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In this work, silicon microcrystals doped with a boron impurity to concentrations corresponding to the metal-dielectric transition in silicon of 5.5·1018 cm−3 and a nickel impurity in the temperature range of 4.2 ÷ 70 K under alternating current in the frequency range of 0.010 ÷ 250 kHz were studied. The features of the frequency response of silicon microcrystals are determined. On the basis of Nyquist diagrams, an equivalent conductivity scheme at low temperatures is proposed. The frequency response of the samples was evaluated and the mechanisms of charge carrier flow were proposed depending on the observation conditions. Conduction mechanisms from quantum mechanical tunneling (QMT) to superlinear power law (SLPL), which can be implemented in crystals, are considered. [ABSTRACT FROM AUTHOR]

The authors investigate deformation-induced changes in the electrophysical parameters of the indium antimonide microcrystals at cryogenic temperatures in strong magnetic fields up to 10 T. It is determined that for strongly doped InSb microcrystals, the gauge factor at liquid-helium temperature is GF4.2K ≈ 72 for the charge carrier concentration of 2·1017 сm–3, while being GF4.2K ≈ 47 for the concentration of 6·1017 сm–3, at ε = –3·10–4 rel. un. For the development of magnetic field sensors based on the magnetoresistive principle, the effect of a giant magnetic resistivity reaching 720% at a temperature of 4.2 K is used.

Sensitive element of multifunctional sensor for measuring temperature, strain and magnetic field induction has been developed based on the studies of electrical conductivity and magnetoresistance of silicon and germanium microcrystals in the temperature range 4.2—70 K, strain ±1.5*10–3 rel.un. and magnetic fields of 0—14 T. The feature of the sensitive element is the using of the p- and n-type conductivity germanium microcrystals as mechanical and magnetic field sensors, respectively, and the p-type silicon microcrystal — as temperature sensor. That allows providing the compensation of temperature influence on piezoresistance and on sensitivity to the magnetic field.

The results of studies of magnetoresistance for GaAs filamentous crystals doped with tellurium admixture to a concentration of 2·1017 сm−3, in the temperature range 4.2–60 K and in the magnetic field ranges 0–14 T are presented. The GaAs filamentary crystal magnetoresistance has shown a sharp positive jump at a low magnetic field (up to 0.2 T) at a temperature near 4.2 K, while at higher magnetic field inductions linear behavior of magnetoresistance occurs. The low field magnetoresistance is discussed in the framework of weak localization of charge carriers due to their spin-orbit exchange interaction. The high-field linear magnetoresistance is connected with electron-electron interaction. [ABSTRACT FROM AUTHOR]

Currently, silicon and germanium, the most common materials in the production of discrete semiconductor devices and integrated circuits, do not always meet all the requirements to the sensing elements of mechanical quantities sensors. Therefore, it is logical to research the properties of other semiconductor materials that could be used as sensing elements in such sensors. A3B5 semiconductor compounds seem promising for such purpose. Effect of hydrostatic pressure up to 5000 bar on the resistance of n-type antimonide gallium whiskers doped by Se or Te was studied. Coefficient of hydrostatic pressure for this crystals was determined, it equals Kh = (16,5—20,0)•10–5 bar–1 at 20°N. Temperature dependence of resistance and coefficient Kh for this crystals in the temperature range ±60°N was studied. Design of the developed hydrostatic pressure sensor based on GaSb whiskers and its characteristics are presented. The possibility to decrease the temperature dependence of sensitive element resistance by mounting GaSb whiskers on the substrates fabricated from materials with different temperature coefficient of expansion was examined. It was shown that mounting of GaSb crystals on Cu substrate gives the optimal result, in this case the temperature coefficient decrease to 0,05%•°N–1, that leads to decrease of output temperature dependence. The main advantages of developed pressure sensor are: the simplified design in comparison with pressure sensors with strain gauges mounted on spring elements; the high sensitivity to pressure that is constant in the wide pressure range; the improvement of sensors metrological characteristics owing to hysteresis absence. The possible application fields of developed sensors are measuring of high and extremely high pressure, chemical and oil industries, measuring of pressure in oil bore-holes, investigation of explosive processes.

The article presents the design of a pressure-temperature sensor based on p-type silicon whiskers, doped with boron, with a resistivity of 0,005 Ohm?cm. The sensor is operable in a temperature range from –100 to +200°C and at pressures from 0 to 20 MPa. The sensor is designed for a wide range of applications.

The article deals with studies of thermoelectric parameters of InSb whiskers with tin concentration of about 4.4·1018 cm–3 in the temperature range 4.2-300 K. The resistance and Seebeck coefficient were measured experimentally. The InSb whiskers have shown rather high values of Seebeck coefficient exceeding the values of bulk materials by 2-3 times. Using a special method of heat transfer in the whisker joints, the thermal conductivity of the whisker was simulated. The obtained threshold on the temperature dependence of thermal conductivity for InSb whiskers and nanowires in the range of about 100 K connecting with phonon capture of charge carriers indicates high reliability of the data obtained. As a result, ZT parameter of InSb whiskers versus temperature in the temperature range 4.2-300 K was calculated. The obtained value of ZT parameter 0.15 at room temperature indicates a possibility of the whisker use for thermal converters design. [ABSTRACT FROM AUTHOR]

The Bi2Se3 whisker temperature dependencies of resistance with palladium doping concentration of (1 ÷ 2)×1019 cm−3 were studied in the range of 1.5 ÷ 77 K. At the temperature of 5.3 K there was found a sharp drop in the whisker resistance. This effect can be explained as a contribution of two processes: electron localization and superconductivity at temperatures under 5.3 K. The magnetoresistance in Bi2Se3 whiskers with n-type conductivity and diverse concentration of Pd that correspond to the metal side of the MIT (metal-insulator transition) was studied at low temperatures and magnetic field in the range of 0 ÷ 10 T. The magnetoconductance was considered in the structure by the weak antilocalization model and attached with subsurface layers of Bi2Se3 whiskers. [ABSTRACT FROM AUTHOR]

The magnetoresistance of GaP0.4As0.6 whiskers doped with silicon with a concentration of acceptor impurity in the range of Na = 1 × 1017 ÷ 5 ×1018 сm - 3 was investigated. The study of the magnetoresistance of GaAs whiskers at cryogenic temperatures gives information on the nature of low-temperature conductivity in such crystals, and can also be used to create magnetic field sensors with a magnetoresistive principle of action. It is interesting to investigate the magnetotransport properties of GaPxAs1-x solid solution. The purpose of this work was to study the magnetic support of GaP0.4As0.6 whiskers doped with silicon with a concentration of acceptor impurity in the range of Na = 1 ×1017 ÷ 5 × 1018 сm - 3 at low temperatures. The composition of the solid solution was chosen from the point of view of the change in the band structure of the varizonic semiconductor. The concentration of charge carriers in crystals was in the vicinity of the metal-insulator transition (MIT). In this work, the transverse and longitudinal magnetoresistances of the whiskers were studied in the range of 4.2-77 K in magnetic fields up to 12 T. For most samples, the exponential temperature dependence of the resistance is obtained, which corresponds to the dielectric side of the MIT. It is established that in the transverse and longitudinal magnetic fields the field dependence of the magnetoresistance of the crystals is quadratic and is determined mainly by the conductivity of localized A+ states of the upper Hubbard zone. However, at low temperatures of 4.2-50 K, a negative magnetoresistance (up to 7 %) in weak magnetic fields (up to 4.5 T) was detected in GaP0.4As0.6 whiskers. A critical magnetic field was determined, in which a transition from negative to positive magnetoresistance occurs. It is shown that the magnitude of the critical magnetic field depends on the temperature and nature of the application of the magnetic field. The possible reasons for the appearance of a negative magnetic resistivity were analyzed: dimensional effect, distribution of impurities in the whiskers. The obtained results indicate that the mesoscopic dimensional effect does not appear in the studied samples due to sufficiently large crystal sizes. The results of mass spectroscopic studies have established a homogeneous distribution of impurities indicating the absence of clusters in the samples. The obtained negative magnetoresistance was probably connected with antiferromagnetic exchange interaction of the magnetic moments of charge carriers in the process of their hopping conductance on the delocalized states of the upper Hubbard zone. [ABSTRACT FROM AUTHOR]

Temperature dependencies of Bi2Se3 whiskers' resistance with Pd doping concentration of (1-2) x 1019 cm − 3 where measured in temperature range 1.5-77 K. At temperature 5.3 K a sharp drop in the whisker resistance was found. The effect observed is likely resulted from the whiskers partial transition in superconducting state at temperature 5.3 K, which is likely connected with β-PdBi2 inclusions in the whiskers. Transverse magnetoresistance in n-type Bi2Se3 whiskers with different doping concentration in the vicinity to the metal-insulator transition from metal side of the transition was studied in magnetic field 0-10 T. The magnetic field suppression of superconductivity allows to determine the main parameters: upper critical magnetic field Bc2 = 1.5 T, superconductor coherence length ξ(0) = 15 nm, superconductive gap Δ ~ 0.8 meV. Besides on the temperature dependence of the whisker resistance and magnetoresistance a minimum was observed in the temperature range 20-25 K that is connected with appearance of Kondo effect. [ABSTRACT FROM AUTHOR]

Temperature dependencies of GaSb whiskers' resistance doped with Te to concentration of 1.7 × 10 18  cm -3 were measured in temperature range 1.5-300 K. At 4.2 K temperature, a sharp drop in the whisker resistance was found. The observed effect is likely connected with the contribution of two processes such as the electron localization in the whiskers and transition in superconducting state at temperature below 4.2 K. The whisker magnetoconductance is considered in the framework of weak antilocalization (WAL) model and connected with subsurface layers of the whiskers. The Shubnikov-de Haas (SdH) oscillatory effect is observed in high-quality n-type GaSb whiskers with tellurium doping concentration near the metal-insulator transition (MIT) for both longitudinal and transverse magnetoresistance.