Tungsten Trioxide Thin Films Research Articles

Durability improvement of electrochromic WO3 thin films by deposition of an ultra-thin Al2O3 layer via atomic layer deposition

Introduction of an ultra-thin Al2O3 protective layer via atomic layer deposition (ALD) significantly enhances the durability and performance of amorphous tungsten trioxide (a-WO3) thin films for electrochromic devices. The Al2O3 layer, despite being less than 4 nm thick, effectively suppresses the dissolution of WO3 that typically occurs through hydration reactions forming WO3·H2O and tungstic acid (H2WO4). XRD and XPS analyses confirmed the presence of Al2O3 and its minimal impact on the amorphous structure of WO3 thin films. Optical transmittance measurements showed that the Al2O3-protected a-WO3 thin films maintained a higher transmittance modulation (ΔT) compared to bare a-WO3 thin films, with the ALD30 sample retaining 87.9 % of its initial transmittance modulation after 1000 cycles, in contrast to the rapid degradation observed in unprotected films. Microstructural analysis revealed significantly fewer surface cracks and reduced thickness loss in Al2O3-coated films after 100 cycles. Additionally, ICP-MS analysis indicated a much lower W concentration in the electrolyte for Al2O3-protected samples, confirming reduced dissolution.

Determination of the optical properties of tungsten trioxide thin film using the transfer matrix method

Determination of the optical properties of tungsten trioxide thin film using the transfer matrix method

Anomalous photo-thermoelectric effects of platinum and tungsten trioxide bilayers

We attempted to deposit a platinum (Pt) layer onto a tungsten trioxide (WO3) thin film (Pt/WO3). The Pt layer deposited on WO3 was oxidized by calcining Pt/WO3 in air to form PtOx/WO3. An n-type anomalous photo-thermoelectric (photo-TE) effect was confirmed for Pt/WO3 and Pt/HyWO3−x. HyWO3−x is a protonated WO3 after the gaschromic (GC) reaction of WO3 in Pt/WO3. The anomalous photo-TE effect was that both the electrical conductivity (σphoto) and the absolute value of the Seebeck coefficient (Sphoto) increased under UV light or visible light irradiation. After stopping the irradiation, σphoto and Sphoto decreased. In contrast, an n-type normal photo-TE effect was observed for PtOx/HyWO3−x after the GC reaction of PtOx/WO3, in which σphoto increased and the absolute value of Sphoto decreased under ultraviolet (UV) light irradiation, and vice versa after stopping the irradiation. These findings indicate that Pt was responsible for the anomalous photo-TE effect due to the electron accumulation capability of Pt, to which electrons were transferred from the conduction band of HyWO3−x. In contrast, electrons could not energetically transfer from HyWO3−x to PtO2, which existed in PtOx particles at the surface. Therefore, PtOx/HyWO3−x behaved similar to sole HyWO3−x, indicating the normal photo-TE effect.

A Study Using Crystal Transport of Ions in Matter When Boron Ion is Implanted into a Tungsten Trioxide Thin Film

A Study Using Crystal Transport of Ions in Matter When Boron Ion is Implanted into a Tungsten Trioxide Thin Film

Effect of In Situ Heating on the Growth and Electrochromic Properties of Tungsten Trioxide Thin Films.

Electrochromism has emerged as a pivotal technology in the pursuit of energy efficiency and environmental sustainability, spurring significant research efforts aimed at the creation of advanced electrochromic devices. Most electrochromic materials are used for smart window applications. However, current electrochromic materials have been applied to new energy vehicles, cell phone back covers, AR glasses, and so on. More application scenarios put forward more requirements for the color of the colored states. Choosing the right color change in the application will be the trend in the future. In this work, tungsten trioxide (WO3) thin films were prepared by adjusting the in situ heating temperature. WO3 with a crystalline structure showed excellent cyclic stability (5000 cycles), electrochromic performance (ΔT = 77.7% at 633 nm, CE = 37.1 cm2/C), relatively fast bleaching/coloring speed (20.0 s/19.4 s), and the darkest coloring effect (L* = 29.32, a* = 7.41, b* = -22.12 for the colored state). These findings offer valuable insights into the manipulation of smart materials and devices, contributing to the advancement of electrochromic technology.

Correlation of Structural Changes and Hydrogen Diffusion in Polycrystalline WO3 Thin Films by Combining In Situ Transmission Measurements and Raman Spectroscopy

AbstractDiffusion in polycrystalline tungsten trioxide (WO3) thin films is studied in a lateral geometry to better understand the impact of hydrogen‐induced structural phase transitions on the diffusion. WO3 thin films are coated with polymethylmethacrylate layer (PMMA). The latter is microstructured in such a way that a narrow stripe‐like gap occurs in the PMMA layer exposing the surface of the WO3 thin film. This stripe serves as the contact to the electrolyte in the intercalation experiment with hydrogen. After intercalation, the lateral diffusion of hydrogen inside WO3 below the PMMA layer can be observed, increasing the analyzable path and time scale by several orders of magnitude compared to the film thickness, thus, significantly improving spatial and temporal resolution of in situ transmission and Raman measurements. Spatially resolved transmission measurements in the wavelength range of 633±55 nm show that the diffusion process is dependent on hydrogen concentration and exhibits two regimes describable by different diffusion coefficients. Time‐resolved Raman spectroscopic measurements at different distances from the electrolyte contact area show that the switching between the two diffusion coefficients occurs at the phase transition from the orthorhombic to the tetragonal phase. The results are further supported by a simulation. The measurement approach is universally applicable for electrochromic films or multilayers.

Study of gold doping in optical and electrical properties of tungsten trioxide thin films deposited by spray method

Study of gold doping in optical and electrical properties of tungsten trioxide thin films deposited by spray method

Improving Properties of Tungsten Oxide Films by Gamma Ray Irradiation

The deposition process and investigation of the physical properties of tungsten trioxide (WO3) thin films before and after gamma irradiation are presented in this paper. The WO3 thin films were deposited, using the pulse laser deposition technique, on glass substrates at laser energies of 600mJ and 800mJ. After deposition, the samples were gamma irradiated with Co60. The structural and optical properties of polycrystalline WO3 thin films are presented and discussed before and after 5kGy gamma irradiation at the two laser energies. X-ray diffraction spectra revealed that all the films consisted of WO3 crystallized in the triclinic form; the dislocation density and lattice strain increased with the absorbed dosage of gamma irradiation. The optical constants, the average diameter and the surface roughness of the WO3 films were calculated before and after gamma irradiation and for the two laser energies. It was found that the WO3 thin films conductivity increased by γ-irradiated and with the increase of the laser energy.

Results of the gasochromic response on hydrogen of WO3 thin films deposited by electron beam evaporation

Among chromogenic materials, tungsten trioxide (WO3) is of great interest. It is a colourlesssemiconductor characterised by a lack of toxicity and high chemical stability. WO3 exhibits gasochromicproperties, meaning that the material undergoes reversible changes in optical properties when it isexposed to gas. These properties make tungsten oxide a suitable material for sensing applications. Thispaper presents the results of an analysis of the surface, structural and optical properties of tungstenoxide thin films fabricated by electron beam evaporation and annealed at 400C to 800C. Opticalproperties, including gasochromic properties, were determined from light transmission spectra inan atmosphere containing hydrogen at the concentrations ranging from 50 ppm to 500 ppm. Theoptical properties of WO3 films without and with a palladium catalyst layer are applied. Annealing thesamples at temperatures above 400C resulted in crystallisation of the layers, and further post-processmodification at 800C led to sublimation, the formation of islands of crystalline grains of large size anda significant deterioration in optical properties. A change in the light transmission coefficient occurredfor all samples with the catalyst layer applied after the introduction of a hydrogen-argon mixture.Based on the results, it can be concluded that the layers annealed at 400C had the best gasochromic properties due to the greatest changes in light transmission under hydrogen. The study confirmsthat it is possible to improve the gasochromic response of tungsten trioxide thin films produced byelectron beam evaporation using thermal modification, which, to the best of current knowledge, hasnot previously been achieved.Keywords: electronics, WO3, electron beam evaporation, gasochromic properties, optical properties,annealing, optical hydrogen gas sensor

Rapid and low-temperature preparation of tungsten oxide electrochromic thin films by oxygen plasma treatment

Electrochromic materials have attracted considerable attention due to their ability to change color reversibly and rapidly under an external electrical stimulus, making them highly promising for use in various applications such as smart windows, displays, and optical memory devices. In particular, tungsten trioxide (WO3) thin films have shown excellent electrochromic properties, leading to their wide application in electrochromic devices. In this study, oxygen plasma treatment was used to convert WCl6 thin film to WO3 electrochromic thin film on ITO glass substrate. Surface morphology, element composition, phase, optical property, and electrochromic characteristics of WO3 film are analyzed. It has been proved that the conversion of precursor films is rapid and efficient, the mean roughness and root mean square of amorphous WO3 thin film are lower than 1.8 nm and 2.2 nm respectively, and the film exhibits good electrochromic performance parameters. The optical modulation range and coloration efficiency of the film can reach 58.5% and 80.2 cm2/C before cycle and 56.3% and 84.0 cm2/C after 100 cycles, coloration time and bleaching time are within 10 s. The method of plasma treatment avoids annealing and prepare WO3 film with good and stable performance. This method has the potential to expand to other electrochromic materials, and provides a new solution for the large area preparation and flexible application of electrochromic materials.

Structural, optical, and electrochromic properties of RT and annealed sputtered tungsten trioxide (WO3) thin films for electrochromic applications by using GLAD technique

Structural, optical, and electrochromic properties of RT and annealed sputtered tungsten trioxide (WO3) thin films for electrochromic applications by using GLAD technique

Investigation of the effect of Mo+2 ion concentration on linear and non-linear optical properties of tungsten trioxide thin films for optoelectronic applications

To achieve the goal of creating a single-phase mixture of transition metal oxides with high electrical efficiency, our investigation focused on studying the linear and nonlinear optical properties of a mixture of transitional oxides that is electrophoretically colored. For finding the best ratios, we also investigated the impact of adding molybdenum ion to tungsten trioxide on the linear and non-linear optical properties of the samples made using the spray pyrolysis method on heated glass substrates. The as-deposited films were amorphous, as demonstrated by the X-ray diffraction (XRD). All of the samples were transferred to the polycrystalline and acquire a triclinic structure after the thermal annealing at 500 °C for 2 h. At room temperature, transmission and reflection measurements in the wavelength range of 300–2500 nm were utilized to evaluate the absorption coefficient. MoxW1-xO3 thin films' optical density, optical energy gap, skin depth, and Urbach's parameters were also estimated. Urbach's energy, EU, decreases from 0.355 to 0.154, eV as Mo-content rises, while Tauc's band gap energy, Eg, decreases from 2.76 to 2.56 eV. The films' static refractive indices dropped from 2.832 to 2.081 in the low-energy region and from 3.832 to 2.446 in the high-energy region. The dispersion energies and other variables were investigated using the Wemple–DiDomenico and Sellmeier models. In addition, various dispersion and nonlinear parameters were estimated and thoroughly discussed. It was observed that the improvement in the crystallinity of W1-xMoxO3 thin films led to a decrease in the values of the third-order nonlinear susceptibility (χ(3)), mainly affected by the constant refractive index, which decays with an increase in Mo concentration. Simultaneously, the conductivity of the films rises proportionally with the photon energy and Mo content, which is attributed to the concurrent increase in the dielectric constants. In this work, new approach for fabrication of quality thin film of MoxW1-xO3 was demonstrated. This is the reason for obtaining the best results, which made these films an effective contribution to many important applications. Furthermore, MoxW1-xO3 thin films perovskite has large nonlinear optical proper. These findings highlight the potential utility of these films in diverse critical optical applications, such as commercial lasers, ultra-fast signal processing in optical communication systems, sensors, environmental monitoring, medicine, manufacturing and materials processing, military applications, as well as scientific instrumentation.

Deposition of tungsten in methane atmosphere using a low energy plasma focus device

Deposition of tungsten in methane atmosphere was performed using a low energy plasma focus device. The resulting compounds were synthesized and investigated during the deposition process. Carbon-rich contamination was identified as an organic viscous liquid crystal defect. Tungsten carbide (W2C) and dark-black oxygen-deficient tungsten trioxide (WO3-x) thin films were synthesized by plasma focus device using different number of focused shots. The synthesis of each thin film, which was dependent upon operation of plasma focus device was verified and discussed. Tungsten carbide W2C was synthesized during the deposition process while the dark-black WO3-x was created after the deposition process in atmosphere. All compounds were investigated by spectroscopy, crystalline, and microscopy methods. Nano indentation test disclosed higher value of hardness for the film containing tungsten carbide compound (10.01 GPa) compared to both pure tungsten (5.72 GPa) and the dark-black WO3-x thin film (6.83 GPa). The verified band gap energy of dark-black WO3-x was around 1.475 eV.

Comparison study of WO3 thin film and nanorods for smart window applications

The WO3 thin films were deposited at oxygen partial pressure of 8x10-4 mbar. A template-free straightforward hydrothermal method is employed to produce vertical alignment hierarchical WO3 nano-architectures on clear conducting substrates (3x2.5 cm2 in size and slides resistance 4 O). After being deposited at ambient temperature, the samples were air annealed at 400 °C for 4 h. The optical, electrochromic, surface and structural morphology behavior of the deposited material after annealing were studied using XRD, Raman, FTIR, SEM, electrochemical analyzer and UV–Visible spectrometer characterization methods. After annealing at 400 °C for 4 h in air, every characteristic peak are matched to a monoclinic (crystalline) WO3 phase. The Nano flower array achieved a considerable coloration efficiency (24.09 cm2/s) and low cathodic peak current (−2.03 mA) compare to the Tungsten trioxide thin film produced by the DC magnetron sputtering method. The vertically oriented geometry and the porosity space between the Nano flower, which improve H+ diffusion and provide a considerable contact area for charge-transfer processes, are primarily responsible for the improved electrochromic properties.

Preparation of additive free tungsten trioxide thin films using spin-coating method for electrochrochemical applications

Preparation of additive free tungsten trioxide thin films using spin-coating method for electrochrochemical applications

A sight of view on electrical impacts, structural properties and surface roughness of tungsten trioxide thin film: effect of substrate temperatures in WO3/Si device fabrication

Monoclinic WO3 thin films have been effectively deposited by a simple spray pyrolysis technique at a molar concentration of 0.01 M on a glass substrate in the temperature range of 473 to 673 K. These WO3 films were used as an interlayer between the metal and the semiconductor, which formed the basic structure of the photodetector. Effect of substrate temperature on WO3 films during the process of the deposition was systematically interpreted with respect to the structural, morphological, optical and electrical properties of the WO3 films. The x-ray diffraction pattern revealed the polycrystalline nature of the prepared films with monoclinic phases. At the substrate temperature of 623 K, the nano-thin films were strongly bonded to each other as observed from the FE-SEM images. Visible and ultraviolet spectroscopies indicated the band gap (Eg) of the WO3 thin film is 3.30 eV. The dc electrical study recorded a sharp increase in the electrical conductivity of the prepared film at substrate temperature of 623 K for tungsten trioxide. It is worth noting that all diodes showed a positive photoresponse under illumination. In particular, the photodetector with the thickness of 300 nm showed higher responsivity 0.02 A/W and detection specificity 8.29 × 1010 Jones.

Coloration mechanism in gasochromic thin films through the analysis of a complex refractive index.

In this paper, the dispersion of a complex refractive index is investigated and proposed as a way to analyze the change of the optical properties of gasochromic material under the influence of diluted hydrogen (3.5% H 2 in Ar) as an active volatile medium. Therefore, a tungsten trioxide thin film and an additional platinum catalyst were deposited by electron beam evaporation and used as a prototype material. Based on experimental verification, it is shown that the proposed method allows one to explain the reasons for the observed changes in the transparency in such materials.

A hydrogel electrolyte based on hydroxypropyl methylcellulose modified polyacrylamine for efficient electrochromic energy storage devices

The electrolyte play a crucial role for the efficient operation of electrochemical devices. In this work, we developed a new hydrogel electrolyte based on hydroxypropyl methylcellulose modified polyacrylamine framework for electrochromic energy storage devices. By using the present electrolyte, the sandwich electrochemical devices based on complementary electrodes of prussian blue (PB) and tungsten trioxide (WO3) thin films exhibited reversible electrochromic switch between colorless and dark blue, with large optical contrast over 80 %, short response time below 2 s, high coloration efficiency over 168 cm2/C, and good cycle stability. Moreover, the devices showed good energy storage ability with an area capacitance of 6.32 mAh/m2 at a current density of 0.02 mA/cm2. The dual functional electrochemical devices showed potential application in energy saving smart windows.

Visible-light-induced superhydrophilicity of crystallized WO3 thin films fabricated by using a newly isolated W6+ complex salt of citric acid.

Transparent tungsten trioxide thin films, which demonstrated visible-light (Vis-light)-induced superhydrophilicity, with thicknesses of 100-120 nm, adhesion strengths greater than 49 MPa, bandgap energies of 2.8-2.9 eV, and haze values of 0.4-0.5%, were fabricated using a solution-based process on quartz glass substrates. The precursor solution was prepared by dissolving a W6+ complex salt isolated from a reacted solution of tungstic acid, citric acid, and dibutylamine in H2O, in ethanol. By heating the spin-coated films in air for 30 min at temperatures higher than 500 °C, crystallized WO3 thin films were obtained. The O/W atomic ratio was evaluated to be 2.90, based on the peak area analysis of X-ray photoelectron spectroscopy spectra of the thin-film surfaces, indicating the co-presence of W5+ ions. The water contact angle on film surfaces, which was approximately 25° prior to light irradiation, decreased to less than 10° upon irradiation with 0.06 mW cm-2 Vis-light for only 20 min at 20-25 °C and a relative humidity (RH) of 40-50%. By comparing the contact angle changes at RH values of 20-25%, it was revealed that the interaction between ambient water molecules and the partially O-deficient WO3 thin films plays an important role in achieving photoinduced superhydrophilicity.

Giant saturation absorption of tungsten trioxide film prepared based on the seedless layer hydrothermal method

Nonlinear materials have gained wide interest as saturable absorbers and pulse compression for pulsed laser applications due to their unique optical properties. This work investigates the third-order nonlinear phenomenon of tungsten trioxide (WO3) thin films. The giant nonlinear absorption and nonlinear refractive index of WO3 thin films were characterized by Z-scan method at 800 nm. We experimentally observed the giant saturable absorption (SA) and nonlinear refractive index of WO3 thin films prepared by the seedless layer hydrothermal method, with SA coefficient being as high as –2.59 × 105 cm⋅GW−1. The SA coefficient is at least one order of magnitude larger than those of the conventional semiconductors. The nonlinear refractive index n 2 of WO3 film has been observed for the first time in recent studies and the corresponding coefficient can be up to 1.793 cm2⋅GW−1. The large third-order nonlinear optical (NLO) response enables WO3 thin films to be promising candidates for optoelectronic and photonic applications in the near-infrared domain.