurements of electrical properties were performed in the frequency range from 50 Hz to 1 MHz. The frequency dependences of phase angle , capacity Cp, conductivity and dielectric loss factor tan were measured at seven di erent temperatures ranging from 148 K to 263 K. It was found that the nanocomposite exhibits the phenomena of voltage resonance and current resonance, characteristic of the conventional RLC circuits with series and parallel connections of elements.

It is shown that the magnetoresistive properties of n–Si/SiO2/Ni, nanostructures containing nanogranular nickel rods in a SiO2 layer’s vertical pores substantially differ from the similar properties in the earlier studied nanogranular Ni films electrodeposited onto the n–Si plates. From the point of view of the electrophysical properties, the nanostructures studied are analogous to a system of two Schottky Si/Ni diodes, which are connected to each other. The magnetoresistance of such structures has been studied in the temperature range from 2 to 300 K and the magnetic field range of up to 8 Tl. It is established that at temperatures of 17–27 K the structures possess a positive magnetoresistive effect, whose value depends on the transverse voltage applied to the structure and increases with a decrease in the longitudinal (along the rods) current intensity. At a current of 100 nA, the relative magnetoresistance in the field of 8 Tl increases from 500 to 35000% by an increase in the transverse voltage from 0 to –2 V. The observed magnetoresistive effect is associated with the influence of the magnetic field on the processes of impact ionization of impurities resulting in an avalanche breakdown of the Ni/Si Schottky barrier. Thus, the possibility of controlling the magnetoresistive effect in n–Si/SiO2/Ni template structures by applying an additional (transverse) electric field to the nanostructure between the silicon substrate (as the third electrode) and nickel rods is proven.

In this paper the results of examinations of nanocomposites Cux(SiOy)100􀀀x produced by ion beam sputtering using argon ions were presented. The examinations were performed by the use of ac devices for measuring frequency in the range 50 Hz - 1 MHz and temperatures from 81 K to 273 K. The measurements were performed for the samples directly after production. Based on temperature dependences of conductivity , which were determined at the frequency 100 Hz, the Arrhenius graphs were prepared. From these graphs conductivity activation energies E were calculated. Dependences of conductivity and activation energy of electrons on the metallic phase content x at the frequency 100 Hz were determined. Analysis of the obtained dependences shows that conductivity is a parabolic function of the metallic phase content x in nanocomposites. Changes of activation energies of nanocomposites, in which metallic phase contents are in the ranges x < 12 at.% and x > 68 at.%, demonstrate negative values and metallic type of conductivity. In the range 12 at:% < x < 68 at:% activation energies have positive values and the dielectric type of conductivity. It was established that for the metallic phase content of about 68 at.% the real percolation threshold occurs, and the conduction changes from dielectric to metallic type.

The present paper investigates the temperature/frequency dependences of admittance Z in the granular Cux(SiO2)1􀀀x nanocomposite lms around the percolation threshold xC in the temperature range of 4 30 K and frequencies of 20 MHz. The behavior of low-frequency ReZ(T) dependences displayed the predominance of electrons hopping between the closest Cu-based nanoparticles for the samples below the percolation threshold xC = 0:59 and nearly metallic behaviour beyond the xC. The high-frequency curves ReZ(f) at temperatures T > 10 K for the samples with x < xC exhibited behavior close to ReZ(f) f􀀀s with s 1:0 which is very similar to the known Mott law for electron hopping mechanism. For the samples beyond the percolation threshold (x > xC), the frequency dependences of ReZ(f) displayed inductive-like (not capacitive) behaviour with positive values of the phase shift angles.

In this work anisotropic magnetoresistance in nanogranular Ni lms and Ni nanorods on Si(100) wafer substrates was studied in wide ranges of temperature and magnetic feld. To produce Ni films and nanorods we used electrochemical deposition of Ni clusters either directly on the Si substrate or into pores in SiO2 layer on the Si substrate. Pores, randomly distributed in the template have diameters of 100-250 nm and heights about 400-500 nm. Comparison of temperature dependences of resistance and magnetoresistance in Ni films and n-Si/SiO2/Ni structures with Ni nanorods showed that they are strongly dependent on orientation of magnetic field and current vectors relative to each other and the plane of Si substrate. Moreover, magnetoresistance values in n-Si/SiO2/Ni nanostructures can be controlled not only by electric field applied along Si substrate but also by additionally applied transversal bias voltage.

The paper presents results of testing electric properties (resistance, capacity and phase angle in an equivalent parallel circuit) of ferromagnetic alloy-dielectric nanocomposites (FeCoZr)x(PZT)(100 x) produced by ion-beam sputtering in vacuum conditions. The measurements have been performed using alternating current within the frequency range of 50 Hz -1 MHz for measuring temperatures ranging from 77 K to 373 K. In nanocomposites (CoFeZr)x(PZT)(100 x), produced by ion beam sputtering using a beam of combined argon and oxygen ions, for x approaching the percolation threshold, frequency dependences of the phase angle 4 that resemble those occurring in RLC parallel circuits have been observed. In the low frequency area, the phase angle of 90 - 0 occurs. It corresponds to the capacitive type of conduction. In the high frequency area, the inductive type of conduction with 0 - 90 occurs. At the resonance frequency f0, characterized by the phase angle of 0 , the capacity value reaches its strong local minimum. A theoretical basis for a model of the AC hopping conduction for metal-dielectric nanocomposites has been developed and on that basis frequency dependences of the phase angle, resistance and capacitive current density components have been analyzed. The obtained theoretical and experimental results have been compared.

Grain structure and the temperature dependences of resistivity, magnetoresistance, Hall and Seebeck coefficients measured in the range from 4 to 300 K were investigated for polycrystalline bismuth films obtained by the melt spinning (MS) and electrochemical deposition (ECD) methods. Charge-carrier concentration and mobilities were calculated assuming the carrier scattering on acoustic deformation potential as the dominant scattering mechanism, parabolicity of holes dispersion law, implying the Lax model for L-band electrons and neglecting the influence of L-band holes on conductivity. The experimental results and calculations have demonstrated that the electrical properties of the Bi films studied are strongly affected by the grain-boundary density.

This presented work investigates the structure and temperature relationship / dependence of the DC conductivity 𝜎(𝑇) in the (Fe0.45Co0.45Zr0.10)x(Al2O3)1−x nanocomposites deposited in Ar atmosphere with composition (30 < 𝑥 < 100 at.%) and temperature (2 < 𝑇 < 300 K). It is shown that VRH 𝜎(𝑇) displayed crossover from Mott-like to Shklovskii-Efros regimes which occurred at temperatures of 100–120K. 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.

The dependences of resistivity, magnetoresistance, Hall effect and thermoEMF in the 4 – 300 K temperature range and in magnetic fields up to 8 T were studied for the Bi1-xSnx (0 ≤ x ≤ 0.006) diluted alloys produced by the melt spinning method. The observed decrease of conductivity and magnetoresistance with doping is explained in terms of charge carriers scattering on tin atoms, whereas the shift of the Hall and Seebeck coefficients to the range of positive values is connected with enhanced contribution of holes in the charge transport.

The paper reports on a comparative study of local Fe states, phase composition and magnetoresistivity of granular nanocomposite films FeCoZr–CaF2 sintered in pure Ar and Ar + O sputtering atmosphere. For the first time peculiarities of temperature and magnetic field dependencies of magnetoresistance are analyzed with respect to partial oxidation of nanoparticles and perpendicular magnetic shape anisotropy.

In the doped crystals TlGaSe2 and TlInS2, using method of temperature dependencies of DC resistance in the temperature range of 100 – 300 K, the phase transitions at the temperatures of 240 – 245 K and 105 – 120 K were observed. The AC conductance measurements at room temperature indicated the hopping mechanism of carrier transport in the studied samples.

The study of electrical resistivity  and magnetoresistance MR in nanogranular Ni films was performed over the temperature range 2 - 300 K and at the magnetic field induction B up to 8 T. The Ni layers having a thickness of about 500 nm were prepared by electrodeposition on n-Si wafers. According to an X-ray diffraction study, a strongly textured face-centered cubic structure was formed in the as-deposited films with an average grain sizes of about 10 - 70 nm. Experiments have demonstrated that the magnetic field and temperature dependences of the MR effect in Ni films shown two main peculiarities: (1) dependencies on the mutual orientations of vectors B, current and the film plane; (2) two contributions to the MR - negative anisotropic magnetoresistance and positive Lorentz-like MR.