Dependence Of Optical Properties Research Articles

Impact of substituents at the para position of C-Nitroso over N-Nitroso diphenylamine on static and frequency dependent nonlinear optical Properties: DFT and TD-DFT

The nonlinear optical property of N and C-nitroso diphenylamine is the focus of the current work but the D-π-A skeleton-based para substituted nitroso benzene served as the starting point for this investigation. For p-methoxy nitroso benzene, a maximum β0 of 10.47 x 10-30 esu was attained. Diphenylamine analogue was letter on chosen for further improvement. For these nitroso diphenylamines, substituent effects of electron donating groups (EDGs) at the para position have been studied for the nonlinear optical property (NLO). The NMe2 derivative of C-nitroso was found to have the highest value of hyperpolarizability (β0) of 57.46 × 10-30 esu, including 570 × 10-30 Debye.esu as molecular hyperpolarizability (µ×β0), out of these two nitroso forms with substituents Me, OMe, OEt, NH2, and NMe2 at para position. H < Me < OMe < OEt < NH2 < NMe2 is the ascending effect for the β0 in the N-nitroso whereas H < Me < OMe < NH2 < OEt < NMe2 in the C-nitroso. These β0 value shows 155.29, 73.69, 13.12 fold increment as compared to diphenylamine (DPA), urea and p-nitroaniline (PNA) respectively. Upon increasing the λmax, value of calculated βTDω also increases calculated in TD-DFT calculations (βTD1064 <βTD1340 <βTD1460 < βTD1907). These values have shown a deviation range of 7–38 % in case of N-nitroso and 11–52 % in case of C-nitroso as compared to static values. Whereas βHRSω increases with increase in the optical frequency (βHRS1064 >βHRS1340 >βHRS1460 > βHRS1907). These values have shown a deviation range of 4–91 % in case of N-nitroso and 1to > 100 in case of C-nitroso as compared to static values.

Hydrostatic pressure and temperature dependent optical properties of double inverse parabolic quantum well under the magnetic field

In this study, we investigated the combined effects of structure parameters such as size and geometry, as well as hydrostatic pressure, temperature, and magnetic field on the electronic and optical properties of a double inverse parabolic quantum well within the framework of the effective mass and parabolic band approximations. It is very important to consider the effects of temperature and hydrostatic pressure, especially in practical applications involving quantum wells such as semiconductor devices and optoelectronics. The results obtained are in good agreement with the literature. Understanding how these factors affect the electronic and optical properties of semiconductor heterostructures helps to optimize the performance and stability of devices operating under different environmental conditions.

Insight on Cu-doping dependent structural, electronic and optical properties of AgZnF3 Fluro-perovskite for solar cell applications: A DFT study

The density function theory (DFT) with GGA and PBE was employed to determine the structural, electrical, and optical characteristics of pure and Cu doped AgZnF3 type Fluro-perovskite. The structural properties of composite are calculated in realistic agreement with those testified in the literature. The band gap of the hybrid AgZnF3 is small and indirect. AgZnF3 contained a calculated band width of 1.52 eV. AgZnF3's total electronic properties were principally controlled by the Zn atom, whereas the Zn-d state and the F-p state had a minor impact on its partial electronic properties and state density. Cu doping modified AgZnF3's electrical band structure by narrowing the band gap. With increasing doping concentrations, the partial densities of states, which are likewise impacted by doping concentrations decreased. This material is appropriate for a variety of applications due to the improvement in optical characteristics and decrease in the band gap.

Study of the photothermal response of a multilayer structure doped with VO2@Au nanoshells

In this paper, we demonstrate a theoretical study of a multiphysics problem to solve for the photothermal response of a one-dimensional multilayer structure containing a layer doped with VO2@Au nanoshells. The VO2@Au nanoshell consists of a gold (Au) shell and a core of the phase change material vanadium dioxide (VO2) where the VO2 core transitions from a semiconductor state to a conductor state at the critical temperature of 68 °C. This behaviour results in thermal induced optical tunability through this reversible phase change of the VO2, due to the temperature dependent optical and thermal properties. The presence of the VO2 core, functioning as an ultra-fast and reversible optical phase-change material, leads to the emergence of photothermal induced bistability. The layer doped with the VO2@Au nanoshell is approximated as an effective medium using the Maxwell-Garnett Theory to enable an analytical solution. In this study, the optical response of the multilayer structure is obtained using the Transfer Matrix Method, while the thermal response for both stationary and transient states is solved using the Green’s Function Method and Kirchhoff’s Transformation. These equations are interconnected through the heat source term in the heat diffusion equations, representing the local heat generation induced by the continuous-wave laser applied to the structure. Our findings indicate that at the wavelengths of 658 nm and 747 nm, there are two distinct photothermal responses arising from the phase change of the VO2 core. At these wavelengths, the absorption of light increases and decreases, respectively, because of the VO2 phase change. This analytical method not only offers a thorough exploration of the fundamentals of induced photothermal responses in multilayer structures but also holds considerable potential for various applications, including solar cells, photothermal therapy, and nanothermal sensors.

Sensitization Strategies of Lateral Flow Immunochromatography for Gold Modified Nanomaterials in Biosensor Development.

Gold nanomaterials have become very attractive nanomaterials for biomedical research due to their unique physical and chemical properties, including size dependent optical, magnetic and catalytic properties, surface plasmon resonance (SPR), biological affinity and structural suitability. The performance of biosensing and biodiagnosis can be significantly improved in sensitivity, specificity, speed, contrast, resolution and so on by utilizing multiple optical properties of different gold nanostructures. Lateral flow immunochromatographic assay (LFIA) based on gold nanoparticles (GNPs) has the advantages of simple, fast operation, stable technology, and low cost, making it one of the most widely used in vitro diagnostics (IVDs). However, the traditional colloidal gold (CG)-based LFIA can only achieve qualitative or semi-quantitative detection, and its low detection sensitivity cannot meet the current detection needs. Due to the strong dependence of the optical properties of gold nanomaterials on their shape and surface properties, gold-based nanomaterial modification has brought new possibilities to the IVDs: people have attempted to change the morphology and size of gold nanomaterials themselves or hybrid with other elements for application in LFIA. In this paper, many well-designed plasmonic gold nanostructures for further improving the sensitivity and signal output stability of LFIA have been summarized. In addition, some opportunities and challenges that gold-based LFIA may encounter at present or in the future are also mentioned in this paper. In summary, this paper will demonstrate some feasible strategies for the manufacture of potential gold-based nanobiosensors of post of care testing (POCT) for faster detection and more accurate disease diagnosis.

Analytical solution for the single scattered radiance of two-layered turbid media in the spatial frequency domain, Part 1: Scalar radiative transfer equation

In this paper analytical solutions to the radiative transport equation are derived for the angular resolved single scattered radiance in a semi-infinite turbid medium having depth dependent optical properties. Explicit formulas are given for a two-layered turbid medium. A difference in the refractive index between the surrounding non-scattering medium and the two-layered medium is considered. The result displays a linear relationship between the phase functions of both layers and the radiance. In order to verify the results, the Monte Carlo method is used to compare calculations for varying configurations of the medium and phase functions. For all cases, the analytical solution and the Monte Carlo simulations show excellent agreement with one another.

Visualizing moiré ferroelectricity via plasmons and nano-photocurrent in graphene/twisted-WSe2 structures

Ferroelectricity, a spontaneous and reversible electric polarization, is found in certain classes of van der Waals (vdW) materials. The discovery of ferroelectricity in twisted vdW layers provides new opportunities to engineer spatially dependent electric and optical properties associated with the configuration of moiré superlattice domains and the network of domain walls. Here, we employ near-field infrared nano-imaging and nano-photocurrent measurements to study ferroelectricity in minimally twisted WSe2. The ferroelectric domains are visualized through the imaging of the plasmonic response in a graphene monolayer adjacent to the moiré WSe2 bilayers. Specifically, we find that the ferroelectric polarization in moiré domains is imprinted on the plasmonic response of the graphene. Complementary nano-photocurrent measurements demonstrate that the optoelectronic properties of graphene are also modulated by the proximal ferroelectric domains. Our approach represents an alternative strategy for studying moiré ferroelectricity at native length scales and opens promising prospects for (opto)electronic devices.

An insight into the transition metal dependent structural, optical, and electrical properties of dysprosium doped lithium zinc borate glasses

A glass series of Dy3+ ions doped zinc vanadium lithium borate with chemical composition xV2O5·(10-x)ZnO·30Li2O·60B2O3 (x = 0, 1, 5, 7, 9, 10) with 1.0 mol% of Dy2O3 has been synthesized by melt quench method. Efforts have been made to identify suitable optoelectronic material by studying the structural, electrical, photo-luminescence (PL), and optical characteristics of the dysprosium ions in the presence of VO2+ ions. PL emission spectra have been explored, depicting that when excited at 386 and 424 nm, the glass matrix is suitable for laser action and at 452 nm, it is apt for cool white light applications.

A comprehensive DFT study on the physical properties of XCrAl (X= Fe, Co, Ni, Cu) half-Heusler alloys for applications in high-temperature technology

In the present work, structural, electronic, magnetic, elastic, mechanical, thermal and optical properties of XCrAl (X = Fe, Co, Ni, Cu) Half-Heusler (H–H) alloys were explored. First-principles study based on the non-polarized and spin-polarized density functional theory (DFT) were employed to get the geometrically relaxed unit cell structures of H–H alloys of investigation. The larger lattice constant values were found due to the spin polarization and the magnetic moments were calculated from the spin density of states (DOS). The higher values of magnetic moments make XCrAl alloys suitable for magnetic device applications. The computational electronic structure analyses at zero applied pressure confirm the zero energy band gap of XCrAl alloys which displayed metallic nature for all the compounds. From the elastic constants calculations, all the studied alloys were found mechanically and thermally stable. The values of melting temperatures were obtained in the range from 2072 to 1883 K and the calculated Debye temperatures followed the same manner of variation. Among the studied compounds, FeCrAl exhibits highest melting temperature and lattice thermal conductivity with the value of 12.94 Wm−1K−1 at 300 K which is in good agreement with the other reported results. These investigations suggest that, FeCrAl is relatively more suitable in accident-tolerant fuel (ATF) cladding material applications over the common Zr-based cladding rods. The frequency dependent optical properties of the studied H–H alloys were also explored comprehensively and the examinations indicate that, XCrAl (X = Fe, Co, Ni, Cu) alloys can also be the good choice for ultraviolet (UV) based optical device applications as they have high absorption coefficient of >200 × 104 cm−1 and maximum reflectivity of >94% in the UV region.

Thickness dependent physical and optical properties of SILAR deposited titania films

Uniform and crystalline titanium dioxide (TiO2) thin films were obtained using Successive Ionic Layer Adsorption and Reaction (SILAR) technique. Films having varied thicknesses over a range from 700 nm to 1000 nm are deposited on glass substrate. Further TiO2 films were annealed at 673 K for 2 h. X-ray diffraction measurements of both annealed and as deposited films were done to analyze the effect of temperature. Crystallite size and micro strain of the TiO2 films were calculated to study their trend with different thicknesses of the film. Morphological and compositional characteristics are studied by Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX) respectively. Images showed formation of uniform film without discontinuities on the base substrate. Optical constants of the films are figured out using UV–vis spectrophotometry. Absorbance spectra showed that as the thickness of the films increased absorbance of the films also increased. Direct and indirect bandgap values of TiO2 films was found using Tauc’s plot.

Insight into thermodynamic, optoelectronic, and magnetic characteristics of V doped BeSe

In present work, the magnetic and optoelectronic features of Be1-xVxSe (x = 6.25%, 12.5%, 18.75%, 25%) alloys are explored utilizing full potential linearized augmented plane wave (FP-LAPW) scheme based on spin dependent density functional theory (DFT). The analysis of spin-dependent electronic properties of V doped BeSe corroborated the half metallic ferromagnetism (HMF) at all V concentrations; spin-up version displays the metallic nature and spin dn channel represents the semiconductor character. The computed total magnetic moment (MTot) is found to be 3.00575, 3.00386, 3.00099 and 3.00023 μB at 6.25%, 12.5%, 18.75%, 25% doping concentrations, respectively, mainly arisen from V-3d state electrons ensured through spin magnetic density. Besides, dielectric function dependent optical properties (extinction coefficient, absorption coefficient, refractive-index, optical conductivity, and reflectivity) are also investigated within range of 0 ˗ 10 eV and obtained high absorption and low reflectance of the considered system in UV region. The overall analysis demonstrated studied material as a potential contender for utilization in spintronics and optoelectronics.

A comprehensive ab-initio insights into the pressure dependent mechanical, phonon, bonding, electronic, optical, and thermal properties of CsV3Sb5 Kagome compound

In this paper, we have presented a comprehensive study of the physical properties of Kagome superconductor CsV3Sb5 using the density functional theory (DFT) methodology. The structural, mechanical, electronic properties (band structure, electronic energy density of states, Fermi surface, and charge density distribution), atomic bonding, hardness, thermodynamics, optical properties, and their pressure dependences have been investigated systematically at different pressures. The calculated ground state lattice parameters and volume are in excellent agreement with available experimental results. The estimated single-crystal elastic constants ensured the mechanical stability of the compound, whereas phonon spectra endorse dynamical stability at zero pressure. The electronic band structure, density of states, and optical properties confirmed the metallic feature. The Pugh ratio and Poisson’s ratio of the compound under study revealed the softness/ductility. The hardness of CsV3Sb5, estimated using several formulae, is quite low while the machinability index predicted good machinability with excellent lubricating properties. The compound shows tendency towards structural instability at a pressure around 18 GPa. The optical constants have also been studied to correlate them with electronic properties (band structure) and predict the possible applications of this compound. Both the mechanical and optical properties show directional anisotropy. CsV3Sb5 is predicted to be an efficient absorber of ultraviolet radiation. The compound is also an efficient reflector of visible light. The superconducting transition in CsV3Sb5 has been revisited following prior studies.

Film thickness dependent electron transport and optical properties of thermochromic VO2

Vanadium dioxide (VO2) thin films are very well known for their efficient thermochromic properties, i.e. temperature dependent reversible switching of their optical and electrical properties, rooted in a first order phase change at the transition temperature of 68 °C. Despite a vast amount of basic and applied research on VO2 thin films, a simultaneous study of the optical and electrical switching properties, especially as functions of film thickness is scarcely reported. Such a study may provide interesting insight into the basics of thermochromic switching and lead to a better designing of more efficient thermochromically switching optical and electrical interactive devices. In this work we have studied the film thickness dependence of the optical and electrical properties of sputter deposited VO2 thin films. The size dependent electrical behavior of these films is examined in the light of the existing theories. Applying Drude model which combines the optical and electrical behaviour, all the relevant parameters (plasma frequency and free electron density) are calculated for the semi-conducting and metallic phases of the VO2 thin films. All the obtained parameters and the strong thermochromic switching behaviour indicate that the films are predominantly made up of VO2. Importance of distinction between optical hysteresis derived transition temperature and the one derived from resistance hysteresis is emphasized. This comprehensive and in-depth study is expected to lead to a better understanding and design of switching devices based on VO2 thin films.

Investigation on ethylene glycol and glycerol mixture concentration dependent optical, dielectric, electrical, rheological, and thermophysical properties of EG+Gly/ZnO semiconductor nanofluids

Wide energy bandgap metal oxide nanomaterials containing semiconductor nanofluids (SNFs) are technologically established as advanced multifunctional materials for progress in high performance soft condensed devices. Therefore, to strengthen this field of materials, the present study reports in detail the optical, dielectric, electrical, rheological, and thermophysical properties of the SNFs based on ethylene glycol (EG) and glycerol (Gly) mixture of an entire concentration range (Gly volume fractions; 0.00, 0.25, 0.50, 0.75, and 1.00) with a fixed amount of zinc oxide (ZnO) semiconductor nanomaterial (0.05 wt%). These green-formulated EG + Gly/ZnO SNF materials showed a longer stability of the suspended nanoparticles in the highly viscous hydrogen bonded base fluid and exhibited an increase in absorbance with the decrease wavelength of visible range photons and the ZnO electronic transition at about 3.2 eV energy of ultraviolet radiations. Dielectric measurements over the 20 Hz–1 MHz range of these SNFs, at 298.15 K, explained a dominant contribution of the electrode and interfacial polarization processes at low frequencies and the molecular dipole polarization of static permittivity about 40 at the higher frequencies. Electrode polarization and conductivity relaxation times enhanced exponentially when the Gly concentration increased in the EG + Gly base fluid which governs the electrical conductivity decrement from 0.79 to 0.04 μS/cm for these SNFs. The rheological study explained the Newtonian characteristics of EG + Gly/ZnO nanofluids with their base fluid mixture concentration controllable dynamic viscosity in the wide range of 17–702 mPa s, at 298.15 K. The density, refractive index, ultrasound velocity, prominent acoustic parameters, and thermal conductivity are determined and discussed to explore the solid-liquid interaction and interfaces formed in these innovative SNF materials.

Growth and temperature-tuned band gap characteristics of LiGd(MoO4)2 single crystals for optoelectronic applications

LiGd(MoO4)2 has been investigated due to its optoelectronic applications, especially for development of light-emitting diodes. In the present paper, LiGd(MoO4)2 single crystals grown by Czochralski method was studied in terms of structural and temperature dependent optical properties. X-ray diffraction analysis showed that the crystal crystallizes in a single phase tetragonal structure. Raman spectrum exhibited six distinguishable peaks around 207, 319, 397, 706, 756 and 890 cm−1. These peaks correspond to vibrational modes of free rotation, symmetrical stretching, symmetric bending, antisymmetric stretching and antisymmetric bending of (MoO4)2− tetrahedron. Infrared transmittance spectrum had eight minima around 2114, 2350, 2451, 2854, 2929, 2960, 3545 and 3578 cm−1 which are due to multiphonon absorptions. Spectral change of transmittance curves at various temperature between 10 and 300 K was utilized to elucidate temperature effect on absorption characteristics. Optical band gap of the material was found using Tauc and spectral derivative methods. The band gap value was obtained as 3.09 eV at room temperature and this value increased to 3.22 eV with decreasing temperature down to 10 K. The detailed analysis on the temperature dependency of the band gap was applied by Varshni model. The band gap at 0 K and change of rate of the band gap were estimated as 3.23 eV and −1.45 × 10−3 eV/K, respectively. Room temperature photoluminescence spectrum of the crystal presented a peak around 709 nm which corresponds to red light emission. LiGd(MoO4)2 is a potential candidate for optoelectronic devices emitting red light.

Growth of Cd1-xMnxTe crystals by vertical Bridgman method and analysis of composition dependence on the bandgap

This article reports the growth of cadmium manganese telluride (Cd1-xMnxTe, CMT) single crystal by vertical Bridgman method and the property measurements for three different Mn compositions (x = 0.05, 0.10 & 0.15). The single crystalline nature of the grown crystals was confirmed with Laue back reflection method. The lattice constants were calculated using single-crystal X-ray diffraction analysis. Phase formation and zinc blende crystal structure were confirmed with powder X-ray diffraction analysis. The shifting of the diffraction peak position indicates the reduction in lattice parameter of Cd1-xMnxTe crystals with Mn concentration. Raman spectra exhibited two mode behavior having CdTe and MnTe-like structures and their longitudinal optical phonon modes displaying peak shift with Mn concentration. The increase in the Mn concentration in CMT lattice made a blueshift in photoluminescence emission band leading to changes in the bandgap from 1.5776 to 1.7250 eV. The experimentally observed IR transmittance was found to be in line with theoretically observed transmittance. The observed Mn concentration dependent structural and optical properties confirm the formation of high quality CMT single crystals by vertical Bridgman technique.

Direct Observation of Al Migration Enhancement by Changing the Al and N Source Relative Position in the Molecular Beam Epitaxy of AlGaN Nanowires

Aluminum (Al)-containing nitrides, including AlN, AlScN, and AlGaN, are emerging material platforms for future-generation photonic, electronic, ferroelectric, and multifunctional semiconductor devices. Nonetheless, the low Al migration mobility in a nitrogen environment is a notorious hindrance to obtaining high-quality Al-containing nitride epilayers. This is particularly the case for the epitaxy of Al-containing nitrides with radio frequency (RF) plasma-assisted molecular beam epitaxy (MBE), due to the use of relatively low substrate temperatures. As such, various approaches have been employed in promoting Al migration such as metal-modulated epitaxy (MME). Despite the progress, the effect of the relative position of the Al and N sources on the Al migration mobility has remained unclear. In this study, we show that MBE-grown AlGaN nanowires can be an effective probe to examine the effect of the Al and N source relative position on the Al migration mobility and demonstrate clearly that Al adatoms appear to be more mobile from the Al source that is far away from the N source, compared to those from the Al source that is near the N source. This study therefore can potentially impact the development of emerging Al-containing semiconductor devices by MBE. Moreover, the demonstrated correlated Al source dependent morphological and optical properties of AlGaN nanowires can naturally help the development of AlGaN-nanowire-based UV light-emitting diodes (LEDs) and lasers.

Analysis of the temperature dependent optical properties of V1−xWxO2 thin films

Vanadium dioxide is one of the most promising materials that can be used to control and tune in real time the optical properties of nanoscale devices due to its ability to perform a Metal-Insulator Transition (MIT). In this paper, we report the optical and structural properties of undoped and W-doped V1-xWxO2 vanadium dioxide thin films deposited on oxidized silicon substrates using magnetron sputtering. The structural properties determined by X-ray diffraction showed not only the transition from a monoclinic to a rutile phase when crossing the metal–insulator transition temperature (TMIT) but also a coexistence of phases for the tungsten-doped VO2 even at room temperature. It is also shown that TMIT decreases from 69.6°C to 41.6°C as x increases from 0 to 3%. A point-by-point fitting method is proposed to reliably extract the refractive index and extinction coefficient from spectroscopic ellipsometry measurements as a function of temperature and tungsten concentration. This approach avoids all the correlations between the thickness and the refractive index well known in absorbent films calling into question the uniqueness of the results. The dielectric function is then calculated from the point by point refractive index. A model based on Tauc-Lorentz oscillators in the insulating phase to which a Drude component is added in the metallic phase provides information on the levels of the energy bands and the plasma frequency of the films. The calculation of reflectance and transmittance of V1-xWxO2 thin films highlights the effect of W doping on thermochromic performance.

Tailoring of morphology and microstructure dependent optical properties of solution processed Ge23Sb7S70 chalcogenide glass films

This paper presents an extensive study carried out to understand the process of tailoring the morphology of solution processed nanostructured Ge23Sb7S70 Chalcogenide glass thin films and to analyze their microstructure dependent optical properties. To tailor the desired morphology of the solution processed ChG films different synthesis parameters have been optimized, step by step. It has been observed that the dissolution time and concentration of Chalcogenide glass precursor solution used for the deposition of solution processed films have the major role in determining their morphology. Annealing of solution processed chalcogenide glass film is an important step to get rid of residual solvent from the film. This study reveals that annealing may disturb the morphological uniformity of solution processed chalcogenide glass films and a careful optimization of annealing step is required to maintain the morphological uniformity. Microstructure dependent optical properties such as refractive index and optical bandgap of solution processed chalcogenide glass films have also been analyzed in this study. It has been observed the size of the microstructures insolution processed chalcogenide glass films greatly influences the optical properties of these films.

Pressure dependent electronic, spintronic, optical and mechanical properties of equiatomic quaternary Heusler alloys NbMnVAl and NbFeCrAl

The pressure dependent physical properties of Nb-based equiatomic quaternary Heusler alloys NbMnVAl and NbFeCrAl have been investigated using full-potential linearized augmented plane wave (FP-LAPW) method with exchange and correlation potentials of the PBEsol scheme. Half-metallic behavior in NbMnVAl (NbFeCrAl) with band gap of 0.32 (0.29) eV in spin-down (spin-up) state at ambient pressure is observed. The total magnetic moments are derived as 2.0 μΒ/f.u. for NbMnVAl and NbFeCrAl alloys, which reconciles with Slater-Pauling rule. Phonon frequencies are computed using Vienna Ab initio Simulation Package (VASP). The exchange interactions and Curie temperatures are determined using spin-polarized relativistic Korringa-Kohn-Rostoker (SPR-KKR) method. Moreover, the computations of mechanical properties revealed the stability and ductile nature of both compounds. The optical properties proved the applicability of these compounds in optoelectronic devices. Pressure dependent half-metallic properties are discussed to show spintronic applications of both the quaternary alloys.