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In this work, we review the physical properties of organic materials and transistors, discussing especially the charge transport mechanisms. Finally, we present an analytical and continuous charge model for Organic Thin Film Transistors (OTFTs) from which analytical expressions of all the total capacitances are obtained. They are developed and finally written as continuous explicit functions of the applied voltage, resulting in a complete charge-based small-signal model composed by a unified charge control model derived from Poisson equation assuming an exponential density of localized states. This charge model was developed from a previously proposed analytical DC current model assuming a hopping based transport. Therefore our complete small signal model has the potential to be successfully used in circuit simulators for the design of OTFTs.

The measurements of SbSCl_xI_1-x(x = 0.2) temperature dependent capacitance were carried out. The temperature of ferroelectric phase transition T_C ≈340 K was measured experimentally. T_C of SbSCl_xI_1-x was calculated theoretically in anharmonic and harmonic approximations. T_C was calculated in anharmonic approximation using temperature dependence of mean potential energy of Sb atoms as a function of the soft B_1u symmetry normal coordinate along c(z)-axis. Moreover, T_C was calculated in harmonic approximation using temperature dependence of vibrational thermodynamic functions (Helmholc free energy). T_C dependence from unit cell parameters a, b and from mixture composition x was carried out.

The temperature dependences of resistance, impedance and capacitance of semitransparent sensor having structure ITO/PTB7-Th:PC${}_{61}$BM/Graphene composite (semisurface type) were investigated. The transparency of the sensor was 58–60%. The dependences of the resistance, impedance and capacitance at different frequencies 100 Hz, 1 kHz, 10 kHz, 100 kHz and 200 kHz and temperature in the range of 23.8–80${}^{\circ }$C for the sensor were studied. It was observed that as the temperature increased from 23.8${}^{\circ }$C to 80${}^{\circ }$C, the resistance and impedance (at 1 kHz) of the samples decreased, on average, by a factor of 3.51 and 3.79, respectively. At same experimental conditions (1 kHz), the capacitances of the samples also decreased by a factor of 9.6. It was also noted that as frequency increased from 100 Hz to 200 kHz, the impedance of the sensor decreased by a factor of 21 and 12, at temperatures 24${}^{\circ }$C and 58${}^{\circ }$C, respectively. Under the same conditions, the capacitance decreased by a factor of 30 and 28, respectively. The temperature resistance coefficients were measured to be −1.31%/${}^{\circ }$C, −1.30%/${}^{\circ }$C, −1.27%/${}^{\circ }$C, −0.84%/${}^{\circ }$C, −0.72%/${}^{\circ }$C and −0.33%/${}^{\circ }$C for R, Z (100 Hz), Z (1 kHz), Z (10 kHz), Z (100 kHz) and Z (200 kHz), respectively. For capacitance measurement, the temperature capacitance coefficients were measured as −1.39%/${}^{\circ }$C, −1.38%/${}^{\circ }$C, −1.37%/${}^{\circ }$C, −1.36%/${}^{\circ }$C and −1.34%/${}^{\circ }$C, respectively. The semitransparent PTB7-Th- and PC${}_{61}$BM-based temperature sensor can be used for measurement of the temperature as a teaching aid in situations where visual control of illumination and light intensity is required.

In this article, the design and operation of a cylindrical capacitive sensor based on the dielectric reactance capacitance and conductance changes of the gap medium is reported. The proposed system was used to determine characteristics of different water liquids as a result of the capacitance and resistance variations. The air gap capacitance (dry signal) is measured and then by filling the gap with a liquid, the capacitance (wet signal) is monitored for different liquids. A reported sensor is used for the distilled, tap, boiled, and salt water measurements and the capacitance and resistance results are compared. A big difference of about 38.5 μF in the measured capacitance values for the salt and distilled water shows a high sensitivity, which can be used to recognize different water liquids. The experimental results are promising for water liquids and verify the successful operation of such a device as a liquid sensor, a useful method for checking the electrical quality of the water that is required for different applications. It is also possible to monitor the resistance change of the filling medium as a function of time.

The capacitance between the origin and any other lattice site in an infinite square lattice of identical capacitors each of capacitance C is calculated. The method is generalized to infinite Simple Cubic (SC) lattice of identical capacitors each of capacitance C. We make use of the superposition principle and the symmetry of the infinite grid.

Cu_0.5K_0.25Tl_0.25Ba₂Ca₃Cu₄O_12-δ superconductor samples were synthesized and their dielectric properties were measured between 80 K and 290 K by means of capacitance (C) and conductance (G) measurements with the test frequency (f) in the range of 10 KHz to 4 MHz. A negative capacitance (NC) occurrence was observed, which most likely arose from the superior Fermi level of ceramic superconductor samples than metal electrodes. Also the NC may be due to the space charge situated at the multiple insulator–superconductor interfaces (grain boundaries) in the materials. The negative dielectric constant (ε′) and loss factor (tan δ) show strong dispersion at low frequencies. The lower thermal agitation at 80 K may boost the polarizability and hence the dielectric constants (ε′ and ε″).

Through the silicon modulation-doping (MD) growth method, the electrical performance of AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) is improved by replacing the commonly uniform-doped (UD) method of n-AlGaN layer. The electroluminescence characterisic measurements demonstrate the MD growth method could effectively enhance the light emission intensity. Both the forward voltage and reverse leakage current of the MD samples are obviously reduced compared to those of the UD sample. Due to the existence of periodic Si-MD superlattices in n-AlGaN layers, which may behave like a series of capacitors, the built-in electric fields are formed. Both the measured capacitance–voltage (C–V) characteristics, and related photoluminescence (PL) intensity with the Si-MD growth method are enhanced. In detail, the effects of these capacitors can enhance the peak internal capacitance up to 370 pF in the MD sample, whereas the UD sample is only 180 pF. The results also mean that with better current spreading ability in the MD sample, the MD processes can effectively enhance the efficiency and reliability of DUV-LEDs. Thus, the investigations of the Si-MD growth methods may be useful for improving the electrical performance of DUV-LEDs in future works. Meanwhile, this investigation may partly suggest the minor crystalline quality improvements in the epi-layers succeeding the MD n-AlGaN layer.

The inverted-gate colossal magnetoresistance-field-effect-transistors (CMR-FETs) were designed and successfully fabricated on the Si substrate by using semiconductor techniques. The studies on the capacitance properties were carried out under different temperatures, different frequencies, and different gate biases. The results indicate that La_0.8Ca_0.2MnO₃ is the typical p-type semiconductor. It was shown that the capacitance increases with the increasing of the temperature under certain gate bias. The sudden increase of the capacitance at 160 K was observed and needeed to be studied further. Meanwhile the capacitance decreased as the frequency increased with first order exponential decay fitting.

BST ceramics with doping of 1, 3, and 5 wt.% ZnBO were prepared by the conventional mixed oxide method and sintered at 1100°. X-ray diffraction analyses were carried out to verify the structural properties. 1, 3, and 5 wt.% ZnBO doped BST ceramics were crystallized with weak tetragonal structure at 1100°C. The grain growth behavior and shapes were investigated by scanning electron microscopy images. The electrical properties of 1, 3, and 5 wt.% ZnBO doped BST ceramics were investigated by impedance spectroscopy at the different temperatures (350, 375, and 400°C). Impedance spectroscopy data presented in Nyquist plot show the existence of both grain and grain boundary effects in all specimens. 1, 3, and 5 wt.% ZnBO doped BST ceramics showed negative temperature coefficient of resistance (NTCR). Also, the capacitances and resistances of grains and grain boundaries for 1, 3, and 5 wt.% doped BST ceramics were simulated through equivalent circuit with the parallelly connected capacitors and resistors. The capacitance and resistance were decreased when temperature and ZnBO dopants were increased.

Tailoring pore-creating method to fit the various demands of different researchers is the frontier issue in the research of electrode capacitance of boron-doped diamond (BDD). Two critical factors in achieving the desired capacitance are the pore size and shape. This work compares the characteristics and applicability of various pore-creating methods, and reveals the influence mechanism of factors such as surface area, size and shape of the pore, on the capacitance of BDD electrodes. Obtained results could facilitate researchers to develop a personalized pore-creating method to achieve the desired capacitance.

RF magnetron sputtering technique was employed for deposition of tantalum oxide films on p-type silicon substrates by sputtering of pure tantalum oxide target in the presence of oxygen and argon gases at a temperature of 303 K. X-ray photoelectron spectroscopic and X-ray diffraction studies indicated that the films annealed at 773 K were stoichiometric and polycrystalline respectively. The accumulation capacitance for the devices in a structure of Al/Ta₂O₅/p-Si has been decreased noticeably lower values for the devices annealed at high temperatures. Improved current–voltage characteristics were observed for all annealed devices with Poole–Frenkel conduction mechanism.

The copper oxide, CuO, and copper hydroxide, Cu(OH)₂ nanomaterials have been prepared by a simple copper salt aqueous solution reaction. The powder X-ray diffraction (XRD) analysis showed the successful formation of Cu(OH)₂ and CuO nanoparticles. The average crystallite size of these Cu(OH)₂ and CuO nanoparticles was estimated and found to be around 17nm (Cu(OH)₂) and 10nm (CuO). The surface morphology and size of the CuO particles were confirmed by Scanning Electron Microscope (SEM) and High-resolution transmission electron microscope (HRTEM). The Raman analysis, dielectric and conductivity of CuO nanoparticles have been performed. The frequency variation of the capacitance (real dielectric constant) and dielectric loss was studied. The capacitance of the CuO nanoparticles is high at low frequencies and decreases rapidly when the frequency is increased. The frequency dependent ac conductivity follows Johnscher’s power law.

In this study, two hydrogen sensors with Pd/SiO₂/Si and Ni/SiO₂/Si structures have been fabricated. Palladium nanoparticles are synthesized and then deposited on the oxide surface using spin coating. Capacitance–voltage curves for the Pd/SiO₂/Si sensor at room temperature and for the Ni/SiO₂/Si sensor at 140${}^{\circ }$C in pure nitrogen and 1% H₂–N₂ mixture are described. The time required for reaching 90% of the steady-state signal magnitude ($t_{90\%}$) for Pd/SiO₂/Si capacitor was 1.4s and for Ni/SiO₂/Si capacitor was 90 s. The time interval for recovery from 90% to 10% of steady-state signal magnitude ($t_{10\%})$ for Pd/SiO₂/Si capacitor was 14s and for Ni/SiO₂/Si capacitor was 40min. For the Pd/SiO₂/Si capacitor, the response is 88% and for Ni/SiO₂/Si capacitor the response is 29%. Comparison of Pd nanoparticles capacitive- and resistance-based sensors shows that the metal-oxide-semiconductor capacitive is faster and more sensitive than the resistance-based hydrogen gas sensors.

This paper investigates the synthesis and enhanced electrochemical behaviors of ZnO and NiO/ZnO nanocomposites for electrode material of supercapacitors. ZnO and NiO/ZnO nanocomposites were produced via sol–gel technique. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were used to determine the size and structure of as-synthesized nanomaterials, respectively. The capacitive behavior and charge–discharge characteristics of the electrode using ZnO and NiO/ZnO nanocomposites (as active material) were individually probed with the help of cyclic voltammetry (CV) and galvanostatic charge-discharge tests, respectively. The specific capacitance of nanocomposites-based electrode calculated from galvanostatic charge-discharge tests was 469F ${\text{g}}^{-1}$ at the scan rate of 1mA ${\text{g}}^{-1}$ in 1M Na₂SO₄ electrolyte. The power density and energy density at the current density of 1mA ${\text{g}}^{-1}$ were determined as 1458.33W ${\text{kg}}^{-1}$ and 91.14Wh${\text{kg}}^{-1}$, respectively. Hence, NiO/ZnO nanocomposites could be reckoned to be a promising electrode material for supercapacitor while comparing to ZnO-based electrode material.

C–V characteristics of ZnO-based ceramic structures used in manufacturing high-voltage and low-voltage varistors of different chemical compositions and manufacturing techniques have been investigated. A correlation between the intensity of electric field corresponding to transition of the C–V characteristics to the negative capacitances and average sizes of grains of a varistor structure has been established. Obtained data have been interpreted with the use of notions of the percolation theory of electric conductivity. The Shklovskii–De Gennes model has been used. It has been shown that on the highly nonlinear segment of C–V characteristics of a varistor structure, the size of an infinite cluster are limited to several intercrystallite potential barriers. This result is observed in all kinds of investigated varistor ceramics.

The influence of temperature on the dielectric properties of sol-gel routed spin-coated molybdenum trioxide (MoO${}_3)$ thin film has been investigated. Prepared films were annealed at temperatures 250${}^{\circ }$C, 350${}^{\circ }$C and 400${}^{\circ }$C. The phase transformation from amorphous to $\alpha$-orthorhombic phase with preferential orientation (0 2 2) has been found by XRD for the film annealed above 250${}^{\circ }$C. The vibration modes of $\alpha$-orthorhombic MoO₃ have been examined by Raman spectrum. The predominant Raman’s band of $\alpha$-orthorhombic MoO₃ thin film has been found at the frequency range 1000–600cm${}^{-1}$. Using the UV–Vis spectrum, the band gap of the film is found to be 3.3–3.8eV. The surface morphology of the MoO₃ films has been examined by scanning electron microscope. The AC conductivity measurement of the MoO₃ film has been carried out in the frequency range 10–10⁶ Hz. The frequency dependence of the impedance has been plotted in the complex plane. The variation of the capacitance and dielectric constant of MoO₃ film with respect to temperature and frequency has been analyzed. Tunability of capacitance and figure of merit of the film are also determined.

This paper reviews the interpretation of impedance and capacitance spectra for different capacitor technologies and discusses how basic electrical characteristics can be inferred from them. The basis of the interpretation is the equivalent circuit for capacitors. It is demonstrated how the model parameters, such as capacitance and equivalent series resistance, can be extracted from the measured spectra. The aspects of measurement accuracy are exemplarily discussed on the measured spectra.

A flexible capacitive three-dimensional (3D) force transducer with four bottom electrodes is proposed. A dielectric layer with ionic effects and pyramid-like microstructures is designed to improve the sensing performance of this sensor. The arrayed sensor exhibits remarkable capabilities in capturing and decoupling 3D forces, showcasing a high sensitivity, a wide response range (0–30kPa), rapid response time (62ms), excellent repeatability under continuous pressure, as well as static and dynamic responses. By assembling a robotic arm to grasp various objects, the sensor demonstrates exceptional sensing capabilities for object roughness, thereby highlighting its potential application as a touch recognition system in human–computer interaction scenarios.

A control volume conductance method is discussed in this paper. The method is designed for materials that exhibit heat transfer. Particular attention is put to problems where convection overpowers the mechanism of conduction. The semi-infinite solid which moves with arbitrary imposed velocities along the X-axis and has various surface conditions at x=0 is a classical problem where convection instantaneously overpowers conduction. The analytical solution for this problem becomes physically unrealistic when the strength of convection is high which is defined by the Peclet number. For small Peclet numbers, the diffusion behavior is reasonably described by linear diffusion coefficients, but at large Peclet numbers lineal behaviors become incorrect and hence bad. The true is that diffusion in the analytical solution has indeed an exponential behavior. The exponential behavior in the convection-diffusion exact solution has an exponential behavior. Here false diffusion which is related to the Peclet number corresponds to the energy being supplemented by continuous falls such as a snowfield. As standard numerical schemes do not have this exponential feature, they eventually cross the zero dividing line. The result is unrealistic solution in the form of numerical oscillations. In this paper, this problem is circumvented with a new augmented conductivity term, where false diffusion is added to the true diffusion via exponential relationships with no need of curve fitting procedures. The novelty of the approach is that convection effects are embedded into the conductivity term. This originates new equivalent governing equations for heat transfer. The control volume numerical solution of the method is similar to that of standard parabolic heat conduction. The method is shown to yield exact solutions, to be accurate and computationally competitive.

In this paper the capacitance-voltage characteristics of InN quantum dots embedded in AlGaN/GaN heterostructure has been studied. This work has been done for the InN quantum dots with different quantum dot size, and energy dispersion and for the AlGaN/GaN heterostructures with different Al mole fraction and number of quantum wells in different temperatures. The presence of InN quantum dot will cause Gaussian shape in capacitance-voltage characteristics approximately, where the peak of curves can evidence the position of quantum dots in the structures. Our calculation results show the Gaussian shape (or negative differential capacitance) is much higher at low temperature and for quantum dots with low energy and higher size dispersion.