Imaginary Dielectric Constants Research Articles

Role of electrolyte concentration on growth kinetics, film thickness, structural, compositional and optical properties of cadmoselite thin films through electrochemical route

For the past few decades Cadmium chalcogenides attracted many researchers due to its interesting band gap nature, structure, electrical, optical and photoelectrochemical properties. The objective of the present work is to determine the modified features of cadmoselite thin film gown by simple, low cost, low temperature electrodeposition technique. Cadmoselite thin films were deposited on Indium doped Tin Oxide substrate. X-ray diffraction results reported that the deposited films were found to be polycrystalline nature with hexagonal structure. The structural parameters viz., crystallite size, rms microstrain, dislocation density and stacking fault probability were determined for the deposited films. Surface morphology along with film composition reported that the deposited films have smooth surfaces with well defined stoichiometry. Optical properties such as transmittance, absorbance and reflectance measurements showed that the deposited films found to exhibit maximum absorbance from the violet to blue region. The band gap value of the deposited films is found to be 1.76 eV. The parameters such as refractive index, extinction coefficient, optical conductivity, real and imaginary dielectric constants were estimated.

First principle study on structural and optoelectronic properties and band-gap modulation in germanium incorporated tin (IV) oxide

First principle calculations on pure and germanium (Ge) incorporated tin (IV) oxide (SnO2) are performed to understand their structural, electronic, and optical properties at the microscopic level. The optimized ground state structures exhibited a reduction in their lattice parameters as well as total energy with increasing germanium concentration. From the band structures of the pristine and doped SnO2, we have observed a reduction in the energy gap due to the incorporation of germanium into stannic oxide (SnO2). As conduction band minimum near Fermi level reaching a lower energy level with an increase in doping concentration, the electron affinity is increasing. The calculated band gaps of pure, 6.25 %, 12.5 % and 25 % ‘Ge’ incorporated tin (IV) oxides are 1.76, 1.73, 1.56 and 1.53 eV, respectively, and all are direct in nature. Further, the calculated electron effective mass at the conduction band minimum is lower than the hole effective mass at the valence band maximum. Hence, the mobility of electrons is found to be higher, suggesting the n-type semiconducting property. The contributions of different atoms on valence and conduction band are studied by calculating the density of states spectra. Optical properties, such as real and imaginary dielectric constants, absorption, reflectivity, refraction and extinction coefficient, loss function, real and imaginary optical conductivity are calculated. The calculated optical absorption shows that both un-doped and doped materials preserve the optical transparency in the infra-red region. Our analysis shows that Ge-doped SnO2 has a tunable band gap and work function, which makes it suitable for applications in photovoltaic devices.

Optical Properties of Blend of PMMA:PVDF

In this study, thin films of PMMA Poly (methyl methacrylate)- Polyvinylidene fluoride(PMMA-PVDF), PMMA polymer and soluble PVDF polymer were prepared at (5%)Toluene and polymeric blends in 1:1 volume ratio of polymers and in different proportions of polymers. The studied films were prepared by the Spin coating method, and the optical parameters of the thin films were measured within a range (300-900)nm and the thickness of the films were constant (223 nm). Absorbance (A), linear absorption coefficient (α), refractive index (n), extinction coefficient (K), real and imaginary dielectric constant (∈r, ∈i), and optical energy gap Eg were studied, as the best edge of optical absorption was 5% PVDF, And electronic transmission between levels was direct transmission.

Structural, Optical and Acoustical Characterization of Polyvinyl Alcohol Dispersed Cadmium Selenide Nanocomposites

Nanosized semiconducting cadmium selenide particles were successfully distributed within the polymer matrix of polyvinyl alcohol (PVA) utilizing the method of heat induced chemical synthesis. The structural characterization of the prepared nanocomposite was conducted using X-ray diffraction for the phase analysis of the nanocrystallites, Transmission electron microscopy (TEM) was used for size and shape determination of the nanoparticles and Fourier transform infrared (FTIR) spectroscopy for identification of the various chemical functional groups possessed by the PVA/CdSe nanocomposites. Various properties of hybrid nanocomposites have been widely scrutinized by researchers during the past few decades because of their unique properties and versatility. The present study involved the behavioral analysis of various optical properties, such as optical absorbance (A), transmittance (T), optical band gap (Eg), refractive index (n), extinction coefficient (k), real and imaginary dielectric constants (ε1 and ε2) and optical conductivity (σopt), of nanocomposite thin films produced by solution casting at temperatures ranging from 303 K to 343 K. The present study also deals with the evaluation of various ultrasonic acoustical properties, like adiabatic compressibility (βad), acoustic impedance (Z), intermolecular free length (Lf), relaxation time (τ) and attenuation coefficient, α, as a function of the square of the frequency (ƒ 1 ), i.e., (α/ƒ 1 ), to permit detailed understanding of behavioral changes in particle-fluid interactions with variation in the solution temperature of the nanocomposite.

New fabricated PMMA-PVA/graphene oxide nanocomposites: Structure, optical properties and application

Graphene oxide nanosheets (GO) bring more interest in the tunable bandgap and enhanced the optical properties of nanocomposites. The developed method successfully mixed the PMMA- dissolved in dimethylformamide (DMF) with PVA dissolved in distilled water (DW) and DMF. New (PMMA-DMF)-(PVA-DW-DMF)/GO nanocomposite was successfully fabricated with various loading ratios of GO nanosheets for the first time. Several factors were applied to get fine desperation and homogeneous using the acoustic-solution casting method. Optical Microscope (OM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and UV–visible spectrophotometer were applied to investigate the structure and optical properties of the PMMA-PVA-GO nanocomposite. The OM images confirmed the fine homogenous matrix and GO distribution in the nanocomposites. FTIR spectra exhibited the most functional group of polymers and GO in the nanocomposites and strong interfacial interaction between the GO and matrix as confirmed by the shifting in the XRD patterns of the PMMA. The optical properties results of the PMMA-PVA/GO nanocomposites revealed an improvement up to 400% of the absorbance, 337% of the absorption coefficient, 51% of the refractive index, 210% of the real and 125% of the imaginary dielectric constants in terms to increase the GO concentrations, whereas the reduction in the transmittance and energy bandgap results of allowed and forbidden indirect transition were exhibited up to 9 and 16.4%, respectively. These results could grow for better and wide applications such as radiation shielding, specific optoelectronic applications, and filters ultraviolet also could use in landfilling the chemical, nuclear, and radioactive waste.

Influence of Ni-Co dual doping on structural and optical properties of CdSe thin films prepared by chemical bath deposition method

Pure and Ni-Co dual doped CdSe thin films were deposited on glass substrate by chemical bath deposition (CBD) technique. The deposited thin films were annealed for 1 h at 500 °C. X-ray diffraction (XRD) and UV–vis Spectroscopy were used to study the structural and optical properties of the prepared thin films. XRD studies revealed the hexagonal phase for pure CdSe, CdSe: 0%Ni-8%Co, CdSe: 2%Ni-6%Co, CdSe: 6%Ni-2%Co and CdSe: 8%Ni-0%Co thin films, while CdSe: 4%Ni-4%Co produced the cubic phase. The XRD results revealed that the dual doping affected strongly the preferred orientation of the crystallites. The optical band gap energy, Urbach energy, Extinction coefficient, refractive index, real and imaginary dielectric constants and optical conductivity were calculated for all obtained thin films. The direct optical band gap energy of pure CdSe film was 1.43 eV and it decreased with Ni and Co dual doping. The lowest optical band gap energy was observed for CdSe: 4%Ni-4%Co. The dual doping with Ni and Co increased the efficiency of CdSe thin films to be used as solar cells.

Effect of Mn-substitution on the structure Co0.6Zn0.4Fe2O4

One Ferrite is a ferromagnetic substance where it is ideally used to manufacture devices such as rectifiers, memory devices, and inductors hearts as well as for various applications of microwave waves. The electrical and structural characterization of ferrites depends on preparation methods, nature of dopant, and dopant concentration. For these reasons, the series samples of Co0.6Zn0.4MnxFe2−xO4 ferrites prepared, using a traditional ceramic process, Mn-Zn ferrites were synthesized and sintered up to 1200 °C for 5 hours. We tested the X Ray diffraction (XRD) for different Mn-substitution (where x = 0, 0.2, and 0.4). XRD studies confirmed that the sample’s structural have a cubic spinel phase. The electrical characterization (such as conductivity, real and imaginary dielectric constant) was measured and discussed, as well.

Impact of MWCNT and GF Incorporation on Optical Properties of GTS Alloy

Aims: To address the physical properties of the growing research topic based on inorganic and organic composite materials under the glassy regime. The incorporation of a small amount of organic content in inorganic chalcogenide alloy could be an interesting topic for the investigation. Such composite materials' optical and structural properties could define their prospective use. Objectives: Considering the prospective utility of the inorganic and organic composite materials, this report’s key goal was to demonstrate the structural and optical properties, like, absorption spectra, extinction coefficient (k), real dielectric constant (εʹ), imaginary dielectric constant (εʹʹ), refractive index (n), absorption coefficient (α) and optical energy band (Eg ) for the Se 55 Te 25 Ge 20 (GTS) alloy, Se 55 Te 25 Ge 20 +0.025% multiwalled carbon nano tubes (MWCNT) and Se 55 Te 25 Ge 20 +0.025 % bilayer graphene (GF) composites. Methods: To synthesize the materials, a direct melt-quenched technique was adopted. Materials microstructural and UV/Visible optical absorption were performed from the Field Emission Scanning Electron Microscope and UV/Visible optical spectrometer equipment’s. Results: The obtained experimental evidences revealed that materials’ optical properties and microstructures slightly altered owing to the incorporation of multi walled carbon nano tubes and bilayer graphene in Se 55 Te 25 Ge 20 regime. To correlate the inorganic-organic material interactions, a schematic has also interpreted based on the bond formation in the solids. Conclusion: The experimental evidences have revealed the existence of MWCNT and GF in diffused form in GTS glassy configuration. The evidences have also revealed the diffused morphologies of the MWCNT and GF could not developed the specific structure within the complex configuration (although they have exhibited rather distinct morphologies), but they influenced the optical properties of the composite materials.

Study of Optoelectronic and Thermoelectric Characteristics of Cesium Based Halides CsYbX3 (X = Br, Cl) for Clean Energy Harvesting

The optoelectronic and transport characteristics of CsYbX3 (X = Br, Cl) are computed for clean energy harvesting. The structural stability has been anticipated by Goldsmith tolerance factor and thermodynamic stability by formation energy. The band gaps 1.66 eV and 1.44 eV for CsYbCl3 and CsYbBr3 are observed in visible energy region, which show their significance for optoelectronic and solar cells. The dielectric constant reveals the polarization of light while absorption coefficient and imaginary dielectric constant ensure maximum absorption in the visible region. Refractive index appears in the range of 1 to 2 and minimum reflectivity also builds their significance for optical applications. The transport properties are elucidated by electrical and thermal conductivities, Seebeck coefficient and figure of merit (ZT). The high value of ZT makes them equally important for thermoelectric devices.

Optical dispersion analysis of template assisted 1D-ZnO nanorods for optoelectronic applications

Morphology and size play crucial influential roles in semiconductor nanotechnology. Capping agents have been adopted in this study for controlled fabrication of symmetrical zinc oxide (ZnO) nanostructures, with a preferred orientation and agglomeration inhibition. Elongated one-dimensional (1D) ZnO nanorods were successfully synthesised in a simple two-step process. X-ray diffraction (XRD) revealed high crystalline films with a preferred (002) plane orientation. Ethylene glycol (EG) surfactant was found to produce substantial effect on both the morphology and crystallinity as relatively small uniform nanorods with crocked ends were observed from morphological analysis. All the synthesised ZnO films depicted optical transmittance of over 50% in the visible range and a strong absorption peak in the UV proximity, at 380 nm. An evaluation of the optical parameters calculated from the measured transmittance indicated that surfactants can be used to modify the refractive index, real and imaginary dielectric constants of ZnO nanorods, to optimize the performance of optoelectronic devices.

Synthesis and Optical Properties of PVA/PANI/Ag Nanocomposite films

Herein flexible nanocomposite films composed of polyvinyl alcohol (PVA), polyaniline (PANI), and silver (Ag) are synthesized using solution cast technique for optoelectronics applications. The X-ray diffraction (XRD), transmission electron microscope (TEM), and UV absorbance have confirmed the successful synthesis of the nanocomposite films with uniform silver nanoparticles (AgNPs) embedded in the PVA/PANI blend. The optical bandgap of PVA/PANI blends and PVA/PANI/Ag nanocomposites is determined by ultraviolet (UV) absorbance, which shows a decrease compared with a pristine PVA film. Meanwhile, Urbach energy, absorption edge (Ed), the number of carbon clusters (N) were estimated. Furthermore, the influence of PANI and AgNPs on the reflection, refractive index, extinction coefficient, real and imaginary dielectric constant, and the optical conductivity is discussed. The results clear that the optical properties of PVA polymer modify by adding PANI and AgNPs. Based on that, the fabricated PVA/PANI/Ag nanocomposites films can be used in optoelectronic devices.

Effect of temperature nano graphite doped polymethylmethacrylate (PMMA) composite flexible thin films prepared by solution casting: Synthesis, optical and electrical properties

We studied the effect of a temperature of graphite nanoparticles (GNPs) on optical properties of flexible PMMA/graphite nanocomposite thin films (PGNTFs). We have fabricated flexible PGNTFs by using solution casting method of 60 μm thicknesses with different concentration of GNPs (0, 1, 2, 5 wt.%). The results show that the absorption, absorption coefficient, extinction coefficient, optical conductivity and imaginary dielectric constants properties are more increasing for high concentration of GNPs but the effect of temperature on these optical properties of flexible PGNTFs are decreasing if we put our nanocomposite flexible thin films at higher temperature. The energy bandgap and transmittance are decreasing with increase of GNPs but the energy bandgap and transmittance are more decreasing for higher temperature. The resistivity are decreasing and conductivity are increasing with increasing different loading levels of GNPs and increasing the temperature.

Role of ZnO content on the structural, morphology and optical properties of (NiO)1-x (ZnO) x thin films prepared by pulsed laser deposition technique

(NiO) 1-x (ZnO) x compounds were prepared with different composition ratios. The compounds were obtained by mixing Nickle oxide and zinc oxide in the appropriate ratio and sintered at 1000°C for six hours. Pulsed laser deposition (PLD) method which is simple and inexpensive method was used to deposit (NiO) 1-x (ZnO) x thin films on glass substrate at ambient temperature. Structural, optical and properties were investigated. The structures investigation obtained from x-ray diffraction showed that the prepared of compound as well as thin films have polycrystalline structure where the diffraction peaks were identical with the cubic NiO and hexagonal ZnO for x=0 and 1.0 while the structure of the residual x values was identical with the both phases. The average values of the crystallite size increases from 29.3 nm to 32.4 nm when x increases from 0 to 1.0. Thickness interferometry measurement showed that thickness of the prepared thin films was ≈150 nm. The optical absorbance and transmittance spectrum provided from UV-spectrophotometer were used to estimate the optical parameters like optical energy gap Eg, refractive index, extinction coefficient and real and imaginary dielectric constants. The data showed that the optical energy gap as well as the optical constants decreases with the increasing of ZnO content in the prepared thin films.

Comparative DFT study of vibrational, electronic, and optical properties of energetic alkali metal salts based on nitrogen-rich 5-aminotetrazole.

This article presents a thorough density functional theory based comparative study on nitrogen-rich 5-aminotetrazole alkali metal salts M 5-At (M = Li, K, Rb, Cs). The calculated structural parameters using plane-wave pseudopotential method are consistent with the experimental results. The computed vibrational frequencies at ambient pressure show that vibrational modes in high energy region are due the NH bond of NH2 group. Pressure variation IR spectra of these materials show clear frequency shifts where Li 5-At shows an overall red shift below 900 cm-1 contrary to the blue shift seen in other materials in this range. The born effective charge values reveal the presence of strong covalency between N, H, and C atoms whereas an increased ionic nature is seen as the atomic number of metal atoms increases. Furthermore, we used full potential linear augmented plane wave (FP-LAPW) method for calculating electronic structure and optical properties with TB-mBJ potential which provides an enhanced band gap for all materials compared to standard GGA functional. Electronic structure calculation reveals that all the compounds are indirect band gap insulators with the exception of Li 5-At. The computed partial density of states show mixed ionic-covalent nature in metal-N/C bonds and covalent nature in NC bonds. In addition, we are also presenting the optical properties such as real and imaginary dielectric constant, absorption, refraction, reflection, loss spectrum as functions of photon energy. From the optical properties we can conclude that all the studied compounds are optically anisotropic in nature and are good absorbers in the ultraviolet (UV) region.

Excitonic effects in the optoelectronic properties of graphene-like BC monolayer

Abstract The excitonic effects and optical properties in the graphene-like hexagonal boron carbide (BC) monolayer investigated by ab-initio many-body calculations using GW approximation plus Bethe-Salpeter equation (BSE) approach. BSE calculations have been carried out on the base of G0W0 to integrate excitonic effects. We obtained that the planar BC has direct band gap with metallic character of 3.18 eV. The investigated optical absorption spectrum is dominated by discrete excitonic peaks due to the excitonic states having a noticeably low binding energy of 0.16 eV. The formation of such bound excitons is attributed to enhance electron-hole interaction in low-dimensional materials. By examining the oscillator strength of excitons with imaginary dielectric constant, we confirmed the high accuracy of the calculation. The graphene-like planar BC monolayer exhibit significantly strong and broad optical absorption in the ultraviolet region, which make it a promising candidate for nanoelectronics and optoelectronic applications.

Synthesis, structural, optical and dispersion parameters of La-doped spinel zinc ferrites ZnFe2-xLaxO4 (x = 0.00, 0.001, 0.005, 0.01 and 0.015)

We investigate the structural and optical properties of ZnFe2-xLaxO4 spinel ferrite (0 ≤ x ≤ 0.015) prepared using sol-gel route. The lattice parameter increases and the crystallite size decreases by La3+ replacements as was demonstrated by X-ray diffraction. UV–visible spectroscopy was used to study the optical properties. The optical band gap increases from 1.8714 to 1.9557 eV, with the increase in La3+ concentration up to x = 0.015. On the contrary, Urbach energy (band tail width), EU was found to be decreased from 0.6027 to 0.4247 eV. In addition, different optical parameters were extracted and associated with the change of La amount such as the absorption coefficient, refractive index, the extinction coefficient, real and imaginary dielectric constant, conductivity optical and electrical conductivity. Finally, the dependency of the refractive index to the wavelength was fitted to Wemple-DiDomenico single oscillator model and the parameters like dispersion energy, single oscillator energy, oscillator length strength, and average oscillator wavelength were also determined.

OPTICAL AND A.C. ELECTRICAL PROPERTIES OF PMMA/CB, PMMA/G AND PMMA/(CB+G) COMPOSITES

Neat PMMA and the PMMA/Carbon Black (CB), and Graphene (G) composites with different loading (PMMA/0.05%(CB), PMMA/0.10%(CB), PMMA/0.15%(CB), PMMA/0.02% (G), PMMA/0.02% (G), PMMA/0.04% (G), PMMA/0.06% (G), PMMA/(0.1%(CB)+0.02%(G) and PMMA/(0.15%(CB)+0.02%(G)) were prepared by dissolving them in the suitable solution and then casted thickness of ~0.3mm.The optical measurements declared that all the prepared samples have an energy gap for the direct allowed transition.The optical energy gap decreases as Carbon black(CB) and Graphene(G) added the PMMA from 5.0 eV to 1.1eV and to 1.0 eV as (CB) and(G) added in the ratio 0.15 and 0.04 % respectively. The transmittance spectra are measured and the optical constants were determined. The measurements showed that the optical constants reveal nonsystematic growing with loading ratio whereas they increase, decrease and return to increase after there. The electrical measurement showed that the A.C conductivity obeys the empirical formula σa.c(ω)=Aωs , where(s) lies between (0.78- 0.0013), σa.c(ω) declared frequency-dependent of the neat PMMA and PMMA doped with 0.06 G while it was frequency independent for all composites samples in hole frequency range. The Real and Imaginary Dielectric Constants showed progressive growth with the rise of the loading ratio.

Electrical and dielectric properties of Ni doped Zn2SnO4 nanoparticles

It is well known that, doping of semiconductor anticipate a huge impact on the AC-DC electric conductivity and its dielectric properties. In our current study, Ni-doped Zn2SnO4 NPs were successfully synthesized via hydrothermal method and then sintered at 500 °C. The XRD pattern exhibits a shift to higher angles which indicating the incorporation of Ni into the ZTO lattice. Moreover, we provide a more general study of electric and dielectric behaviours of Ni-doped Zn2SnO4 as a function of temperature and frequency. The impedance data were fitted using an equivalent circuit which mainly composed of resistors and constant phase elements (CPE). Complex impedance study highlighted the presence of a non-Debye type relaxation. At higher temperature, impedance measurements showed an improvement in the conductivity of ZTO -NPs. While the ZTO-NPs were less resistive before doping, they become more resistant with increasing Ni concentration and frequency. Also, we noted that for low frequencies, Ni doping reduces largely the values of both the imaginary dielectric constant (ε”) and dielectric loss, suggesting that Ni-doped ZTO is an adequate material for low frequency device applications. Further, the imaginary part M″ of the complex electric modulus exhibited a shift toward high frequency upon the increase of temperature in the relaxor peak. Taken together the results obtained, indicating that the modified ZTO, could be a promising candidate for high-frequency device application.

Structural and wavelength dependent optical study of thermally evaporated Cu2Se thin films

Abstract The present work encloses structural and optical characterization of copper (I) selenide (Cu2Se) thin films. The films having thickness 85 nm have been deposited using thermal evaporation technique in initial step of work. The structural and morphological studies of deposited thin films are then done by X-ray diffraction (XRD), scanning electron microscope (SEM), and surface profilometer measurements. Later on, ultraviolet-visible-near-infrared (UV-VIS-NIR) spectrophotometer and Raman spectroscopic measurements are performed for optical characterization of films. The structure and morphology measurements reveal that deposited material of films is crystalline. The optical band gap estimated from the optical transmission spectra of the film has been found 1.90 eV. The mean values of refractive index, extinction coefficient, real and imaginary dielectric constant are received 3.035, 0.594, 9.623, and 3.598, respectively. The obtained results are compared and analyzed for justification and application of Cu2Se thin films.

The synthesis and dielectric properties of a new phenylbenzoate-based calamitic liquid crystal

The dielectric investigation has a great importance in liquid crystal studies as a supportive method to DSC for a complete characterization of liquid crystals as well as in the electronic applications. In this study, the synthesis, mesomorphic characterization and dielectric properties of a new phenylbenzoate-based three-ring calamitic liquid crystal which composed of ester linking groups, (S)-3,7-dimethyloctyloxy chiral unit at one of terminals and n-octyloxy chain at the other end of the molecule, have been reported. The new calamitic liquid crystal 4-[4-((S)-3,7-dimethyloctyloxy)phenoxy)carbonyl]phenyl 4-(n-octyloxy)benzoate (DPCPB) has been characterized using 1H, 13C-NMR and MS-QTOF. The liquid crystalline behavior of the target compound has been investigated by differential scanning calorimetry and optical polarizing microscopy. DPCPB exhibits an enantiotropic non-tilted smectic mesophase in a wide temperature range. The real and imaginary dielectric constant, conductivity mechanism, impedance and dielectric relaxation mechanism of DPCPB have been investigated depending on frequency at different temperatures.