Parts Of Complex Dielectric Constant Research Articles

Analysis of the effect of low dye concentration for electrical system applications of reactive red 45 dye loaded hydrogels

Structural, optical and dielectric properties determining the conduction mechanism were investigated using appropriate measurement techniques to determine the suitability of low-concentrations (LC) (1000 μL, 500 μL, 250 μL and 125 μL) reactive red 45 (RR-45) dye loaded hydrogels for electrical circuit applications. The UV spectra of the all samples displayed a fluctuating behaviour depending on the concentration. It was found that the dielectric plane plots for all the samples are compatible with the Cole-Cole relaxation model and correspond to an equivalent electrical circuit (RC) representing with the impedance circuit in the Smith Chart. It was concluded that RR-45 dye loaded hydrogels could be a suitable material for electrodes used in electroencephalography and electrocardiography systems due to the decrease of the real part of complex dielectric constant and impedance values with increasing frequency. The s-parameter for the samples, which determines the conductivity mechanism, was calculated separately for different regions.

Characterization of Gallium Oxide/glass thin films grown by RF magnetron sputtering

In the present work, Gallium Oxide (Ga2O3) were deposited as thin films by radio frequency (RF) magnetron sputtering at 300 °C substrate temperature on glass substrate using Ga2O3 target with 99.99% purity. The crystalline structure, morphology, optical properties of the Gallium Oxide films were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Visible Spectrometry, respectively. Experimental results show that annealing has an important role in the changes observed in the characterization of the Gallium Oxide thin films. All thin films produced were amorphous, except for the annealed P4-500. SEM pictures reveal the morphology of prepared Gallium Oxide thin films. The refractive index and real part of complex dielectric constant increased as the film deposition pressure increased.

The SMOS-Derived Soil Water EXtent and equivalent layer thickness facilitate determination of soil water resources

The assessment of water resources in soil is important in understanding the water cycle in the natural environment and the processes of water exchange between the soil and the atmosphere. The main objective of the study was to assess water resources (in 2010–2013) in the topsoil from satellite (SMOS) and in situ (ground) measurements using the SWEX_PD approach (Soil Water EXtent at Penetration Depth). The SWEX_PD is a result of multiplying soil moisture (SM) and radiation penetration depth (PD) for each pixel derived from the SMOS satellite. The PD, being a manifold of the wavelength λ0 equal to 21 cm, was determined from the weekly SMOS L2 measurement data based on the real and imaginary part of complex dielectric constant. The SWEX_PD data were compared with soil water resources (WR) calculated from the sum of components derived from multiplication of soil moisture (SM) and layer thickness in nine agrometeorological stations located along the eastern border of Poland. Each study site consisted of seven neighbouring Discrete Global Grid pixels (nodes spaced at 15 km) including the central ones with agrometeorological stations. The study area included different types of soils and land covers. The agreement between the water resources obtained from the SWEX_PD and ground measurements (WR) was quantified using classical statistics and Bland–Altman's plots. Calibrated Layer Thickness (CLT = dbias) from 8 to 28 cm was obtained with a low values of bias (close to zero), limits of agreements, and confidence intervals for all the SWEX_PD, depending on the pixel location. The results revealed that the use of the SWEX_PD for assessing soil water resources is the most reliable approach in the study area. Additionally, the data from Bland–Altman plots and the equation proposed in these studies allowed calculation of the Equivalent Layer Thickness (ELT = d_{ei}^{SWEX}), which corresponds to the water resources derived from the SMOS satellite at the same time as (SM) measurements performed in the agrometeorological stations. The ranges of the mean, standard deviation, minimum, maximum, and coefficient of variation (CV) of ELT among all pixels and stations were 8.28–28.7 cm, 3.27–12.66 cm, 3.03–10.87 cm, 19.23–94.97 cm, and 24.72–98.79%, respectively. The ranges of the characteristics depended on environmental conditions and their means were close to the values of the calibrated layer thickness. The impacts of soil texture, organic matter, vegetation, and their interactive effects on the differentiation and agreement of soil water resources obtained from SWEX_PD vs. data from ground measurements in the study area are discussed. Further studies are required to address the impact of the environmental factors to improve the assessment of soil water resources based on satellite SM products (retrievals).

Electric and dielectric parameters in Au/n-Si (MS) capacitors with metal oxide-polymer interlayer as function of frequency and voltage

In the present work, Au/(MgO-PVP)/n-Si (MPS) capacitors were fabricated and their electric and dielectric parameters were examined via impedance spectroscopy method (ISM) and compared with each other between – 2 and 3 V biases and 10 kHz/5 MHz frequencies. Both the capacitance (C) and conductance (G/ω) values have large dispersion in inversion, depletion, and accumulation regions due to the existence of surface states/traps (Nss/Dit), interface/dipole polarizations, series resistance (Rs), and (MgO-PVP) organic interlayer. Among them, Nss and polarization are effective in inversion and depletion regions at low–intermediate frequencies, but Rs and interlayer are effective only at accumulation region at high frequencies. The voltage and frequency-dependent Nss and Rs were extracted from the Hill–Coleman and Nicollian–Brews methods, respectively. Some basic electrical parameters such as diffusion potential (VD), Fermi energy (EF), depletion region width (WD), and barrier height (ΦB) were calculated from the intercept and slope of the linear regimes C−2–V curves as function of frequency. Additionally, the real and imaginary parts of complex dielectric constant (e*), complex electric modulus (M*), and ac conductivity (σac) were extracted from the C and G/ω data as function of frequency and voltage. The e' value of the (MgO-PVP) interlayer was found as 5.0 even at 10 kHz which is very high when compared conventional insulator layer by traditional method such as SiO2 above 10 kHz in respect of easy grown processes, low cost, flexibility and high mechanical strength. These results show that the used (MgO-PVP) polymer interlayer leads to a large polarization and more storage charges/energy in the MPS-type capacitors rather than MOS capacitors.

Dielectric and transport properties of ‘Sr’ modified lead free double perovskite

The polycrystalline sample Ba0.5Sr1.5FeVO6 is prepared by high temperature solid solution route. The real (ε') and imaginary (ε'') part of complex dielectric constant of the sample was recorded over wide range of frequency (100 Hz–5 MHz) and temperature (30–500 °C). The frequency dependent ac conductivity (σac = ωε0ε'') obtained by using dielectric data was consistent with Jonscher’s power law. Temperature dependent conductivity give a typical texture of ionic conduction. I-V characteristics suggest semiconducting nature in the material.

INDIUM INCORPORATION EFFECTS ON OPTICAL PROPERTIES OF QUATERNARY CHALCOGNIDE Se-Zn-Te-In FILMS

Amorphous semiconducting thin films of Se90-xZn5Te5Inx (x=0, 2, 4, 6, 8 and 10 at. %) are deposited on glass substrates by thermal evaporating technique with thickness about of 1000 nm. The transmittance spectra are investigated by Swanepoel method to compute the optical coefficients and parameters in the spectral region of (400–2500) nm, such as absorption coefficient α, extinction coefficient k, optical band gap, Eg and refractive index, n. The optical absorption edge is described by using the non-direct transition model in terms of Tauc relation. The obtained values of both n and k were found to be dependent of the In content in the investigated samples. Also, other parameters have been computed like the real, (εr) and imaginary (εi) parts of complex dielectric constants. The dispersion parameters (dispersion energy, Ed, oscillation energy Eo) were discussed according to the single oscillator Wemple–DiDomenico model. The non-linear refractive index, n2 was computed by using Tichy-Ticha and Fourier-Snitzer relationships.

The effect of SiO2 nano-filler on dielectric properties of epoxy resin

The paper presents the impact of SiO2 nano-filler in epoxy resin (ER) on changes of dielectric properties and time to the breakdown. Several composites were tested with the mass fraction of 0.5 wt%, 1 wt% and 2 wt% of SiO2, respectively. The frequency spectra of the real and imaginary parts of complex dielectric constant were measured by a capacitance method within the frequency range from 1 mHz to 1 MHz. The mass fraction 0.5 wt% nanoparticles (NPs) in ER caused the evident decrease of the complex permittivity, while 1 wt% or 2 wt% yielded similar permittivity as measured in the pure ER sample. This change of the permittivity with the nano-filler concentration is discussed on the basis of the multi-core model. Moreover, SiO2 NPs also caused the frequency shift of the local maximum of permittivity to lower frequencies which corresponds with the α-polarization process. The internal partial discharges in the ER and its mixtures with the SiO2 nano-filler by the galvanic method and acoustic method are presented. The decrease of the time to breakdown with the increase of SiO2 the mass fraction is reported, too.

Electric and dielectric characteristics of Al/ZrO2/IL/n-Si MOS capacitors using three-frequency correction method

Abstract In this study, MOS capacitors of Al/ZrO2/IL/n-Si (IL: interface layer) have been fabricated. Bias scan and frequency scan data of measured parallel capacitance (Cm) and parallel resistance (Rm) have been taken in the frequency of ∼1 kHz to 2 MHz. To correct external frequency dispersion of parasitic parameters, we have used five-element model (including MOS capacitance C, parallel resistance Rp, IL capacitance Ci, IL resistance Ri, and series resistance Rs) and three-frequency correction method. Extracted capacitance C by the three-frequency correction method has negligible frequency dependence from 0.38 nF to 0.34 nF in the average frequency of ∼3.7 kHz to 1.54 MHz. The frequency dispersion of Rp, Ci, Ri, and Rs are explained by some physical mechanisms. Small relative errors ΔC/C, ΔRp/Rp, ΔCi/Ci, ΔRi/Ri and ΔRs/Rs are less than 0.2%, 2%, 3%, 1.2% and 0.4% respectively. We have also used two existing double-frequency methods of three- and four-element models for comparison, and the extracted capacitances show abnormal frequency dependence. Above results indicate the three-frequency method of five-element model is necessary, effective and convenient in providing sufficient list data for bias voltage dependence or frequency dependence. The dielectric parameters, such as relative dielectric constant, conductivity, imaginary part of complex dielectric constant, and dielectric loss tangent have been calculated. The mechanisms of frequency dispersion for the dielectric parameters have been analyzed.

Temperature and Interfacial Layer Effects on the Electrical and Dielectric Properties of Al/(CdS-PVA)/p-Si (MPS) Structures

In the present study, cadmium sulphide (CdS) nanopowders were prepared by using a simple physical ball milling technique, and their x-ray diffraction (XRD) analysis confirmed the formation of hexagonal wurtzite structure of CdS. The morphology of CdS nanopowders was characterized by scanning electron microscope (SEM). Dielectric and electrical properties of the manufactured Al/(CdS-PVA)/p-Si (MPS) type structures were investigated by capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements as functions of temperature and applied bias voltage at 500 kHz. Some main parameters of the structure such as real and imaginary parts of complex dielectric constants, e′(= e′–je″), loss tangent (tan δ), a.c. electrical conductivity (σac), and real and imaginary parts of complex electric modulus, M*(= M′ + jM″) of the structure were investigated in the temperature range between 230 K and 340 K. Ln(σac)–q/kT curve showed a linear behavior. The value of activation energy (Ea) was obtained as 0.0601 eV at 5.0 V from the slope of this curve. Moreover, argand diagrams of complex modulus were studied to determine relaxation process of these structures.

First-principle study on the electronic structure and optical property of new diluted magnetic semiconductor (Y0.75Sr0.25) (Cu0.75Mn0.25)SO

In this research, we investigated the electronic structure and optical property of new diluted magnetic semiconductor (Y0.75Sr0.25) (Cu0.75Mn0.25)SO with decoupled charge and spin doping by first-principle calculation. We also compared (Y0.75Sr0.25) (Cu0.75Mn0.25)SO with pure YCuSO, and found that (Y0.75Sr0.25) (Cu0.75Mn0.25)SO is still a direct semiconductor with a band gap 1.20eV. The important difference from YCuSO is that the DOS of (Y0.75Sr0.25) (Cu0.75Mn0.25)SO presents asymmetry around fermi surface, leading to obvious spin order and ferror-magnetism due to the p-d hybridization through Mn 3d and S 3p. In case of the optical properties (including reflectivity coefficient, absorption coefficient, the imaginary part and real part of complex dielectric constant), the intensity of all peaks for both pure and doped YCuSO tends to zero above 15.5eV. However, the value of all the peaks for (Y0.75Sr0.25) (Cu0.75Mn0.25)SO reduces to some extent due to the Sr and Mn dopant. In addition, the position of all the peaks for (Y0.75Sr0.25) (Cu0.75Mn0.25)SO have a “red shift”, probably originating from the impurity states generated by the p-d hybridization through Mn 3d and S 3p. This will be beneficial for searching new 1111 phase DMS.

Impedance properties and comparison effects of different dose safranin doped hydrogels

Frequency evolution of dielectric characteristics of different dose safranin (SR) doped hydrogels was studied by impedance spectroscopy (IS) at room temperature (RT). Real and imaginary parts of complex dielectric constant, impedance, electric modulus and conductivity of SR doped hydrogels were analyzed in the frequency range of 100Hz to 40MHz for pH5.0 value. Phase angle, capacitance, surface resistivity, tangent factor (tan δ) for all samples were recorded with the same frequency range. Surface and bulk polarization effects were dominant on impedance at low and high frequency regime, respectively. Fluctuation effect of SR doped hydrogels was observed from the dielectric measurements. Tutorial of radio frequency, RF, impedance matching were realized by using the Smith chart. The coulomb interaction between SR-cations and hydrogels may be anticipated to enhance the organic electrical performance. The potential applications of SR doped hydrogels were presented to microbial fuel cells.

Synthesis and characterization of a new hydrogen bonded side chain liquid crystal block copolymer and investigation of electrical properties

Abstract A new PEG-containing liquid crystalline side chain block copolymer HBC-PEG550 was prepared from poly(ethylene glycol)-b-poly(2-(diethylamino) ethyl methacrylate copolymer (BC-PEG550) and 8-(4-cyanobiphenyl-4′-oxy) octan-1-ol (LC8) by molecular self-assembly processes via hydrogen bond formation between amine group of HBC-PEG550 and hydroxyl group of the LC8. The formation of H bond was confirmed by using FTIR spectroscopy. The liquid crystalline behavior of the HBC-PEG550 was investigated by differential scanning calorimeter (DSC) and polarized optical microscopy. Dielectric properties of HBC-PEG550 and HBC-PEG550 has been studied by impedance spectroscopy. Real and imaginary parts of complex dielectric constant, impedance, and energy loss tangent factor for HBC-PEG550 and HBC-PEG550 have been characterized in the frequency range of 100 Hz–15 MHz.

Effect of substrates and thickness on optical properties in atomic layer deposition grown ZnO thin films

Atomic Layer Deposition technique was used to grow high quality, very low roughness, crystalline, Zinc Oxide (ZnO) thin films on silicon (Si) and fused quartz (SiO2) substrates to study the optical properties. Spectroscopic ellipsometry results of ZnO/Si system, staggered type-II quantum well, demonstrate that there is a significant drop in the magnitudes of both the real and imaginary parts of complex dielectric constants and in near-band gap absorption along with a blue shift of the absorption edge with decreasing film thickness at and below ∼20nm. Conversely, UV–vis absorption spectroscopy of ZnO/SiO2, thin type-I quantum well, consisting of a narrower-band gap semiconductor grown on a wider-band gap (insulator) substrate, shows the similar thickness dependent blue-shift of the absorption edge but with an increase in the magnitude of near-band gap absorption with decreasing film thickness. Thickness dependent blue shift, energy vs. 1/d2, in two different systems, ZnO/Si and ZnO/SiO2, show a difference in their slopes. The observed phenomena can be consistently explained by the corresponding exciton (or carrier/s) deconfinement and confinement effects at the ZnO/Si and ZnO/SiO2 interface respectively, where Tanguy-Elliott amplitude pre-factor plays the key role through the electron-hole overlap factor at the interface.

Determination and analysis of optical constants for Ge15Se60Bi25 thin films

Thin films of Ge15Se60Bi25 were deposited, at room temperature, on glass substrates by thermal evaporation technique. The optical reflectance and transmittance of amorphous Ge15Se60Bi25 films were measured at normal incident in the wavelength range (500–2500nm). The optical constants, the refractive index n and the absorption index k, were determined and analyzed according to different approximate methods using the transmittance measurements only and accurate method using the transmittance and reflectance measurements. Analysis of the absorption index k data reveal the values of the optical band gap Egopt, the width of tails Ee and the type of transitions. Some optical parameters such as, high frequency dielectric constant ε∞, dispersion parameters (oscillation energy Es and the dispersion energy Ed), real and imaginary parts of complex dielectric constant (ε1 and ε2) and dielectric parameters (dissipation factor tanδ, dielectric relaxation time τ, the volume and surface energy loss functions) were estimated by analyzing the refractive index n data.The relative errors for all optical parameters depending on different approximate methods were identified and discussed.

Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz.

Electrical Properties of Hot Press Sintered NASICON Ceramics

Sodium superionic conductor, NASICON ceramic (Na1+xZr2SixP3-xO12, x=2), was hot-press sintered under different temperatures and the electrical properties of the obtained different samples were investigated. Results show that the relative density of the ceramics can be improved by hot-press process efficiently and the crystal size of the samples are closely related to sintering temperature. With the increase of sintering temperature, both the density and the crystal size of samples increase obviously, resulting in the increase of ionic conductivity of samples as the sintering temperature. When the sintering temperature reaches 1150oC, the ionic conductivity of sample is as high is 3.6×10-3S/cm, which is obviously higher than that of sample sintered at 1000oC (2.13×10-3S/cm). As the frequency increase, the real parts and the imaginary parts of complex dielectric constants for all the samples decrease in 8.2 GHz~12.4GHz frequency band. The ceramics obtained at the higher temperature possess the higher dielectric constant.

Spectroscopic ellipsometry study on TiO 2 thin films modified by N 2–H 2 plasma surface treatment

We analyzed successfully the refractive index, n, and extinction coefficient, k, of three samples such as as-deposited single-phase anatase–TiO 2 polycrystalline thin films on slide glass substrates (#1), the sample surface-treated by N 2–H 2 mixed-gases plasma (#2), and the sample being additionally anneal-treated in N 2 gases (#3), by spectroscopic ellipsometry (SE). The double-layered film configuration named as the surface and the bulk layers is employed in SE analysis. The optical properties of the surface layer are confirmed to be important to explain the significant red shift of the absorption edge of both surface-treated samples observed in the preceding report. Particularly, the obtained imaginary part of complex dielectric constant of the surface layer of the samples #2 and #3 shows significant difference from that of the sample #1. This is due to the absorptive transitions not by solely anatase–TiO 2 but by mixed formation of TiO 2− x N x and TiN with metallic characteristics.

Terahertz time-domain spectroscopy of low-energy excitations in glasses

The low-energy excitations in glasses were studied by the terahertz time-domain spectroscopy (THz-TDS). The coherent THz radiation by a femto-second pulse laser enables the determination of the real and the imaginary parts of complex dielectric constants in the frequency range between 0.3 and 2.4 THz. The complex dielectric spectra of glasses clearly show the existence of broad low-energy excitations called boson peaks.

Terahertz time domain spectroscopy of complex dielectric constants of boson peaks

Using THz time domain spectroscopy we have observed both the real and the imaginary parts of complex dielectric constants in the far-infrared region for a glassy polymethyl methacrylate (PMMA). The intensity and phase of transmittance of PMMA were accurately measured in the frequency range between 5 and 110 cm −1. The strong absorption appeared around a boson peak (BP) frequency, which was also observed by Raman scattering. The broad peak of an imaginary part related to BP shows a similar line-shape to the reduced depolarized Raman spectrum.

Observation of collective excitation in Sr 14− xCa xCu 24O 41 compounds

We report the systematic investigation of the real and imaginary parts of complex dielectric constant of Sr 14− x Ca x Cu 24O 41 in the microwave and millimeter wave regions. For slightly hole-doped compounds, the real part of the conductivity along the ladder direction shows a strong frequency dependence at low temperatures, and shows a resonance-like peak around about 55 GHz (∼ 0.2 meV). This conductivity peak survived up to 150 K (∼10 meV), strongly suggesting the presence of collective excitation.