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Drastic Improvement of Dielectric Performances by Nanocomposite Technology
Published in Toshikatsu Tanaka, Takahiro Imai, Advanced Nanodielectrics, 2017
Muneaki Kurimoto, Kazuyuki Tohyama, Yasuhiro Tanaka, Yoshinobu Mizutani, Toshikatsu Tanaka, Masayuki Nagao, Naoki Hayakawa, Takanori Kondo, Tsukasa Ohta
How are dielectric spectra obtained? The method of obtaining dielectric spectra depends on the frequency range of the voltage used for the measurement. In general, the dielectric characteristics at ≤108 Hz are obtained by measuring the AC impedance (capacitance and dielectric tangent) of specimens. As shown in Fig. 5.3, a plate or sheet of insulating material is used as a specimen, and is sandwiched with circular metal electrodes to form a capacitor. To avoid gaps between a specimen and electrodes, a metal is vapor-deposited or a metal paste is coated on the specimen. Although guard electrodes are generally used to avoid the effect of electric distortion at the edges of the capacitor, the guard electrodes may not be used if the electrode area is sufficiently large compared with the thickness of the specimen. A Schering bridge, an inductance, capacitance, and resistance (LCR) meter, and an impedance analyzer are used for measurement.
Capacitance Spectroscopy for MOS Systems
Published in Jian V. Li, Giorgio Ferrari, Capacitance Spectroscopy of Semiconductors, 2018
Salvador Dueñas, Helena Castán
This study requires the use of an RF Impedance Analyzer, allowing to realize measurements up to the GHz range. This kind of equipment has been recently introduced in the market and nowadays is possible to make up this characterization. Capacitance and conductance of MOS devices are obtained by scanning the frequency of the RF signal while keeping the gate voltage at a given value. A whole RF characterization is obtained by varying the voltage from accumulation to inversion regime. The influence of the gate voltage on the RF characteristics is obtained in this way. Figure 10.23 plots RF admittance curves of a W/HfO2/Si MOS structure. The most noticeable point is the fact that the frequencies of the inflection point of the capacitance signal and the maximum of the conductance signal depend on the bias voltage: more positive voltages yield to higher relaxation frequencies. In this case, MOS capacitors are in the inversion regime for positive bias and in accumulation for negative ones. The main conclusion is that the inversion layer at the interface channel affects to the dipole relaxation in such a way that it occurs at higher frequencies. In accumulation, the voltage drop in the oxide is equal to the applied gate voltage, whereas in depletion or inversion regime, part of the applied voltage drops in the semiconductor layer close to the interface. Hence, higher electric field exists on the accumulation regime and dipole orientation is more effective in this regime, and dipoles could not respond to so high frequencies as in the inversion regime. Figure 10.24 shows this effect from a three-dimensional point of view.
Effect of polymer concentration on the electro-optical, dielectric and photoluminescence properties of confined ferroelectric liquid crystals composites
Published in Liquid Crystals, 2022
Praveen Malik, Garima Chauhan, Pankaj Kumar, Akash Deep
The dielectric measurement is carried out to understand the dynamic behaviour and interaction mechanics of FLC molecules. The studies were carried out with the help of an impedance analyser (Wayne Kerr, Model- 6500B, UK) in the frequency range of 100 Hz–10 MHz. Two main parameters, a real part of permittivity called dielectric permittivity () and the imaginary part of permittivity called dielectric loss (), are measured by using Equations (4) and (5), respectively. To reduce the high- and low-frequency effects, the calibration of cells was carried out with benzene and air [48]. The following equations were applied to measure the dielectric permittivity and dielectric loss of the prepared samples.