Influence of dopant content on morphology and optical constants of ZnO:Na films by sol-gel method

Undoped and Na-doped ZnO films were deposited by sol-gel method.The effects of sodium incorporation on structure,surface morphology and optical constants of the films were investigated.X-ray diffraction patterns show the hexagonal wurtzite polycrystalline structure and that the sodium incorporation leads to the change in the structural characteristics of ZnO films.The SEM observations show that the surface morphology of the films is affected by the sodium incorporation.The transmission spectra show that the average transmittance of the films is above 85% in the visible range.The absorption edge initially blue-shifts and then red-shifts with the increase of Na doping content.The optical constants of these films were calculated using transmission spectra.Refractive indices of the films in the visible range decrease at first and then increase with increasing Na doping content.

Simultaneous estimation of aerosol optical constants and size distribution from angular light-scattering measurement signals

The angular light-scattering measurement（ALSM） method combined with an improved artificial bee colony algorithm is introduced to determine aerosol optical constants and aerosol size distribution（ASD） simultaneously. Meanwhile, an optimized selection principle of the ALSM signals based on the sensitivity analysis and principle component analysis（PCA）is proposed to improve the accuracy of the retrieval results. The sensitivity analysis of the ALSM signals to the optical constants or characteristic parameters in the ASD is studied first to find the optimized selection region of measurement angles. Then, the PCA is adopted to select the optimized measurement angles within the optimized selection region obtained by sensitivity analysis. The investigation reveals that, compared with random selection measurement angles, the optimized selection measurement angles can provide more useful measurement information to ensure the retrieval accuracy. Finally,the aerosol optical constants and the ASDs are reconstructed simultaneously. The results show that the retrieval accuracy of refractive indices is better than that of absorption indices, while the characteristic parameters in ASDs have similar retrieval accuracy. Moreover, the retrieval accuracy in studying L-N distribution is a little better than that in studying Gamma distribution for the difference of corresponding correlation coefficient matrixes of the ALSM signals. All the results confirm that the proposed technique is an effective and reliable technique in estimating the aerosol optical constants and ASD simultaneously.

Thickness dependence of the optical constants of oxidized copper thin films based on ellipsometry and transmittance

Thin oxidized copper films in various thickness values are deposited onto quartz glass substrates by electron beam evaporation. The ellipsometry parameters and transmittance in a wavelength range of 300 nm-1000 nm are collected by a spectroscopic ellipsometer and a spectrophotometer respectively. The effective thickness and optical constants, i.e., refractive index n and extinction coefficient k, are accurately determined by using newly developed ellipsometry combined with transmittance iteration method. It is found that the effective thickness determined by this method is close to the physical thickness and has obvious difference from the mass thickness for very thin film due to variable density of film. Furthermore, the thickness dependence of optical constants of thin oxidized Cu films is analyzed.

Study on optical constants inversion and infrared transmission characteristics of aerosol particles

Based on the experimental infrared spectral transmittances,an inverse model has been developed to determine the optical constants of the aerosol particles (SiO2 and Al2O3).Combined with the Mie theory and Kramers-Kronig (K-K) relations,the complex refractive indices of the SiO2 and Al2O3 particles are retrieved.The effects of the measurement errors on the inverse results are also investigated.With the optical constants inversed from the experiment,the discrete ordinate method (DOM) is used to calculate the infrared transmission characteristics of the aerosol particle cloud.Considering the multi-scattering and self-emission of the particles,the equivalent transmittance ratio (ETR) is suggested to evaluate the infrared transmission characteristics of the aerosol particles.Particular attention is given to analyze the effects of the volume fraction and diameters on infrared transmission characteristics.When the volume fraction is larger than 0.001,the particle diameter has little effect on the infrared transmission characteristics.For the uniform monodisperse particles in the detection waveband range of 3-5 μm and 8-12 μm,there exists a critical diameter where the ETR reaches the minimum value.In addition,the ETR of 3-5 μm is smaller than that of 8-12 μm with the same volume fraction and particle diameter.

Extraction of optical constants and thickness of nanometre scale TiO2 film

TiO2 thin films were deposited on glass substrates by sputtering in a conventional rf magnetron sputtering system. X-ray diffraction pattern and transmission spectrum were measured. The curves of refraction index and extinction coefficient distributions as well as the thickness of films calculated from transmission spectrum were obtained. The optimization problem was also solved using a method based on a constrained nonlinear programming algorithm.

Variable angle spectroscopic ellipsometry and its applications in determining optical constants of chalcogenide glasses in infrared

The principle of variable angle spectroscopic ellipsometry（VASE） and the data analysis models, as well as the applications of VASE in the characterization of chalcogenide bulk glasses and thin films are reviewed. By going through the literature and summarizing the application scopes of various analysis models, it is found that a combination of various models, rather than any single data analysis model, is ideal to characterize the optical constants of the chalcogenide bulk glasses and thin films over a wider wavelength range. While the reliable optical data in the mid-and far-infrared region are limited, the VASE is flexible and reliable to solve the issues, making it promising to characterize the optical properties of chalcogenide glasses.

Inversion Methods of Optical Constants of Semitransparent Solid Materials from Transmittance Spectrograms

The direct calculation models of spectral transmittance of single and double slabs consisted of semitransparent solid materials were developed based on ray trace method, and a new inversion method of optical constants （k is extinction coefficient and n is refractive index ） of materials was proposed based on transmittance spectrograms of double slabs. Differences between the new method and two others currently used methods were studied, and application range of methods was also investigated. Optical constants of selenide glass attained in references were selected as true values, and spectral transmittances of glass simulated based on direct calculation model were regarded as experimental values. Optical constants of selenide glass were achieved by inverse models. Influences of measurement error on inverse results were also determined. The results showed that ： （ 1 ） based on transmittance spectrograms of double slabs in which thickness of single slab is the same, the new proposed method can attain optical constants of materials; （2） the effect of optical constants n and k on three inversion methods are urgent larger, but inversed calculation precision of optical constants are higher in most application ranges ; （ 3 ） the influence of measurement errors existed in experimental datum on the inverse precision of three methods are urgent distinctness.

CALCULATION OF INFRARED OPTICAL CONSTANTS FOR CO_2 LASER HOLLOW WAVEGUIDE MATERIALS

A simple method was deduced for calculat-ing optical constant, optical loss and transmittance per meter of hollow-core optical fiber using data analysis method, ge-ometerical optical and electromagnetic theory. The method was used to study the Na2O-ZnO-GeO2-SiO2-PbO and Sb2O3 sysem. The glasses have nr<1 region. When the core diameter ao is 0. 5mm, the hollow waveguides of the Sb2O3-containing . glass is predicted with minimum loss of 0. 8 dB/m at 940cm-1

Determination of Optical Constant and Thickness for Thin Film by Using Improved FTM

A new method to determine the optical constant and thickness of thin films is proposed. Based on the Fresnel’s optical expression, the improved flexible tolerance method(FTM) is employed in the case of a digital model of thin film to fit the curve of measured reflectance spectrum. The simulation results show a satisfactory correlation of the optical constant with the thickness of the target film. By taking the influence of nonlinear condition into account as well as more direct and indirect limitation, the precision and value-searching efficiency have been improved. Furthermore, the problem of dimension degradation, which exists in “Downhill Simplex”, has been successfully avoided. No initial input is needed for the procedure of optimization to achieve optical solution, which makes the whole processing of value calculation much more convenient and efficient.

Nickel Antimony Sulphide Thin Films for Solar Cell Application: Study of Optical Constants

Chemical bath deposition technique has been used to deposit Ni-doped Sb2S3 thin films onto glass substrate. Doping was carried out by adding 1, 3 and 5 wt% of Ni. Bath temperature was kept as 10℃ and films were annealed at 250℃ under vacuum. Polycrystalline nature of films with an orthorhombic phase was analyzed by X-ray diffraction technique. Scanning electron microscopy was used for morphological study which shows that grains are spherical. Optical measurements using transmittance data indicated that films have a direct band gap of 1.00 - 2.60 eV with an absorption coefficient of ~104 cm-1 in visible range. The average value of electrical conductivity was calculated as 1.66, 1.11 and 1.06 (Ω·cm)-1 for as-deposited films and 1.90, 2.08 and 1.15 (Ω·cm)-1 for annealed films while refractive indices were found as 2.18 - 3.38 and 1.91 - 3.74 respectively. The obtained films can be used for solar cell applications due to their good absorbing properties like higher absorption coefficient and refractive index values.

DDI METHOD FOR MEASURING OPTICAL CONSTANTS OF THIN FILMS

By double beam and double wave interferomatric (DDI) method, the optical constants of thin films, i.e. refractive index, extinction coefficient and thickness may be determined in infrared (3.39 μm) and in visible (0.633 μm) wavelengths in the same optical path with a tunable double wave He Ne laser designed by ourselves. The measuring principle and the device are describod.

Proton radiation effects on optical constants of Al film reflector

The Al film reflectors can yield a high-reflectance over a broad wavelength region, and have been widely used in the spacecraft optical instruments for high quality optical applications. Under the irradiation of charged particles in the Earth radiation belt, the reflectors could be deteriorated. In order to reveal the deterioration mechanism, the change in optical constants of Al film reflector induced by proton radiation with 60 keV was studied in an environment of vacuum with heat sink. Experimental results showed that when the radiation damage primarily occurs in the Al reflecting film, the extinction coefficient k will gradually decrease with increasing radiation fluence, which results in the decrease of the energies of reflective light. Therefore, the proton radiation induced an obvious degradation of spectral reflectance in the wavelength region from 200 to 800nm on the Al film reflector.

Extraction of optical constants in the terahertz band using material dispersion models

This study proposes a method based on material dispersion models to computationally simulate terahertz(THz)time-domain spectroscopy signals.The proposed method can accurately extract the refractive indices and extinction coefficients of optically thin samples and high-absorption materials in the THz band.This method was successfully used to extract the optical constants of a 470-μm-thick monocrystalline silicon sample and eliminate all errors associated with the Fabry-Perot oscillation.When used to extract the optical constants of a 16.29-mm-thick polycarbonate sample,our method succeeded in minimizing errors caused by the low signal-to-noise ratio in the extracted optical constants.

Optical constants and their dispersion of Ag-MgF_2 nanoparticle composite films

Ag-MgF_2 composite films with different Ag fractions were prepared through a co-evaporation method. Microstructure analysis shows that the films are composed of amorphous MgF_2 matrix and embedded fcc-Ag nanoparticles. The optical constants and their dispersion of the films, within the wavelength range of 250 - 650 nm, were measured by reflecting spectroscopic ellipsometry. The maximum of the imaginary part ε~″ of the complex dielectric permittivity attributing to the surface plasmon resonance polarization of the Ag nanoparticles in an Ag-MgF_2 film, and the tangent of the phase-shift angle δ resulting from the dielectric loss of the film, occur at λ= 435 nm and λ= 420 nm, respectively. Based on Maxwell-Garnett effective medium theory, the experimentally observed dispersion spectra were reasonably described.

Optical constants of DUV/UV fluoride thin films

High-refractive-index materials LaF3, NdF3, and GdF3 and low-refractive-index materials MgF2, A1F3, and Na3A1F6 single thin films are deposited by a resistive-heating boat at different depositing rates and specific substrate temperatures on single crystal MgF2 substrates. Transmittances of all fluoride thin films are measured using commercial spectrometer in the ambient atmosphere and under vacuum using synchrotron radiation instrument in the wavelength region from 190 to 500 am. The optical constants of these materials are determined by envelope method and iterative algorithm on the basis of transmittance measurements.

Convenient and inexpensive determination of optical constants and film thickness of blended organic thin film

This work presents the study of optical constants and film thickness of blended organic thin films, emphasizing on the modeling procedure with modified genetic algorithm aided by absorption or transmittance spectra of both pure materials and the blends. Taking the blending of copper phthalocyanine(Cu Pc) and fullerene(C60) as an example, a simple, convenient and low-cost method for the determination of the optical constants and film thickness of blended organic thin films was demonstrated. New scheme for optical modeling of blended organic thin film was proposed by introducing peak energies of Cody-Lorentz oscillators of the pure materials, which were determined by fitting the film absorption of pure materials. These oscillators of pure materials could be recognized in the transmittance spectrum of their blends, and were further used as the initial searching ranges in the simulation of blended films. As a result, the constraint bounds of the unknown parameters were significantly reduced and modeling efficiency as well as fitting accuracy was improved. For instance, the fitting of the transmittance curves of blended films with different blending ratios reached reliable results in comparison with extinction coefficients obtained from experiment.

Influence of sputtering pressure on optical constants of a-GaAs_(1-x)N_x thin films

Amorphous GaAsl-xNx （a-GaAsl-xNx） thin films have been deposited at room temperature by a reactive magnetron sputtering technique on glass substrates with different sputtering pressures. The thickness, nitrogen content, carrier concentration and transmittance of the aseposited films were determined experimentally. The influence of sputtering pressure on the optical band gap, refractive index and dispersion parameters （Eo, Ed） has been investigated. An analysis of the absorption coefficient revealed a direct optical transition characterizing the asdeposited films. The refractive index dispersions of the as-deposited a-GaAsl-xNx films fitted well to the Cauchy dispersion relation and the Wemple model.

Determination and Analysis of Optical Constant of Annealed Sn_2Sb_2S_5 Thin Films

The effects of annealing on structural, optical and electrical properties of Sn2Sb2S5 thin films were studied. Sn2Sb2S5 thin films were deposited on no-heated glass substrates by single source vacuum evaporation method. The as- deposited films were annealed in air for 1 h at 100, 200 and 300 ℃. XRD study shows that annealed films are crystallized according to the preferential orientation （602）. Optical measurements show that the thin films have relatively high absorption coefficients in the range of 10s-106 cm-1 in the energy range of 2-3.25 eV. It is also found that Sn2Sb2S5 exhibit two optical direct transitions. The models of Wemple-DiDomenico and Spitzer-Fan were applied for the analysis of the dispersion of the refractive index and the determination of the optical and dielectric constants. The electrical resistivity measurements are recorded, and two activation energy values are determined. The layers annealed at 200 and 300 ℃ exhibit a resistive hysteresis behavior. The properties reported here offer perspective to Sn2SbES5 for its application in many advanced technologies.

Optical constants study of YAG：Ce phosphor layer blended with SiO2 particles by Mie theory for white light-emitting diode package

Optical constants, including scattering coefficient, absorption coefficient, asymmetry parameter and reduced scattering coefficient, of cerium-doped yttrium aluminium garnets （YAG：Ce） phosphor blended with SiO2 particle for white light-emitting diode （LED） packages were calculated based on Mie theory in this study. Calculation processes were presented in detail. Variations of the optical constants with the changes of phosphor weight fraction, dopant weight fraction, phosphor particle radius and SiO2 particle radius, were shown and analyzed separately. It was found that the asymmetry parameter is the intrinsic characteristic of the particles, and the increase of the phosphor weight fraction （or concentration） will lead to the increase of the optical constants. It was also discovered that the increase of the dopant weight fraction will enhance the scattering coefficient, but result in the decreases of the reduced scattering coefficient and the absorption coefficient.

Optical Constant and Electrical Resistivity of Annealed Sn3Sb2S6 Thin Films

In this study,we report the annealing effects on the physical properties of Sn_3Sb_2S_6 thin films.Sn_3Sb_2S_6 thin films were prepared onto non-heated glass substrates via thermal evaporation technique.The as-deposited films were annealed in air for 1 h in the temperature range from 100 to 300 °C.X-ray diffraction results show that the crystallinity of the thin films increased after annealing.The microstructure parameters crystallite size,dislocation density,lattice strain and stacking fault probability were calculated.The optical properties were obtained from the analysis of the experimental recorded transmittance and reflectance spectral data over the wavelength range 300–1800 nm.High absorption coefficient（10~5cm^（-1）） reached to the visible and near-IR spectral range.A decrease in optical band gap from 1.92 to 1.71 e V by increasing the air annealing temperature was observed.Oscillator energy E_o and dispersion energy E_d of the films after annealing were estimated according to the model of Wemple–Di Domenico single oscillator.Spitzer–Fan model was applied to determine the electron free carrier susceptibility and the ratio of carrier concentration to the effective mass.The layers annealed at temperatures 〉150 ℃ undergo abrupt changes in their electrical properties and exhibit a resistive hysteresis behavior.These properties confer to the material interest perspectives for its application in diverse advanced technologies such as photovoltaic applications and optical storage.