Deposited Tungsten Oxide Research Articles

Simulation and deposition of Tungsten oxide (WO3) films using DC sputtering towards UV photodetector for high responsivity

Tungsten trioxide (WO3) detects UV radiation with great sensitivity while disregarding visible light, and it also has excellent electron mobility, allowing for efficient charge transport and fast response times. This work aims to develop a highly sensitive UV photodetector using WO3 material by optimizing the deposition parameter partial oxygen pressure (PaO2) and annealing the samples at various temperatures to determine the best PaO2 and annealing temperature that results in an improvement in the UV photodetector's sensitivity. The material WO3 was coated on glass substrates using DC magnetron sputtering while altering the PaO2 as 6 × 10−2 Pa, 4 × 10−2 -2 Pa, and 2 × 10−2 Pa, and then each as-deposited sample from varied PaO2 was annealed at temperatures ranging from 100°C to 400°C. When the sample's responses were compared, it was observed that the sample deposited at PaO2 2 × 10−2 Pa and annealed at 400 °C exhibited good photodetection capabilities, as evidenced by several characterization techniques such as SEM, XRD, and IV characterization. The work was subsequently carried out by evaluating the sample deposited at PaO2 2 × 10−2 Pa and annealed at 700 °C, which produced a good result for UV photodetection with the device's responsivity of 1e+4 A/W.

Tungsten Oxide Thin Films for Electrochromic Applications: Pulse Width‐Controlled Deposition by High‐Power Impulse Magnetron Sputtering

Tungsten oxide (WO3) thin films have been of prime interest among electrochromic materials because of their chemical stability, strong adherence to various substrates, and high coloration efficiency. High‐power impulse magnetron sputtering (HiPIMS) holds great potential in fabricating durable WO3‐based electrochromic layers. However, the tungsten target–plasma interactions in reactive‐HiPIMS deposition of WO3 and their role in modulating the electrochromic function of the resulting WO3 coatings are yet to be understood. Herein, by controlling the HiPIMS pulse length, the stoichiometry of tungsten oxide structures can be tuned to optimize the transparency and electrochromic function of the coatings. X‐ray photoelectron spectroscopy data shows that at pulse lengths shorter than 85 μs, the concentration of suboxide compounds is less than that of tungsten trioxide, while for pulse lengths longer than 100 μs, this balance is reversed. The average optical transparency of the coatings in the range of visible light is higher than 80%. The optical transmittance modulation (ΔT) of 38.1, 36.2, and 34.3% and coloration efficiency of 41.3, 38.4, and 35.9 cm2 C−1 are measured for the WOx samples deposited at pulse lengths of 70, 85, and 100 μs, respectively. Tuning the HiPIMS pulse characteristics is a simple strategy to deposit tungsten oxide films with tuned electrochromic properties for an array of applications, from smart windows to wearable displays.

Enhancing electron interaction between Pt and support for superior electrochemical performance through atomic layer deposition of tungsten oxide

The stabilization of platinum (Pt) catalysts through strong metal-support interactions is crucial for their successful implementation in fuel cell applications. Tungsten oxide (WO3) has demonstrated excellent CO tolerance and has been recognized as a promising substrate for anchoring and stabilizing Pt nanoparticles (NPs). However, the limited specific surface area of conventional tungsten oxide restricts its effectiveness in dispersing noble metal NPs. In this study, we present a pioneering approach by employing atomic layer deposition (ALD) to create a WO3 interlayer between Pt NPs and a carbon substrate. Using nitrogen-doped carbon nanotubes (NCNT) as the foundation, WO3 nanoparticles (2–5 nm) were selectively synthesized, followed by the subsequent deposition of Pt NPs using a bottom-up approach. The Pt-WO3-NCNT catalyst, with a WO3 bridge layer effectively inserted between the active site and carbon support, has displayed a notable augmentation in electrocatalytic activity and notable stability when compared to commercial Pt catalysts in oxygen reduction reaction (ORR). The detailed microstructure and the enhanced electrochemical reaction mechanism of Pt-WO3-NCNT catalyst has been investigated by X-ray adsorption spectrum and density functional theory (DFT) calculations. This work presents an innovative approach for enhancing the stability of Pt catalysts through the utilization of the ALD technique.

Optical and electrochromic properties of DC magnetron sputter deposited tungsten oxide thin films at different electrolyte concentrations and vertex potentials for smart window applications

Optical and electrochromic properties of DC magnetron sputter deposited tungsten oxide thin films at different electrolyte concentrations and vertex potentials for smart window applications

Monoclinic tungsten trioxide (WO3) thin films using spraying pyrolysis: electrical, structural and stoichiometric ratio at different molarity

Chemical spraying pyrolysis technique has used to deposit tungsten oxide on glass substrates with varied concentrations ranging from 50 to 90 mM at the optimum deposition temperature of 350 ͦ C. All films exhibit a monoclinic phase, with highest structural properties at a molar concentration of 80 mM. Miller's plain at (200) was found to be the most dominant in all films. The film has a fibrous network with an increasing diameter with increasing concentration, according to FE-SEM. The EDX revealed that the ratio of W/O at the optimum concentration (80mM) was 2.62, with a stoichiometric of 68.6%. The rate of grain size grew with concentration, whereas the rate of roughness reduced with concentration, according to atomic force microscopy investigations of thin films. The mean electrical conductivity increased gradually with concentration up to 4.176 x10-8 S/cm-1 and subsequently declined to 4.542x 10-10 S/cm-1 , while the activation energy climbed gradually with concentration up to reach 0.298eV before decreasing significantly

Chronoamperometric deposition of transparent WO3 film for application as power efficient electrochromic auxiliary electrode

Inorganic oxide electrochromic electrodes can be made more robust by adopting suitable deposition techniques. Electrochemically deposited tungsten oxide (WO3) film through chronoamperometry has been studied here for application as electrochromic auxiliary electrode. Thoroughly characterized film using electron microscopy, x-ray diffraction and Raman spectroscopy has been used for electrochromic measurements. The electrode shows reversible transparent to blue color switching when biased with a very small bias of 1 V. Bias dependent in-situ spectroelectrochemistry measurements have been performed which shows excellent results in terms of reversibility, cyclability, color contrast, appreciable switching time and good current stability at low working potential. The results thus pave the way to an excellent deposition technique designed particularly for electrochromic applications.

Plasma Sputtered Tungsten Oxide Thin Film on Poly(lactic acid) for Food Packaging Applications

Biodegradable and bio-derived plastics such as poly(lactic acid) (PLA) are a promising solution to solve the huge environmental and economic issues caused by the enormous consumption of conventional oil-derived polymers, especially in food packaging applications. However, their poor gas barrier properties and high transparency to UV radiation limit their currently commercialization. Therefore, this study is focused on the deposition of tungsten oxide (WOx) thin films on commercial PLA in order to enhance its overall performance. Coatings with different thickness (25, 50 and 100 nm) were deposited by means of radiofrequency (RF) plasma magnetron reactive sputtering. Morphological characterization was carried out with atomic force microscopy (AFM) and scanning electron microscopy (SEM). In order to evaluate surface chemical changes due to plasma treatments, Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis were performed. The PLA/WOx samples demonstrated remarkable improvements both in UV protection and oxygen barrier properties. In particular, light transmittance was reduced by approximately 95% in the UV-B region, 70% in the UV-A region and 50% in the visible region compared to pristine PLA. Regarding oxygen permeation, a reduction of at least 99.9% was achieved. In addition, the PLA/WOx antibacterial properties against Escherichia coli were also investigated, showing a reduction greater than 5 log10 CFU cm−2 after 24 h for the 50 and 100 nm samples. These results demonstrate the potential of WOx thin coating for sustainable food packaging applications.

Ultrasensitive ppb-level trimethylamine gas sensor based on p–n heterojunction of Co3O4/WO3

Trace poisonous and harmful gases in the air have been harming and affecting people’s health for a long time. At present, effective and accurate detection of ppb-level harmful gas is still a bottleneck to be overcome. Herein, we report a ppb-level triethylamine (TEA) gas sensor based on p–n heterojunction of Co3O4/WO3, which is prepared with ZIF-67 as the precursor and provides Co3O4 deposited tungsten oxide flower-like structure. Due to the introduction of Co3O4 and the 3D flower-like structure of WO3, the Co3O4/WO3-2 gas sensor shows excellent gas sensing performance (1101 for 10 ppm at 240 °C), superb selectivity, good long-term stability and linear response for TEA concentration. Moreover, the experimental results indicate that the Co3O4/WO3-2 gas sensor also possesses a good response to 50 ppb TEA, in fact, the theoretical limit of detection is 0.6 ppb. Co3O4 not only improves the efficiency of electron separation/transport, but also accelerates the oxidation rate of TEA. This method of synthesizing p–n heterojunction with ZIF as the precursor provides a new idea and method for the preparation of low detection limit gas sensors.

The effect of palladium doping on optical and electrochromic properties of sol-gel ‎deposited tungsten oxide films

In this paper, palladium doped-tungsten oxide thin films have been prepared by sol-gel deposition method. In this way, tungstic ‎acid obtained by Kudo method was doped by different amounts of palladium chloride and were deposited on transparent ‎conductive oxide of ITO/glass by dip-coating method. The effect of Pd doping on morphology and optical properties as well as ‎electrochemical characteristics were investigated using scanning electron microscopic (SEM), UV-Vis spectroscopy, cyclic ‎voltammetry (CV) and optical transmission at 632.8 nm constant wavelength. SEM revealed that the WO3 layers have a thickness ‎of 450-500 nm were obtained with smooth and uniform surfaces. Also, the transparency of layers was above 85%, for which the ‎optical gap was decreased by increasing Pd content. The voltammetry results showed that the doped palladium reduces the ‎catholic potential, increases the chemical stability of tungsten oxide thin films, stabilizing the electrochemical performance of ‎these layers. Finally, we measured the electrochromic response time and the corresponding electrochemical efficiencies

Atomic Layer Deposition of Tungsten Oxide Using Nitrogen Dioxide: A Comparative Study with Other Oxygen Sources

Atomic layer deposition of tungsten oxide thin films using bis(t-butylimido)-bis(dimethylamido)tungsten is investigated using various oxygen precursors. Significant amounts of unreacted nitrogen or...

Use of TiO2-WO3 architecture for Photoelectrochemical Alcohol Oxidation

Ethanol, the major component of biofuel mixture, has significantly lower heat capacity compared to that of longer-chain alcohols such as butanol. As a result, oligomerization of ethanol has gained much attention. A three-step process that includes transition metal catalyzed C-alkylation was proposed for alcohol oligomerization. This cycle includes: (I) alcohol oxidation to the corresponding carboxylic acid, (II) dimerization via carboxylic acid terminals, and (III) further reduction of the oligomer to form the saturated alcohol. In this context, TEMPO has been vastly utilized for the electrochemical oxidation of alcohols. This process suffers from shortcomings such as limited turnover frequency of the reagent and small conversion yield of the synthesis. There have been some reports on the application of semiconductor electrodes for oxidizing certain types of alcohols. This approach, however, has shown some pitfalls such as high oxidation overpotential, low reaction yield, and low stability of the working electrode.The goal of this research is to fabricate a novel photoanode for oxidizing alcohols to their corresponding carboxylic acids. In this work, we aimed at fabricating an architecture shown in Fig. 1. To prepare such an electrode, a 10 nm layer of Ti was first deposited over fused silica substrate via thermal deposition method. Then, TiO2 with thickness of 500-µm was deposited with application of sol-gel technique, and finally WO3 was loaded onto the TiO2 with application of controlled-potential pulse deposition. Our experimental results have shown that this electrode have great stability toward photoelectron corrosion and the yield of conversion is the function of the deposited tungsten oxide. Figure 1

Electrophoresis Deposition of Tungsten oxide Nanoparticles for Corrosion Inhibition

In the present research, electrophoretic deposition technique (EPD) was used to deposit tungsten oxide (WO3) nanoparticles onto galvanized steel from a tungsten oxide ethanol suspension at various concentrations of (1.7×10−2, 2.5×10−2 and 3.4×10−2 M) for corrosion protection application. The (WO3) nano coating was used as a barrier layer for the corrosion protection of galvanized steel in saline solution. (WO3) nanoparticles were characterized by measuring the Fourier transform infrared spectroscopy, UV-Visible and X-ray diffraction techniques. The morphology of the (WO3) nanoparticles was investigated using Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). Results indicated that (WO3) nanoparticles layer was efficiently deposited onto galvanized steel using (EPD), also, the deposited nanoparticles film was found to be homogenous and smooth. (EPD) and the partial reduction of the (WO3) nanoparticles occurred simultaneously under the applied electrical fields. Moreover, the anti-corrosion performance of the (WO3) nanoparticles –EPD layers was characterized using Tafel polarization method. Polarization studies identified the coated (WO3) nanoparticles behave as a mixed type inhibitor. Protection efficiencies data were increased as the (WO3) nanoparticles concentrations and temperature increased, indicating chemisorption protection mechanism.

Spectroelectrochemistry of Poly(3,4-Ethylenedioxythiophene)–Tungsten Oxide Composite Films in Dilute Sulfuric Acid Solution

Using electrochemical deposition of tungsten oxide from a metastable acidic solution of isopolytungstates into a poly(3,4-ethylenedioxithiophene) film, composite films were obtained on optically transparent electrodes made of fluorine-doped tin oxide on glass. In situ electronic spectra of poly(3,4-ethylenedioxithiophene)–tungsten oxide composite films and their components, poly(3,4-ethylenedioxithiophene) and tungsten oxide films, were studied using the spectroelectrochemistry method at various electrode potentials. The good additivity of the spectra of the composite and its constituent components suggests that there is no pronounced specific chemical interaction between the components, except for the electrostatic interaction between positively charged polymer fragments and negatively charged polymer oxo anions of tungsten oxide.

Atmospheric-pressure spatial chemical vapor deposition of tungsten oxide

Atmospheric-pressure spatial atomic layer deposition (AP-SALD) and atmospheric-pressure spatial chemical vapor deposition (AP-SCVD) are rapid, open-air techniques for the deposition of conformal, pinhole-free films over large areas. In this work, a precursor nebulizer and an ozone generator are incorporated into an AP-SALD system to enable the deposition of tungsten oxide (WO3) films by AP-SCVD. The precursors bis(t-butylimido) bis(dimethylamino) tungsten(VI) and ozone are used with a film deposition temperature of 350 °C to achieve a growth per cycle of 1.2 Å/cycle. A bandgap of 3.26 eV and a refractive index of 2.36 were obtained, consistent with the previous reports for WO3 films. The pinhole-free films were found to be a mixture of hexagonal and monoclinic WO3, with an increasing monoclinic nature after annealing. Additionally, the as-deposited film was substoichiometric with an O/W ratio of 2.3, which increased to 2.36 after annealing at 450 °C. The successful open-air deposition of tungsten oxide via the incorporation of a precursor nebulizer and ozone generator paves the way for large-area deposition of tungsten oxide for commercial applications.

Insights on the electrodeposition mechanism of tungsten oxide into conducting polymers: Potentiostatic vs. potentiodynamic deposition

In this work we have investigated the electrochemical deposition of tungsten oxide into different conducting polymer films from the metastable acidic solution of isopolytungstate. Two different in the nature conducting polymer (CP) materials, namely, poly-3,4-ethylenedioxythiophene (PEDOT) and poly-3,4-ethylenedioxypyrrole (PEDOP) were used as electrode substrates for electrodeposition. Electrodeposition of tungsten oxide into freshly prepared conducting polymer films was performed by two electrochemical methods: potentiostatic and potentiodynamic. The electrochemical behavior of CP/WO3 composites, obtained with variation of synthesis conditions, was investigated by cyclic voltammetry in 0.5 M sulfuric acid. The comparison of electrochemical properties of composites allows to conclude on the mechanism of WO3 deposition. It was shown that precipitates of WO3 in CPs, electrodeposited by potentiodynamic method, display very symmetrical and sharp peaks of the redox transformation of WO3, which are rarely reported for tungsten oxides.The effect of electrochemical deposition method on the growth of WO3 precipitates on conducting polymer film electrodes and the electrochemical properties of composites was also investigated by combined cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). The role of polyoxotungstate anion species trapping in CPs during p-doping process and facile formation of tungsten oxide nanostructures in CPs matrix is considered. A mechanism for the electrodeposition of tungsten oxide into PEDOT and PEDOP polymers was proposed.

Formation of the Phase Composition, Porous Structure, and Morphology of Membrane Catalysts Based on Tungsten Carbides

Membrane catalysts are prepared by the chemical vapor-phase deposition of tungsten oxides on a corundum porous microfiltration membrane. The massive layer of tungsten oxides formed on the substrate is converted to carbides by temperature-programmed carbidization with С3Н8/Н2 and СН4/Н2 mixtures. Changes in the porous structure and phase composition of the catalytic layer at stages of vapor-phase deposition and carbidization of oxides deposited on the corundum substrate are considered. Dependence of the depth of distribution of tungsten compounds on the deposition temperature is studied by electron scanning microscopy and X-ray spectroscopy. A relationship is established between the synthesis conditions of tungsten carbide-based membrane catalysts and their phase composition, porous structure characteristics, and morphology.

Microgravimetric study of electrochemical properties of PEDOT/WO3 composite films in diluted sulfuric acid

Poly-3,4-ethylenedioxythiophene composite films with tungsten oxide (PEDOT/WO3) were obtained by potentiodynamic deposition of tungsten oxide from acidic metastable solution of isopolytungstates into poly-3,4-ethylenedioxythiophene film, pre-deposited on an Au-quartz crystal. The electrochemical deposition of tungsten oxide into poly-3,4-ethylenedioxythiophene was investigated by electrochemical quartz microgravimetry (EQCM), the masses of PEDOT and tungsten oxide deposits were estimated. The electrochemical behavior of PEDOT/WO3 composite films with different masses of deposited tungsten oxide was studied by cyclic voltammetry and EQCM in the 0.5 M sulfuric acid electrolyte. The change of the fraction of tungsten oxide in the PEDOT/WO3 composite film results in the change of the slope of the Δf–E dependency in the potential region, corresponding to WVI/WV redox process. It is due to an oppositely directed mass transport (anion and cation) during the redox process in the composite film. The average molar mass of transferred species involved in the redox process in tungsten oxide was estimated to be 26 ± 4 g mol−1. It was shown that the fraction of electrochemically active tungsten oxide deposit is dependent on its mass in the composite, with increase of the mass of tungsten oxide in PEDOT/WO3, the fraction of electroactive tungsten oxide WO3 decreases due to decrease in its active area.

Growth of WOx from Tungsten(VI) Oxo-Fluoroalkoxide Complexes with Partially Fluorinated β-Diketonate/β-Ketoesterate Ligands: Comparison of Chemical Vapor Deposition to Aerosol-Assisted CVD.

Tungsten(VI) oxo complexes of the type WO(OR)3L [R = C(CH3)2CF3, C(CF3)2CH3, CH(CF3)2, L = hexafluoroacetylacetonate (hfac), ethyl trifluoroacetoacetonate (etfac), acetylacetonate (acac)] bearing partially fluorinated alkoxide and/or chelating ligands were synthesized. Thermal decomposition behavior and mass spectrometry (MS) fragmentation patterns of selected examples were studied. The thermolysis products of WO(OC(CF3)2CH3)3(hfac) were characterized by nuclear magnetic resonance and gas chromatography-MS. Studies of the sublimation behavior of the complexes demonstrated that their volatilitydepends on the degree of fluorination. Comparative studies of the deposition of tungsten oxide by chemical vapor deposition (CVD) and aerosol-assisted CVD were carried out using WO(OC(CF3)2CH3)3(hfac) as a single-source precursor. WOx materials were successfully deposited by both deposition methods, but the deposits differed in morphology, structure, and crystallinity.

Effect of Electrode Material on Electrodeposition of Tungsten Oxide

Influence exerted by the nature of an electrode-substrate on the electrochemical deposition of tungsten oxides from a metastable acid solution of isopolytungstate was studied. As substrates for obtaining tungsten oxide deposits served metallic electrodes made of gold and platinum, films of mixed indium-tin oxide on glass (ITO-electrodes) and also glassy carbon electrodes and glassy carbon electrodes coated with films of conducting polymers: polyaniline, polypyrrole, and poly-3,4-ethylenedioxythiophene. It was shown that the nature of a substrate noticeably affects the electrochemical properties of tungsten oxide deposits. These differences are attributed to the adsorption of hydrogen on platinum in the range of the deposition potentials of tungsten oxide and to the chemical interaction of polytungstate ions with the thiophene sulfur of the polymer.

Effect of film thickness on electrochromic performance of sol-gel deposited tungsten oxide (WO3)

In recent year, considerable interest has been addressed towards the high energy usage in buildings for indoor comfort due to the less energy efficient windows. Electrochromic (EC) smart window is a new technology that is capable of changing from transparent to opaque and has the potential in energy saving applications. Tungsten oxide (WO3) is a transition metal oxide with a wide range of applications which include electrochromic (EC) smart windows, displays and rear-view mirrors. In EC smart windows, WO3 is the key element where it is responsible for the colouring and bleaching of the device. Therefore the properties of WO3 will affect the EC performance. In this work, WO3 films were deposited on tin doped indium oxide (ITO) coated glasses via the sol-gel spin-coating technique. The WO3 film thicknesses were varied by means of number of deposited layers. The film thickness, morphological, structural, optical and EC properties were characterised by using step profilometer, scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, ultraviolet-visible (UV-Vis) spectrophotometer and cyclic voltammetry (CV) and chronoamperometry (CA) measurements, respectively.