Surface Energy Loss Functions Research Articles

The manufacture, optical properties, and mechanical aspects of europium-doped borate glasses

An investigation into the optical and mechanical properties of a novel borate glasses with the chemical composition of 70 B2O3-10 Li2O-10ZnO-5Bi2O3-5CaO-xEu2O3 was conducted. The glassy specimens of Eu3+-doped borate were prepared by the melting-quenching technique. An enhanced density from 3.0860 to 3.2176 g cm−3 and reduced molar volume from 29.27819 to 29.17447 (cm3 mol−1) are the outcome of increasing the concentration of Eu3+ in glasses. Plotting the extinction coefficient, dielectric constant (ε1, ε2), and refractive index (n) against wavelength reveals that they all rise as level of Eu3+ elements in the glass lattice increases. An increase in Eu3+ concentration results in a decrease in both the volume (VELF) and surface (SELF) energy loss functions. Also, all elastic-mechanical moduli (such as Young’s, Bulk, Shear, and Elongation) increase with increasing the quantity of Eu3+ ions in the glass lattice. The Young’s modulus (Y, GPa) of the glassy specimens was 34.512, 36.089, 36.504, 36.730 and 37.114 GPa for x equal 0, 0.25, 0.5, 0.75 and 1 mol ratio in the glass system, and coded by Eu-0.0, Eu-0.25, Eu-0.5, Eu-0.75 and Eu-1.0, respectively. Growing Eu2O3 levels resulted in an increase in Micro-Hardness from 2.050 to 2.146 GPa. Poisson’s ratio values for Eu-0.0, Eu-0.250, Eu-0.5, Eu-0.75 and Eu-1.0 were 0.273, 0.275, 0.277, 0.277 and 0.278, respectively.

Direct Calculations of the Dielectric and Optical Parameters of Some Compound Semiconductors: A Study Using the Lorentz Oscillator and Wemple-DiDomenico Models

The Lorentz single oscillator model is widely utilized to describe the electron-phonon interaction in solids. The use of this model to calculate the dielectric function and optical parameters of compound semiconductors represents a novel approach in materials science which may lead to develop new materials with tailored optical properties and consequently can offer vast applications in areas such as quantum computing and quantum information processing. This work presents direct calculations of the complex dielectric function and some optical parameters, such as refractive index, extinction coefficient, and reflectivity for some selected III-V and II-VI compound semiconductors using Lorentz oscillator model. The dielectric and optical dispersion parameters among the infrared and visible electromagnetic spectra follows the so-called Transmission-Absorption-Reflection-Transmission (TART) trend. The TART curve provides information about how a material interacts with light at different wavelengths, which is crucial for understanding and optimizing various optoelectronic devices. Moreover, dielectric loss functions such as loss tangent, surface energy loss function and volume energy loss function are investigated. The refractive index dispersion is analyzed using Wemple–DiDomenico single effective oscillator model and Sellmeier equation. The energy of the effective single oscillator (Eo) and the dispersion energy (Ed) are estimated.

Investigations on structural and opto-electrical characterization of Ag-TCNQ (metal-organic frameworks) as complex thin films for potential device applications

The silver- (7, 7, 8, 8-tetracyanoquinodimethane (Ag-TCNQ) organometallic complex was synthesized chemically as a nano-powder and thereafter deposited as a thin film by thermal evaporation. The monoclinic, needle-like, polycrystalline structure of the Ag-TCNQ complex was analyzed employing x-ray diffraction (XRD) and a scanning electron microscope (SEM). Whereas their chemical structure and stability were explored using Fourier transformation infrared (FTIR) techniques. The findings imply a charge transfer of degree −0.5 between TCNQ° and TCNQ−, as revealed by the shift of the bands of the C≡N stretching and the (C═C-H) bond positioned at 2198 and 824 cm−1, respectively. As well as the optical properties of Ag-TCNQ thin film were studied using spectrophotometric measuring in the wavelength ranging 200 to 2500 nm. The measurement of transmittance and reflectance spectra were employed to calculate the refractive index (n), dielectric constant, absorption index (k), surface and volume energy loss functions, and optical conductivity. In the normal dispersion zone, optical characteristics such free charge carrier concentration, infinity dielectric constant (ε ∞), lattice dielectric constant (ε L), oscillator energy (Eo), and dispersion energy (Ed) were estimated. Furthermore, the optoelectronic nonlinear optical features and electronic transitions for the Ag-TCNQ thin film were assessed. Finally, these findings are promising milestones on the path to providing convincing evidence for the synthesis of stoichiometric thermally stable Ag-TCNQ thin film by conventional thermal evaporation technique that is potential to be utilized in optoelectronic devices applications.

Synthesis, microstructural and optical characterizations of sol-gel grown gadolinium doped cerium oxide ceramics.

In this study, through the utilization of the sol-gel combustion tactic, gadolinium (Gd)-doped cerium oxide (CeO2), Ce1-xGdxO2 (x = 0.00, 0.10, 0.20 and 0.30 (GDC)) ceramics were attained. The synthesized GDC ceramics were investigated using X-ray diffraction (XRD) to scrutinize their crystal structures and phase clarities. The obtained GDC ceramics have a single-phase cubic structure and belong to the crystallographic space group fm3̄m (225). The measurement of the diffraction angle of each reflection and the subsequent smearing of the renowned Bragg's relation provided coarse d-interplanar spacings. The stacking fault (SF) values of pure and Gd-doped CeO2 ceramics were assessed. To muse the degree of preferred orientation (σ) of crystallites along a crystal plane (h k l), the texture coefficient (Ci) of each XRD peak of GDC ceramics is gauged. By determining the interplanar distance (dh k l), the Bravais theory sheds light on the material's development. By exploiting Miller indices for the prime (1 1 1) plane, the lattice constants of GDC ceramics and cell volumes were obtained. Multiple techniques were employed to ascertain the microstructural parameters of GDC ceramics. A pyrometer substantiated the density of GDC ceramics. The room temperature (RT) Fourier transform infrared (FTIR) spectra of both un-doped and Gd-doped CeO2 were obtained. The UV-vis-NIR spectrometer recorded the GDC ceramics' reflectance (R) spectra at RT. For both undoped and Gd-doped CeO2, the absorption coefficient (α) spectra showed two distinct peaks. The R-dependent refractive index (η) and the α-dependent extinction coefficient (k) were determined for all GDC samples. The optical band gap (Eg) was obtained by integrating the Tauc and Kubelka-Munk approaches for GDC ceramics. For each GDC sample, the imaginary (εi) and real (εr) dielectric constants, as well as the dissipation factor (tan δ), were determined local to the characteristic wavelength (λc). Calculations were made for the Urbach energy (EU) and Urbach absorption coefficient (α0) for GDC ceramics. The minimum and maximum values of optical (σo) and electrical (σe) conductivity for GDC ceramics were determined. The volume (VELF) and surface (SELF) energy loss functions, which depend on the constants εi and εr, were used to measure electrons' energy loss rates as they travel across the surface. Raman spectroscopy revealed various vibrational modes in GDC ceramics. Finally, the implications are discussed herein.

Gamma-irradiated fluorophosphate glasses doped with various transition metals: A spectroscopic study

The 20NaF–60P2O5–20Na2O fluorophosphate glass systems doped with 3 wt% of CoO and NiO were manufactured using traditional melting techniques. Optical parameters were investigated for the studied composites before and after irradiation by 20 kGy of gamma rays. For the studied composites, the presence of defects within the glass network can explain the decrease of the Urbach energy (Eu) due to gamma irradiation or the increase in it due to the addition of the transition metals (nickel oxide and cobalt oxide) to the base composite. After gamma irradiation, a red shift was seen in the spectrum of the dissipation factor (tan δ). According to the calculated values of volume energy loss function (VELF), and surface energy loss function (SELF), the energy lost at the surface of the composites under investigation is larger than the energy lost within the composites' constituent materials. All investigated composites demonstrated an insulating property by obtaining the values of the covalency parameter (M) less than unity. All of the nonlinear optical parameters were increased after irradiation of the studied composites, whereas the highest values were recorded for the irradiated composite doped by CoO. Following the intrinsic and extrinsic defects produced by the former oxide itself and by added modified oxide dopants inside the glassy network was important to explain changes inside the network by ESR spectra for prepared fluorophosphate composites. Moreover; defects induced inside the glass network by 20 kGy of γ-ray have been followed to continue the ongoing study of the nature of the prepared glassy network.

Synthesis and Characterization of PANI/ZnFe2O4 nRs with Different Doping Concentrations for Potential Applications in Various Fields

The wide-ranging potential of polyaniline (PANI) composites in energy storage, electrochemical, sensing, and electromagnetic shielding applications emphasizes researchers to improve its properties. Here, the doping of ZnFe2O4 nRs by 1, 3, and 5 wt. % within polyaniline has been done. Then, we characterize the doped material using techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) to verify the successful incorporation of polyaniline onto the nRs. TGA showed that doping of PANI with ZnFe2O4 nRs enhanced the interfacial interactions between the two components. This provided a more stable matrix structure and enhanced the thermal stability of the composite. The transmission of light has been increased by about 18% due to the increase in crystallinity accompanied by ZnFe2O4 doping. As the ZnFe2O4 nRs doping rose, our PANI samples’ optical band gap values slightly decreased by about 10%. In addition, it has been found that the optical characteristics such as refractive index, extension coefficient, surface, and volume energy loss function essentially showed ZnFe2O4 doping dependency. The nonlinear constants of the doped samples have increased due to the new charge carriers and altered the electronic and optical properties of the composite material. Our obtained results show that PANI@ ZnFe2O4 nRs have potential applications such as optical sensors, electrochemical, optoelectronics, and photocatalysis.

Influence of tungsten oxide concentration on structural, morphological, compositional, linear and non-linear optical properties, and vibrational properties on NiO:WO3 thin films

Mixed nickel-tungsten oxide, NiO:WO3 (90:10, 85:15) thin films with different tungsten oxide (WO3) concentrations of 10 and 15% were deposited using the radio frequency (RF) sputtering technique. An X-ray diffraction analysis reported the amorphous nature of the films. A SEM study showed smooth morphology. EDAX confirms the compositional purity, in which the nickel content decreases, while the tungsten and oxygen content increase with an increased WO3 concentration. The average transmittance of the NiO:WO3 (90:10, 85:15) films decreases from 79 to 75% as a consequence of increased thickness. The Urbach energy (Eu) enhances because of increased defects (localized states) inside the films induced by tungsten oxide addition. The energy bandgap decreases from 2.66 to 2.48 eV due to the formation of new localized energy states inside the band gap (Eg). The refractive index (n) acquired from different proposed models for the entire UV–Vis–NIR region has increased with increasing WO3 concentration, implying the escalation in densification (or packing density) of prepared films. The optical parameters like n, k, ε1, ε2, electronic polarizability (αp), optical conductivity (σop), electric conductivity (σe), volume and the surface energy loss function (VELF AND SELF) vary with WO3 concentration. The dispersion energy parameters (Eo, Ed), resulting from the Wemple and Didomenico (WD) model, decreases. The optical non-linear susceptibility, χ(3), decreased with increasing WO3 concentration. The photoluminescence (PL) emissions were perceived at 368 nm and 423 nm, assignable to 3 d8 Ni2+ ions transitions. Micro-Raman detected peaks at 570 cm−1 and 1100 cm−1 ascribing Ni–O bond vibrations, whereas the peak spotted at 870 cm−1 is ascribed to a W–O bond vibration. The deposited films are good enough for electrochromic and optoelectronic device fabrications.

“Extraction and studies of optoelectrical parameters in LaFeO3-polyvinyl alcohol composite films for optoelectronic application”

Ceramic LaFeO3 (LFO) nanoparticles were synthesized using the solid state reaction method. To grow and study the various optoelectrical parameters of polyvinyl alcohol (PVA) and LFO-PVA nanocomposite films (wt%), the solution casting technique were used. To study optical properties, these films were subjected to Ultraviolet–Visible spectroscopy. From the UV–visible spectra, the high reflectance and low transmittance nature of the sample was observed. The refractive index and extinction coefficient of these films were obtained from reflectance and transmittance data. The optical results reveal that increasing LFO doping concentration decreases the energy band gap (Eg) values from 5.20 to 2.74 eV, while Urbach energy (Eu) increases from 0.423 eV to 4.871 eV. With doping, the value of single oscillator energy (Eo) decreases from 6.212 eV to 3.658 eV, while dispersion energy (Ed) increases from 8.481 eV to 158.92 eV. With LFO doping concentration, optical constants and parameters such as refractive index, extinction coefficient, dielectric constants and electron energy loss function were determined from transmittance and reflectance data. The refractive index (n) and extinction coefficient (k) are calculated to be in the ranges from 1.4 to 12 and 5.85 × 10−5 ‒ 26 × 10−3, respectively. The real (ε1) and imaginary (ε2) dielectric constants vary from 2 to 138.8 and 3.01 × 10−4 ‒ 3.25 × 10−2, respectively. The volume and surface energy loss functions were determined to be 1.96 × 10−4 ‒ 1.03 × 10−6 and 1.34 × 10−4 ‒ 3.14 × 10−7, respectively. The optical density and skin depth (δ) shows variation with filler concentration (wt%). The maximum optical conductivity σ1(ω) and σ2(ω) for 48% (wt%) sample were found to be 1.5 × 105 and 1.08 × 109 S−1 at 220 nm. The wavelength dependent real and imaginary parts of the optical dielectric functions and the WDD model were used to calculate the fundamental parameters, including Nopt/m*, ε∞, τ, μopt, ωp, ωd, ρopt, and n0. The value of Nopt/m* was increased from 8.61 × 1052 m3Kg−1 to 5.60 × 1054 m3Kg−1. The reflection loss (RL) and average molar refraction (Rm) were found to increase with doping concentration. For these samples, the optical non linear susceptibility (χ(3)) was determined to be in the range from 3.77 × 10−15 to 2.94 × 10−7. The value of electronic polarizability αp decreases from 2.57 × 10−23 to 7.33 × 10−24 for PVA, while for the composite films the value of αp increases from 7.81 × 10−25 to 3.59 × 10−24 in the wavelength range 200–1000 nm. Also, these calculated parameters shows a decreasing trend with LFO doping contents. It was further observed that the investigated parameters exhibit a strong dependence on the LFO doping content. Based on these optoelectronic properties of this material, it could be used for possible optoelectronic applications.

Electrospinning and Optical Properties of Polyacrylonitrile/Titanium Dioxide Nanocomposite Fibers

In situ polymerization was used in this work to prepare polyacrylonitrile (PAN) and titanium dioxide (TiO2) nanocomposite at various ratios (5, 10, 15, and 20 weight percent of TiO2). PAN/TiO2 nanofibers were created using the electrospinning process from a homogenized solution. X-ray diffraction data demonstrated that a structural change to an amorphous state had taken place. Using scanning electron microscopy (SEM), the morphology of the high-aligned fibers with PAN diameters of roughly 33 nm and 51 nm of PAN/(10wt%)TiO2 was examined. A spectrophotometer was used to examine the optical characteristics of the nanofiber films at wavelengths between 200 and 900 nm. The energy gap (Eg) of the nanofiber films was computed, and it decreased as the weight ratio of the TiO2 nanoparticle increased. With 5, 10, and 15% weight percentage of TiO2, respectively, the energy gap (Eg) of PAN nanofibers changes from 3.92 eV to 3.72, 3.39, 3.19 eV. Several other parameters have also been calculated, including the excitation coefficient (k), refractive index (n), Urbach tail (Et), dielectric constant (e1), dielectric loss (e2), and volume and surface energy loss functions (VELF) and (SELF).

Investigation on Bi-induced changes on linear and non-linear optical parameters of As45-Se (55-x)-Bix chalcogenide glasses for photonic application

The Bi-incorporated As45-Se(55-x)-Bix (x = 0, 2, 4, 6 at.%) chalcogenide glasses have been synthesized by deploying the conventional melt quenching method. The non-appearance of the peak in the X-ray diffraction pattern confirms the amorphous characteristics of these materials. The alteration in non-linear and linear optical properties has been investigated from UV–Vis spectroscopy data and associated empirical formulae. Tauc's plot show that the values of optical band gap energies decrease from 1.82 eV to 1.59 eV, while the assessed Urbach energies increase from 0.048 eV to 0.056 eV with Bi addition. The reflection and transmission data have been analyzed within the range of 300–800 nm. Various important optical parameters like refractive index, absorption coefficient, extinction coefficient, surface and volume energy loss functions, optical density, skin depth, third-order nonlinearity, thermal emissivity, etc., have been investigated. The Wimple Didomenico model has been used to analyze several dispersion parameters. The Chemical bond approach model has been used to estimate the cohesive energy, which is found to decrease from 2.761 eV to 2.747 eV. The increase in non-linear refractive index and third-order non-linear optical susceptibility indicates the possibility of these materials being used in optical switching devices as well as photonic devices.

Electronic Properties, Linear and Nonlinear Performance of KAgCh (Ch = S, Se) Compounds: A First-Principles Study

In the current study, the peculiar nonlinear optical (NLO) properties of KAgCh (Ch = S, Se) and their structural, electronic, and thermodynamic properties are computed utilizing the FP-LAPW (full-potential linearized augmented plane wave) approach as embedded in Wein2K code. The Perdew–Burke–Ernzerh of generalized gradient approximation (PBE-GGA) was considered for the structural optimization. The computed bandgaps are found to be 2.57 and 2.39 eV for KAgS and KAgSe, respectively. Besides the structural and electronic properties, we also computed the refractive indices n(ω), surface energy loss function (SELF), and nonlinear optical susceptibilities. The estimated refractive indices, energy band gap, and their frequency dependence for the investigated KAgCh (Ch = S, Se) compounds, along with the NLO coefficients, are found to be in good agreement with the earlier reports. These current findings suggest that KAgCh (Ch = S, Se) can be recommended for nonlinear optical applications in the near-infrared spectrum.

Optical and dielectric properties of PVC/TiO2/TBAI ionic liquid polymer electrolyte

Polyvinyl chloride (PVC)/TiO2/x wt % tetrabutylammonium iodide (TBAI) polymers were formed using sol gel and casting methods. Rietveld refinement was used to investigate the structure and microstructure of TiO2. X-ray diffraction, Fourier transform infrared and energy dispersive X-ray analysis techniques were used to explore the present of TiO2 and TBAI over PVC matrix. SEM analysis was carried out to study the impact of loading the TiO2 nanofiller and TBAI on the surface morphology of host polymer. The possibility of using PVC/TiO2/TBAI in UV shielding is explored. The direct and indirect optical bandgap energies for PVC were reduced from (5.49, 5.15) to (5.47, 5) eV, respectively, as it was loaded with nano TiO2. Upon loading the PVC/TiO2 with different amounts of TBAI, the direct and indirect optical band gaps reduced further to (5.33, 4.61) eV and another two bands appeared (3.74–3.8, 2.96–3) eV for direct transition and (2.99–3.19, 2.19–3.36) eV for indirect transition. The values of dielectric constant, optical conductivity and nonlinear optical parameters became highest as the amount of TBAI became 25 wt % while the values of the surface and volume energy loss functions became highest as the content of TBAI became 5 wt %. The fluorescence intensity of the pristine PVC was greatly enhanced when it was loaded with TiO2. Further enhancement in luminescence intensity was obtained upon doping PVC/TiO2 with different weight percents (5, 10, 15, 20, and 25 wt%) from TBAI.

Linear and Nonlinear Optical Properties of PVA:SA Blend Reinforced by TiO2 Nanoparticles Prepared by Flower Extract of Aloe Vera for Optoelectronic Applications

In this study, a polyvinyl alcohol–sodium alginate blend, PVA:SA 3:1 (w:w), was doped with different contents of TiO2 nanoparticles (NPs) prepared by aloe vera leaf extract to form the investigated nanocomposites. The nonlinear parameters of third-order susceptibility (χ(3)) and refractive index (n2) were detected by using UV-Vis spectroscopy and Z-scan techniques. Some different optical parameters were also determined, including the refractive index (n), optical dielectric parameters, volume and surface energy loss functions, and some others. The best solar skin protection factor (SSPF) was investigated by 5 wt.% of TiO2 NPs doped in PVA:SA 3:1, which was about 84.6% compared to the corresponding value of the host blend (41%). The studied nanocomposites were examined for their utility in the optical limiting of CUT-OFF laser filters utilizing a continuous He-Ne laser working at 632.2 nm. As a result, our finding demonstrated that TiO2 NPs doped in the host blend of PVA:SA positively influences a laser light blocking for the investigated laser source. Using the estimated gap energies values, different models were used to deduce theoretical values of the linear refractive index (n). The presence of Ti peaks in the EDX spectrum confirmed the doping of TiO2 NPs in the nanocomposites. SEM showed that the TiO2 NPs are homogeneously dispersed through the host blend with some agglomerates. XRD spectra showed that the values of the lattice strain εstr. detected at 2ϴ = 19.78° are 0.058, 0.055, and 0.060, corresponding to 1, 3, and 5 wt.% of TiO2 NPs doped in the PVA:SA blend.

Divulging the Potential of Sodium Carbide Thin Film for Semiconductor Applications

The work reported in this article is an attempt to introduce the least explored sodium carbide as a thin film and to explore its semiconducting behavior. The sodium carbide thin film deposited by the radio frequency sputtering technique is subjected to morphology, structure, and spectroscopic characterizations. The floral petal‐like morphology, understood from the field‐emission scanning electron microscopy and atomic force microscopy images, helps in enhancing interaction with the radiation that is revealed through the UV–visible absorption spectrum. X‐ray diffraction, photoelectron and Raman spectroscopic analyses confirm that the film is sodium carbide. The optical emission behavior of the sodium carbide thin film in the blue region is unveiled through the photoluminescence spectrum, power spectrum, color purity, and chromaticity diagram. Employing the refractive index and extinction coefficient values from the specular reflectance data, optical and electrical conductivities, nonlinear refractive index, linear and nonlinear optical susceptibility, dissipation factor, and surface and volume energy loss functions and their wavelength dependence due to interfacial polarization are investigated. The transfer matrix method is used to understand the spatial variation of the induced electric field and optical current density.

Extraction of Optical Constants and Dispersion Parameters of CdTe/CdSe Bi-Layer Thin Films

The current study focuses on the annealing-induced changes in the optical constants and dispersion parameters of the CdTe/CdSe bi-layer films deposited onto glass substrates by thermal evaporation technique. The slight shift in transmission threshold towards higher wavelength region with increasing annealing temperature revealed the systematic reduction in optical energy band gap (1.92 to 1.37 eV) of the films. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal dispersion in the transparent region. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion parameters and dielectric constants were evaluated. The increase in the refractive index with the annealing temperature modified the other linear parameters such as optical density, dissipation factor, volume, and surface energy loss function. The increase in the optical conductivity value is good for the CdSe film to be used as a semitransparent solar cells absorbing layer.We have made an attempt to discuss and correlate these results with the annealing temperature of possible mechanisms underlying the phenomena.

Chemical Bath Deposition Grown Zno Thin Films: Role of Manganese Doping

In this study, the effect of Mn doping concentration on the structural, microstructural, linear and nonlinear optical properties of ZnO was investigated. Pristine and Mn-doped ZnO films were prepared by chemical bath deposition on a glass substrate. The crystal structure and surface morphology of the films were determined by X-ray diffraction and force electron scanning microscopy (FESEM). X-Ray Diffraction (XRD) analysis revealed that the films had a polycrystalline structure and all films were ZnO with a hexagonal structure. In addition, a shift was detected in the XRD pattern of the films with the Mn doping process. According to the FESEM results, the surface of the films has irregularly shaped particles. Linear and nonlinear optical parameters were estimated using transmittance and absorbance measurements. And then, optical absorption coefficient, extinction coefficient, refractive index, optical dielectric constants, surface, and volume energy loss functions, optical band gap values, and optical and electrical conductivity were determined as linear optical properties. It was determined that these properties were affected by Mn-doped ratios. It was determined that nonlinear optical properties such as linear optical properties were also affected by the doping process.

Influence of γ-irradiation dose on the structure, linear and nonlinear optical properties of BiI3 thick films for optoelectronics

In this study, 900 nm of BiI3 thick films were prepared using the thermal evaporation technique. There were exposed to different doses (0, 50, 100, 150, 200, 250, and 300 kG) of γ-radiation. The microstructure properties (Crystallite size and lattice strain) were calculated in terms of Scherrer’s equation. With increasing γ-radiation doses, the Crystallite size increases, Both the refractive index and the film thicknesses have been calculated using Swanepoel's method. The optical band gap was measured in terms of transmittance and reflection spectrum in the high region of the absorption. The possible optical transition in the as-deposited and treated films are found to allow direct transition with energy gap increases with increasing γ-radiation doses. Dielectric constant, volumeenergy-loss function (VELF), and surface-energy-loss function (SELF) for as-deposited films were discussed in terms of γ-radiation doses. The change in optical parameters has been interpreted in terms of the change in microstructure parameters. In terms of changes in energy gap and optical constants as a function of γ-radiation doses, BiI3 thick films are recommended to use in optical devices and solar cells.

Investigation of Optical Properties and Electronic Transfer of Temperature-Dependent ZnO Nanocolumnars Grown by DC Sputtering

The morphology of zinc oxide (ZnO) can determine the distribution of defects in the system, which plays an important role in determining its optical and electronic properties. Here, we investigate the optical and electronic transfer properties of different ZnO surface morphologies. ZnO nanocolumnar was synthesized by direct-current (DC) sputtering followed by annealing using a ratio of T / Tm are 0.15, 0.20, and 0.25. The x-ray diffraction (XRD) results show that an increase in annealing temperature causes an increase in crystal size accompanied by a decrease in lattice strain. Furthermore, the surface morphology of the sample changed with increasing annealing temperature treatment, following the structural zone model. The optical and electronic transfer properties of the samples were investigated in three regions; region 1 ( T / Tm is 0.15), region 2 ( T / Tm is 0.20), and region 3 ( T / Tm is 0.25) using optical modeling. The highest surface electronic transfer was noted in region 2, which is indicated by the highest surface energy loss function (SELF). This research can provide a good understanding in designing optoelectronic systems based on their morphological features. DOI: 10.17977/um024v7i22022p086

The more accurate determination of surface excitation parameters, the more accurate quantitative surface analysis

The accurate quantitative surface analysis for the study of nanostructures practically used for e.g. photocatalysis, electrocatalysis, energy storage and sensing applications is of high importance. Moreover, the accurate quantitative electron spectroscopy and analytical microscopy of semiconducting nanomaterials such as nano-photocatalysts relies on the accurate determination of surface excitation parameters (SEP). Reflection electron energy loss spectroscopy (REELS) as a surface sensitive technique could be applied for the determination of SEP. The chemical, mechanical, thermal stability, optical and dielectric properties of Ni6MnO8 as binary metal oxide makes such structure suitable for practical applications. Therefore, here Ni6MnO8 due to its great importance in its special applications was typically studied by REELS using the Yubero-Tougaard algorithm, which is based on dielectric response theory. After an extrapolation process applied to the obtained REELS spectrum, the energy gap (Eg) of this material was obtained to be 3 eV. The surface and bulk energy loss functions of the material were also determined. The values of inelastic mean free path (IMFP) of the electrons of different energies in the range of 500–4000 electron volts travelled in Ni6MnO8 were determined. In addition, from the obtained energy loss function (ELF), by using the Kramers-Kronig transformations of the real and imaginary parts of dielectric function (ε), the important optical parameters of Ni6MnO8 such as refractive index (n), attenuation coefficient (k) and absorption coefficient (μ) were determined. Finally, as a critical parameter in quantitative electron spectroscopy, the SEP and its angular distribution were determined. It was found that the Pauli-Tougaard model requires a modification to make it better descriptive to well fit the SEP data for a given material. Therefore, a more accurate model was obtained to make a better surface analysis and analytical microscopy.

Investigating the impact of growth time of CdSe quantum dots on the structure and optical properties of its nanocomposites with SiO2 for improvement of optical devices

This study effectively succeeded in synthesizing CdSe QDs and CdSe- SiO2 nanocomposites with controllable tunable size and spectacular morphology by using a solvothermal technique. UV–visible spectroscopy was used to study the effect of the growth time of CdSe QDs on the optical properties of its nanocomposite with SiO2. The structure of the prepared nanocomposites of CdSe- SiO2 was studied through the measurements of X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy FTIR. The Effective Mass Approximation model (EMA), Simple Exponential Function (SEF), and Polynomial Fitting Functions (PFF) were employed to compute nanoparticle sizes, providing particle sizes of 3.86, 4.19, and 3.72 nm, respectively, for CdSe- SiO2 nanocomposites (2 min). For the same nanocomposite, these theoretical values were comparable to the experimental values of the particle sizes deduced from measurements of TEM (4.5 nm) and XRD (3.4 nm). The deduced optical parameters of CdSe-SiO2 nanocomposite, such as refractive index, dielectric constant, optical conductivity, electrical susceptibility, and some others, relied on the growth time of CdSe QDs. The absorption peaks of CdSe -SiO2 nanocomposites suffered from a bathochromic shift which increases as the growth time of CdSe QDs increases. Increasing the growth time of CdSe QDs resulted in increasing the reflection loss factor and decreasing the optical electronegativity. The values of the volume energy loss function (VELF) are greater than the values of the surface energy loss function (SELF) for the different nanocomposites. Consequently, the fast electrons miss their energies through their propagation within the studied materials more than through traveling on their surfaces. The enhancement of n values of nanocomposites of CdSe-SiO2 by increasing the growth time can candidate them to be usefully applied as antireflection coating for solar cells.