Effect of cycle numbers on the structural,linear and nonlinear optical properties in Fe2O3 thin films deposited by SILAR method

Fe₂O₃ thin films were deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrates at different cycle numbers to investigate structural, linear and nonlinear optical properties. X-Ray Diffraction (XRD) analysis revealed that the Fe₂O₃ thin films have a non-crystalline nature. The morphological properties of the films were investigated by Field Emission-Scanning Electron Microscopy (FE-SEM) and the results show that the films’ surfaces are porous. The linear and nonlinear optical parameters were evaluated and analyzed by using transmittance and absorbance measurements. For these measurements, UV–Vis spectroscopy at room temperature was used. The refractive index values were calculated in the range of 1.45–3.23 for visible region (400–700 nm). Obtained results reveal that direct optical band gap changed between 2.62 and 2.68 eV and indirect optical band gap changed between 1.67 and 1.77 eV. Additionally, optical electronegativity, optical dielectric constants, surface and volume energy loss functions, nonlinear refractive index, linear optical susceptibility, third-order nonlinear optical susceptibility, optical and electrical conductivity, and loss tangent values were calculated and discussed in detail. It was found that each parameter studied is dependent on the cycle numbers. Also, it can be stated that Fe₂O₃ thin films are promising candidate for solar cells and optoelectronic device technology.     

Influence of MgO on structure and optical properties of alumino-lithium-phosphate glasses

MgO doped lithium alumino phosphate glasses (PLA: P₂O₅+Li₂O+Al₂O₃+MgO) were prepared by melt quenching technique. Raman spectra display three significant peaks at 698, 1164 and 1383 cm⁻¹ attributed to: symmetric stretching vibrations of the bridging oxygen (BO) in the P–O–P chains, symmetric stretching vibrations of the PO₂ groups, and the asymmetric vibrations vas(PO₂) of the non-bridging oxygen (NBO) atoms, respectively. Also, the density, molar volumes and ion concentration have been discussed and correlated with the structural changes within the glassy matrix. Some optical constants such as refractive index and dispersion parameters (E_o: single-oscillator energy and E_d: dispersive energy) of the glasses were determined. Finally, the values of the optical band gap for direct and indirect allowed transitions have been determined from the absorption edge studies. It is deduced that the values of E_opt increase with increasing MgO content. It was assigned to structural changes induced from the formation of non-bridging oxygen. The Urbach energy (ΔE) was found to decrease from 0.578 to 0.339 eV with increasing MgO content from 0.5 to 2 mol.     

Atomic and electronic structures of lutetium oxide Lu2O3

The chemical composition, electronic structure, structure, and physical properties a lutetium oxide Lu₂O₃ film are studied by X-ray photoelectron spectroscopy, ellipsometry, and X-ray absorption spectroscopy. The short-range order in Lu₂O₃ is found to correspond to its cubic modification. The binding energies of the 1s and 2p levels of oxygen and the 4d _5/2 and 4f _7/2 levels of lutetium are 529.2, 5.0 and 7.4, 195.9 eV, respectively. The energy gap determined from the electron energy loss spectrum of the film is 5.9 eV. The electron energy loss spectra have two peaks at 17.4 and 22.0 eV, which can be attributed to the excitation of bulk plasma oscillations. The dispersion of the refractive index is measured by spectral ellipsometry. The refractive index is shown to increase from 1.82 at 1.5 eV to 2.18 at 5.0 eV, and the high-frequency permittivity of Lu₂O₃ is 3.31.     

Optical characteristics of amorphous V2O5 thin films colored by an excimer laser

The V₂O₅ films were prepared by an RF sputtering method, and the amorphous films were colored by an UV excimer laser. The crystallinity of the as-grown V₂O₅ film was degenerated greatly by laser irradiation, as determined by X-ray diffraction (XRD) and Raman studies. The transmission and complex refractive index spectra of the V₂O₅ film were affected by variations in the microstructure, including the surface morphology, crystalline structure, and substoichiometry with an oxygen deficiency. Considerable emissions due to oxygen vacancies and band transition of photoluminescence (PL) peaks were observed, and the peaks were significantly changed after laser irradiation. The variations in the optical properties in both films may be attributed to oxygen deficiency induced by laser irradiation.     

Optical properties of Tl2In2Se3S layered single crystals

The optical properties of Tl₂In₂Se₃S layered single crystals have been analyzed using transmission and reflection measurements in the wavelength region between 500 and 1100 nm. The optical indirect transitions with a band gap energy of 1.96 eV and direct transitions with a band gap energy of 2.16 eV were determined from analysis of absorption data at room temperature. Dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single-effective-oscillator model. The refractive index dispersion parameters – oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index – were found to be 4.67 eV, 45.35 eV, 1.38 × 10¹⁴ m ^{? 2} and 3.27, respectively. Transmission measurements were also performed in the temperature range 10–300 K. As a result of temperature-dependent transmission measurements, the rate of change in the indirect band gap with temperature, i.e. γ = ?5.6 × 10^?4 eV/K, and the absolute zero value of the band gap energy, E _gi(0) = 2.09 eV, were obtained.     

Structural, morphological and optical properties of CuAlS2 films deposited by spray pyrolysis method

The structural, morphological and optical properties of CuAlS₂ films deposited by spray pyrolysis method have been investigated. CuAlS₂ in the form of films is prepared at different deposition conditions by a simple and economical spray pyrolysis method. The structural, surface morphology and optical properties of the films were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and absorbance spectra, respectively. The films were polycrystalline, crystallized in a tetragonal structure, and are preferentially orientated along the (1 1 2) direction. Grain size values, dislocation density, and d% error of CuAlS₂ films were calculated. The optical band gap of the CuAlS₂ film was found to be 3.45 eV. The optical constants such as refractive index, extinction coefficient and dielectric constants of the CuAlS₂ film were determined. The refractive index dispersion curve of the film obeys the single oscillator model. Optical dispersion parameters E_o and E_d developed by Wemple-DiDomenico were calculated and found to be 3.562 and 12.590 eV.     

基于透射光谱确定溶胶凝胶ZrO2薄膜的光学常数

基于溶胶凝胶ZrO₂薄膜的紫外/可见/近红外透射实验光谱,采用Swanepoel方法结合Wemple-DiDomenico色散模型,方便地导出了ZrO₂薄膜在200—1200nm波长范围内的光学常数,包括折射率、色散常数、膜层厚度、吸收系数及能量带隙.研究发现,溶胶凝胶ZrO₂薄膜具有高折射率(1.63—1.93,测试波长为632.8nm)、低吸收和直接能量带隙(4.97—5.63eV) 等光学特性,而且其光学常数对薄膜制备过程中的重要工艺 关键词： 光学常数 Swanepoel方法 2薄膜')" href="#">ZrO₂薄膜 热处理     

Effect of annealing on structure and optical properties of Ga5Se95 films

To investigate the effect of annealing on the structural and optical properties of a binary compound Ga₅Se₉₅, thin films of Ga₅Se₉₅ have been deposited on quartz substrates at room temperature by the thermal evaporation technique. X-ray diffraction patterns showed that the films before and after annealing at 573 K have polycrystalline texture and exhibit tetragonal structure. The dependences of the optical constants, the refractive index n and extinction coefficient k were studied in the spectral range of 200 nm to 2500 nm. The normal dispersion of the refractive index of the films could be described using the Wemple–DiDomenco single-oscillator model. Analysis of absorption index data reveals that as-deposited Ga₅Se₉₅ films has indirect transitions with optical energy gap of 1.685 eV.     

Gamma irradiation effects on structural and optical properties of amorphous and crystalline Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> thin films

The structural and optical properties of RF sputtered Nb₂O₅ thin films are studied before and after gamma irradiation. The films are subjected to structural and surface morphological analyses by using X-ray (XRD) and field emission scanning electron microscope techniques. In the wavelength range of 300–2000 nm, the optical parameters for amorphous and crystalline Nb₂O₅ thin films are estimated at differently exposed γ-irradiation doses (0, 50, 100 and 200 kGy). The optical constants, such as optical energy band gap, absorption coefficient, refractive index and oscillators parameters of amorphous and crystalline Nb₂O₅ thin films are calculated. The optical band gaps of γ-irradiated amorphous and crystalline Nb₂O₅ thin films are determined. In the non-absorbing region, the real part of the refractive index of amorphous and crystalline Nb₂O₅ thin films slightly increases with the increase in the exposed γ-irradiation dose.     

Structural and optical properties of Bi3.25Nd0.75Ti3O12 ferroelectric thin films

Ferroelectric Bi_3.25Nd_0.75Ti₃O₁₂ (BNT) thin films were grown on (111)Pt/Ti/SiO₂/Si substrates by a chemical solution method. The films were composed of large rod-like grains. XRD and Raman spectroscopy measurements showed they were polycrystalline perovskite structure with a good crystallinity. Pt/BNT/Pt capacitors had been fabricated and showed good ferroelectricity. The optical constants (n, k) of BNT thin films in the wavelength ranges of 0.2–1.7 μm and 2.5–11.4 μm were obtained by spectroscopic ellipsometry measurements. The dispersion of the refractive index in the interband transition region followed the single electronic oscillator model. The optical band gap was found to be about 3.61 eV. PACS 77.84.-s; 78.20.Ci; 77.80.-e     

Synthesis,structural and ellipsometric evaluation of oxygen-deficient and nearly stoichiometric zinc oxide and indium oxide nanowires/nanoparticles

Oxygen-deficient (OD) and nearly stoichiometric (NST) ZnO and In₂O₃ nanowires/nanoparticles were synthesized by chemical vapor deposition on Au-coated silicon substrates. The OD ZnO and OD In₂O₃ nanowires were synthesized at 750 and 950°C, respectively, using Ar flow at ambient pressure. A mixture of flowing Ar and O₂ was used for synthesizing NST ZnO nanowires and NST In₂O₃ nanoparticles. Growth of OD ZnO nanowires and NST In₂O₃ nanoparticles was found to be via a vapor–solid (VS) mechanism and the growth of NST ZnO nanowires was via a vapor–liquid–solid mechanism (VLS). However, it was uncertain whether the growth of OD In₂O₃ nanowires was via a VS or VLS mechanism. The optical constants, thickness and surface roughness of the prepared nanostructured films were determined by spectroscopic ellipsometry measurements. A three-layered model was used to fit the calculated data to the experimental ellipsometric spectra. The refractive index of OD ZnO, NST ZnO nanowires and NST In₂O₃ nanoparticles films displayed normal dispersion behavior. The calculated optical band gap values for OD ZnO, NST ZnO, OD In₂O₃ nanowires and NST In₂O₃ nanoparticles films were 3.03, 3.55, 2.81 and 3.52?eV, respectively.     

基于透射光谱确定溅射Al2O3薄膜的光学（已撤稿）

基于反应磁控溅射Al₂O₃薄膜的紫外—可见—近红外透射实验光谱,采用Swanepoel方法结合Wemple-DiDomenico色散模型,方便地导出了Al₂O₃薄膜在200—1100 nm波长范围内的光学常数,包括折射率、色散常数、膜层厚度、吸收系数及能量带隙.研究发现反应磁控溅射Al₂O₃薄膜具有高折射率(1.556— 1.76,测试波长为550 nm)、低吸收和直接能量带隙(3.91—4.20 eV)等光学特性,而且其光学常数对薄膜制备过程中的重要工艺参数——膜层后处理温度表现出强烈的依赖性.此外,在膜层的弱吸收和中等吸收光谱区域内,计算得到的折射率色散曲线与分光光度法的测试结果基本符合,说明本实验中所建立的计算方法在确定反应磁控溅射Al₂O₃薄膜光学常数方面的可靠性. 关键词： 光学常数 Swanepoel方法 2O₃薄膜')" href="#">Al₂O₃薄膜 热处理     

Investigation of the optoelectronic properties of columbite ZnNb2O6 crystal

A high-quality ZnNb₂O₆ single-crystal grown by optical floating zone method has been used as a research prototype to analyze the optoelectronic parameters by measuring the absorption coefficient and transmittance spectra along the b-axis from 200 nm to 1000 nm at room temperature. The optical interband transitions of ZnNb₂O₆ have been determined as a direct transition with a band gap of 3.84 eV. The refractive index, extinction coefficient, and real and imaginary parts of the complex dielectric constants as functions of the wavelength for ZnNb₂O₆ crystal are obtained from the measured absorption coefficients and transmittance spectra. In the Urbach tail of 3.16–3.60 eV, the validity of the Cauchy–Sellmeier equation has also been evaluated. Using the single effective oscillator model, the oscillator energy E_o is found to be 4.77 eV. The dispersion energy E_d is 26.88 eV and ZnNb₂O₆ crystal takes an ionic value.     

Refractive index behavior of SiO2-P2O5 glass in optical fiber application

The refractive index of SiO₂-P₂O₅ glass prepared by a modified chemical vapor deposition method is measured using an interference microscope. It is found that the refractive index in bulk form increases linearly at 9.5×10^-4 (mol.%)^-1 as the P₂O₅ concentration increases. It is also found that quenching at extremely high speed reduces the refractive index over 2 mol.% P₂O₅. The wavelength dispersion of the refractive index dn/dλ is constant up to 5 mol.% P₂O₅ producing a refractive index difference of 5×10^-3 compared with fused silica. Consequently, this glass materials is thought to be suitable for wide band-width optical fiber applications.     

射频磁控反应溅射制备的Ag2O薄膜的椭圆偏振光谱研究

Ag₂O薄膜在新型超高存储密度光盘和磁光盘方面具有潜在的应用前景.利用射频磁控反应溅射技术, 通过调节衬底温度在沉积气压为0.2 Pa、氧氩比为2:3的条件下制备了一系列Ag₂O 薄膜.利用通用振子模型(包括1个Tauc-Lorentz振子和2个Lorentz 振子)拟合了薄膜的椭圆偏振光谱.在1.5-3.5 eV能量区间,薄膜的折射率在2.2-2.7之间, 消光系数在0.3-0.9之间. 在3.5-4.5 eV能量区间,薄膜呈现了明显的反常色散,揭示Ag₂O薄膜的等离子体振荡频率在 3.5-4.5 eV之间. 随着衬底温度的升高,薄膜的光学吸收边总体上发生了红移, 该红移归结于薄膜晶格微观应变随衬底温度的升高而增大. Ag₂O薄膜的光学常数表现出典型的介质材料特性.     

Thickness dependent supercapacitor behaviour of sol-gel spin coated nanostructured vanadium pentoxide thin films

Vanadium pentoxide thin films of various thicknesses have been prepared by sol-gel spin coating method on glass and conducting substrates. X-ray diffraction analysis reveals crystalline nature for the 6–12 layered films (170–310?nm). The crystalline films indicate a preferential orientation of the crystallites along the (200) plane. FTIR studies of the V₂O₅ xerogel show the presence of V–O–V and V=?O bond confirming the formation of V₂O_5. The scanning electron microscope images reveal formation of nanostructures in the 6–12 layered films. Optical absorption studies indicate a band gap of 2.2–2.5?eV. Pseudocapacitance behaviour of the V₂O₅ films was studied using cyclic voltammetric technique and impedance analysis. V₂O₅ films of thickness 202?nm (8 layers) exhibit a specific capacitance of 346?F/g at a scan rate of 5?mV/s.     

Spectroscopic study of nanocrystalline V2O5·nH2O films doped with Li ions

Optical properties of nanocrystalline, Li_xV₂O₅·nH₂O films (0<x<22 mol%), are explored in the present work. These films have been produced by the sol–gel technique (colloidal route), which was used for the preparation of high purity and homogeneity films. Optical measurements were carried out using a double-beam spectrophotometer. The optical constants such as refractive index n, the extinction coefficient k, absorption coefficient α, and optical band gap of the films material have been evaluated. The optical absorption coefficient was calculated from the measured normal reflectance, R, and transmittance, T, spectra. The optical spectra of all samples exhibited two distinct regions: at high energy, which suggests a direct forbidden transition with optical gap ranging from 1.75 to 2.0 eV and increases with increase in Li-content. On the other hand a second low-energy band suggests a direct allowed transition with optical gap ranging from 0.40 to 0.42 eV. The width of the localized states (band tail) E_e was also estimated for all samples. Additional calculations applying the real part of the optical dielectric function led to the evaluation of the charge carrier concentration and their effective mass.     

Influence of γ-irradiation on the optical and electrical properties of Se(0.85) Te(0.15) films

Abstract

Se_(0.85) Te_(0.15) films were prepared by thermal evaporation under vacuum on glass substrate. The optical and electrical properties of as deposited and irradiated Se_(0.85) Te_(0.15) films with different γ-doses are reported.

The optical constants (absorption coefficient (α), extinction coefficient (k), refractive index (n) and dielectric constants (?, ?) of unirradiated and irradiated films were calculated. The value of allowed direct optical energy gap of Se_(0.85) Te_(0.15) films increased from 1.47 eV. to 1.72 eV. with increasing the γ-doses to 2.5 Mrad. The irradiated films have lower resistivity than those as deposited films (unirradiated). The activation energy (ΔE) increases from 0.72 eV. to 0.86 eV. with increasing γ-doses to 2.5 Mrad.     

Optical properties of V6O13 single crystals in the metallic and the semiconducting phase

The optical reflection of V₆O₁₃ single crystals has been studied between 0.06 and 3 eV at temperatures both below and above the semiconductor-to-metal transition temperature (T_t?150K). In addition to the metallic reflection, present only at T>T_t, discrete resonances are observed in both phases: four with polarization E//b and three with E⊥b.The results of a dispersion analysis using classical-oscillator and Drude terms are presented. The resonances above 2 eV are attributed to oxygen 2p - vanadium 3d interband transitions. The maxima at the lower energies are interpreted as transitions between vanadium 3d subbands.     

Thickness dependent optical dispersion parameters and nonlinear optical properties of nanostructured Cr doped CdO thin films

Cr doped CdO thin films were deposited on glass substrates by reactive DC magnetron sputtering with varying film thickness from 250 to 400 nm. XRD studies reveal that the films exhibit cubic structure with preferred orientation along the (2 0 0) plane. The optical transmittance of the films decreases from 92 to 72%, whereas the optical energy band gap of the films decreased from 2.88 to 2.78 eV with increasing film thickness. The Wemple–DiDomenico single oscillator model has been used to evaluate the optical dispersion parameters such as dispersion energy (E_d), oscillator energy (E_o), static refractive index (n_o) and high frequency dielectric constant (ε_∞). The nonlinear optical parameters such as optical susceptibility (χ⁽¹⁾), third order nonlinear optical susceptibility (χ⁽³⁾) and nonlinear refractive index (n₂) of the films were also determined.