Volt-watt Sensitivity Research Articles

ОСОБЛИВОСТІ АНІЗОТРОПНОГО БІПОЛЯРНОГО ТЕРМОЕЛЕМЕНТА

Modern information communication networks include monitoring subsystems. The operation of monitoring subsystems is based on the operation of various sensors. Among the sensors used in the monitoring subsystems, thermoelectric sensors occupy an insignificant share. In order for thermoelectric sensors to become more widespread, it is necessary to solve the problem of a small value of thermoelectric efficiency. It is proposed to solve this problem by switching to sensors based on anisotropic bipolar thermoelement. In the presented work, the influence of thermoelectric vortices with turbulent flow on the sensitivity of sensors based on anisotropic bipolar thermoelements was studied. The dependence of the value of the transverse thermal-EMF of this structure on the anisotropy coefficient K of the anisotropic bipolar thermoelectric material was determined. Corresponding singular points and limits of their existence are revealed. The dependence of the directions of rotation of vortices with a turbulent nature of the flow on the direction of approach to these points was established. The temperature sensitivity of the sensor based on an anisotropic bipolar thermoelement made of single crystals of cadmium antimonide with both unipolar and bipolar characteristics was evaluated. Research results show a significant increase in the temperature sensitivity of such sensors based on anisotropic bipolar thermoelements, which can be used as thermal sensors for monitoring individual elements of the information communication system. Such thermoelements will have an improved coefficient of temperature dependence of volt-watt sensitivity compared to anisotropic unipolar thermoelements. The conducted numerical calculations show the prospects of using anisotropic bipolar thermoelements as sensors for monitoring modern information and communication systems for collecting information, both about the system itself and the environment.

Influence of the resonant interaction of surface magnetostatic waves with exchange modes on the EMF generation in YIG/Pt structures

The characteristics of EMF (U) generation in the thin-film Pt/YIG structures caused by hybridization of propagating magnetostatic surface waves with exchange modes of YIG film were studied. It was shown that at frequencies f* corresponding to the dipole-exchange resonances (DER) the magnitude of EMF U increases by several times in comparison with the frequencies different from DER (f?f*). The Volt-Watt sensitivity was estimated for the Pt/YIG structures with different geometries of Pt microstrips. Keywords: Spintronics, spin waves, EMF generation, electron drag effect , dipole-exchange resonance.

Влияние резонансного взаимодействия поверхностных магнитостатических волн с обменными модами на генерацию ЭДC в структурах YIG/Pt

The characteristics of EMF (U) generation in the thin-film Pt/YIG structures caused by hybridization of propagating magnetostatic surface waves with exchange modes of YIG film were studied. It was shown that at frequencies f* corresponding to the dipole-exchange resonances (DER) the magnitude of EMF U increases by several times in comparison with the frequencies different from DER (f≠f*). The Volt-Watt sensitivity was estimated for the Pt/YIG structures with different geometries of Pt microstrips.

Chemical bath deposited CdxPb1−xS solid solution films: composition, structure, and optical properties

Films of cubic substitutional CdxPb1−xS solid solutions have been synthesized by the chemical bath deposition with varying cadmium acetate salt Cd(CH3COO)2 in the reaction mixture within 0.01–0.08 mol/l on quartz substrates. The crystal structure, chemical composition and morphology were studied by the X-ray diffraction, scanning electron microscopy, elemental analysis, Auger spectroscopy, and Raman spectroscopy, as well as the evolution of the optical and photoelectric properties was determined. The thickness of the deposited films changes from ~ 0.4 to ~ 1.0 μm, and the content of cadmium x in the CdxPb1−xS solid solution varies from 0.036 to 0.090. All the CdxPb1−xS films have B1 crystal structure (NaCl type), but differ in the morphology (the size, form and predominant orientation of the particles forming the films). Forming the substitution solid solution is confirmed by the shift of the Raman lines at 72 and 134 cm−1 toward higher frequencies. The optical band gap determined from the absorption spectra varies from 0.46 to 0.70 eV. The dependences of the photoresponse value (volt-watt sensitivity) and the dark resistance on cadmium acetate concentration in the solution are represented.

Gradient Heatmetry Advances

The paper describes a unique method of heat flux measurement, i.e., gradient heatmetry. Gradient heatmetry is performed using gradient heat flux sensors (GHFS) developed on the anisotropic thermoelements basis. The principle of GHFS’ operation leads to the fact that their response time is about 10 ns, and the volt-watt sensitivity does not depend on the thickness. GHFS are compared with other types heat flux sensors, with the GHFS features depending on the materials being described. The theory and examples of gradient heatmetry applications in thermophysical experiment are provided.

Измерение существенно нестационарных тепловых потоков градиентным датчиком на основе висмута

In this work we performed calibration of the gradient heat flux sensor made of bismuth single crystal. The value of the volt-watt sensitivity of the sensor is found and a data processing method based on the one-dimensional heat equation for a thin plate is presented. An experimental study of the heat flux on the frontal surface of the cylinder after a laser discharge was carried out. The data obtained as a result of the experiment were processed by the proposed method.

Effect of “Sodium Sulfite–Ascorbic Acid” Complex Antioxidant Additive on the Composition, Structure and Semiconducting Properties of PbSe Film

Comparative experimental data, using dynamic light scattering methods, scanning electron and atomic force microscopy, on the composition, crystal structure, semiconductor and photoelectric properties of PbSe films deposited at the presence of sodium sulfite Na2SO3 and “sodium sulfite–ascorbic acid” complex antioxidant additive are presented. Significant changes in morphology, elemental and phase composition, the period of the crystal lattice of PbSe films been synthesized in the presence of Na2SO3 and Na2SO3 + C6H8O6 anti-oxidants before and after their thermoactivation at 653 K are found. It is shown that the introduction of a complex additive in comparison with Na2SO3 increases the homogeneity of the particles forming the layer, decreases the microstresses in it, reduces the value of thermal band gap from 0.349 to 0.308 eV, and increases the volt-watt sensitivity of the films by 28–30%.

The combination of PIV and heat flux measurement in study of flow and heat transfer near a circular finned cylinder

The flow and heat transfer of the finned cylinder are investigated by the methods of PIV, gradient heat flux measurement and thermometry. On the hollow model of a circular cylinder heated by saturated water vapor at atmospheric pressure, five annular fins of 20 mm high and of 10 mm thick are mounted. For the first model, the “acting” fin was hollow, for the second, it was solid and made of titanium alloy VT22. The remaining four fins simulated flow blockage. To visualize the flow in the intercostal space, the fin simulators were made of Perspex. Battery gradient heat flux sensors (GHFSs) with volt-watt sensitivity of 10 mV/W, were installed on the “acting” fin at different distances from the surface of the carrier cylinder. The cylinder rotated around its axis at an angle of φ = 0…180°, which made it possible to obtain the distribution of heat flux over the surface of the fin. By combining PIV diagnostics and gradient heat flux measurement, it was possible to obtain a complex 3D structure of the flow in the intercostal space and the distribution of heat flux on the surface of the fin. The values of the local heat transfer coefficients (HTCs) were also obtained. The dependence of HTC on flow mode and intercostal space is revealed. Comparison of the obtained characteristics for models with hollow and solid fins allowed us to determine in experiment fin efficiency for different intercostal spaces and free-stream velocities. The combination of all three technologies opens up new possibilities in study of flow and convective heat transfer.

Non-Selective Magnetoelectric Thermal Radiation Receiver Based on Cadmium Antimonide

The ways of increasing the sensitivity of a non-selective thermal radiation receiver based on cadmium antimony using the phenomenon of electromagnetic induction are considered and investiga­ted. It has been shown that the application of ani­sotropic NdFeB anisotropic magnet increases the volt-watt sensitivity of the thermal radiation recei­ver by 30 %. When a more powerful magnet is used, an additional increase in sensitivity is observed, but not in proportion to the magnitude of the additio­nal magnetic induction. The dynamic range of the created thermal radiation receiver, which is from 10 to 200000 W/m-2, is investigated.

Visible and near-infrared photodetector on chemically vapor deposited diamond

A photodetector of the visible and near infrared wavelength ranges based on chemically vapor deposited (CVD) boron-doped diamond is fabricated and tested. The principle of its operation is based on the creation of holes by incident radiation not in a CVD diamond film itself, but in an adjoining bimetal Cr/Au layer. The latter serves simultaneously as one of the Schottky contacts with an external circuit. Due to small thickness of this layer in the order of 10 nm the generated holes do not have enough time to recombine with electrons because of diffusion in the CVD diamond film. There the holes are accelerated by the electric field of a hole depletion region and create a photocurrent. For optimized boron doping profile of the CVD diamond film the photodetector Volt-Watt sensitivity in the order of 1 mV/(W/cm2) at wavelength 445 nm and 0.1 mV/(W/cm2) at 532 nm was measured. For a constant forward bias voltage 2.5 V its Ampere-Watt sensitivity at 445 nm is 0.7 A/W. For zero bias voltage this figure is 5 ⋅ 10−5 A/W at 445 nm, 3 ⋅ 10−6 A/W at 532 nm, and 1.8 ⋅ 10−7 A/W at 1.06 μm. The photodetector time response was measured in the current mode at 532 nm. It is in the order of 600 ns without a bias voltage and 200 ns with a constant reverse bias voltage 2.5 V.

Tasks and Solutions in Gradient Heat Flux Measurement

A method for determining the local heat flux per unit area, namely, gradient heat flux measurement, is proposed based on transverse the Seebeck effect. The structure of skew layer composites is described, the dependencies are given, which allow calculating volt-watt sensitivity of the sensors. Technology of sensor production based on metals, alloys and semiconductors is considered.

Nonlinear current resonance in a spin-torque diode with planar magnetization

The microwave sensitivity of a spin diode consisting of a tunnel junction with two magnetic electrodes is investigated. The specific feature of the magnetic tunnel structure under consideration is a skew of the electrode magnetizations in the plane of the layers, arising due to exchange interaction with the adjacent antiferromagnetic layers with different superparamagnetic blocking temperatures. Within the framework of the macrospin model the stability analysis of the stationary magnetization states is carried out as a function of the electric current and the skew angle between the magnetizations of the magnetic layers on the angle-current plane, taking into account the effect of spin torque transfer. For the obtained stationary states, variations of the resonant response to an ac current of microwave range and volt-watt sensitivity of the spin diode far away from and near the critical bias-current lines of the transition to self-oscillations are determined. It is shown that with increasing the bias current upon the approach to the critical point, hysteresis of the frequency branches of resonant response appears, induced by the nonlinear microwave modulation of torque. This effect is different from the foldover-effect under the condition of initial Lorentzian character of the ferromagnetic resonance with a constant linewidth. Furthermore, micromagnetic simulation of the diode sensitivity for similar magnetic parameters is carried out.

Sensitivity and Noise of Cold-Electron Bolometer Arrays

We perform experimental and theoretical studies of the series-parallel arrays of the cold-electron bolometers integrated into a cross-slot antenna and composed with an immersion silicon lens. This work is aimed at determining the efficiency of radiation absorption by bolometers, their volt-watt sensitivity, and equivalent noise power. The absorbed power was found using two independent methods, which ensured a better reliability of the results. The first method is based on comparing the experimental current-voltage characteristics of bolometers with the model based on the heat-balance equation. The second approach involves simulation of the electromagnetic properties of the system including the antenna, the lens, the bandpass filters, and the radiation source. The discrepancy among the results obtained using various methods does not exceed 30%. Optimization of the experimental setup is proposed to reach the photon-noise detection regime.

Nonlinear spin-torque microwave resonance near the loss of spin state stability

Abstract The paper analyzes microwave resonant response of the spin-torque diode. The considered spin-torque diode is a magnetic tunnel junction with a nano-pillar structure. The magnetization of the free layer has a tilt caused by an action of the inclined magnetic field in the plane of the structure. Taking into account the effect of spin torque transfer we define stability regions of stationary states of magnetization in the free layer as a function of the azimuth angle of the magnetic field and bias DC current. Microwave volt-watt sensitivity of the spin diode for the obtained stationary states is calculated. It is shown that non-linear frequency shift of the resonance line width limits maximum sensitivity of the spin diode near the critical bias current corresponding to the point of the transition to the self-oscillating mode. Besides that, overlapping of frequency branches occurs in the resonant response as the critical point approach, which is different from the foldover effect in the nonlinear ferromagnetic resonance induced by an alternating magnetic field.

Influence of structural inhomogeneities on the formation of the pyroelectric phase in polymers

One of the possible methods of increasing the pyroelectric coefficient in order to enhance the volt-watt sensitivity of polymer films has been considered. The sensitivity of the relative variation in the volt-watt sensitivity of a thin polymer film in an inhomogeneous temperature field has been estimated.

Sensing Microwave-Terahertz Detectors Based on Metal-Semiconductor-Metal Structures With Symmetrical I–V Characteristic

We discuss the characteristics of new sensing elements based on a symmetrical metal-semiconductor-metal structure, which are designed for detection of microwave-terahertz signals. The schemes of connection of the sensing elements in the high-frequency path and the low-frequency measuring circuit are considered. Expressions for the volt-watt sensitivity and the noise-equivalent power are obtained. Comparison of the obtained characteristics with those of the detector zero-bias Schottky (Mott)-barrier diode is carried out. It is shown that the characteristics of the symmetrical sensing elements are comparable with or exceed in some cases similar characteristics of the detector zero-bias diodes.

Resistance of In2О3–p-InSe photoconverter to different types of irradiation

The article presents the results of irradiation of In 2 O 3 –p-InSe photoconverters by braking γ-quanta, high-energy electrons and gamma-neutrons. In particular, their electrical and photoelectrical parameters were analyzed. The latest were compared to the similar parameters of test solar IТО–SiO 2 – n -Si element . For the initial doses, depending on the type of irradiation, the major changes consisted in: - the improvement of the rectification factor K at 10-100% and the monochromatic volt-watt sensitivity S U at 18-44%; - the maintenance or increase of voltage of idle running U хх ; - the increase of the short-circuit current J кз at 7% ( under the action of gamma-neutrons and electrons) and the monochromatic ampere-watt sensitivity of S I at 11-28% ( under the action of γ-quanta and electrons). In other cases, the listed parameters have been experiencing the minimal decline (up to 5%). The imperfection coefficient ВАХ n has remained constant or has even slightly improved (under the action of gamma-neutron). With further radiation, it was fixed: values ​​ U хх , J кз , S U and S I were saved in case of γ-quanta; U хх and S U increased under the action of electrons, K value was significantly improved and U хх was unchanged in case of gamma neutrons. The decline of the rest of the parameters was in the range 2-12%. The specific changes in the spectral contours of photoresponse were not detected (except the irradiation by electrons). The possible mechanisms of radiation damages were discussed. In case of γ- and electron radiation, this is the generation of point defects - Frenkel pairs, in case of neutron radiation - formation of vacancy and internodal clusters. At the same time, the used doses and types of radiation have caused severe damage of IТО–SiO 2 –n-Si structure

Influence of Temperature on the Performance of a Spin-Torque Microwave Detector

We analyzed the influence of temperature on the main characteristics of a passive spin-torque microwave detector (STMD): volt-watt sensitivity, signal-to-noise ratio, and minimum detectable microwave power. We reveal that these parameters do not always improve with the decrease of temperature. The developed formalism can be used for the optimization of the practical parameters of a STMD in a wide range of temperatures.

Silicon field-effect transistors as radiation detectors for the Sub-THz range

The nonresonance response of silicon metal-oxide-semiconductor field-effect transistors (Si-MOSFETs) with a long channel (1–20 μm) to radiation in the frequency range 43–135 GHz is studied. The transistors are fabricated by the standard CMOS technology with 1-μm design rules. The volt-watt sensitivity and the noise equivalent power (NEP) for such detectors are estimated with the calculated effective area of the detecting element taken into account. It is shown that such transistors can operate at room temperature as broadband direct detectors of sub-THz radiation. In the 4–5 mm range of wavelengths, the volt-watt sensitivity can be as high as tens of kV/W and the NEP can amount to \({{10^{ - 11} - 10^{ - 12} W} \mathord{\left/ {\vphantom {{10^{ - 11} - 10^{ - 12} W} {\sqrt {Hz} }}} \right. \kern-\nulldelimiterspace} {\sqrt {Hz} }}\). The parameters of detectors under study can be improved by the optimization of planar antennas.

Photoelectric characteristics of nanostructured hydrochemically deposited films of the Pb0.975Sn0.025Se substitutional solid solution

The photoelectric characteristics of Pb0.975Sn0.025Se solid solution films prepared by the hydrochemical codeposition of PbSe and SnSe with the subsequent heat treatment in air at 573–700 K have been investigated. The thermal and optical band gaps, the temperature coefficient of the optical band gap, the dark resistance, the volt-watt sensitivity, and the range of spectral sensitivity have been determined in the temperature range of 220–300 K. It has been found that, after heat treatment below 573 K, the films of the Pb0.975Sn0.025Se solid solutions possess metallic conductivity, while being heat treated at elevated temperatures, they become semiconductors with p-type conductivity. The composition of the solid solution is independent of the heat treatment temperature; it is formed during deposition.