Optical Properties of Vanadium Pentoxide Thin Films Prepared by Thermal Evaporation Method (original) (raw)
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Optical and structural studies of vanadium pentoxide thin films
Nanosystems: Physics, Chemistry, Mathematics, 2016
Recently, transition metal oxides like Vanadium pentoxide have become a subject of intensive studies. The particular physical and chemical properties of these materials allow a wide range of practical applications such as electrochromic devices, cathode electrodes for lithium batteries, humidity sensors. The V 2 O 5 film was prepared by an electrodeposition technique. The structural and optical properties were studied by X-Ray Diffraction (XRD), scanning electron microscopy (SEM), UV-Visible and Fourier Transform Infrared Spectroscopy (FT-IR). XRD spectra recorded has been observed and compared with the JCPDS values. SEM images showed very smooth surface morphology and the elemental compositions of the film were confirmed by EDAX. The transmittance of the V 2 O 5 films showed 75 % at 425 nm for the as-deposited substrate. The energy band gap of the films was found to be 2.45 eV and the band assignments of the V 2 O 5 film are comparable with the reported values.
Effect of solution molarity on the characteristics of vanadium pentoxide thin film
Applied Surface Science, 2006
Vanadium pentoxide (V 2 O 5) thin films have been prepared by spray pyrolysis technique. The influence of solution molarity on the characteristics of the V 2 O 5 has been investigated. X-ray diffraction analysis (XRD) showed that, the films deposited at !0.1 M were orthorhombic structure with a preferential orientation along h0 0 1i direction. Moreover, the crystallinity was improved by increasing solution molarity. The microstructure parameters have been evaluated by using a single order Voigt profile method. The optical band gaps, determined by using Tauc plot, have been found to be 2.50 AE 0.02 and 2.33 AE 0.02 eV for the direct and indirect allowed transition, respectively. Also the complex optical constants for the wavelength range 300-2500 nm are reported. At room temperature, the dark conductivity as a function of solution molarity showed the range of 5.74 Â 10 À2 AE 0.03 to 3.36 Â 10 À1 AE 0.02 V À1 cm À1. While at high temperature, the behaviour of electrical conductivity dominated by grain boundaries. The values of activation energy and potential barrier height were 0.156 AE 0.011 and 0.263 AE 0.012 eV, respectively.
Study on some optical properties of thermally evaporated V 2O 5 films
Vacuum, 1999
O "lms have been thermally evaporated on unheated glass substrate with di!erent "lm thicknesses using high-purity V O powder. The structural characteristics of the V O powder as well as a sample of 181 nm thickness were investigated using X-ray di!raction. The optical properties of the prepared "lms were studied by transmittance and re#ectance measurements, and the integrated transmittance (¹ 34 ,¹ 4 ,¹ ,'0 ) and absorptance (A 34 , A 4 , A ,'0 ) in the UV, VIS and NIR regions were calculated. They were found to be strongly a!ected by the "lm thickness. The dependence of absorption coe$cient and the refractive index on wavelength for the prepared sample was also reported.
International Journal of Applied Science and Technology
Vanadium pentoxide (V 2 O 5) thin films have been prepared by Sol-Gel technique. The fluid resin which was prepared by dissolving V 2 O 5 powder (99.6%) in H 2 O 2 was spin coated on a glass substrate at room temperature. The effect of preparation conditions, such as spin speed and acceleration, on the film thickness has been investigated. Speed was found to be the most affecting parameter on the film thickness. Transmittance and reflectance spectra were made at normal incidence on these films in the range of 350-900 nm. SCOUT program was used to find out the thickness of all samples. In the region of the fundamental absorption edge, the absorption coefficient was calculated directly from the experimental transmittance and reflectance data using a formula that is nearly valid for non-uniform inhomogeneous films. Moreover, the band-gap energy was found to be around 2.3 eV. The refractive index of the films was calculated using PUMA code which is based on a certain fitting procedure for transmittance spectra according to Swanepoel formula. All results were in good agreement with those found in literature.
On the Optical Properties of Thin‐Film Vanadium Dioxide from the Visible to the Far Infrared
Annalen der Physik, 2019
The insulator-to-metal transition (IMT) in vanadium dioxide (VO2) can enable a variety of optics applications, including switching and modulation, optical limiting, and tuning of optical resonators. Despite the widespread interest in optics, the optical properties of VO2 across its IMT are scattered throughout the literature, and are not available in some wavelength regions. We characterized the complex refractive index of VO2 thin films across the IMT for free-space wavelengths from 300 nm to 30 µm, using broadband spectroscopic ellipsometry, reflection spectroscopy, and the application of effective-medium theory. We studied VO2 thin films of different thickness, on two different substrates (silicon and sapphire), and grown using different synthesis methods (sputtering and sol gel). While there are differences in the optical properties of VO2 synthesized under different conditions, they are relatively minor compared to the change resulting from the IMT, most notably in the ~2-11 µm range where the insulating phase of VO2 has relatively low optical loss. We found that the macroscopic optical properties of VO2 are much more robust to sample-to-sample variation compared to the electrical properties, making the refractive-index datasets from this article broadly useful for modeling and design of VO2-based optical and optoelectronic components.
Vanadium pentoxide (V 2 O 5 ) thin films were deposited by spray pyrolysis technique. Precursor solution was prepared in two ways:(i) ammonium meta-vanadate (AMV) was dissolved in distilled water to prepare 0.1 M precursor solution; (ii) required amount of AMV was taken in a beaker and a few ml of concentrated nitric acid was added to it, which was then heated and maintained at 60 º C for 10 minutes. After naturally cooling the solution to the room temperature, required amount of distilled water was added to this to prepare 0.1 M aqueous solution. Fluorine doped vanadium oxide films were prepared adding ammonium fluoride of 5 wt. % and 15 wt. % in separate solution. These precursor solutions were used to deposit V 2 O 5 and fluorine doped V 2 O 5 films on the microslide glass substrate at 400°C. X-ray diffraction results show that the deposited films are in the mixed phase of V 2 O 5 and VO 2 .Increasing the concentration of ammonium fluoride in the precursor solution suppresses the growth of VO 2 phaseand effectively modifies the surface morphology of the prepared thin films. The average visible transmittance of theVanadium oxide films in the wavelength range of 500-800 nm increases due to fluorine doping. Further, fluorine doping in V 2 O 5 film does not alter the band-gap energy appreciably.
XPS and optical properties of sol-gel processed vanadium pentoxide films
Lithuanian Journal of Physics, 2008
Vanadium pentoxide xerogels were prepared by using sol-gel technology. As-prepared samples of xerogels were heated up to 580 K in order to remove the bonded water. The chemical composition of xerogel samples and thin films has been studied by X-ray photoelectron spectroscopy (XPS). XPS data have shown that pure V2O5 compound was formed. After thermal treatment, in the XPS spectra the main changes occurred in the vicinity of the O 1s peak due to the removal of water from xerogel. The optical properties of V2O5 films were studied by optical transmission and spectroscopic ellipsometry. Ellipsometric measurements have been carried out in the spectral range of 0.5-5.0 eV at 300 K. The changes in the optical spectra were observed after thermal annealing of as-prepared xerogel samples. The obtained data have shown that thermal treatment of V2O5 thin films has strongly influenced the optical transitions involving both localized and higher-lying conduction bands.
Journal of Physics: Conference Series, 2018
The sol-gel and spin-coating methods were used for deposition of thin transparent V 2 O 5 films on optical glass substrates and silicon wafers. Different synthesis and deposition conditions, including synthesis temperatures and post-deposition annealing, were used aiming at obtaining transparent films with high refractive index and good optical quality. The surface morphology and structure of the films were studied by SEM and XRD. The optical properties (refractive index, extinction coefficient and optical band gap) and thickness of the V 2 O 5 films were determined from their transmittance and reflectance spectra. The potential application of the films as building blocks of optical sensors was demonstrated by preparation of multilayered structures comprising both V 2 O 5 and BEA-type zeolite films and testing their response towards acetone vapors.
Thermal annealing effect on the crystallization and optical dispersion of sprayed V2O5 thin films
Journal of Physics and Chemistry of Solids, 2010
Polycrystalline vanadium pentoxide (V 2 O 5) thin films have been deposited by spray pyrolysis technique on preheated glass substrate. The influence of thermal annealing on the crystallization of V 2 O 5 has been investigated. X-ray diffraction analysis (XRD) revealed that the films deposited at T sub =350 1C were orthorhombic structures with a preferential orientation along /0 0 1S direction. Moreover, the degree of crystallinity was improved by thermal annealing. Optical properties of these samples were studied by spectrophotometer in the wavelength range 300-2500 nm. Some of the important optical absorptions such as optical dispersion energies E o and E d , dielectric constant e, ratio between number of charge carriers and effective mass N/m n , wavelength of single oscillator l 0 , plasma frequency o p , single resonant frequency o 0 and the average of oscillator strength S o , have been evaluated. In the annealing process, the dielectric properties have weak dependencies of film thickness and annealing time. Furthermore, a value of carrier concentration was obtained of 3.02 Â 10 25 m À 3 for the as-deposited film and slight changes with annealing time.