Electrochromic and morphological investigation of dry-lithiated nanostructured tungsten trioxide thin films

Electrochromic properties of porous nanostructured thin films of tungsten trioxide were investigated. Films were fabricated at normal and high vapor incidence angles with the technique of glancing angle deposition in a thermal evaporation chamber. A dry lithiation method was subsequently used to intercalate films with lithium atoms. Coloration in both visible and near-infrared regions was observed with lithium insertion. We report on the morphology, porosity, and optical properties of as-deposited and lithiated films, and discuss the role of substrate tilt in comparing the coloration efficiency of these films.     

有机基质表面无机非金属膜的合成

综述了用溶胶－凝胶法、离子交换－化学沉积法和仿生合成法在有机基质表面制备无机非金属膜的原理和制备过程,重点讨论了仿生合成法,介绍了有机基质表面二氧化锡、氧化铁和碳酸钙膜及图案膜的仿生合成。     

Electrochromic properties of N-doped tungsten oxide thin films prepared by reactive DC-pulsed sputtering

In depositing nitrogen doped tungsten oxide thin films by using reactive DC-pulsed magnetron sputtering process, nitrous oxide gas (N₂O) was employed instead of nitrogen (N₂) as the nitrogen dopant source. The nitrogen doping effect on the structural and electrochromic properties of WO₃ thin films was investigated. X-ray diffraction (XRD) results show that the films are amorphous. Morphological images reveal that the films are characterized by a hybrid structure comprising nanoparticles embedded in amorphous matrix and open channels between the agglomerated nanoparticles, which promotes rapid charge transport through the film. Increasing the nitrogen doping concentration is found to decrease the nanoparticle size and the band gap energy. The electrochromic properties were studied using cyclic voltammetric and spectroeletrochemical techniques. The film with N content of ~ 5 at.% exhibits higher optical modulation and coloration efficiency as well as faster ion transport kinetics. The results reveal that electrochromic and lithium ion transport properties are moderately enhanced relative to the un-doped tungsten oxide thin films by appropriate content of dopant, due to the effects of nitrogen doping.     

Hot-wire chemical vapor deposition of WO3−x thin films of various oxygen contents

We present the synthesis of tungsten oxide (WO_3−x) thin films consisting of layers of varying oxygen content. Configurations of layered thin films comprised of W, W/WO_3−x, WO₃/W and WO₃/W/WO_3−x are obtained in a single continuous hot-wire chemical vapor deposition process using only ambient air and hydrogen. The air oxidizes resistively heated tungsten filaments and produces the tungsten oxide species, which deposit on a substrate and are subsequently reduced by the hydrogen. The reduction of tungsten oxides to oxides of lower oxygen content (suboxides) depends on the local water vapor pressure and temperature. In this work, the substrate temperature is either below 250 °C or is kept at 750 °C. A number of films are synthesized using a combined air/hydrogen flow at various total process pressures. Rutherford backscattering spectrometry is employed to measure the number of tungsten and oxygen atoms deposited, revealing the average atomic compositions and the oxygen profiles of the films. High-resolution scanning electron microscopy is performed to measure the physical thicknesses and display the internal morphologies of the films. The chemical structure and crystallinity are investigated with Raman spectroscopy and X-ray diffraction, respectively.     

Eu-doped indium tin oxide thin films fabricated by sol-gel technique

We have fabricated Eu-doped indium tin oxide thin films via the conventional sol-gel technique, and confirmed that the doped Eu atoms were chemically incorporated into the indium tin oxide lattice by substituting the In sites. Optical spectra indicated that the Eu-doped films were free of any impurities leading to additional vibrational effects. Valence states of Eu ions in our Eu-doped indium tin oxide films were discussed in connection with Eu concentration.     

Electrochromic Properties of Sol-gel Deposited V2O5 and TiO2-V2O5 Binary Thin Films

Transparent mixed phase (1- x)V205-xTiO2 (x=0,0.1,0.2,0.3,0.4) thin films were prepared on indium tin oxide (ITO) coated glass via sol-gel process. The films were characterized by cyclic voltammetry, optical spectroscopy, scanning electron microscopy, IR and X-ray diffractometer.     

Properties of chemically vapor-deposited Tungsten thin films on silicon wafers

Tungsten thin films were deposited onto silicon wafers by the thermal decomposition of W(CO)₆. The non-corrosive nature of W(CO)₆ and its decomposition products, tungsten and CO, allows deposition without damage to the wafer surface. The deposition rate is dependent on such parameters as the wafer temperature and the pressure of W(CO)₆. The effects of annealing on film characteristics were studied.The tungsten films show good uniformity and adhesion after deposition and also after annealing. The resistivity depends on the film thickness and, for a film 2200 Å thick, is 15 x 10^-5 ω cm. Wafer annealing is done at 800–900°C under vacuum in an atmosphere of forming gas. After the films have been annealed for 30 min, the resistivity decreases to 1.5 x 10^-5 ω cm.Auger analysis of the films shows that some CO is trapped in the tungsten matrix after deposition at a ratio of about one CO molecule to every four tungsten atoms. Annealing for 30 min drives off the CO, reducing the ratio to less than one CO molecule per 30 tungsten atoms.     

Electrochromic performance of hybrid tungsten oxide films with multiwalled-CNT additions

In this study, tungsten oxide films were prepared by sol–gel technique. Various amounts of multiwalled carbon nanotubes (MWCNTs) were added during sol–gel process to obtain hybrid WO₃/MWCNT films. The original and hybrid films were characterized by thermogravimetric analysis, X-ray diffraction analysis, and scanning electron microscopy analysis, whereas the electrochromic performance was evaluated by measuring changes in the optical transmittance caused by potentiostatic charge–discharge intercalation. The influence on the structure and properties of tungsten oxide film due to MWCNT addition was also investigated. The results showed that all of the films were amorphous and exhibited porous microstructure. The electrochromic performance of pristine WO₃ film was improved by adding MWCNTs that served as a template for the growth of WO₃ and resulted in more porous microstructure. The hybrid tungsten oxide films with 0.1 wt.% MWCNT addition exhibited the best electrochromic performance.     

ITO用作铁电薄膜电极的研究

研究了sol-gel掺锡氧化铟（ITO溶胶在SiO2/Si衬底和光学玻璃衬底上的成膜及结晶性能,并与CVD法生长的ITO薄膜作了对比。结论是：sol-gelITO膜,虽然具有与CVD ITO膜相似的结晶性能和较高的导电性,但以sol-gel ITO膜作下电极,无法使PLT、PZT的sol-gel膜具有明显的结晶取向。因漏电太大,sol-gel ITO也无法作sol-gel铁电膜（如PLT,PZT）的上电极。但在CVD ITO膜上,sol-gel铁电膜能很好结晶,且Au/PLT/ITO电容,具有良好的电学性能。     

Insertion of H, Li, Na and K into thin films prepared from silicotungstic acid—a photoelectron spectroscopy study

Electrochemical insertion by a set of different ions (H⁺, Li⁺, Na⁺ and K⁺) into a tungsten oxide thin film was studied by photoelectron spectroscopy. The tungsten oxide thin film incorporating Si atoms was produced from a silicotungstic acid (SiWA) solution. The insertion compounds were measured by core level photoelectron spectroscopy (W 4f) and the contributions from ions of different oxidation states could be monitored simultaneously. SiWA films having a W⁶⁺/W_tot ratio of 0.7 could be prepared for all cations investigated. At this ratio the W 4f core level electronic structure for H⁺ inserted SiWA films was found to be very similar to that of H⁺ inserted into crystalline monoclinic WO₃ in that both films show the presence of W⁴⁺, W⁵⁺ and W⁶⁺. The measurements on Li⁺ inserted SiWA films indicate an electronic structure very similar to that of the smaller (H⁺) ion. The K⁺ inserted film displays a similar behaviour although the existence of W⁴⁺ was difficult to ascertain. Interestingly, a different behaviour was observed for the Na⁺ inserted compound. In this case, the binding energy shift of the W 4f peak upon reduction is clearly different from that obtained for the other insertion materials.     

Thin-film characterization using a scanning laser acoustic microscope with surface acoustic waves

The use of surface acoustic waves in a scanning laser acoustic microscope for the characterization of the mechanical or acoustic properties of thin films deposited on piezoelectric substrates is demonstrated. Quantitative measurements of mass loading effects of 5000-A-thick tungsten films deposited on lithium niobate substrates were obtained using 100-MHz surface acoustic waves. No information about the tungsten film could be obtained using 100-MHz compressional waves. Methods of generating surface waves on nonpiezoelectric materials so that this technique could be used on arbitrary substrates are discussed.     

Thermodesorption of samarium from oxidized tungsten surface

Thermodesorption of samarium (Sm) atoms and samarium oxide (SmO) molecules from samarium films deposited in vacuum onto tungsten substrates covered with thin (<1 nm thick) layers of tungsten oxides has been studied. It is established that samarium reduces tungsten from its oxides. The parameters of Sm and SmO desorption from an oxidized tungsten surface are determined.     

Effect of tungsten on the electrochromic behaviour of sol-gel dip coated molybdenum oxide thin films

The paper describes the results obtained on the performance of Mo oxide and mixed W/Mo oxide thin films for possible electrochromic applications. Mo and W/Mo oxide films were deposited on conductive (FTO) glass substrates using sol-gel dip coating method. The films were annealed at 250 °C for 30 min. The structure and morphology of Mo and W/Mo oxide films were examined using XRD, SEM and EDS. XRD results indicate the amorphous nature of the Mo and W/Mo oxide films annealed for 30 min. The CV measurements revealed that the films prepared with 10 wt.% of tungsten exhibit maximum anodic/cathodic diffusion coefficient of 24.99/12.71 × 10⁻¹¹ cm²/s. The same film exhibits a maximum transmittance variation (ΔT%) of 83.4% at 630 nm and 81.06% at 550 nm with the optical density of 1.00 and 1.13 respectively.     

Kirkendall void formation during room-temperature air-oxidation of thin aluminium and aluminium – lithium alloy films

Abstract

The effect of room-temperature (~20°C) air-oxidation on void formation in sputter-deposited thin films of aluminum and its alloys was investigated using a transmission electron microscope. It was found that after air-oxidation, only lithium-bearing aluminum alloy films exhibited a high (~4 × 10¹⁶ cm^?3) density of small (~2 nm) voids, whereas pure aluminum or lithium-free aluminum alloy films did not contain any voids. In lithium-bearing aluminum alloy films, both aluminum and lithium atoms migrate to the surfaces to form their surface oxide during room-temperature ageing after film deposition. In the course of the atom migration, excess vacancies are generated as a result of the large diffusivity difference existing between aluminum and lithium atoms (D_LiinAl ? D_Al) in the alloy matrix. The agglomeration of these excess vacancies led to the formation of so-called Kirkendall voids inside the alloy. Thus the presence of both aluminum and lithium in the alloys was a key factor for generating these Kirkendall voids in the films.     

Changes of tungsten oxide nanostructures in flame vapor deposition process depending on process variables

Tungsten oxide thin film in 1-dimensional (1-D) nanostructures shows high photocatalytic activity and the flame vapor deposition (FVD) process is fast and economical method to prepare 1-D nanostructured tungsten oxide thin films of high purity and crystallinity. We investigated the morphology changes of tungsten oxide thin film prepared by FVD process for various process variables such as total gas flow rate, flame temperature and substrate temperature. For the experimental conditions in this study, we confirmed that the selection of suitable total flow rate is a key factor for 1-D nanostructure growth in fuel-rich condition. As we increase the flame and substrate temperatures, the longer and thinner 1-D nanotubes were obtained, which have the advantages of high surface area and shorter diffusion length of proton for the application to photoelectrochemical water splitting. This study would provide the basic information for the design of FVD process to prepare 1-D nanostructures in future.     

Preparation and characterization of metalorganic chemical vapor deposited nickel oxide and lithium nickel oxide thin films

Thin films of nickel oxide and lithium nickel oxide were deposited through the pyrolysis of nickel acetylacetonate and lithium nickel acetylacetonate, respectively in the temperature range 350–420 °C. The single solid source precursors, nickel acetylacetonate and lithium nickel acetylacetonate were prepared and characterized using Energy Dispersive X-Ray Fluorescence (EDXRF), X-Ray Diffraction (XRD) and infrared spectroscopy. The composition, optical and electrical properties of the prepared thin films were analysed using a variety of techniques, including, Rutherford Backscattering Spectroscopy (RBS), EDXRF, XRD, UV–Visible Spectrophotometry and van der Pauw conductivity method. The amount of metals in the prepared thin films did not reflect the ratio of the metals in the precursor but was found to depend on the deposition temperature. The energy gaps of the nickel oxide and lithium nickel oxide thin films are 3.7 and 3.2 eV, respectively. The electrical conductivity showed that lithium nickel oxide thin film has an activation energy of 0.11 eV. The conduction was explained by a hopping mechanism.     

氧化钨多孔薄膜的制备及光学性质

多孔结构可以使氧化钨薄膜的气敏、电致变色等性能得到增强,但目前多孔氧化钨薄膜的制备仍存在困难。本文采用W和Al双靶磁控溅射的方法得到了W-Al合金薄膜后,把合金薄膜浸入NaOH溶液中处理,其中的Al被腐蚀同时W被氧化,从而得到了多孔的氧化钨薄膜。利用SEM观察多孔氧化钨薄膜样品的表面形貌,用XPS分析样品中W的价态,用XRD分析样品的晶体结构,用紫外-可见-近红外分光光度计测量样品的光学性质。结果显示:制得的多孔氧化钨薄膜的平均孔径在100nm左右,呈海绵状疏松结构;薄膜中W的价态以+5价为主;薄膜属于非晶相;在可见光区域,多孔氧化钨薄膜具有较高的透过率,而在近红外区域则具有近似平直的透过率曲线。     

Construction and characterization of tunable meso-/macroporous tungsten oxide-based transmissive electrochromic devices

Recent developments in the processing of porous transition metal oxide thin films have opened up new opportunities in the construction of electrochromic (EC) devices with enhanced properties. Tungsten oxide (WO₃) is one of the most promising materials for EC devices. In this work, we report on the synthesis of meso-/macroporous WO₃ thin films using tungstic acid as precursor and organically modified silane (ORMOSIL) as a templating agent. Calcination of the film at 500 °C resulted in nanocrystalline monoclinic tungsten oxide (m-WO₃) with crystallite sizes of ~16 nm. The meso-/macroporous structure is retained after calcination. An asymmetric EC device based on the meso-/macroporous m-WO₃ thin film was constructed. Thus constructed EC device was characterized by micro-Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction (XRD). Detailed micro-Raman and XRD studies of the intercalation and deintercalation of lithium (Li) in the meso-/macroporous m-WO₃ layer of the EC device as a function of the applied voltage were performed. The meso-/macroporous WO₃ layer, which was found to be monoclinic before Li intercalation, transforms to its higher symmetric phase of tetragonal and toward cubic phase when Li is intercalated into it. Upon complete deintercalation, these phase transitions were reversed and m-WO₃ is recovered. Optical transmission studies were performed in conjunction with Raman and XRD studies. This study shows that meso-/macroporous m-WO₃ layer-based EC device exhibit a high color contrast during the coloration and bleaching.     

纳米粒子陶瓷薄膜结构稳定性的工艺控制

主要基于前期研究工作结果 ,并参考了国内外相关研究成果 ,介绍和阐述了利用溶胶 -凝胶技术制备的氧化钼、氧化钛、钛酸锶陶瓷薄膜过程中 ,控制薄膜稳定性的主要工艺因素。特别对以无机盐为原料的溶胶 -凝胶工艺 (ISG工艺 )溶胶稳定性原理和措施做了较为详细描述和说明不同出发原料、溶剂和络合剂相匹配性很重要。以钼酸铵为原料 ,乙二醇和水为溶剂 ,柠檬酸为络合稳定剂 ,溶胶在室温下可稳定存放 2年以上。干燥控制剂 (DCCA)添加于溶胶中 ,可调整凝胶膜网络质点及其间孔隙的大小与分布 ,减小热处理过程中膜层应力和薄膜开裂     

Electrochemical properties of tungsten oxysulphide thin films as positive electrodes for lithium microbatteries

Several WO_yS_z tungsten oxysulphide thin films were tested as positive electrodes for lithium microbatteries. The amorphous WO_1.05S₂ thin film was found very promising. A capacity decrease occurred during the first few cycles, after which the films were able to intercalate reversibly up to 11 lithium ion per formula unit under high regime (75 μA/cm²). They were tested for 250 charge-discharge cycles, between 30 V and 1.2 V. X-ray photoelectron spectroscopy measurements were performed on different compounds in both intercalated (Li₁WO_1.05S₂, Li_2.7WO_1.05S₂ and Li_3.8WO_1.05S₂) and partially deintercalated (Li₁WO_1.05S₂) states in order to understand the redox processes occurring during the first dischargecharge cycle. The analysis of both the W4f and the S2p peaks has shown that the redox processes involve not only the tungsten atoms but also sulphur atoms. At the beginning of the intercalation, W⁶⁺ was first partially reduced into W⁵⁺, and then into W⁴⁺, but the important stage was the reduction of W⁴⁺ into W⁰. In W⁰, the electron binding energy was very close to that of metallic tungsten. At the same time, S ₂ ^2- ions were partially reduced into S^2- ions. But only the reduction process of tungsten atoms appeared to be totally reversible.