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The field and temperature magnetoresistance dependences of the Si1− xGe x ( x = 0.05) whiskers at low temperatures were studied in the magnetic field range of 0−14 T with using of the Bitter magnet. The investigated whiskers with diameters 5−15 μm were grown by chemical vapour deposition with a doping concentration in the vicinity to the metal-insulator transition ( Nc ≈ 7.8 ⋅ 1018 cm−3). The linear magnetoresistance effect of the solid solution Si1- xGe x whiskers was found in all range of the magnetic fields due to the surface coherence scattering of charge carriers as a result of conduction in the whisker core-shell structure.

The temperature dependences of resistance of n-type conductivity Bi2Se3 whiskers with doping concentration (1–2)⋅1019 cm−3 were studied in the temperature range 1.6–300 K. The sharp drop of the resistance was detected that is a result of a partial transition to the superconductive state at the critical temperature Tc = 5.3 K and probably due to the inclusion of β-PdBi2 phase in the studied samples. The transverse magnetoresistance of Bi2Se3 whiskers with various concentration of Pd doping impurity corresponding to the metal side of metal-insulator transition was studied in a magnetic field of 0–10 T. Superconductivity suppression effect by the magnetic field was found that permits to create the basic parameters such as the upper critical field Bc2 = 1.5 T, the coherence length of the superconductor ξ (0) = 15 nm and the superconducting gap Δ ≈ 0.8 meV. Studies of the n-type conductivity Bi2Se3 whiskers allow to create on their basis magnetic field sensors with a sensitivity of about 3.5% / T, capable in the temperature range of 4.2–77 K. The investigated crystals can also be used in the magnetic switch-control sensors magnetic switches due to the transition to the superconducting state at the critical temperature Tc, depending on a magnetic field induction.

The article studies the motivational sphere of 4-6 year old preschool children with autism spectrum disorder (ASD). The study involved 20 children (15 boys and 5 girls) with ASD and 20 healthy peers (15 boys and 5 girls) from pre-school organisations of Lviv. The indicators of ASD children’s development were determined by Binet-Simon Scale for Measuring Intelligence and the Child Autism Assessment Scale (CARS). The average rates of mental development of ASD children were lower than the rates corresponding to their biological age; their delay ranged from 1 year and 2 months to 5 years and 10 months. The investigated children were distributed by autism levels in the following manner: 53% of the children had the low level, 42% had the average level and 5% had the high level of autism. Since the children’s emotions and their self-esteem are important for description of their motivational sphere, these indicators were determined by A. Prizhozhan’s method and M. Lusher's (eight-) colour test. The children’s learning motivation was studied with the questionnaire determining the priority of children’s motives. The healthy children demonstrated the prevalence of social motives over cognitive ones, whereas the ASD children demonstrated the opposite trend. In addition, the ASD children were more interested in a learning process, not in learning results. On the contrary, their healthy peers were more focused on success achievement. The analysed factors allowed us to construct the structural and functional model of learning motivation formation for children with ASD. The model was used in the preschool group for 6 months and ASD children’s motivation was significantly increased (by the following indicators: satisfaction of the need in safety, the psychological climate of a group, formation and partial satisfaction of cognitive needs). The identified changes were reliable, exceeding possible age-related and adaptation changes of the indicators; so, this model can be efficiently used for formation of learning motivation at children with ASD in the Ukrainian pre-school educational organisations.

The measurements of the magnetoresistance for p-type poly-Si with concentration 2.4 × 1018 cm−3 were carried out in the low temperature range 4.2–20 K and in the magnetic field up to 14 T. The results showed the presence of a negative magnetoresistance in polycrystalline silicon films in SemOI-structures. The low-temperature transport of charge carriers in p-type polycrystalline silicon films was considered within the framework of hopping conductivity and can be described by the spin–orbital interaction in the theory of weak localization. The calculated values of the coherence phase length 3–4 nm and the spin–orbit coherence length 30–50 nm at low temperatures 4.2–30 K correlate with parameters of hopping conductance and grain size, respectively, which show a contribution of Rashba spin–orbit interaction with energy ΔSO = 1.6 meV in the conductance not only inside the grains, but also its surface and between grain boundaries of polycrystalline silicon in SemOI structures.

The transverse and longitudinal magnetoresistances of GaSb microcrystals with tellurium doping concentration of 1.7 × 1017 cm−3 under the influence of uniaxial compression strain were studied in high magnetic fields of 0–14 T. Low-temperature Shubnikov–de Haas oscillations were observed for unstrained and strained n-type conductivity GaSb microcrystals in the whole range of the magnetic fields. The magnetoresistance oscillation amplitude decreases with the temperature increasing in the range of 4.2–30 K. The Shubnikov–de Haas oscillation period was changed due to the strain influence, and it was found to be 0.039 T−1. The emergence of the splitting at a magnetic field of about 7 T was revealed in the longitudinal magnetoresistance of GaSb microcrystals doped to a concentration in the vicinity of the metal–insulator transition. The value of the g-factor was found in the strained samples, and it has a value of 53. The strain influence on the effective mass of the electron mc and the Dingle temperature TD were also studied. The appearance of the Berry phase caused by the strain was revealed in GaSb microcrystals allowing their transition to the topological insulator state.

The Schumann resonances (SR) in Earth’s atmosphere are electromagnetic waves of extremely low frequencies (ELF). The first four modes propagate at 7.4 Hz–26 Hz. Recently, the massive particles emitted by the Sun/stars have been detected by two acoustical methods including the acousto-electric properties of 10 MHz quartz oscillators and ELF vibrations of suspended lightweight crystals. In this work, the frequencies of solar/stellar massive particles propagating through the atmosphere and landing on Earth are revealed and compared with SR frequencies. The measurements of acousto-electric admittance Y of free vibrating quartz oscillators reveal that Y(F) are changed from known resonance-antiresonance curve to a pulse type dependency Yp(F) with a number of deep minima. They occur when piezoelectric crystal axis is oriented toward a star emitting massive particles. The waveforms (WF) of vibrating suspended light-weight quartz crystals were detected by a laser Doppler vibrometer. The Fast Fourier transform spectra obtained from the Yp(F) and WF time dependencies reveal the spectra of massive particles M(F) with which they were hitting the crystals. The M(F) spectra extend from 2 to ∼30 Hz, which correlates with SR spectra. In addition, the maxima in SR modes and M(F) spectra are very close or coincide.

Giant magnetoresistance (up to 700%) of the deformed InSb whiskers with doping concentration 6×1016-2×l017 cm−3 was observed in magnetic fields with induction up to 10 T at temperature range 4.2–70 K. The effect was explained taking into account two-channel conductivity of the whiskers with core-shell structure. Besides, the obtained results were discussed in the framework of the quantum magnetoresistance theory. The obtained results allow to design the magnetic field sensor on the deformed InSb whiskers.

The paper proposes a comprehensive approach for the investigation of polycrystalline layers of SemOI- structures in a wide range of concentrations of dopant from 2.4×10−18 go 1.7×10−20 cm−3 for the temperature range 4.2-70 K by studying the frequency response in the frequency range from 0.010- 250 kHz and its analysis by the equivalent circuit method.

Studies of polysilicon in a wide range of concentrations from 2.4 × 1018 to 1.7 × 1020 in temperature range 1.6–300 K and high magnetic fields up to 14Т were carried out in order to predict the characteristics of a material suitable for the creation of microelectronic sensors of physical values based on SemOI-structures. One of the advantages of SemOI-structures is the ability to receive layers with difference in resistivity in a wide range: several orders of magnitude. As it is determined by studies at low temperatures the transfer of charge carriers in polysilicon occurs due to hopping on localized impurities. There have also been found combined mechanisms of current flow at low temperatures, which, depending on the observation temperature, are evident in the transition from the Mott law to the percolation mechanism of Shklovskii-Efros. Those effects can be used to create elements of sensor technology. Sensors of thermal quantities for cryogenic temperatures were developed with TCR = − 9% × K−1 in the range of 4.2–50 K and mechanical quantities for cryogenic temperatures were developed for ultra-sensitivity with coefficient of gauge-factor K = 15500 in the range of 4.2–50 K. Investigation in wide range of cryogenic temperatures was conducted with the purpose of optimizing the geometry of the sensor membrane (its thickness and surface area) in order to obtain optimal stresses and deformations in the membrane. This process is essential for the sensor to be able to provide a sufficient amount of the output signal while maintaining the strength of the membrane and the sensor structure as a whole.

The half-inch diameter quartz oscillators are set for free vibrations. The crystal admittance (Y) versus frequency of ultrasound (F) is measured near fundamental harmonic of 9-10 MHz. The quartz crystallographic axes X, Y, interplain and rotated are oriented in space toward the sky locations of the Sun, center of the Milky Way galaxy or another star. It is demonstrated that Y(F) spectra are sensitive to an alignment of the crystallographic axes with space direction toward the stars. The two general results include: (1) changing Y(F) from a few to tens of percents under aligning crystallographic axes toward the stars and (2) occurring periodic minima in Y(F)-dependencies taken during some seconds with a tracking generator synchronized with a spectrum analyzer. The deepest minima in Y(F) appear when the azimuths of crystal axes coincide with those of the stars. These changes may be explained by electrically neutral massive particles (mp) emitted from a star and interacting with the crystals. The mass of a single mp-particle is estimated around ∼5 × 10−21 kg. RUS measurements correlate with the data from a crystal pendulum having a quartz bob and starts swinging when mp-particle hits it. RUS of free vibrating oscillators is perspective for detecting stellar massive particles.

Job placement of persons with special needs is a problem in Ukraine, because of absence of qualified tutors for accompaniment at a workplace. The aim of the article is presentation and development of the institute of tutorship, necessary for the effective job placement of persons with autism spectrum disorders (ASD). Tutors must solve two important tasks: 1) the diagnostics of professional competences of persons with ASD; 2) the support of persons with ASD at job placement and at the primary stage of their work. Using the method “Adolescent and Adult Psychoeducational Profile” (AAPEP) there were studied professional competences of 30 teenagers with ASD from Lviv workshop “Kolping business”. The results demonstrated the high level of independence, satisfactory behavior at a workplace, middle level of professional mastership and low level of social interaction in teenagers with ASD. The obtained data indicate the necessity of introduction of the post of a tutor for supporting persons with ASD at a workplace. There was elaborated the curriculum for training tutors for job placement of persons with invalidism. The educational program includes 22 credits of theoretical and practical courses and also probations that must be introduced by the development of dual education

An influence of a magnetic impurity distribution on the AC transport of charge carriers in silicon whiskers doped with boron and nickel at low temperatures was investigated. The concentration of Ni impurities obtained from impedance and magnetization data was shown to coincide and equal to 3×1017 cm−3. The obtained hysteresis of the whisker magnetization was used to design multifunctional sensor as well as storage device.

The article deals with the studies of strain influence of n-type GaSb whiskers magnetoresistance at low temperatures 4.2 – 60 K The crossover from WAL to WL occurs under the compressive strain at 4.2 K The field dependency of the whiskers magnetoresistance was used for design of sensor of magnetic field induction in the range 1-11 T.

Germanium whiskers with gallium concentration $2\times 10^{17}\mathrm {c}\mathrm {m}^{-3}$ were chosen to investigate magnetoconductance in the range 0-14 T at 4.2 K under compressive strain up to - $2\times 10^{-3}$ rel.un. Strain influence on spin-orbital splitting on the valence band spectrum was studied. As result, the splitting of light and heavy hole branches was found under compressive strain according to kp-method. The spin splitting energy $\Delta \mathrm {s}\mathrm {o}$ as well as Rashba cubic parameter $\beta \mathrm{so}$ was found due to studying the longitudinal magnetoconductance of Ge whiskers at low temperatures.

The basis of the research of this work is to predict the characteristics of sensors of the thermal quantities based on silicon whiskers admixture with B & Ni impurities. In these samples, the concentration of the transport impurity of boron corresponds to the phase transition of the metal-insulator in silicon from the metallic side. On the basis of experimental temperature dependences of resistance of microcrystals Si (B, Ni) with a concentration of boron NB≈l×1019 cm−3 and resistivity crystals P300k=0.007 Ohmxcm in the temperature range 4,2-300 K, the linear dependence of the resistance versus temperature with positive values of the temperature resistance coefficient is shown. Determined by the temperature of liquefied helium maximum magnetoresistance reaches no more than 4% in magnetic fields with induction do14T. Proposed thermoresistive sensor is working in harsh operating environment and is resistant to the influence of destabilizing factors.

Silicon whiskers with boron concentration 2×1018cm-3 were chosen to investigate magnetoconductance in the range 0–14 T at 4.2 K under compressive deformation up to -2×10-3 rel.un. Deformation influence on spin-orbital splitting on the valence band spectrum was studied. As result, the splitting of light and heavy hole branches was found under compressive deformation according to kp-method. The spin splitting energy Δ so was found due to studying the longitudinal magnetoconductance of Si whiskers at 4.2 K.

The previously unknown energetic dark particles (EDP) of (4±1.5)10E15 eV mass-energy from the Milky Way center (CMW) are directly detected. Particles are named Navitens. The vibrations in piezoelectric crystals are theoretically calculated along with nonlinear effects due to frictional influence of EDP producing changes in the spectra of vibrations under orientation of crystallographic axes toward CMW. The mechanism of EDP-crystal interaction may be associated with the gravitational influence of EDP and their quantum properties, such as matter waves. The EDP energy density is 0.3 – 0.7 (GeV/ cm cub.) near Earth, which agrees with the existing astrophysical bounds for dark matter in the solar neighborhood. The uncertainties are due to different times of observations. The EDP can transfer their momenta-energy to a media of propagation. The influence of Navitens on vibrating atoms are detected from 10 different samples during several years. The micro-void tracks of EDP-particles are also observed in the vibrating plates of fused quarts and silica glasses. It happens because EDP may decay inside solid media. The existence of EDP-Naviten particles agrees with recent detection of ∼10E15 eV energy neutrinos from the CMW region and rare observations of the cosmic rays of so-called knee-energy.

Магнітопровідність ниткоподібних кристалів Si з концентрацією легуючої домішки 2 x 1018 см – 3 досліджували в інтервалі магнітних полів 0-14 Тл при кріогенних температурах за деформації стиску до – 2 x 10 – 3 відн. од. Легування кристалів бором здійснювали у процесі росту методом хімічного парофазного осадження і концентрація носіїв заряду, згідно холлівських вимірювань, становила порядку 2 x 1018 см – 3. Одновісну деформацію ниткоподібних кристалів здійснювали шляхом їх закріплення на підкладках з використанням термічної деформації за рахунок різниці коефіцієнтів термічного розширення кристала і матеріалу підкладки. Досліджено поздовжній магнітоопір для недеформованих і деформованих зразків Si в інтервалі температур 4.2 ÷ 70 К. Недеформовані зразки мають квадратичну залежність магнітоопору від індукції магнітного поля. Деформація приводить до появи великого від’ємного магнітоопору з максимальною величиною до 15 %. Обговорюються можливі причини цього ефекту. Найбільш вірогідною причиною виникнення від’ємного магнітоопору є слабка локалізація носіїв заряду. Згідно з розрахунками у моделі слабкої локалізації носіїв заряду показано, що довжина когерентності Lφ і довжина спін-орбітальної взаємодії Lso пропорційна T– 0.53 і T – 0.45, відповідно, що відповідає теоретичним даним T– 1/2 для двовимірної системи. Це свідчить про те, що основний внесок у провідність ниткоподібних кристалів Si вносить транспорт носіїв заряду у приповерхневих шарах кристалів. Досліджено вплив деформації на спін-орбітальне розщеплення та спектр валентної зони ниткоподібних кристалів. В результаті розрахунків згідно k-p-методу виявлено значне розщеплення гілок легких і важких дірок під дією деформації стиску. Отримано енергію спін-орбітального розщеплення підзони важких дірок ∆SO, яка становить 1.8 меВ. Silicon whiskers with doping concentration of 2 × 1018 cm– 3 were chosen to investigate magnetoconductance in the range of 0-14 T at cryogenic temperatures under compressive strain up to – 2 × 10– 3 rel. un. The whiskers were doped with boron during the growth process by chemical vapor deposition method, and the concentration of charge carriers, according to Hall studies, was about 2 × 1018 cm– 3. The uniaxial strain of whiskers was carried out by fixing them to the substrates using thermal strain due to the difference between the coefficients of thermal expansion of the crystal and the substrate material. Longitudinal magnetoresistance for unstrained and strained Si whiskers was studied in the temperature range of 4.2 ÷ 70 K. The unstrained whiskers have a quadratic dependence of the magnetoresistance on the magnetic field induction. The strain leads to the appearance of negative magnetoresistance with sufficiently large magnitude (up to 15 %). The possible reasons of the effect were discussed. The most probable reason of negative magnetoresistance appearance is weak localization (WL) of the charge carriers. According to calculations within the WL model, the coherence length Lφ and spin-orbit length Lso are proportional to T− 0.53 and T− 0.45, respectively. The latter one is closed to T− 1/2 expected from the theoretical data for a twodimensional system. This fact is the evidence of the conclusion that conductance in Si whiskers mostly occurs in the subsurface layers of crystals. Strain influence on spin-orbit splitting and the valence band spectrum was studied. As a result, the splitting of light and heavy hole branches was found under compressive strain according to the k-p-method. The spin splitting energy for sub-band of heavy holes ∆SO was found to be 1.8 meV.

Whiskers are a new material that is characterized by high structural perfection, chemical resistance and strength which reaches the theoretically possible limit for crystals of small transverse dimensions. The test whiskers were synthesized by the method of chemical transport reactions in a closed bromide system using gold as the initiator of growth. The crystals were irradiated by protons with an energy of 6 MeV and doses of 5×10 13 , 10 15 and 1×10 17 p + /cm 2 at 40 °C in a U-120 cyclotron. The effects of proton irradiation and high magnetic fields on the magnetoresistance of Si 1- x Ge x ( x = 0,03) whiskers in the 4.2–300 K temperature range has been studied. A slight decrease in the electrical resistance of the crystals in the 4.2–40 K temperature range during irradiation with small proton doses and a significant increase in their resistance in the entire investigated temperature range for a dose of 1×10 17 p + /cm 2 have been found. The ionization energy of the impurity atoms in different magnetic fields has been calculated. It has been revealed that the energy level of the impurity depends on the magnetic field but slightly which in turn indicates a independence of the concentration of holes on the magnetic field. It has been shown that a significant magnetoresistance at all studied temperatures was due to the magnetic field-caused decrease in the mobility of free carriers (holes). It has been found that the concentration of holes depends on magnetic field but a little. Conclusion has been made about a negligible expansion of the band gap in magnetic fields of up to 8 T.

Negative magnetoresistance of InSb whiskers with different impurity concentrations 4.4 × 1016–7.16 × 1017 cm−3 was studied in longitudinal magnetic field 0–14 T in the temperature range 4.2–77 K. The negative magnetoresistance reaches about 50% for InSb whiskers with impurity concentration in the vicinity to the metal–insulator transition. The negative magnetoresistance decreases to 35 and 25% for crystals with Sn concentration from the metal and dielectric side of the transition. The longitudinal magnetoresistance twice crosses the axis of the magnetic field induction for the lightly doped crystals. The behavior of the negative magnetoresistance could be explained by the existence of classical size effect, in particular boundary scattering in the subsurface whisker layer.

Study the magnetic properties of Si whiskers, the concentration of which corresponds to a dielectric and metal side of metal-insulator transition, is performed. Percolation laws of the magnetic clusters formation, that is important for development of spintronic devices, are considered.

Negative magnetoresistance of Si p-type whiskers with different impurity concentration $10^{18} - 5\times 10^{18}$ cm−3 which corresponds to the transition of a metal-dielectric in silicon and diluted with nickel were studied in longitudinal magnetic field 0–14 T in the temperature range 4.2–77 K. The large negative magnetoresistance values correspond to hopping conductance on the twice occupied by electrons impurity states. It is established that in order to predict the magnetoresistance of crystals, it is necessary to take into account the polarization component due to the nature of the hopping conductance at low temperatures

Temperature dependencies of the n-type conductivity Bi 2 Se 3 whiskers doped with palladium Pd dopant to the concentration of $(1\div 2)\times 10^{19}\text{cm}^{-3}$ which correspond to the metal side of the metal-insulator transition (MIT) were studied at low temperatures down to 1.5 K. The sharp drop was revealed on the temperature dependencies of the whiskers resistance at temperature of 5.3 K. The contribution of some effects as an electron localization, Kondo effect and the superconductivity were observed in the temperature range $1.5\div 77\text{K}$ . The magnetoresistance in the n-type conductivity Bi 2 Se 3 whiskers doped with different Pd concentration were measured in the magnetic field $0\div 10\text{T}$ and the same temperature range. The weak antilocalization model was considered as result of the magnetoconductance studies due to surface spin-orbit interaction in the n-type conductivity Bi 2 Se 3 whiskers.

A sensitive element of a magnetic field sensor with a resistive principle of action was proposed using microcrystals of silicon doped with boron to a concentration of 5 × 1018 cm−3, which corresponds to the metal-insulator transition in silicon with a nickel layer formed on the crystal's surface, as well as the construction of a spin filter whose working capacity is due temperature mode below 100K. Sensitive elements of magnetic field — temperature sensors were created on the basis of microcrystals Si , working at cryogenic temperatures with a thermosensitive element for which temperature coefficient of resistance (TCR) = 20% × K−1. Developed a sensitive elements of magnetic field — deformations sensors with a strain-sensitive element for which K = 165 at a temperature of 4.2 K.

The point defects in the spectra of photoluminescence of Lithium niobate (LN) and Lithium tantalate (LT) can be categorized as noble gases, heavy metals, and others. The distribution of charged defects (DCD) reveals peaks and valleys in a direction perpendicular to the z-axis, in both single crystals (SC) and periodically poled (PP) crystals. The distance between consecutive peaks and valleys equals the length of a ferroelectric domain in PPLT. The position of the ferroelectric domain wall with respect to point defects extrema is different in PPLT in comparison to PPLN. The DCD influences acousto-electric properties including electromechanical transduction (EMT) and electromechanical coupling coefficient (ECC), in a direction perpendicular to the z-axis. The results may be used to explain nonclassical nonlinearity in LN and LT crystals.

The energetic dark matter particles (EDP) of (4 + 1.5) x 1015 eV mass-energy propagating from the central region of the Milky Way galaxy (CMW) are directly detected with the help of half-inch ~10 MHz quartz vibrators. The spectra of acousto-electric vibrations of thin piezoelectric crystal are theoretically calculated, and a nonlinear effect of external frictional influence is taken into account. The EDP produce the changes in the spectra of vibrations under specific orientation of the crystallographic axes toward the CMW. The mechanism of EDP-crystal interaction may be associated with the gravitational influence of EDP and their quantum properties, such as matter waves. The EDP average energy density is 0.71 + 0.29 (GeV/cm3) near Earth, which agrees with the expectations and existing astrophysical bounds of dark matter density in the solar neighborhood. The EDP can transfer their momenta-energy to a media of propagation. The influences of EDP, or naviten, on vibrating atoms are detected from 10 different samples during 5 years. The micro-void tracks of EDP-particles are also observed in the vibrating plates of fuzzed quartz, which appear due to EDP decay inside solid media. The existence of EDP-particles is in agreement with recent detection of the ~1015 eV energy neutrinos from the CMW region.

Silicon-on-insulator structures are an important material for modern microelectronic devices, in particular, for sensors of various physical values. As the electro-transport properties of such initially polycrystalline dispersed structures vary with the treatment of poly-silicon layer, this will determine, in particular, the device implementation of SOI at low temperatures. In this paper we report on extended AC and DC studies of low-temperature electrical conductivity of SOI-structures with initial boron concentrations in the vicinity to metal–insulator transition (2.4×1018 сm−3 and 4.8×1018 сm−3 for non-recrystallized and recrystallized samples, respectively) and its peculiarities at the influence of high magnetic fields. In particular, together with the results of DC studies of resistivity the observation of negative magnetoresistance at low magnetic fields imply the hopping conductivity of poly-silicon layers at low temperatures (ln ρ~Т−1/4). The study of the properties of poly-silicon layers in SOI structures by impedance analysis method (AC measurements) allowed for determining the effect of material dispersion on its low-temperature conductivity and for separating and identifying the contributions of various microstructure elements in the sample conductivity. In both the DC and AC cases the Mott law hopping conductivity in non-recrystallized poly-Si samples has been confirmed at cryogenic temperatures around liquid helium point. A capacitive type of Nyquist plot in turn supported this assumption. In laser-recrystallized poly-Si layers the charge carrier transport is limited by grain barriers and corresponds rather to percolation type of conduction, obeying the Shklovskii–Efros law.

The parallel and transverse magnetoresistance in InSb and GaSb whiskers doped with tin and tellurium, respectively, were investigated in the temperature range 4.2–77 K and magnetic field 0–14 T. Shubnikov-de Haas magnetoresistance oscillations were revealed at low temperatures for both semiconductor materials with impurity concentration near the metal-insulator transition. The following parameters of InSb and GaSb whiskers as oscillation periods, cyclotron effective mass of electrons, g-factor and Dingle temperature were defined.

The article deals with the influence of the magnetic impurities on magnetoresistance of silicon whiskers. The features of transition of the metal impurities (nickel) in silicon crystals are investigated. It is shown that the interaction between nickel impurities and the crystal lattice of silicon promotes the formation of magnetic conglomerates on the surface of the crystal. The polarized conglomerates (polarons) can influence the transport properties of the crystal. The temperature of the cluster formation in the range of cryogenic temperatures was also calculated. A comparative analysis of the magnetoresistance of unalloyed crystals and crystals with magnetic impurities showed that the nickel impurity has a significant effect on the magnetoresistance of the crystal. It is proved that these samples can be used as switches in microelectronics under the influence of both the magnetic field and the temperature below 150K.

The spectra of photoluminescence (PL) from a YZ-cut Lithium niobate (LN) plate reveal point defects of heavy metals Fe and Ba. The distribution of point defects (DPD) is nonuniform and exhibits peaks and valleys, in a direction parallel to the z-axis. The distance between consecutive peaks and consecutive valleys is not more than a few mm. The point defects are sensitive to local electric polarization and influence the electromechanical transformation (EMT) at the local point of the crystal. The EMT is estimated by reading an electric potential (V) generated while applying a constant mechanical stress, at steps of hundreds of microns parallel to the z-axis. The distribution of EMT in LN is nonuniform; the distance between consecutive peaks and consecutive valleys is similar to the DPD. Higher the concentration of point defects more is the EMT, and lower the concentration of point defects lower is the EMT. The point defects are manifested as peaks and valleys in the frequency dependence of admittance measurements. The presence of point defects excites ultrasonic modes in the crystal when radio-frequency current propagates through it.The spectra of photoluminescence (PL) from a YZ-cut Lithium niobate (LN) plate reveal point defects of heavy metals Fe and Ba. The distribution of point defects (DPD) is nonuniform and exhibits peaks and valleys, in a direction parallel to the z-axis. The distance between consecutive peaks and consecutive valleys is not more than a few mm. The point defects are sensitive to local electric polarization and influence the electromechanical transformation (EMT) at the local point of the crystal. The EMT is estimated by reading an electric potential (V) generated while applying a constant mechanical stress, at steps of hundreds of microns parallel to the z-axis. The distribution of EMT in LN is nonuniform; the distance between consecutive peaks and consecutive valleys is similar to the DPD. Higher the concentration of point defects more is the EMT, and lower the concentration of point defects lower is the EMT. The point defects are manifested as peaks and valleys in the frequency dependence of admittance measu...

The concentration of point defects is investigated along the neighboring domains in a ZX-cut periodically poled lithium niobate (PPLN) plate. PPLN is a ferroelectric phononic crystal (FPC) in which the inversion of polarization occurs across the interdomain wall. The spectra of photoluminescence (PL) are recorded along the domain structure parallel to the x-axis, at room temperature. The PL spectra reveal a nonuniform distribution of defects along the PPLN. The striking result is that some defects have narrow extrema in PL-intensity right in the interdomain wall location. The spread in PL intensity from the average is higher in PPLN when compared to single crystal lithium niobate. Engineering application of these findings may be new non-destructive characterization method of ferroelectric phononic crystals.

The magnetization and magnetoresistance of Si whiskers doped with to boron concentrations corresponding to the metal-insulator transition (2 × 1018 cm−3 ÷ 5 × 1018 cm−3) were measured at high magnetic fields up to 14 T in a wide temperature range 4.2–300 K. Hysteresis of the magnetic moment was observed for Si p-type whiskers with nickel impurity in a wide temperature range 4.2–300 K indicating a strong interaction between the Ni impurities and the possibility of a magnetic cluster creation. The introduction of Ni impurity in Si whiskers leads to appearance and increase of the magnitude of negative magnetoresistance up to 10% as well as to the decrease of the whisker resistivity in the range of hopping conductance at low temperatures. The abovementioned effects were explained in the framework of appearance of magnetic polarons leading to modification of the conductive channels in the subsurface layers of the whiskers.

Polycrystalline silicon layers on the surface of oxidized silicon substrate, i.e. SOI-structures, with initial boron concentration (of about 2.4 × 1018 cm-3 ÷ 1.7 × 1020 cm-3) in the vicinity to metal-insulator transition have been investigated. Experimentally the AC performances for both non-recrystallized and recrystallized layers correlate with DC measurements. Conductivity caused by the hopping between localized states with energy magnitude close to the Fermi level, has a weak temperature dependence in the ranges where the Shklovskii-Efros law applies. In this case, the percolation type of charge carrier transport is observed. In contrast, the hopping conduction between localized states near the band edges has a strong temperature dependence, where the Mott law is obeyed. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A split-mode ultrasonic transducer is investigated in both theory and experiment. This transducer is a two-dimensional structure of periodically poled domains in a ferroelectric wafer with free surfaces. The acoustic vibrations are excited by a radio frequency electric current applied along the length of the wafer, which allows the basal-plane surfaces to be free of metal coatings and thus ready for further biomedical applications. A specific physical property of this transducer consists of the multiple acousto-electric resonances, which occur due to an acoustic mode split when the acoustic half-wavelength is equal to the domain length. Possible applications include ultrasonic generation and detection at the micro-scale, intravascular sonification and visualization, ultrasound therapy of localized small areas such as the eye, biomedical applications for cell cultures, and traditional nondestructive testing including bones and tissues. A potential use of a non-metallized wafer is a therapeutic application with double action that is both ultrasound itself and an electric field over the wafer. The experimental measurements and theoretical calculations are in good agreement.

Studies of the effects of strain and elemental composition on thermoelectric properties of SiGe microwires for sensor applications at the influence of strong magnetic fields have been performed. Magnetoresistance of compressed samples was substantially suppressed in comparison with their unstrained counterparts. The Seebeck coefficient for both kinds of SiGe wires remained weakly dependent on magnetic field intensity. Magnetic effects on transport properties of SiGe promoted with increase of Ge content in solid solution. Assessments of applicability of the developed thermoelectric sensors of temperature at strong magnetic fields were performed.

The paper deals with the solution of scientific and applied problems of development of elements of sensing equipment on the basis of silicon-on-insulator structures (SOI) doped with boron impurities. The paper presents the impedance measurements of electrical properties of polycrystalline silicon films (with concentration ranged from 2.4×1018 cm−3 to 1.7×1020 cm−3) in the silicon-on-insulator structures obtained in the temperature range 4,2–70K in the frequency range from 10Hz to 250kHz as well as checking a possibility of their use as components of solid state electronics efficient at cryogenic temperatures. Based on silicon-on-insulator structures the discrete solid state elements (inductive, capacitive elements) and combined elements (oscillatory circuits) implemented by positioning technologies were developed. To design the oscillatory circuit a combination of two elements consisting of SOI-structure with a dopant concentration corresponding to the dielectric and metal side of metal-insulator transition (obtaining by double diffusion of boron impurities in polysilicon) was used.

Transverse and longitudinal magnetoresistance of Ge and InSb whiskers with various impurity concentrations were studied at temperature range 4.2 – 77 K and in magnetic fields 0 – 14 T. Magnetophonone oscillations of heavily doped n-Ge whiskers and Shubnikov-de Haas oscillations for n-type InSb whiskers with various impurity concentrations were revealed in longitudinal magnetoresistance at low temperatures in magnetic fields up to 14 T. The effective masses of light and heavy electrons in n-Ge whiskers and cyclotron effective mass of electrons in n-InSb were estimated. Doped Ge and InSb whiskers could be used for creation of strain-temperature sensors, operating in high magnetic fields and at low temperatures.

We report the observations of nonstructural acousto-injection luminescence (NAIL) from tantalized LiNbO3 wafers. The samples under study are the X cut or Y cut wafers with the silver paste electrodes on opposite surfaces. The thickness is 1 to 2 mm and other linear dimensions are in the range of 2 to 25 mm. Experiments are done at room temperature in the MHz-frequency range. Mainly the fundamental shear ultrasound modes are excited in the samples. Experimentally are measured the spectra of NAIL, photo-luminescence spectra, acousto-electric properties, X Ray diffraction under NAIL. The NAIL and other effects appear above certain threshold amplitude of the acoustical strain that is about 10E-5. The involvement of the microstructural non-uniformity in the effects observed is experimentally identified by the photo-luminescence of point defects taken from different micro-regions of the samples. The data are explained in terms of the considerable acoustic stresses and piezoelectric fields that are capable injecting charge carriers from the metal contacts into a crystal., Comment: 12 pages, 7 figures, 171 Meeting of the American Acoustical Society (May,2016)

Проблематика. Ниткоподібні кристали твердого розчину Si1-xGex з низьким вмістом германію мають максимальне відношення рухливості до фононної теплопровідності, що перспективно для термоелектрики. Теплопровідність нанодротів SiGe є нижчою, ніж об'ємних зразків, що є також перспективним для покращення термоелектричної добротності та розвитку високоефективних термоелектричних мікроконвертерів. Вивчено температурну поведінку коефіцієнта Зеєбека ниткоподібних кристалів твердого розчину Si1-xGex в діапазоні температур від 4,2 К до температур вище кімнатної. Особливості ниткоподібних кристалів, зумовлені їх геометрією успішно використовуються для визначення термоелектричних параметрів кристалів, однак такі дослідження не проводились для ниткоподібних кристалів твердого розчину SiGe. Мета досліджень. Вивчення можливого впливу геометрії ниткоподібних кристалів Si1-x Gex на їх термоелектричні параметри. Методика реалізації. Ниткоподібні кристали SiGe вирощували методом хімічного осадження в закритій бромідній системі. 3ω метод було використано для визначення температурної залежності теплопровідності ниткоподібних кристалів Si1-xGex (х = 0,01-0,05) в інтервалі температур 300-400 К. Опір кристалів вимірювали двохзондовим методом. Отримані вольт-амперні характеристики хрестоподібних зростків були використані для визначення типу провідності матеріалу кристалів. Результати досліджень. Для НК SiGe діаметром від 100 до 10 mμ із зменшенням їх теплопровідності спостерігається збільшення коефіцієнта Зеєбека та опору, що супроводжується підвищенням показника якості (до 0,12 за температури 300 К). Використання ниткоподібних кристалів з великою конусністю, призводить до невеликого підвищення їх коефіцієнта Зеєбека (близько 10-15%). Висновки. Досліджено термоелектричні властивості ниткоподібних кристалів твердого розчину Si1-xGex (х = 0,03), легованих домішкою бору з концентрацією 1⋅10^17–1⋅10^19 cм^-3 в інтервалі температур 300-420 К. Встановлено вплив морфології ниткоподібних кристалів, зокрема, їх діаметрів і геометрії, на коефіцієнт Зеєбека, теплопровідність та опір. Background. Si1-xGex solid solution whiskers with low germanium content have maximum ratio of mobility to the phonon thermal conductivity, which is promising for thermoelectrics. Thermal conductivity of SiGe nanowires is lower than of bulk samples that is also prospective for improvement of thermoelectric figure-of-merit and development of high efficiency thermoelectric microconverters. The temperature behavior of Seebeck coefficient of Si1-xGex solid solutions whiskers in temperature range from 4.2 K to above room temperatures was studied. Peculiarities of whisker shape have been successfully used to determine their thermoelectric parameters, but these investigations were not conducted for SiGe solid solution whiskers. Objective. The aim of the paper is study of possible influence of Si1-xGex whisker geometry on their thermoelectric parameters. Methods. SiGe whiskers were grown by CVD method in closed bromide system. The 3ω method was used to determine the temperature dependence of the thermal conductivity of Si1-xGex (x = 0.01-0.05) whiskers in the temperature range 300-400 K. Resistance of whiskers was measured by a two-probe method. The resulting I-U characteristics of cross-shaped growths were used to determine the conductivity type of the whisker material. Results. Seebeck coefficient and resistance was shown to increase, while thermal conductivity to decrease when the whisker diameter drops from 100 to 10 μm, that is accompanied by a rise of figure of merit (up to 0.12 at 300 K). Use of the whiskers with large obliquity leads to a small increase (of about 10-15 %) of their Seebeck coefficient. Conclusions. Thermoelectric properties of Si1-xGex (x = 0.03) solid solution whiskers doped with B impurities to the concentrations 1⋅10^17–1⋅10^19 cm^-3 were studied in temperature range 300-420 K. An influence of the whisker morphology, in particular their diameters and obliquity, on Seebeck coefficient, thermal conductivity and resistance was investigated. Проблематика. Нитевидные кристаллы твердого раствора Si1-xGex с низким содержанием германия имеют максимальное отношение подвижности к фононной теплопроводности, что перспективно для термоэлектричества. Теплопроводность нанопроводов SiGe ниже, чем объемных образцов, что является также перспективным для улучшения термоэлектрической добротности и развития высокоэффективных термоэлектрических микроконвертеров. Изучено температурную поведение коэффициента Зеебека нитевидных кристаллов твердого раствора Si1-xGex в диапазоне температур от 4,2 К до температур выше комнатной. Особенности нитевидных кристаллов, обусловленные их геометрией успешно используются для определения термоэлектрических параметров кристаллов, однако такие исследования не проводились для нитевидных кристаллов твердого раствора SiGe. Цель исследований. Изучение возможного влияния геометрии нитевидных кристаллов Si1-xGex на их термоэлектрические параметры. Методика реализации. Нитевидные кристаллы SiGe выращивали методом химического осаждения в закрытой бромидной системе. 3ω метод был использован для определения температурной зависимости теплопроводности нитевидных кристаллов Si1-xGex (х = 0,01-0,05) в интервале температур 300-400 К. Сопротивление кристаллов измеряли двухзондовим методом. Полученные вольт-амперные характеристики крестообразных сростков были использованы для определения типа проводимости материала кристаллов. Результаты исследований. Для НК SiGe диаметром от 100 до 10 μm с уменьшением их теплопроводности наблюдается увеличение коэффициента Зеебека и сопротивления, что сопровождается повышением показателя качества (до 0,12 при температуре 300 К). Использование нитевидных кристаллов с большой конусностью, приводит к небольшому повышению их коэффициента Зеебека (около 10-15%). Выводы. Исследованы термоэлектрические свойства нитевидных кристаллов твердого раствора (х = 0,03), легированных примесью бора с концентрацией 1⋅10^17–1⋅10^19 cм^-3 в интервале температур 300-420 К. Установлено влияние морфологии нитевидных кристаллов, в частности, их диаметров и геометрии, на коэффициент Зеебека, теплопроводность и сопротивление.

Optical spectra of light reflection are detected under an influence of ultrasonic wave (UW)on a GaAs wafer. The differential spectrum is calculated as a difference between those taken under UW and without that influence on a sample. This acousto-optic differential reflectance(AODR) spectrum contains some bands that represent the energetic levels of the shallow centers in a sample. A physical basis of this technique is related to a perturbation of local states by UW. Here, a method is developed for characterization of local states at the surfaces and interfaces in crystals and low-dimensional epitaxial structures based on microelectronics materials. A theoretical model is presented to explain AODR spectra. Also, experiments using epitaxial GaAs structures doped by Te were made. Finally, theoretical and experimental results show that acousto-optic reflectance is an effective tool for characterization of shallow trapping centers in epitaxial semiconductor structures.En este trabajo, utilizamos el espectro de la luz reflejada en una muestra de Arsenuro de Galio (GaAs) bajo la influencia de una onda ultrasónica. El diferencial espectral es calculado como una diferencia entre el espectro del material obtenido bajo la influencia del ultrasonido y aquél obtenido sin dicha influencia. Este diferencial de reflectancia espectral acusto-óptico (AODR) contiene algunas bandas que representan los niveles energéticos de los centros en la superficie de la muestra. Esta técnica está basada en la perturbación de los estados locales generada por el ultrasonido. Particularmente, este trabajo presenta un método para caracterizar los estados locales en la superficie y las interfaces en los cristales, así como estructuras epiteliales de baja dimensión basadas en materiales semiconductores. Para ello, se presenta un modelo teórico para explicar dicho espectro de reflectancia diferencial (AODR). También se realizaron experimentos con estructuras de GaAs epitelial contaminado con Teluro (Te). Los resultados teóricos y experimentales obtenidos muestran que este método es una buena herramienta para caracterizar las trampas superficiales en estructuras epiteliales de semiconductores.

The aim of this paper is to study the strain-induced low-temperature behavior of Si1−xGex whiskers' magnetoresistance and to estimate the prospects for the creation of physical values and sensing elements on the basis operating in strong magnetic fields. We have investigated the magnetoresistance and piezomagnetoresistance of low germanium fraction Si1−xGex solid solution whiskers under the uniaxial strain (−4.3×10−3 to +4.7×10−4 rel. un.) at 4.2 K in a wide range of magnetic fields up to 14 T. Whiskers have been doped to the impurity concentration corresponding to both the insulator and the metal side of metal–insulator transition (MIT). It has been shown that magnetoresistance substantially depends on the doping level, the type and magnitude of samples' strain. The hopping conductivity with ΔЕ2 and ΔЕ3 activation energies at strain effect has been observed. The exponential character of magnetoresistance field dependencies has been obtained for heavily doped “metallic type” Si1−xGex whiskers, while for weakly doped samples at the insulator side of MIT a square-law field dependencies of magnetoresistance have been observed at 4.2 K. A non-monotonic magnetoresistance change depending on the doping level of Si and Si1−xGex whiskers in the vicinity of MIT.

In this paper thermal conductivity of boron-doped Si and SiGe (3-5 at.% of germanium) whiskers has been measured by means of slightly modified 3ω -method in the range of 290-400 K. We have shown that obtained thermal conductivity temperature dependence of micron-scale whiskers agrees well with expected for bulk Si and SiGe with 3 to 5% of Ge content and at room temperature is equal to 150 and 100 Wm-1K-1respectively, which evidences the reliability of proposed modification of 3ω -method. Prospects of possible thermoelectric application of nanoscaled SiGe solid solutions have been considered. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

S 38677 The point defects in ferroelectrics may influence the physical properties of phononic crystals LiTaO3 (LT) and LiNbO3 (LN). The initial wafers, periodically poled (PP) structures of LT with 1-mm-domains, and PP-LN with 0.45-mm-domains are investigated. Photoluminescence (PL) is taken at room temperature 310-nm -excitation. The slit width in optical spectrometer is set to 1 nm. The PL spectra of LT reveal multiple impurities including Fe + ,W, Th, Cs, Kr, Cu, Xe. Unlike PL from LN, there are no lines of the F-center, Ar and some other elements. The intensities of PL-lines in both LT and LN demonstrate a saw-type periodicity along the direction normal to the Z-axis. For instance, the PL line of Fe + defect in LT varies ± 15% with periodicity about 200 ± 40 nm. In the case of PP LT phononic crystals, the difference in Fe + line amplitude remains about the same; however, the periodicity becomes equal to a ferroelectric domain length of 1 mm. There is a difference between the two periodicities of charged defects in PP-LT and PP-LN; the positions of maxima in PL-lines are close to the interdomain walls in PP-LN, but it is not the case for PP-LT. Possible practical applications are discussed.