Refractive Index Dispersion Curves Research Articles

Structural, optical and electrical properties of F-doped ZnO nanorod semiconductor thin films deposited by sol–gel process

Structural, optical and electrical properties of fluorine-doped ZnO nanostructure semiconductor thin films prepared by sol–gel spin coating method have been investigated. The thin films have polycrystalline structure with a preferential growth along the ZnO (0 0 2) plane. The grain size for the films was found to be in the range of 24–35 nm. Scanning electron microscopy (SEM) images clearly revealed that the 10% F-doped ZnO film was composed of nanorods. Transmittance spectra of the films indicate that the films have high transparency. The optical band gap and Urbach energy of the F-doped ZnO films vary with fluorine doping. The refractive index dispersion curve of 20% F-doped ZnO film obeys the single-oscillator model. The dispersion parameters, E o and E d were found to be 6.104 and 12.045 eV, respectively. For 10% F-doped ZnO film, temperature-dependent conductivity studies revealed that the conduction mechanism is changed from the thermally activated conductivity to the grain boundary scattering with increase in temperature.

Influence of depressed-index outer ring on evanescent tunneling loss in tapered double-cladding fibers

A tapered fiber with a depressed-index outer ring is fabricated and dispersion engineered to generate a widely tunable (1250-1650 nm) fundamental-mode leakage loss with a high cutoff slope (-1.2 dB/nm) and a high attenuation for stop band (>50 dB) by modification of both waveguide and material dispersions. The higher cutoff slope is achieved with a larger cross angle between the two refractive index dispersion curves of the tapered fiber and surrounding optical liquids through the use of depressed-index outer ring structures in double-cladding fibers.

A spectroelectrochemical study on single-oscillator model and optical constants of sulfonated polyaniline film

The optical properties of sulfonated polyaniline (SPAN) thin film prepared by electrochemical method have been investigated. Polychromic behavior of SPAN thin film (transparent yellow-green-dark blue) was observed when the cyclic voltammograms were taken between −0.25 V and +1.90 V (vs. Ag/AgCl, sat.) during the growth of polyaniline film. In situ UV–vis spectra of the polymers-indium tin oxide (ITO) glass electrode were taken during the oxidation of the polymers at different applied potentials. The direct band gap values of SPAN thin film changed from 3.771 eV to 3.874 eV with the applied potentials. From in situ UV–vis spectra, the optical constants such as refractive index and dielectric constant of the SPAN thin film were determined. The important changes in absorption edge, refractive index and the dielectric constant were observed due to the applied potentials. The refractive index dispersion curves of the film obey the single-oscillator model and oscillator parameters changed with the applied potentials. The most significant result of the present work is in situ spectroelectrochemical method, which can be used to modify the optical band gaps and constants.

粉末焼結法による高純度透明シリカガラスの作製と真空紫外透過特性

Transparent silica glasses were obtained by sintering a green compact in diverse atmospheres. The green compacts were fabricated by slip-casting methods for high-purity silica glass powder. The relationships between sintering atmosphere and sintering temperature that result in transparent, sintered silica glass were shown. It was found that the transparency-forming region of sintered silica glass corresponds to a sintering temperature above 1400°C and high-vacuum (10−4 Pa) atmosphere conditions. We investigate the fabrication of transparent and hydroxyl-free silica glass by a powder-sintered method. The sintered silica glass with 10 ppm OH content exhibited the highest transmittance at 157 nm (76% for 2 mm sample thickness). Refractive index dispersion curves in the wavelength region of 0.194μm to 3.584μm are presented for the sintered silica glass by minimum deviation method.

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 (112) 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 3.45eV. 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 Eo and Ed developed by Wemple–DiDomenico were calculated and found to be 3.562 and 12.590eV.

Electrical conductivity, optical and metal–semiconductor contact properties of organic semiconductor based on MEH-PPV/fullerene blend

The electrical conductivity, optical and metal–semiconductor contact properties of the MEH-PPV:C 70 organic semiconductor have been investigated. The electrical conductivity results show that the MEH-PPV:C 70 film is an organic semiconductor. The optical band gap of the film was found to be 2.06 eV and the fundamental absorption edge in the film is formed by the direct allowed transitions. The refractive index dispersion curve of the film obeys the single oscillator model and E d and E o dispersion parameters were found to be 10.61 and 3.89 eV, respectively. The electrical characterization of the ITO/MEH-PPV:C 70 diode have been investigated by current–voltage characteristics. ITO/MEH-PPV:C 70 diode indicates a non-ideal current–voltage behavior with ideality factor n (2.50) and barrier height φ B (0.90 eV) values.

Optical properties of amorphous hydrogenated silicon nitride thin films

This paper presents a study of the optical properties of amorphous hydrogenated silicon nitride (a-Si3N4:H) films under deposition temperature influence. The films were deposited by low-frequency plasma-enhanced chemical vapor deposition at temperatures of 200, 300, and 400°C and 0.6-Torr pressure. The mixture gases were silane (SiH4), ammonia (NH3), and hydrogen (H2). The optical properties of the films samples were obtained by means of the transmittance spectra and from spectroellipsometry measurements. Then, the optical parameters of the films were determined using the Swanepoel, Cauchy, and Sellmeier models. The refractive index dispersion curves were well fitted with both the Cauchy and the Sellmeier theoretical model. The equivalence between the parameters that characterize the two models is established.

A new dioxime ligand and its trinuclear copper(II) complex: Synthesis, characterization and optical properties

The synthesis and characterization of a new dioxime ligand, (H2L), (III) and its trinuclear copper(II) complex, [Cu3L2(H2O)2](ClO4)2, (V) is described. IR spectra show that the ligand acts in a tetradentate manner and coordinates N4 donor groups of H2L to copper(II) ion. The structure of the metal chelate is clarified with the help of elemental analysis, magnetic moment, conductometric and spectroscopic measurements. The optical absorption studies reveal that the transition is direct with band gap energy values are calculated. The optical constants such as refractive index and dielectric constant of the compound were determined. The refractive index dispersion curves of the films obey the single-oscillator model and oscillator parameters. Optical dispersion parameters E0 and Ed developed by Wemple–DiDomenico were calculated.

The effect of FeCl 3 on the optical constants and optical band gap of MBZMA- co-MMA polymer thin films

The effects of the FeCl 3 dopant on the optical constants and optical band gap of the methylbenzyl methacrylate (MBZMA)- co-methyl-methacrylate (MMA) polymer thin films have been investigated by the optical characterization. The optical constants of the thin films are changed with FeCl 3 dopant. The refractive index dispersion curves of the thin films are fitted by Cauchy–Sellmeier model and dispersion parameters ( a 1 and n 0) change with FeCl 3 dopant. The magnitude of the refractive index increases with increasing FeCl 3 dopant. The electric susceptibility of the thin film materials was calculated and the electric susceptibility increases with FeCl 3 content. The optical band gap values of the thin films were determined. The obtained band gap values are decreased with FeCl 3 dopant. The FeCl 3 dopant changes the width of localized states in the optical band gaps of the thin films. The optical band E g of the thin films changes from 3.52 to 3.05 eV with increasing FeCl 3 dopant, while the width of localized states in optical band gap changes from 1101.47 to 596.3 meV. It is concluded that the optical constants and optical band gap of the MBZMA- co-MMA polymer thin films change by the FeCl 3 dopant.

Effects of In, Al and Sn dopants on the structural and optical properties of ZnO thin films

Effect of In, Al and Sn dopants on the optical and structural properties of ZnO thin films have been investigated by X-ray diffraction technique and optical characterization method. X-ray diffraction patterns confirm that the films have polycrystalline nature. The thin films have (0 0 2) as the preferred orientation. This (0 0 2) preferred orientation is due to the minimal surface energy which the hexagonal structure, c-plane to the ZnO crystallites, corresponds to the densest packed plane. The grain size values of the films are found to be 29.0, 35.2 and 39.5 nm for In, Al and Sn doped ZnO thin films, respectively. The optical band gaps of the films were calculated. The absorption edge shifts to the lower wavelengths with In, Al and Sn dopants. The inclusion of dopant into films expands also width of localized states as E UIn > E UAl > E USn. The refractive index dispersion curves obey the single oscillator model. The dispersion parameters and optical constants of the films were determined. These parameters changed with In, Al and Sn dopants.

Electrical conductivity, optical and structural properties of indium-doped ZnO nanofiber thin film deposited by spray pyrolysis method

The indium-doped ZnO nanofiber thin film has been deposited by spray pyrolysis method. Donor level and barrier height energies for the film were determined from the temperature dependence of the conductivity and were found to be E D = 0.026 and E B = 0.55 eV , respectively. The conduction mechanism of the indium-doped ZnO nanofiber thin film was shifted from band conduction including ionized impurity scattering to grain boundary scattering. The optical band gap values of the indium-doped ZnO nanofiber thin film at different annealing temperatures were calculated and were found to be in the range of 3.304–3.245 eV. The direct optical band gap shifted to the lower energy as a consequence of the thermal annealing on film. The Urbach energy of the film was changed with annealing temperature. The refractive index dispersion curve of the film annealed at 500 °C obeys the single oscillator model. The E o and E d dispersion parameters were found to be 4.132 and 12.605 eV, respectively.

The optical properties of ultra-thin films fabricated by layer-by-layer adsorption process depending on dipping time

The layer-by-layer (LBL) self-assembled polyelectrolytes adsorption process is a very slow process. For the fabrication of low-cost application, fabrication time must be decreased. In this work, we measured optical properties of poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) thin films depending on deposition time and added impurities. As dipping time was short from 900 s to 180 s, thickness was almost the same. The reason for this was that adsorption quantity was almost the same between 900 s and 180 s from frequency shift of the quartz crystal microbalance measurement. When dipping time was 900 s and 180 s, the refractive index dispersion curves were different before HCl treatment. However, the refractive index dispersion curves were almost the same after HCl treatment. The total fabrication time of the anti-reflection (AR) film decreased from about 6 h (dipping time 900 s) to 2 h (dipping time 180 s), three times faster. Luminous reflection of the film decreased from 0.5 to 0.2, performing 2.5 times better. We propose a high-performance AR film fabrication method for LBL process by the optimization of the film thickness.

Determination of radial structural properties and spectral dispersion curves of poly(aryl ether ether ketone) fibre

AbstractPoly(aryl ether ether ketone) (PEEK) fibre was studied using a variable wavelength interferometric technique (VAWI). This technique was used in conjunction with a Pluta polarizing interference microscope to determine the spectral dispersion curves of fibre refractive indices and birefringence fibre. The results were used to calculate the dispersion properties of the fibre, ie dispersion and oscillation energies, Cauchy's constants of dispersion relation and the natural wavelength of the fibre. The radial refractive index and birefringence profiles were also determined, taking into consideration the refraction of light beam by the fibre, and some radial structural profiles were then calculated using a ring‐zonal model. The measurements of these radial profiles are required for optimizing the spinning and processing of manufactured textile fibres. The Fraunhofer diffraction pattern of a He–Ne laser beam was used to determine the average thickness of the fibre. Microinterferograms are presented for illustration. Copyright © 2003 Society of Chemical Industry

Polymeric multilayers for integration into photonic devices

Multilayer structures of two commercial polymers, poly(9-vinylcarbazole) and poly(vinyl alcohol), have been deposited on silica glass substrates by spin-coating. A study of the transmittance of single layers provides a determination of the refractive index and absorption coefficient dispersion curves for those materials, in the range 400–1100 nm. This allows an accurate modelling of the transmittance spectra for structures with several pairs of layers. The good agreement found between simulation and measurements confirms thickness uniformity achieved along the fabrication direction, and a good quality of surfaces and interfaces. The high spectral sensitivity upon variations of thickness opens the way to perform easy and inexpensive filters and sensors, including the integration into other active devices.

Effect of compositionally graded configuration on the optical properties of BaxSr1−xTiO3 thin films derived from a solution deposition route

BaxSr1−xTiO3 (BST) thin films with gradients in composition were deposited on Si(100) and fused quartz substrates by a modified sol–gel technique. A special heating treatment procedure was employed in this study to form the uniform composition gradients at below 750°C. XRD diffraction clearly shows that the perovskite structure of the graded films formed around 730°C. The (200) peaks of the BST (10/90), BST (50/50), and the graded BST films were analyzed, the peak from the graded film is broad and centered at 46.3°. The optical band-gap energy and the absorption coefficient were determined at room temperature in the wavelength range of 200–900nm from spectrophotometer measurements of the transmittance. The optical band-gap energy (Egap) decreases from 4.29 to 3.68eV with an increase of annealing temperatures from 350 to 730°C. The refractive index dispersion curves rise rapidly toward shorter wavelengths and a smaller variation of the refractive index was found in graded film than the single-composition samples. There are two distinct absorption bands found about 3.15 and 2.78eV corresponding to the impurities absorption.

Extension of Phase Modulation Ellipsometry to Measure Refractive Indices of Liquid Crystals

We present an extension of phase modulation ellipsometry to measure refractive indices in the visible and near infrared spectrum of multilayer and anisotropic structures, in particular liquid crystal cells, with arbitrary orientation of optical axis. An original software code was derived to process ellipsometer measurements, based on Jones formalism to express sinusoidal components of detected optical intensity reflected by a sample for different angles of the polariser and analyser respect to the sample orientation. In this way it is possible to obtain independent equations whose unknowns are the reflection matrix coefficients. Since it is possible only to obtain values of detected intensity and reflection coefficients given the refractive indices of the sample by using Berreman formalism, an algorithm has been developed to search best refractive index values which fit intensity measurements at each wavelength. Dispersion curves of refractive indices of 5CB have been obtained with accuracy of about 1%.

Relationship between Coloration of Polypropylene Gels and Wavelength Dispersions of Refractive Indices of Components

The coloration of polypropylene gel was investigated by light scattering theory, in which wavelength dispersion of refractive indices for polypropylene and solvent is particularly noted. The coloration and thermochromic phenomena of polypropylene gel were concluded to be caused by the selective light scattering from size-controlled polypropylene networks with a solvent, that have the same refractive index as that of polypropylene at a certain wavelength in the visible region, but with degree of wavelength dispersion larger than that of polypropylene, since maximum transmittance wavelength in transmittance spectra of the gels obtained experimentally is in fair agreement with that estimated from wavelength dispersion curves of refractive indices of solvent and polypropylene obtained from independent experiments. The change of the transmittance spectra at a definite temperature with the elapse of time reflects change of the refractive index in the vicinity of the interface of polypropylene network in the gel prepared under confinement and change of the interface structure of the polypropylene networks in the gel.

Electron–hole pairs binding energies in quantum wires and quantum dots

In a previous paper, we have calculated the binding energies for excitons in quantum wells [A. Simões Baptista, H. Santos, Microelectron. Eng. 43–44 (1998) 481–487]. This was done by solving simultaneously the Schrödinger and the Poisson equations, which determine the interaction potential, both in a fractional dimensional space [F.H. Stillinger, J. Math. Phys. 18 (6) (1977) 1224–1234]. Using the same mathematical framework, we now analyse the so-called one-dimensional and zero-dimensional structures. The results we obtain are essential for simulations of optical-electronic devices that use the optical absorption and the refractive index dispersion curves.

Electronic Bandgap and Refractive Index Dispersion of Single Crystalline Epitaxial ZnGeN2

AbstractThe electronic band gap of single crystalline ZnGeN2 epitaxial layer grown on sapphire substrate by metal organic chemical vapor deposition has been measured by optical transmission and room temperature photoluminescence. The band gap energy is 2.99eV at room temperature, and the band gap is a direct transition type. The interference oscillations of the transmission spectra together with rutile prism coupling measurements have been used to determine the r fractive index and the dispersion characteristics of the single crystal ZnGeN2 below the band gap energy. The rutile prism coupling measurement displays the wave guide modes of the film at 6 2.8nm wavelength of the He-Ne laser, enabling determination of the film thickness and refractive index precisely at the wavelength. The refractive index of ZnGeN2 crystal is 2.35 at 6328Å wavelength. The measured refractive index dispersion curve can be fitted with the first-order Sellmeier equation n2(λ) = A + λ2/(λ2-B), using fitting parameters A=4.3 1, B=0.076.

Refractive index and material dispersions of multi-component oxide glasses

Refractive index dispersion curves in the wavelength region of 0.40 to 5.03 μm are presented for multi-component oxide glass systems: borate, silicate, aluminate, germanate, tellurite, antimonate and heavy metal gallate. The material dispersion was determined using the refractive index data. Reflection spectra in the ultraviolet and infrared regions were measured to investigate the effects of electronic transitions and lattice vibrations on the material dispersion. Thallium tellurite, thallium antimonate and lead gallate glasses exhibit zero material dispersion wavelengths (ZMDWs) over 2.4 μm. The factors affecting the ZMDW are discussed.