Refractive Index Gap Research Articles

An investigation on structural and optical properties of nanocolumnar ZnTe thin films grown by glancing angle technique

In this paper, Zinc Telluride (ZnTe) thin films have been deposited on glass substrate by glancing angle deposition (GLAD) technique at different flux angles. The structural and optical properties of the prepared specimens have been studied with the help of x-ray diffraction (XRD), FESEM, and UV–vis analyses, respectively. According to these tests, remarkable changes in the morphology and the structure of the as-prepared samples have occurred. More significantly, using UV–vis analysis the optical properties including refractive index and band gap energy of the samples have been modified at higher deposition angles, which are promising to be applicable in optoelectronic devices.

Modeling Physico-Chemical Properties of Quinolone Derivatives Using GA-MLR as a Computational Study.

In this study, we used a hierarchical approach to develop quantitative structure-activity relationship (QSAR) models for modeling physico-chemical properties of quinolone derivatives. The relationship between some of the molecular descriptors with physic-chemical properties such as refractive index (n), polarizability (α) and HOMO-LUMO energy gap (ΔEH-L) was represented. Quantum mechanical calculations using abinitio method at the #HF/6- 31++G** level were carried out to obtain the optimized geometry and then, the comprehensive set of molecular descriptors was computed by using the Dragon software. Genetic algorithm using multiple linear regression (GA-MLR) with backward method by SPSS software were utilized to construct QSAR models. The analytical powers of the established theoretical models were discussed using leaveone- out (LOO) cross-validation technique. A multi-parametric equation containing maximum three descriptors with suitable statistical qualities was obtained for predicting the studied properties. The QSPR analysis for the prediction of the refractive index, the polarizability and the HOMO-LUMO energy gap of 40 quinolone derivatives using GA-MLR method was performed. The achieved results showed that the best model for predicting the refractive index, the polarizability and the HOMO-LUMO energy gap contains maximum three descriptors. MLR analysis, using genetic algorithms as suitable descriptors selection method showed that the three selected descriptors play a vital role in the prediction of physicochemical properties of quinolone derivatives. It can be noted that the best descriptors in the final obtained models can be used to design and screen new drugs.

Measurement of multiple physical parameters of dense gaseous hydrogen-deuterium mixture under double-shock compression: Evaluating theoretical models from multiple views

A series of reverberating shock experiments on the precompressed hydrogen-deuterium (H-D) mixture were performed by using a two-stage light gas gun, and an elaborately designed diagnostic configuration was presented to probe the multishock states of dense fluid H-D mixtures. The particular diagnostics allowed multiple physical parameters, including the equation of state (EOS), refractive index, reflectivity, molecular polarizability, and energy gap, of H-D mixtures under double-shock compression to be simultaneously determined in a single shot. The multiple parameters obtained provide a comprehensive evaluation for existing theoretical models from multiple perspectives. It is found that, compared with the semilocal Perdew–Burke–Ernzerhof xc functional, the EOS data predicted by a nonlocal van der Waals exchange-correlation (xc) functional (vdW-DF1) are in much better agreement with the experimental results. Furthermore, the commonly used Gladstone–Dale relation is not appropriate for describing the refractive index in high-pressure-temperature regions, and the refractive index and reflectivity can be well reproduced by the Heyd–Scuseria–Ernzerhof hybrid xc functional. These observations may provide insights into future theoretical developments and a better understanding of material properties under extreme pressure-temperature conditions.

Morphological and optical properties of V2O5:TiO2 thin film prepared by PLD technique

In this work, pure and doped Vanadium Pentoxide (V2O5) thin films with different concentration of TiO2 (0, 0.1, 0.3, 0.5) wt were obtained using Pulse laser deposition technique on amorphous glass substrate with thickness of (250)nm. The morphological, UV-Visible and Fourier Transform Infrared Spectroscopy (FT-IR) were studied. TiO2 doping into V2O5 matrix revealed an interesting morphological change from an array of high density pure V2O5 nanorods (~140 nm) to granular structure in TiO2-doped V2O5 thin film .Transform Infrared Spectroscopy (FTIR) are used to analyze structural properties of as-deposit. The transmittance and absorption of each film, in the spectral range 300 to 1100 nm, were measured from which the optical constants (Refractive index, Absorption coefficient, Extinction coefficient and Energy gap) were determined .The energy band gap of the films was found to be change from (2.38 to 2.9) eV when the concentration of TiO2 increases from (2.78 to 2.9 ) eV The results showed a significant improvement in the transmittance and refractive index in TiO2 doped V2O5 thin films .All measured values were in consistent with other previous studies.

OPTICAL PROPERTIES OF V2O5:TIO2 THIN FILM PREPARED BY PLD TECHNIQUE

In this work, pure and doped Vanadium Pentoxide (V2O5) with TiO2 of different ratios (0, 0.1 , 0.3, 0.5) wt were obtained using Pulse laser deposition technique on amorphous glass substrate with thickness of (250)nm at T=373k. The morphological, UV-Visible was studied. The Transmittance and Absorption of each Film, in the spectral range (300 to 1100) nm, were measured from which the optical constants (Refractive index, Absorption coefficient, Extinction coefficient and Energy gap) were determined .The energy band gap of the films was found to be change from (2.44 to 4.07) eV when the concentration of TiO2 increases from (2.66 to 4.07 ) eV The results showed a significant improvement in the transmittance and refractive index in TiO2 doped V2O5 thin films .All measured values were in consistent with other previous studies.

Optical Properties of Nonstoichiometric Silicon Oxide SiOx (x < 2)

The optical properties of amorphous nonstoichiometric silicon oxide (SiOx) films of variable composition (x = 0.62–1.92) formed by plasma-enhanced chemical vapor deposition are studied in the spectral range of 1.12–4.96 eV. Spectral ellipsometry showed that the refractive index dispersion character allows one to assign the formed SiOx films to silicon-like films, dielectrics, or intermediate-conductivity-type films depending on the content of oxygen in the gas phase during synthesis. A model of the SiOx structure for ab initio calculations is proposed and describes well the experimental optical spectra. Ab initio calculations of the dependences of the SiOx refractive index and band gap on stoichiometry parameter x are performed.

Optical and Surface Properties of Nanostructured ZnO Semiconductor Thin Films Synthesized by RF Magnetron Sputtering

In this research, ZnO thin films were deposited on glass microscope slides in three separate experiments with RF input powers of 50 W, 100 W and 125 W by means of RF magnetron sputtering technique. Each deposition process was conducted for 30 minutes. Spectroscopic reflectometer , UV-VIS spectrophotometer and atomic force microscope (AFM) were used to examine the effect of sputtering power on the optical and surface properties of the produced thin films. The level of reflectivity and transparency, refractive index and band gap energy values as well as surface homogeneity and roughness were observed to rely on the RF input power. The optical band gap energy values were about 3.83-3.87 eV. The produced highly transparent ZnO thin films can be used in various optoelectronic devices and future transparent conductive electrode implementations.

Studies on Surface Morphology and Electrical Conductivity of PS Thin Films in Presence of Divalent Complexes

Optical properties and surface morphology of pure and doped Polystyrene films with different divalent metals of Zn, Cu and Sn and one concentration percentage have been studied. Measurements of UV-Vis spectrophotometer and AFM spectroscopy were determined. The absorbance, transmittance and reflectance spectrums were used to study different optical parameters such as absorption coefficient, refractive index, extinction coefficient and energy gap in the wavelengths rang 200-800nm. These parameters have increased in the presence of the metals. The change in the calculated values of energy gaps with doping metals content has been investigated in terms of PS matrix structural modification. The value of optical energy gap was found decreasing from 4.5eV of pure PS to reach 4.45, 4.38 and 4.32eV for Zn, Cu and Sn respectively. Measurement by AFM spectroscopy was done for two and three dimensional topographic images. From figures, the data of roughness average were 7.29, 7.31, 3.37 and 6.73nm for samples (Blank, Zn, Cu and Sn) respectively.

Influence of phase composition on optical properties of TiO2: Dependence of refractive index and band gap on formation of TiO2-II phase in thin films

Atomic layer deposition was applied to grow TiO2 thin films containing anatase, rutile and mixture of TiO2-II and rutile phases with the aim to investigate the dependence of optical parameters on the formation of metastable TiO2-II phase. The films were grown at a substrate temperature of 450 °C using TiCl4 and O3 as the precursors. The crystal structure obtained depended on the substrates used. The films deposited on amorphous SiO2 substrates contained only the anatase phase when the film thicknesses did not exceed 88 nm while in thicker films, anatase with inclusions of rutile was formed. The films deposited on α-Al2O3 substrates contained epitaxial rutile without traces of other crystalline phases on α-Al2O3(0 1 1̄ 2) (r-sapphire) and epitaxial TiO2-II with inclusions of rutile phase on α-Al2O3(0 0 0 1) (c-sapphire) substrates. The films that contained TiO2-II had refractive indices of 2.8 at a wavelength of 500 nm and 2.61–2.67 at 633 nm. These values were higher than those of anatase films (2.6 and 2.48–2.49, respectively) and rutile films (2.74 and 2.57–2.62, respectively). Optical band gaps of 3.28–3.36 eV obtained for the films containing TiO2-II were by 0.20 ± 0.08 eV wider than the band gaps of rutile films and by 0.06 ± 0.05 eV narrower than the band gaps of anatase films. A band gap value of 3.00 ± 0.08 eV was measured for a non-epitaxial film that was deposited on amorphous SiO2 and contained anatase with inclusions of rutile.

ZnCdO thick film: a material for energy conversion devices

We report fabrication and characterization of low cost ZnCdO thick film deposited on glass substrate by screen coating technique. For structural properties, x-ray diffraction investigation revealed the presence of hexagonal and cubic structure with strong orientation along (101) where as Scanning electron microscopy analysis illustrated porous morphology of the fabricated film. For optical properties, UV-visible spectroscopy has been evaluated in the spectral wavelength range 300–900 nm for analysis of optical parameters such as absorption coefficient, optical conductivity, refractive index, extinction coefficient and band gap. Fourier transform infrared spectroscopy investigation revealed the information about vibrational bands pertaining to (Zn–O and Cd–O) stretching modes. Electrical resistivity measurement showed the semiconducting behaviour of the prepared thick film.

The Infrared Optical Properties of Al0.5In0.5Sb Alloy With Nano Coatings

In this article, the SiC/Nano GaAs and SiC/Nano InP coatings on Al0.5In0.5Sb alloy are investigated in a theoretical framework. A Special program code written by MATLAB version 10 was performed to describe the reflectivity of coatings as a function of the nano-particles sizes, refractive index, and energy gap. This program is based on the Brus model and the Characteristic Matrix Theory. The results connected with nano-particle size of 3.6 nm in multilayer coatings indicate that our designs achieve high reflectivity. Such as, with six layers, the Air/SiC/Nano GaAs/Al0.5In0.5Sb design gives the reflectivity for S-Polarization Rs=99.9% and for P-Polarization Rp=98.0% for oblique incidence of ????=45° and R=99.9% for the perpendicular incidence. Similarly, the Air/SiC/Nano InP/Al0.5In0.5Sb gives Rs=99.9% and Rp=98.5% for oblique incidence of ????=45° and R=99.8% for the perpendicular incidence. This study set out with the aim of assessing the importance of Air/SiC/Nano GaAs/Al0.5In0.5Sb composition in industrial applications as a highly reflective coating for CO2 laser resonators in the far infrared region.

Optical and surface properties of ZnN thin films manufactured by radio frequency reactive magnetron sputtering

ZnN is a relatively new material and its physical properties are not yet well studied. In this research, ZnN thin films having different thickness values were deposited on glass substrates by means of radio frequency (RF) reactive magnetron sputtering technique at room temperature and some physical properties of ZnN thin films were investigated by several techniques. UV–vis spectrophotometer and reflectometer were employed to investigate the optical properties of the produced thin films. The surface properties were investigated by using tensiometer and atomic force microscope (AFM). The effects of film thickness on the optical and surface properties of ZnN thin films were discussed. The refractive index and band gap values were found to be dependent on thickness of ZnN thin films. The AFM investigations indicated that the surfaces of the films are compact and smooth. From the wetting experiments, it was found that the surfaces of the films are hydrophobic and surface free energy values are low as reported in literature.

Facile synthesis and optical characterization of graphene oxide-doped TiO2/polyvinyl alcohol nanocomposites: optical limiting applications

In this present research, PVA polymer was utilized as a host polymer to fabricate free-standing PVA/TiO2: GO nanocomposites films. The fabricated films were subjected to different structural inspections; at first the surface topography was examined by scan electron microscopy, SEM. The analyzed PVA/TiO2 doped 30 ml graphene oxide film revealed in most a smoothed surface without any microcracks or physical and/or chemical treatment (as a representative sample). Secondly, The crystal structure of the fabricated samples (PVA/TiO2:doped GO) was analyzed through its recorded XRD patterns. At normal incidence, spectrophotometric properties such as: transmittance, Reflectance and absorbance, Abs were characterized to estimate the Optical constants such as refractive index (n) and extinction coefficient (k) for the fabricated samples. The linear and nonlinear propagation of probe normal light beam in PVA/TiO2: GO nanocomposites were inspected and elucidated in wavelength from 250 to 2500 nm. The estimated values of the oscillator energy and strength are increased with the doping ratio from 0 to 40 ml. The calculated value of the group velocity is less (c = 3 × 108 m sec−1) and decreases with increasing of the GO-doping ratio. The extracted value of static refractive index and direct energy gap was found to be decreased from 5.42 to 1.22 and from 2.12 to 1.49 as GO-doping ratio was increased from 0 to 40 ml GO, respectively. The evaluated Attenuation power of the fabricated free-standing PVA/TiO2: GO samples elucidated that the optical limiting results studies showed that it may be suitable to attenuate the laser power by utilizing the fabricated PVA/TiO2: GO films.

Searching for materials with high refractive index and wide band gap: A first-principles high-throughput study

Materials combining both a high refractive index and a wide band gap are of great interest for optoelectronic and sensor applications. However, these two properties are typically described by an inverse correlation with high refractive index appearing in small gap materials and vice-versa. Here, we conduct a first-principles high-throughput study on more than 4000 semiconductors (with a special focus on oxides). Our data confirm the general inverse trend between refractive index and band gap but interesting outliers are also identified. The data are then analyzed through a simple model involving two main descriptors: the average optical gap and the effective frequency. The former can be determined directly from the electronic structure of the compounds, but the latter cannot. This calls for further analysis in order to obtain a predictive model. Nonetheless, it turns out that the negative effect of a large band gap on the refractive index can counterbalanced in two ways: (i) by limiting the difference between the direct band gap and the average optical gap which can be realized by a narrow distribution in energy of the optical transitions and (ii) by increasing the effective frequency which can be achieved through either a high number of transitions from the top of the valence band to the bottom of the conduction or a high average probability for these transitions. Focusing on oxides, we use our data to investigate how the chemistry influences this inverse relationship and rationalize why certain classes of materials would perform better. Our findings can be used to search for new compounds in many optical applications both in the linear and non-linear regime (waveguides, optical modulators, laser, frequency converter, etc.).

Effect of annealing temperature and laser pulse energy on the optical properties of CuO films prepared by pulsed laser deposition

In this work; copper oxide films (CuO) were fabricated by PLD. The films were analyzed by UV-VIS absorption spectra and their thickness by using profilometer. Pulsed Nd:YAG laser was used for prepared CuO thin films under O2 gas environment with varying both pulse energy and annealing temperature. The optical properties of as-grown film such as optical transmittance spectrum, refractive index and energy gap has been measured experimentally and the effects of laser pulse energy and annealing temperature on it were studied. An inverse relationship between energy gap and both annealing temperature and pulse energy was observed.

Design of graphene-based hybrid waveguides for nonlinear applications

The extraordinary properties of a monolayer graphene can be effectively utilized in integrated optoelectronic devices. Therefore, the optical properties and the effective parameters on the graphene’s conductivity are calculated at the telecom wavelength 1.55 µm. Next, the different types of photonic and plasmonic hybrid waveguides based on graphene are designed for nonlinear applications such as frequency conversion processes. The fundamental proposed structure consists of a LiNbO3 layer, a single graphene layer and a dielectric gap between the graphene and LiNbO3 to support the nonlinear applications such as second harmonic generation. The waveguide’s performance is analyzed in terms of the intensity of electric field, LiNbO3 thickness, the gap refractive index, mode effective index and propagation loss while the graphene’s chemical potential is varied with an applied gate voltage. According to the results, a sudden rise in propagation loss at µc = 0.493 eV (where the permittivity of graphene is almost zero) is observed. At last, a plasmonic hybrid waveguide consisting of a silver strip and a graphene layer placed between the metal and LiNbO3 layer is presented and the effect of the graphene’s chemical potential on the mode effective index and the propagation length are studied.

Spectroscopic and structural properties of Zinc-Phthalocyanine prepared by pulsed laser deposition

Zinc Phthalocyanine (ZnPc) was prepared by pulsed laser deposition using Q-Switching Nd:YAG laser with wavelength 1064nm, frequency 6Hz and energy 240mJ at room temperature under vacuum condition with 10−3torr. Ultra violet-Visible spectra were used to evaluated the optical properties included the absorption coefficient, extinction coefficient, refractive index and energy gap of the ZnPc films and the results were discussed. The energy gap of ZnPc film with different thickness are varied from (1.7 to 1.5 eV) at Q-band and from(3 to 2.7eV)at B-band for increasing thickness from (150 to 500 nm).The optical transition was found to be direct and allowed transition. X-ray diffraction (XRD) was used to analyze the ZnPc organic thin films with different thickness that the preferential orientation around (111) at 7 degree. FTIR spectra for ZnPc and metal free phthalocyanine (H2Pc) is used to find the molecular vibration . It can be observed that a strong peak around 3500 Cm−1 which refers to N-H bond for metal free phthalocyanine where absents for ZnPc and appear a new strong line around 730 Cm−1 which refers to Zn metal.

Comparative studies on polarisability, and optical properties of BiZnBo–SLS and PbZnBo–SLS glass

Soda Lime Silica (SLS), mainly composed of SiO2, was utilised in this study as the source of SiO2 for fabrication of glass. A study of physical and optical properties was performed for the glass system of x [RmOn] (0.50−x) [ZnO] 0.20 [B2O3] 0.30 [SLS], where RmOn are Bi2O3 and PbO with x = 0.05, 0.10, 0.20, 0.30, 0.40, and 0.45 mol. The glass was prepared by melt-quenching method. Optical properties of the glass samples were obtained using UV–visible absorption measurements. The main objective of this study was to compare the structural, polarizability, and optical properties of these two series synthesized silica based glass. The structure of the glass system was determined by X-ray diffraction (XRD). The density and molar volume were found to increase as Bi2O3 and PbO concentration increased. The optical band gap, Eopt values for bismuth glasses were between 2.58 and 2.92 eV and varied from 2.42 to 2.92 eV for lead glasses. The highest concentration of Bi2O3 and PbO in glass system showed the smallest Eopt. Bi2O3 glass exhibit the significant value towards direct or indirect band gap in optoelectronic field compared to PbO glass. Refractive index of glass samples was measured by UV–visible spectrophotometer. The value lay between 2.42 and 2.52 for bismuth glass and 2.42 and 2.57 for lead glass and the value increased as bismuth ion (Bi3+) and lead ion (Pb2+) concentration increased. Metallisation criterion was investigated on the basis of refractive index and band gap. The metallisation criterion of the glass sample linearly decreased with increasing concentration of bismuth and lead ions as a result of increasing number of refractive indices and decreasing number of band gap energy. The positive value of metallisation criterion indicates that the glass materials are insulators or not metallic. In conclusion, the obtained results show that the addition of bismuth oxide in silica glass improved its structural and optical properties compared to lead glass.

Оптические свойства нестехиометрического оксида кремния SiO-=SUB=-x-=/SUB=- (x<2)

Abstract The optical properties of amorphous nonstoichiometric silicon oxide (SiO_ x ) films of variable composition ( x = 0 . 62–1 . 92) formed by plasma-enhanced chemical vapor deposition are studied in the spectral range of 1 . 12–4 . 96 eV. Spectral ellipsometry showed that the refractive index dispersion character allows one to assign the formed SiO_ x films to silicon-like films, dielectrics, or intermediate-conductivity-type films depending on the content of oxygen in the gas phase during synthesis. A model of the SiO_ x structure for ab initio calculations is proposed and describes well the experimental optical spectra. Ab initio calculations of the dependences of the SiO_ x refractive index and band gap on stoichiometry parameter x are performed.

A systematic study of multifunctional xTiO2/(100 − x)SiO2 thin films prepared by sol–gel process

It is known that TiO2/SiO2 nanocomposite thin films have several properties improved when compared with the TiO2 or SiO2 pure thin films. In this work, a systematic study of xTiO2/(100 − x)SiO2 films (x = 0, 20, 40, 60, 80, and 100%) with different numbers of layers (1–5), i.e., different thicknesses, prepared by sol–gel process using dip-coating deposition was made. The films were thermally treated and characterized by UV–Vis spectroscopy and ellipsometry to evaluate the optical properties and thicknesses. Transmittance of the films were discussed by means of the interference fringes and refractive index modulation as a TiO2/SiO2 ratio function. The values of refractive index, extinction coefficient, and band gap obtained from ellipsometric analyses were related to the changes in UV–Vis spectra. The construction of the xTiO2/(100 − x)SiO2 structural models for a precise ellipsometric analyses were based on a comprehension of theoretical models. The glass substrate and SiO2 film were modeled by Cauchy; TiO2 film by Tauc–Lorentz and TiO2/SiO2 by Bruggeman theories. A graded refractive index function was necessary to fit the thicker films with low mean square error (MSE). Moreover, the refractive index values permitted the calculation of total porosity of the films, using Lorentz–Lorentz equation. Atomic force microcopy images showed clearly the effect of SiO2 addition on TiO2, reducing the particle size and root mean square roughness (from 1.4 to 0.3 nm). The lowest roughness of TiO2/SiO2 films was correlated with their enhanced hardness. All TiO2/SiO2 films showed a persistent super hydrophilicity that makes them suitable for applications in environmental and energy fields.