Static Refractive Index Research Articles

Correlation between the static refractive index and the optical bandgap: Review and new empirical approach

The static refractive index no of different types of materials, like semiconductors, insulators, oxides, thin-films, and glasses, has been reported in many publications in attempts to estimate how it can be correlated to the optical bandgap. Reviewing of the previous studies to correlate the optical refractive index and energy gap led to concluded that Reddy Ahmmed approximation was selected to develop a new realized form that can give a good fit to the experimental data and, hence, be used directly as an accurate formula in the theoretical studies. The obtained formula correlates the optical/static refractive index to the energy bandgap and the oxygen atom's electronegativity. Such a new relation has been used to calculate the refractive indices for more than 96 materials (elements/compounds) with a high agreement with the experimental data.

Electronic density of states and optical spectra of zigzag SiC nanoribbons from first principles

The electronic and optical behavior of zigzag silicon carbide nanoribbons (ZSiCNRs) have been simulated exploiting density functional theory (DFT) formalism. Our results show that zigzag silicon nanoribbons (w = 14 to 20) have metallic behavior. The optical graphs confirm that ε1x(ω), ε1y(ω), nx(ω), and ny(ω) are less than that of the z polarization at energies below 2.5 eV. The static refractive index of ZSiCNRs is almost close to that of the other nanoribbons, except for the GNRs, which have a considerably larger static refractive index. Last but not least, the optical susceptibility shows that ZSiCNRs with larger width have a weaker polarization field which eventuates in lower optical susceptibility for the ZSiCNRs (w = 20).

Role of Bismuth incorporation on the structural and optical properties in BixIn35‐xSe65 thin films for photonic applications

AbstractThe present paper investigated the influence of Bi concentration on the structural, linear, and non‐linear optical properties of thermally evaporated BixIn35‐xSe65 (x = 0, 5, 7, 10, 15 at %) thin films. The structural analysis by the XRD measurements showed the crystalline nature at 7 and 15% Bi while the other concentrations showed amorphous nature. The corresponding bonding change was analyzed by Raman spectroscopy. The optical study by UV‐Vis spectroscopy showed the decrease in transmittance and an increase in absorbance property. The linear optical parameters such as absorption coefficient, extinction coefficient, optical density increased while skin depth decreased with Bi additives. The direct, as well as the indirect optical bandgap, decreased along with the decrease in the Tauc parameter. The variation is well explained on the basis of density of defect states by the Mott and Davis model. The non‐linear refractive index and non‐linear susceptibility increased significantly with Bi % which is good for non‐linear optical applications. The static linear refractive index as calculated by the Dimirov and Sakha empirical relation showed an incremental behavior with Bi% concentration and satisfied Moss's rule. The surface structure and elemental concentration were analyzed by FESEM and EDX analysis. The result of the above investigation suggests that these materials can be used as an absorbing layer for several optoelectronic and photonic applications.

Effect of Doping on the Photoelectric Properties of Borophene

Borophene is a new type of two-dimensional material with a series of unique and diversified properties. However, most of the research is still in its infancy and has not been studied in depth. Especially in the field of semiconductor optoelectronics, there is no related research on the modulation of photoelectric properties of borophene. In this work, we focus on the effect of doping on the photoelectric properties of borophene by using the first-principles pseudopotential plane wave method. We calculate the geometric structure, electronic structure, Mulliken population analysis, and optical properties of impurity (X = Al, Ga) doped α-sheet borophene. The results show that α-sheet borophene is an indirect band gap semiconductor with 1.396 eV. The band gap becomes wider after Al and Ga doping, and the band gap values are 1.437 eV and 1.422 eV, respectively. Due to the orbital hybridization between a small number of Al-3p electrons and Ga-4p state electrons and a large number of B 2p state electrons near the Fermi level, the band gap of borophene changes and the peak value of the electron density of states reduces after doping. Mulliken population analysis shows that the B0-B bond is mainly covalent bond, but there is also a small amount of ionic bond. However, when the impurity X is doped, the charge transfer between X and B atoms increases significantly, and the population of the corresponding X-B bonds decreases, indicating that the covalent bond strength of the chemical bonds in the doped system is weakened, and the chemical bonds have significant directionality. The calculation of optical properties shows that the static dielectric constant of the borophene material increases, and the appearance of a new dielectric peak indicates that the doping of Al and Ga can enhance the ability of borophene to store electromagnetic energy. After doping, the peak reflectivity decreases and the static refractive index n0 increases, which also fills the gap in the absorption of red light and infrared light by borophene materials. The research results provide a basis for the development of borophene materials in the field of infrared detection devices. The above results indicate that doping can modulate the photoelectric properties of α-sheet borophene.

Halide double perovskite Cs2AgInBr6 for photovoltaic’s applications: Optical properties and stability

Theoretical calculations on halide double perovskite Cs2AgInBr6 electronic properties and optical spectra are carried out. The hybrid functional B3LYP calculations have been used indicating a 1.427 eV direct to band gap. The optical absorption coefficient has been determined showing a high-absorption (> 104 cm−1) within a large absorption range suggesting that the perovskite of interest-based solar cells may reach a good solar efficiency. Based on the refractive index spectrum, the Cs2AgInBr6 static refractive index is estimated and found to be 2.09. The stability, phonon spectrum, electron effective mass and absorption spectrum with solar spectrum at AM1.5 of Cs2AgInBr6 have been computed and verified.

Influence of Annealing Temperatures on Nonlinear Optical, Dielectric, Semiconducting Results, and Fermi Level Position for CdP0.03Te0.97 Thin Film

CdP0.03Te0.97 thin films were deposited at room temperature using thermal evaporation and annealed at 100 and 200°C. The effect of annealing temperature Tann on both dispersion energy Ed and oscillating energy Eo were studied. The lattice dielectric constant εL and free carrier concentration/effective mass N/m* were calculated for these samples. The values of the first order of moment M-1, the third order of moment M-3, and static refractive index no were determined. Both of dielectric loss ε\ and dielectric tangent loss ε\\ for these films increased with photon energy (hν) and had the highest value higher than the energy gap Eg. All of the optical parameters such as real part of optical conductivity σ1, the imaginary part of optical conductivity σ2 and the relation between Volume Energy Loss/ Surface Energy Loss (VEL/SEL) were determined. The linear optical susceptibility χ(1) increased with Tann. The influence of annealing temperatures on all of the non-linear refractive index n2, the third-order non-linear optical susceptibility χ(3), and non-linear absorption coefficient βc were studied. Both of the electrical susceptibility χe and relative permittivity εr increased with Tann and had the highest value higher than Eg. The dependence of density valence band, conduction band, and position of Fermi level Ef were studied.

Electronic and optical properties of pristine and Li/Na/K/Mg/Ca decorated net-Y: First-principles calculations

In this manuscripts, first principles based on density functional theory are used to study the optical properties of pristine and alkali/alkaline-earth metal atoms decorated net-Y. Based on the data of reflection, absorption, refraction, complex dielectric function and loss function under three different polarization, the optical properties of pristine and decorated net-Y are studied for the first time. The results show that the alkali/alkaline-earth metal decorated net-Y exhibits a significant optical response in a wide frequency range of 0 eV–27.0 eV. Under Ex and Ey polarization, alkali metals and alkaline-earth metals can notably change the reflection, refraction, absorption, and energy loss of net-Y. Under Ez polarization, except that net-Y exhibits a certain optical response in the higher ultraviolet band, there is no obvious response in other frequency ranges, and the modification of alkali/alkaline-earth metals will not have a significant impact on the optical properties of net-Y. Meanwhile, under Ex and Ey polarization, with the increase of the modified atomic number, the static dielectric constant, the maximum reflection coefficient, the static refractive index and the maximum absorption coefficient all show different degrees of oscillation behavior, not monotonic changes. Under Ez polarization, the relative optical property coefficients do not change significantly. These results imply that the optical performance of net-Y can be effectively controlled by changing the type of modified alkali/alkaline-earth metals atoms.

Effect of carbon nano tube in the structural and physical properties of polyvinyl chloride films

Polyvinyl chloride (PVC) films loaded by different concentration of Carbon Nano Tubes (CNT) are prepared through a solution casting method. CNT are characterized using transmission electron microscope (TEM) and x-ray diffractometer (XRD). The analysis of the PVC-CNT films is carried out by using XRD, scanning electron microscope (SEM), and Fourier transform infrared (FTIR) to study the change in the polymer structure. UV–vis spectrophotometer is used to determine the optical parameters depending on the optical absorption data. It is found that, the direct and indirect optical band gap decrease with an increase in CNT nanoparticle content in the PVC matrix. The refractive index, optical dielectric parameters, and optical conductivity of the polymer films are investigated using the optical absorption data. These parameters are enhanced with the increase in the CNT concentration in the PVC matrix. The Wemple-DiDomenico model is used to calculate the optical dispersion parameters (like; oscillator energy, dispersion energy, static refractive index, dipole strength, and static optical dielectric constant). In addition, nonlinear refractive index, linear optical susceptibility, and third-order nonlinear optical susceptibility are investigated.

Strain Induced Electronic and Optical Properties of 2D Silicon Carbide Monolayer Using Density Functional Theory

Using the first principle calculation, we investigated the structural, electronic, and strain-dependent optical properties of the two-dimensional hexagonal Silicon Carbide (SiC) Monolayer. We found that the biaxial compressive strain loading gradually changes the direct bandgap SiC into indirect bandgap semiconductor. The compressive strain increases the bandgap but reduces the values of static dielectric constant and refractive index. Conversely, the biaxial tensile strain loading decreases the bandgap but increases the value of static dielectric constant and refractive index. The result shows that the electronic and optical properties of SiC can be engineered to the desired value by applying strain. The large bandgap issue for the SiC monolayer is limiting its uses in different applications which can be overcome with the help of biaxial strain.

Stimulated band structure by external isotropic static pressure and its impact on optoelectronic properties of PbZrO3: An ab-initio calculation

Computational perspective to explore the influence of external pressure on phase stability, optical properties and band gap tailoring of PbZrO3 is presented. The energy band structure shows that upper limit of valence band is electronically meticulous by the O-2p and Zr-4d orbitals. The band gap demonstrates the almost undeviating downward movement (2.759 eV–1.887 eV) with the increase in external pressure. However, when pressure exceeds from 50 GPa the phase stability breaks down sharply. Moreover, optical properties have also been measured by dynamic dielectric function to understand the effects of band gap reduction on optical properties. The optical properties demonstrate that as the pressure increases, the static refractive index rises. Highest value of the absorption peak is analytically transferred to a higher energy, while the maximum value of the plasmon peak is transferred to a lower energy, which is an indication of a decrease in the band difference.

A first principle investigation of the non-synthesized cubic perovskite LiGeX3 (X=I, Br, and Cl)

A self-consistent calculation within Density Functional Theory (DFT) using norm-conserving pseudopotential plane-wave and the precise hybrid functional HSE06 were performed. The stability, elastic, originatemechanical, electronic, and optical properties of the cubic perovskites LiGeX3 (X = Br Cl, and I) are investigated. The behaviour of the stability and elastic characteristics under hydrostatic pressure is also presented and studied. Band structure analysis using PBE, GW-Approximation, and HSE06, show that LiGeX3 (X = Br Cl, and I) are direct bandgap semiconductors. The structures are most stable at the computed relaxed lattice parameters (a=b=c=5.880,5.470and5.190Ao)for the LiGeI3, LiGeBr3, and LiGeCl3, respectively. The Pressure dependence of cubic perovskite elastic moduli, bulk modulus B, shear modulus/constant (G,Cs), Young's modulus E, the Poisson's ratio σ, Vickers hardness Hv, Lame's constants (λ,μ), Cauchy pressure C12−C44, the Anisotropy factor A, Kleinman parameter ζ, and the P-wave modulus Pw, elastic wave velocities v, Debye temperature θD is presented. The optical properties including the static refractive index and dielectric constant are found to be related to the direct bandgaps, proportionally. The refractive index, extinction coefficient, complex dielectric function, energy loss function, optical conductivity, reflectivity, and absorption coefficient for 0–25eVincident photon energies are also presented.

Characteristics of Poly(vinyl Alcohol) (PVA) Based Composites Integrated with Green Synthesized Al3+-Metal Complex: Structural, Optical, and Localized Density of State Analysis.

The influence of dispersing Al-metal complex on the optical properties of PVA was investigated using UV–visible spectroscopy. Polymer composite films with various Al3+-complex amounts in the PVA matrix were arranged by solution casting technique by means of distilled water as a widespread solvent. The formation of Al3+-metal complex was verified through Ultraviolet–visible (UV-Vis) and Fourier-transform infrared spectroscopy (FTIR) examinations. The addition of Al-complex into the polymer matrix led to the recovery of the optical parameters such as dielectric constant (εr and εi) and refractive index (n). The variations of real and imaginary parts of complex dielectric constant as a function of photon wavelength were studied to calculate localized charge density values (N/m*), high-frequency dielectric constant, relaxation time, optical mobility, optical resistivity, and plasma angular frequency (ωp) of electrons. In proportion with Al3+-complex content, the N/m* values were amplified from 3.68 × 1055 kg−1 m−3 to 109 × 1055 kg−1 m−3. The study of optical parameters may find applications within optical instrument manufacturing. The optical band gap was determined from Tauc’s equation, and the type of electronic transition was specified. A remarkable drop in the optical band gap was observed. The dispersion of static refractive index (no) of the prepared composites was analyzed using the theoretical Wemple–DiDomenico single oscillator model. The average oscillator energy (Eo) and oscillator dispersion energy (Ed) parameters were estimated.

Linear and Nonlinear Optical Properties of CuO NPs for Photonics

The optical properties of various nanomaterials make them quite interesting and play a vital role in the fabrication of devices used in the optoelectronic and photonic fields. The research community around the world is curios to understand the physical phenomena behind such nanomaterials. In this study, copper oxide (CuO) nanoparticles (NPs) were prepared by a sonochemical method and their detailed optical properties analyzed by ultraviolet–visible (UV–Vis) spectroscopy. The normal dispersion of the refractive index of the CuO NPs was illustrated by the Wemple–DiDomenico single-oscillator method to yield the oscillator strength, static refractive index, dispersion energy (Ed), energy of effective dispersion oscillator (Eo), carrier concentration, and N/m* values. In addition, nonlinear optical parameters such as the refractive index, third-order nonlinear susceptibility, and optical polarization were also estimated. The nonlinear optical performance of the CuO NPs was simulated by using optiFDTD software, and the acceptance angle, spectral bandwidth, and nonlinear output power obtained. The findings could be used in optoelectronic device applications.

Ab initio studies of A2PtH6 (A = K,Rb) materials for hydrogen storage purposes and optoelectronic applications

A2PtH6 (A = K,Rb) are reported to be promising materials for hydrogen storage and optoelectronics. This contribution deals with band structure, structural and elastic properties, phonon spectra, mechanical and dynamical stabilities, hydrogen storage properties, and optical responses of Rb2PtH6 and K2PtH6 compounds. The computations are carried out using first-principles all electrons density-functional calculations. The authors results regarding the recorded bulk modulus of the materials under focus indicate that Rb2PtH6 has higher resistivity against volume change than K2PtH6. Both materials under focus are found to be stable mechanically and dynamically and ductile in nature. The present band structure calculations showed that Rb2PtH6 and K2PtH6 are X-X wide direct gap semiconductors with band-gap energies of 7.053 and 5.608 eV, respectively. The gravimetric hydrogen density and the hydrogen desorption temperature are recorded as 1.62 wt% and 803.44 K, respectively for Rb2PtH6 and 2.16 wt% and 799.38 K, respectively for K2PtH6. The material Rb2PtH6 has been found to have a static refractive index n(0) of 1.17 and a static dielectric constant ε(0) of 1.38, while K2PtH6 has values of n(0) = 1.50 and ε(0) = 2.25. Both compound materials of interest show a high optical absorption coefficient with a wide absorption band.

Investigation of amorphous-crystalline transformation induced optical and electronic properties change in annealed As50Se50 thin films

The present work reports the amorphous-crystalline phase transformation in thermally evaporated As50Se50 thin films upon annealing at below Tg (423 K) and above Tg (523 K). The structural transition was probed by XRD, Raman and X-ray photoelectron spectroscopy. The composition and surface morphology were probed by EDS and FESEM techniques. The transmittance and reflectance spectra over the wavelength range 500 nm–1200 nm were used to deduce the optical parameters. The various optical parameters of the as-prepared and annealed As50Se50 thin films were estimated and discussed in terms of density of defect states and disorders. The indirect optical energy gap decreased for the 423 K annealed film and abruptly increased for 523 K annealed film as compared to the as-prepared film. The Swanepoel envelope method, WDD model, and Sellemeire postulates were employed for the analysis of refractive index, static refractive index, oscillator energy, dispersion energy, oscillator wavelength and dielectric constant. The changes in the linear and nonlinear properties showed opposite behavior for the two annealed films. The non-linear refractive index and 3rd order susceptibility were found to be increased for 423 K annealed film and decreased for the 523 K annealed film. The optical as well as the electrical conductivity changed with annealing and the electrical susceptibility increased for 523 K annealed film. The tunable optical properties can be applied for several optoelectronic applications. The amorphous to crystalline structural transformation occurred at annealing above Tg. The 3rd order susceptibility was found to be more at 423 K annealing and less at 523 K annealing.

Improvement of optoelectronic and spintronic properties of nanocrystalline Zn1-xGdxS films deposited by electron beam technique

This paper reports the enhancement of the optoelectronic and spintronic properties of nanocrystalline Gd-doped ZnS thin films synthesized by electron beam evaporation method. The structure and microstructural revealed the cubic structure film, and its average crystallite size reduced from 28.92 nm (x = 0) to 22.26 nm (x = 0.1), that confirmed the nanocrystalline nature of the film. Optical measurements exhibit that the Gd doping in ZnS caused the optical band gap to decrease due to the increase of defects. In addition, the refractive index n evaluated from the optical transmittance spectra through Swanepoel method is found to increase with Gd doping level owing to the increase in the polarizability. The dispersive oscillator parameters such as the single oscillator energy Eo, the dispersion energy Ed, the static refractive index n0 were calculated by Wemple and DiDomenico (WDD) model. The Non-linear optical parameters; third-order non-linear optical susceptibility χ(3) and non-linear refractive index n2 are evaluated from dispersive oscillator parameters. The results show that the tunability of the optical band gap and dispersive oscillator parameters of Gd-doped ZnS films reflects the enhancement of the non-linear optical parameters, making it suitable for optoelectronic device applications. Finally, the magnetic measurements results show that the Gd-doped ZnS film has intrinsic room temperature ferromagnetic behavior. These results indicate that Gd-doped ZnS film is effective for designing spintronic devices.

Magnetic, opto-electronic, and thermodynamic properties of half-metallic double perovskite oxide, Ba2YbTaO6: a density functional theory study

Double perovskite oxide, Ba2YbTaO6 (BYT), has been studied under the realm of DFT-based calculation implemented in Wien2K code. Spin-polarized electronic and magnetic calculations show the 100% spin polarization across the Fermi level and confirm the half-metallic ferromagnetic (HMF) character for the compound. Bandgap (~ 3.47 eV) is calculated using the mBJ exchange correlation and found to be in good agreement with its reported experimental (3.95 eV) value. It has been found that Yb-f orbitals have major contribution in density of states (DOS) near and at Fermi levels. Optical spectra show that static refractive index is more than one (~ 4.5) and well correlated with the Penn Model. Both absorption and optical conductivity spectra show significance for its application in UV-based opto-electronic devices. Our studied electronic, optical, and magnetic properties suggest that material has significance in spintronic and optical devices.

Electronic, optical and lattice dynamics properties of layered GaSe1-xSx

The electronic, optical and lattice dynamics properties of GaSe1-xSx are investigated in detail using Density Functional Theory (DFT). The results indicate that the calculated dielectric and Raman spectra are in agreement with the experimental data. As the proportion of S-atoms increases, there is an increase in the band gaps and a decrease in the lattice parameters. Further, there are reductions in both the static electronic dielectric ε1(0) and refractive index n(0), with the lattice vibrations of Ga-X (X = Se or S) bonds gradually strengthening and shifting towards the high-frequency region. These variation tendencies indicate a gradual increase in the interaction of Ga-X bonds with the increasing ratio of S-atoms. From the differential charge densities, the inter-layer and intra-layer interactions of GaSe0.75S0.25 are the weakest, with those of GaS being the strongest. Due to the highly anisotropic bonding forces, optical spectra of GaSe1-xSx present clear polarization anisotropy in the direction of vector E. The absorption and reflectivity spectra show that GaSe1-xSx are transmitted when frequencies are lower than 2.36 eV(525 nm).

Optical properties of double walled carbon nanotubes

Density functional theory was utilized to simulate the electronic band structure and optical spectra of double walled (4, 4) @ (8, 8) carbon nanotubes. The dielectric constants and dielectric function were calculated for the perpendicular and parallel to the tube axis polarizations. The output indicates that for the DWCNTs, the effect of the 2pz orbitals overlapping on the static refractive index in the parallel to the tube axis polarization outweighs that of the perpendicular to the tube axis polarization. The real part of the dielectric functions shows that for the z polarization of DWCNTs (4, 4) @ (8, 8), the optical refraction (n) for the most of the allowed energies is higher compare to the n of the SWCNTs (4, 4) and SWCNTs (8, 8). E11(eV), E22(eV), E12(eV) and E21(eV) optical band gap of DWCNTs (4, 4) @ (8, 8) are equal to 1.41 eV, 1.92 eV, 1.47 eV and 0.12 eV respectively. The first optical absorption’s maximum of the SWCNTs (4, 4) and SWCNTs (8, 8) also happens at 2.1 eV and 1.2 eV respectively for the x and y polarization.

Structural, linear and non-linear optical properties of Cr-doped ZnO thin film for optoelectronics applications

Abstract In this work, optical properties of undoped zinc oxide (ZnO) and chromium (Cr) doped ZnO prepared at different concentrations of Cr (2, 3, and 5 wt.%) on glass substrates by a spray pyrolysis method are reported. The structural properties investigated by X-ray diffraction revealed the hexagonal wurtzite structure, noting that the crystallite size of the films decreases with increasing Cr content. The optical characterization of the samples was carried out using spectral transmittance. The refractive index, energy gap, and extinction coefficient of pure and Cr-doped ZnO thin films have been calculated. The single oscillator model of Wemple–DiDomenico was used to study the dispersion of the refractive index. The oscillator parameters, the single oscillator energy, the dispersion energy, and the static refractive index were determined. The linear optical susceptibility and non-linear optical susceptibility were also studied and discussed. These promising results achieved by Cr-doping of ZnO exhibited an important behavior for technological applications in electronic, optoelectronic devices and non-linear optical applications.