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In this study, the density of interface states (NSS) and series resistance (RS) were examined for both frequency and voltage in PrBaCoO-nanofiber interface layered metal-semiconductor (Au/nSi) structures. For this purpose, capacitance-voltage (C-V) and conductivity-voltage (G/w-V) measurements were performed at room temperature, 1 kHz-1 MHz frequency and (+-3 V) voltage range. Frequency and voltage-dependent distributions of interface states were obtained from Hill Coleman and high-low capacitance (CHF-CLF) methods, and RS from Nicollian-Brews method. Interfacial states and their lifetime were obtained from the Admittance/Conductance method developed by Nicollien and Goetzberger. Experimental results show that NSS states in impedance measurements are particularly effective in the regions of depletion and inversion while RS is only effective in the accumulation region and at high frequencies. The measured capacitance and conductivity values are corrected for high frequencies to minimize the RS effect on the measured C-V and G/w-V pilots.

The physical validation of devices must comply with the principles of causality, passivity, and stability. For linear and time-invariant devices, it can be proved that passivity implies a causal transfer function. In this sense, it is understood that causality is a consequence of the passivity condition. Moreover, if the real part of the admittance is non-negative, it can also be demonstrated that the device is passive. The main subject of this work is a novel class of one-port passive devices presenting negative real part admittances on certain frequency ranges. Thus, the equations expressing the passivity condition, as far defined, are not applicable and the causality condition must also be checked. A theoretical model able to explain this effect and a generalization of the passivity condition, which fully address the applicability of the passivity-causality theorem are provided. The experimental verification of a specific device having this property is also shown. In this way, we report the results of a practical realization of a resonant circuit having negative real part values and a tunable positive to negative real part transition. As a possible outcome, novel passive circuits, such as oscillators and phase modulators covering the full trigonometric circle may be constructed. We also discuss the causality condition, show that negative real part admittances are causal and provide a new causality test that is in full consistence with the Kramers-Kronig relations.

In this study, thin film of titanium dioxide (TiO2) was deposited onto n-type silicon substrate by radio frequency (RF) magnetron sputtering system. The admittance (capacitance and conductance) measurements were performed in the frequency range of 500 Hz - 500 kHz and at room temperature. The dielectric parameters such as dielectric constant (ε′), loss (ε″), loss tangent (tan δ), ac conductivity (σac) and complex modulus (M∗) of the MIS structure were obtained from these measurements. While the C value decreases with an increase of the frequency, the G increases. The change in C and G with frequency is attributed to the presence interface states. The value of ε′ and ε″ decreases with increasing frequency. On the other hand, the value of ac conductivity increases with increasing frequency. [ABSTRACT FROM AUTHOR]

The capacitance-voltage ( C – V ) and conductance-voltage ( G/\omega – V ) data for Al/(0.07Zn-doped polyvinyl alcohol)/p-Si structure have been performed (at ±6-V biases) in a frequency interval of 1–400 kHz at room temperature. Utilizing form conductance method, N\textsf {ss} values were specified from admittance measurements. The reason of higher C and G values obtained at lower frequencies was ascribed to the surface states located at MS interface and insulator layer. The increment at capacitance and conductance was occurred in consequence of the ac signal that followed easily by the surface states at these lower frequencies. The surface states existence also generates peaks at conductance versus logarithm of frequency ( Gp/\omega -log (f) ) plots under distinct voltage values. The acquired values of N\text {ss} and relaxation time (\tau ) are in the interval of \textsf {1.94} \times \textsf {10}^{\textsf {14}} – \textsf {1.67}\times \textsf {10}^{\textsf {14}} eV ^-\textsf 1\cdot \textsf cm^-\textsf 2 and \textsf 2.81 \times \textsf 10^-\textsf 3 – \textsf 1.30 \times \textsf 10^-\textsf 5 s, respectively. [ABSTRACT FROM PUBLISHER]

The increasing requirements for improved reliability of electrical power devices and optimisation of dielectric insulation design means that the analysis of impact due to overvoltages is of high importance. This analysis should also consider propagation of overvoltages transferred through power transformer windings to other parts of the electrical network. Hazard levels of overvoltages affected the insulation systems of electrical devices are determined by wave propagation conditions of overvoltages as well as the protection level of applied overvoltages protection. The analysis of overvoltages transferred to low voltage networks is very important due to the increasing number of electrical devices and electronic apparatus with low resistance to overvoltages. This study presents a detailed analysis of the propagation of overvoltages transferred through distribution transformer windings, in typical medium and low‐voltage electrical networks. The analysis is based on simulation results carried out by the use of electromagnetic transients program–alternative transients program (EMTP–ATP). A high‐frequency model for transformers done on the basis of frequency characteristics of admittance measurements was used in simulations. Detailed analysis of influence of length of medium‐ and low‐voltage lines connected to the distribution transformers and metal oxide surge arresters on switching overvoltages transferred to low‐voltage networks are presented in the study. [ABSTRACT FROM AUTHOR]

A metal-polymer-semiconductor (MPS) structure based on 5 wt% graphene (Gr) doped polyvinyl alcohol (PVA) thin film was fabricated by using the electrospinning method. Admittance (Y = G + iωC) based measurements of Al/Gr-PVA/p-Si (MPS) structure were performed in the frequency range from 5 kHz to 5 MHz at room temperature. Significant shifts in capacitance (C) and conductance (G) characteristics were observed for the MPS structure. The C and G value decrease with increase in frequency. The variation of C and G with frequency comes from the existence of interface states. the interface state density (N ss) was estimated by various methods such as low-high frequency capacitance (C LF -C HF), Hill-Coleman and conductance. The N ss value obtained from all methods decreased as the frequency increased. Because as the frequency increases, the interface states cannot follow alternating current (ac) signal. Meanwhile, the measured capacitance and conductance were corrected taking into account the effect of series resistance (R s). • The fabricated of Al/Gr-PVA/p-Si (MPS) structures. • The characterization electrical parameters by using admittance spectroscopy method. • Frequency and voltage dependent profiles of interface state and series resistance. • The effect of interfacial organic layer (Gr doped PVA) on the impedance measurements. • The N ss vs V profiles extracted from three different methods (low-high frequency capacitance, conductance and Hill-Coleman). [ABSTRACT FROM AUTHOR]

The frequency dependence of admittance measurements (capacitance--voltage (C--V) and conductance--voltage (G/ω--V)) of Au/SnO2/n-Si (MOS) capacitors was investigated by taking into account the effects of the interface states (Nss) and series resistance (Rs) at room temperature. Admittance measurements were carried out in frequency and bias voltage ranges of 1 kHz-1 MHz and (-5 V)-(+9 V) respectively. The values of Nss and Rs were determined by using a conductance method and estimating from the admittance measurements of the MOS capacitors. At low frequencies, the interface states can follow the AC signal and yield excess capacitance and conductance. In addition, the parallel conductance (Gp/ω) versus log(f) curves at various voltages include a peak due to the presence of interface states. It is observed that the Nss and their time constant (τ) range from 1.23x1012 eV-1 ⋅ cm-2 and from 7.29x10-5 to 1.81x10-5s, respectively [ABSTRACT FROM AUTHOR]

Abstract: An accurate determination of the valence band discontinuity of the lattice matched GaAs/InGaP heterostructure is performed by admittance spectroscopy measurements in p+/MQW/n+ structures grown by metal-organic vapour phase epitaxy (MOVPE) using tertiarybutylarsine and tertiarybutylphosphine as alternative precursors for the V group elements. Through the analysis of the temperature dependence of the resonance frequency ϖ at which the isothermal curves of the conductance over frequency G(ω)/ω have the maximum, the energy separation of 336±5meV between the lowest heavy hole quantum level in the GaAs wells and the InGaP valence band top is obtained. A valence band discontinuity of ΔE V =346±5meV is then derived by accounting for the calculated confinement energy of heavy holes (). Experimental values of ΔE V previously reported in the literature spread over the wide range of 300–400meV. [Copyright &y& Elsevier]