Fabrication study of proton injection layer suitable for electrochromic switchable mirror glass

An electrochromic (EC) switchable mirror glass can change between a reflective state and a transparent state with voltage application. The conventional device has a multilayer of Mg₄Ni/Pd/Al/Ta₂O₅/WO₃/indium-tin oxide on a transparent substrate. A palladium thin film was used as the proton injection layer. For practical use, we attempted to reduce the amount of palladium thin film from the viewpoints of the reduction in total fabrication cost and the efficient use of resources. The thickness of the film was related to the optical switching properties of the device. Although the device with a 1-nm-thick palladium film showed a high transmittance of 63% in the transparent state, its low switching durability was not suitable for practical application.Moreover, we were able to adapt a palladium-based alloy (Pd_0.8Ag_0.2) which is a well-known hydrogen permeation membrane as the proton injection layer to reduce the amount of palladium thin film. As a result, we found that a 4-nm-thick Pd-Ag thin film has good adaptability to the EC switchable mirror.     

Optical and electrochemical properties of all-solid-state transmittance-type electrochromic devices

Using a vacuum dry process, we constructed an all-solid-state transmittance-type electrochromic (EC) device consisting of five thin layers: ITO/IrO_x/Ta₂O₅/WO₃/ITO. We measured the optical and electrochemical properties of the EC device. By using Ta₂O₅ film as a proton conducting solid electrolyte, the device exhibited a fast response speed of 0.2 s and stable coloration characteristics. With an AC impedance method, we determined the properties of the device under varying temperature and environmental conditions. In the solid electrolyte (Ta₂O₅), the ion resistance controlled the response speed; the ionic conductivity and activation energy were 3 × 10^− 6 S/cm and 0.31 eV, respectively.     

Polyvinyl chloride seal layer for improving the durability of electrochromic switchable mirrors based on Mg-Ni thin film

Electrochromic switchable mirrors consisting of a multilayer of Mg₄Ni/Pd/Al/Ta₂O₅/H_XWO₃/indium tin oxide on a glass substrate degrade when subjected to changes in humidity and temperature. Polyvinyl chloride was applied as a seal layer to such a device in an attempt to improve its durability. The optical switching properties of the device were investigated through an accelerated degradation test conducted at a constant temperature of 30 °C and a relative humidity of 80%. Although the device with a seal layer was thicker, it showed superior optical switching properties with a transmittance as high as 54% in the transparent state due to interference at the multilayer. Furthermore, the device with a seal layer exhibited higher durability after 35 days in an accelerated degradation environment, as well as higher switching durability.     

Preparation of inorganic solid state thin film for electrochromic application

All oxide solid state ITO (indium tin oxide)/Li_yWO_3−x/Li_1−zMn₂O₄/ITO stacked structure was deposited on a silica glass substrate by pulsed laser deposition for its electrochromic application. The Li doped amorphous tungsten trioxide Li_yWO_3−x thin film prepared at room temperature and in oxygen pressure of 7 Pa got the color of blue due to the mixture valence state of tungsten. We found that the amorphous Li_1−zMn₂O₄ thin film was suitable for the electrochromic application in spite of the low ion conductivity along in-plane direction. The ITO electrode thin film deposited at room temperature showed the relatively high transmittance and the usable conductivity. The transmittance at a wavelength of 750 nm for the ITO/Li_yWO_3−x/Li_1−zMn₂O₄/ITO stacked film changed from 50% to 80% by the applied voltage, while the transmittance at around 450 nm did not change. The blue-colored electrochromic property could be observed for the all oxide solid state film.     

Tantalum oxide film prepared by reactive magnetron sputtering deposition for all-solid-state electrochromic device

Inorganic-solid-state electrolyte tantalum oxide thin films were deposited by reactive DC magnetron sputtering to improve the leakage and deterioration of traditional liquid electrolytes in electrochromic devices. O₂ at 1–20 sccm flow rates was used to deposit the tantalum oxide films with various compositions and microstructures. The results indicate that the tantalum oxide thin films were amorphous, near-stoichiometric, porous with a loose fibrous structure, and highly transparent. The maximum charge capacity was obtained at an oxygen flow rate of 3 sccm and 50 W. The transmission change of the Ta₂O₅ film deposited on a WO₃/ITO/glass substrate between colored and bleached states at a wavelength of 550 nm was 56.7%. The all-solid-state electrochromic device was fabricated as a multilayer structure of glass/ITO/WO₃/Ta₂O₅/NiO_x/ITO/glass. The optical transmittance difference of the device increased with increasing applied voltage. The maximum change was 66.5% at an applied voltage of ± 5 V.     

Highly a-oriented SrBi2Ta2O9 thin film on (111) Pt/TiO2/SiO2/Si substrate by eclipse pulsed laser deposition

A highly a-oriented SrBi₂Ta₂O₉ thin film with a polycrystalline structure was deposited on a preferentially oriented (111) Pt/TiO₂/SiO₂/Si substrate by eclipse pulsed laser deposition (PLD) method. The SrBi₂Ta₂O₉ thin film exhibited flat and smooth surface with the surface roughness of about 0.5 nm resulting from reducing particulates generated by on-axis PLD. The SrBi₂Ta₂O₉ thin film showed a good ferroelectric property with the high remanent polarization of 12 μC/cm² and the low coercive electric field of 140 kV/cm. For the highly a-oriented SBT thin film, domain switching and reading were performed by Kelvin probe force microscope (KFM). The KFM data indicate a good ferroelectric property of the highly a-oriented SrBi₂Ta₂O₉ thin film with high KFM signals that reflect ferroelectric polarizations.     

Characterization of flexible switchable mirror film prepared by DC magnetron sputtering

An electrochromic switchable mirror on a flexible plastic sheet was developed taking into consideration practical use, low cost and high adaptability. The mirror has a multilayer of Mg₄Ni/Pd/Al/Ta₂O₅/WO₃, which was fabricated by DC magnetron sputtering on an ITO-coated PET sheet. In the previous research, when the mirror was exposed to air for a long period of time, its optical switching properties disappeared. This work focused on the mechanism of degradation of the mirror in different environments. When the mirror was stored in a desiccator for 50 days as a means of preservation, its switching speed was seven times higher as compared with the mirror exposed to air. It is also well known that oxygen and moisture in air easily penetrate PET sheets. The features of the PET sheet strongly affected the durability of the optical switching layer. When the state of the optical switching layer was changed to nonmetallic due to the formation of oxide and hydroxide, the optical switching properties almost disappeared.     

Characterization of nanocrystalline indium tin oxide thin films prepared by ion beam sputter deposition method

Indium tin oxide (ITO) thin films were deposited on glass substrates by ion beam sputter deposition method in three different deposition conditions [(i) oxygen (O₂) flow rate varied from 0.05 to 0.20 sccm at a fixed argon (1.65 sccm) flow rate, (ii) Ar flow rate changed from 1.00 to 1.65 sccm at a fixed O₂ (0.05 sccm) flow rate, and (iii) the variable parameter was the deposition time at fixed Ar (1.65 sccm) and O₂ (0.05 sccm) flow rates]. (i) The X-ray diffraction (XRD) patterns show that the ITO films have a preferred orientation along (400) plane; the orientation of ITO film changes from (400) to (222) direction as the O₂ flow rate is increased from 0.05 to 0.20 sccm. The optical transmittance in the visible region increases with increasing O₂ flow rate. The sheet resistance (R_s) of ITO films also increases with increasing O₂ flow rate; it is attributed to the decrease of oxygen vacancies in the ITO film. (ii) The XRD patterns show that the ITO film has a strong preferred orientation along (222) direction. The optical transmittance in the visible spectral region increases with an increase in Ar flow rate. The R_s of ITO films increases with increasing Ar flow rate; it is attributed to the decrease of grain size in the films. (iii) A change in the preferred orientations of ITO films from (400) to (222) was observed with increasing film thickness from 314 to 661 nm. The optical transmittance in the visible spectral region increases after annealing at 200 °C. The R_s of ITO film decreases with the increase of film thickness.     

Electrodeposition of SmS optical thin films on ITO glass substrate

SmS optical thin films were deposited on the surface of ITO glass with an electrodeposition method using aqueous solution containing SmCl₃·6H₂O and Na₂S₂O₃·5H₂O. The phase composition was analyzed by X-ray diffraction (XRD) and microstructure of the film was characterized by atomic force microscope (AFM). It is showed that SmS thin film could be obtained in the solution with n(Sm)/n(S) = 1:4, pH = 4.0 and annealing in Ar atmosphere at 200 °C for 0.5 h. The as-prepared thin films on the ITO glass exhibit a dense microstructure. The band gap of the thin film has been found to be 3.6 eV.     

All-solid-state reflectance-type electrochromic devices using iridium tin oxide film as counter electrode

We prepared an all-solid-state reflectance-type electrochromic device (ECD), consisting of the following five layers: Al/WO₃/Ta₂O₅/Ir_xSn_1 − xO₂/ITO. Using RF ion plating, we prepared a film containing dispersed iridium oxide in a tin oxide matrix; this film acts as the counter electrode in the all-solid-state ECD. Protons were used as coloration ions in the ECD. The size of the ECD was 150 cm², and the reflectance changed between more than 60% from 15%. The coloration and bleaching response times were less than a few seconds. We analyze the optical characteristics of the ECD, and report the results of a consecutive drive test and a high-temperature heat resistance test.     

Characterization of flexible switchable mirror film prepared by DC magnetron sputtering

An electrochromic switchable mirror on a flexible plastic sheet was developed taking into consideration practical use, low cost and high adaptability. The mirror has a multilayer of Mg₄Ni/Pd/Al/Ta₂O₅/WO₃, which was fabricated by DC magnetron sputtering on an ITO-coated PET sheet. In the previous research, when the mirror was exposed to air for a long period of time, its optical switching properties disappeared. This work focused on the mechanism of degradation of the mirror in different environments. When the mirror was stored in a desiccator for 50 days as a means of preservation, its switching speed was seven times higher as compared with the mirror exposed to air. It is also well known that oxygen and moisture in air easily penetrate PET sheets. The features of the PET sheet strongly affected the durability of the optical switching layer. When the state of the optical switching layer was changed to nonmetallic due to the formation of oxide and hydroxide, the optical switching properties almost disappeared.     

An investigation on electrochromic properties of (WO3)1−x-(Fe2O3)x thin films

In this research, the effect of Fe₂O₃ content on the electrochromic properties of WO₃ in thermally evaporated (WO₃)_1−x-(Fe₂O₃)_x thin films (0 ≤ x ≤ 0.4) has been studied. The atomic composition of the deposited metal oxides was determined by X-ray photoelectron spectroscopy analysis. The surface morphology of the thin films has been examined by atomic force microscopy. The surface roughness of all the films was measured about 1.3 nm with an average lateral grain size of 30 nm showing a smooth and nanostructured surface. The electrochromic properties of (WO₃)_1−x-(Fe₂O₃)_x thin films deposited on ITO/glass substrate were studied in a LiClO₄ + PC electrolyte by using ultraviolet-visible spectrophotometry. It was shown that increasing the Fe₂O₃ content leads to reduction of the optical density (ΔOD) of the colored films and also leads to increasing the optimum coloring voltage from 4 to 6 V in which ΔOD shows its maximum values, in our experimental conditions. Furthermore, by using this procedure, it is possible to make an electrochromical filter which behaves similar to the colored WO₃ film in the visible region, while it can be nearly transparent for near-infrared wavelengths, in contrast of the pure colored WO₃ film.     

Preparation and characterization of La0.9Sr0.1Ga0.8Mg0.2O3−δ thin film electrolyte deposited by RF magnetron sputtering on the porous anode support for IT-SOFC

Thin films of solid electrolyte La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM) were deposited by RF magnetron sputtering onto porous La_0.7Sr_0.3Cr_0.5Mn_0.5O_3−δ (LSCM) anode substrates. The effects of substrate temperature, sputtering power density and sputtering Ar gas pressure on the LSGM thin film density, flatness and morphology were systematically investigated. RF sputtering power density of 7.8 W cm⁻², substrate temperature of 300 °C and sputtering Ar gas pressure of 5 Pa are identified as the best technical parameters. In addition, a three-electrode half cell configuration was selected to investigate the electrochemical performance of the thin film. The LSGM film deposited at optimum conditions exhibited a lower area specific ohmic resistance of 0.68 Ω cm⁻² at 800 °C, showing that the practicability of RF magnetron sputtering method to fabricate LSGM electrolyte thin film on porous LSCM anode substrates.     

Fabrication of high frequency ZnO thin film SAW devices on silicon substrate with a diamond-like carbon buffer layer using RF magnetron sputtering

Diamond-like carbon (DLC) film is a promising candidate for surface acoustic wave (SAW) device applications because of its higher acoustic velocity. A zinc oxide (ZnO) thin film has been deposited on DLC film/Si substrate by RF magnetron sputtering; the optimized parameters for the ZnO sputtering are RF power density of 0.55 W/cm², substrate temperature of 380 °C, gas flow ratio (Ar/O₂) of 5/1 and total sputter pressure of 1.33 Pa. The results showed that when the thickness of the ZnO thin films was decreased, the phase velocity of the SAW devices increased significantly.     

Effect of deposition ambient on structural and optical properties of Mg<Subscript>x</Subscript>Zn<Subscript>1−x</Subscript>O alloy thin films grown by RF sputtering

Mg_xZn_1−xO thin films were deposited on Corning eagle 2,000 glass substrates by a RF magnetron sputtering using a ceramic target. The effect of Ar/O₂ ratios on structural and optical properties was investigated. The XRD results showed that the film demonstrated the best structural properties when the Ar/O₂ ratio equal 7:3. Sputtering ambient seemed to have minor effect on the optical properties of Mg_xZn_1−xO thin films.     

Ferroelectric and fatigue-free properties of Au/(Bi,La)4Ti3O12/ITO thin film capacitors by pulsed laser deposition

Ferroelectric Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films were deposited on indium-tin-oxide (ITO) coated glass substrates by pulsed-laser-ablation method. Films deposited at 400 °C and annealed at 650 °C resulted in remnant polarization and coercive field values of 14-16 μC/cm² and 90-100 kV/cm, respectively. The fatigue measurements were conducted until 1 × 10¹¹ cycles but the individual switched and unswitched polarizations showed unequal magnitudes. Such an unequal switching polarization proves that an extrinsic effect mainly associated with the electrode exists in this thin film capacitor. The overall switching polarizations showed no polarization degradation, suggesting that BLT films are fatigue resistive even on hybrid-metal-oxide electrodes.     

Indium Tin Oxide thin film gas sensors for detection of ethanol vapours

Indium Tin Oxide (ITO: In₂O₃ + 17% SnO₂) thin films grown on alumina substrate at 648 K temperatures using direct evaporation method with two gold pads deposited on the top for electrical contacts were exposed to ethanol vapours (200-2500 ppm). The operating temperature of the sensor was optimized. The sensitivity variation of films having different thickness was studied. The sensitivity of the films deposited on Si substrates was studied. The response of the film with MgO catalytic layer on sensitivity and selectivity was observed. A novel approach of depositing thin stimulating layer of various metals/oxides below the ITO film was tried and tested.     

Ion sensing properties of vanadium/tungsten mixed oxides

Vanadium/tungsten mixed oxide (V₂O₅/WO₃) sensing membranes were deposited on glassy carbon substrates and used as the H⁺ sensor of the extended gate field effect transistor (EGFET) device. X-ray diffractograms indicated a decrease of the interplanar spacing of V₂O₅ after the insertion of WO₃ revealing that the lamellar structure is under compressive stress. The crystallinity increases with increasing WO₃ molar ratio. The film is not homogeneous, with more WO₃ material sitting at the surface. This influences the response of pH sensors using the EGFET configuration. The maximum sensitivity of 68 mV pH⁻¹ was obtained for the sample with 5% WO₃ molar ratio. For higher WO₃ molar ratios, the behavior is not linear. It can be concluded that V₂O₅ dominates for acidic solutions while WO₃ dominates for basic solutions. Therefore, the mixed oxide with low amount of WO₃ is the main candidate for further use as biosensor.     

Simultaneous determination of the thermal expansion coefficient and the elastic modulus of Ta2O5 thin film using phase shifting interferometry

Abstract

This paper reports on the application of a phase shifting interferometry technique for the concurrent measurement of the thermal expansion coefficient α_f and the elastic modulus E_f /1 - V_f of Ta₂O₅ thin film. The Ta₂O₅ films were prepared by ion beam sputter deposition. The stresses in the thin films were measured with the phase shifting interferometry technique using two types of circular discs with known thermal expansion coefficients, Young's moduli and Poisson's ratios. The temperature-dependent stress behaviour of Ta₂O₅ films was obtained by heating samples in the range from room temperature to 70°C. The internal stresses of Ta₂O₅ thin films deposited on the BK-7 and Pyrex glass substrates were plotted against the stress measurement temperature, showing a linear dependence. From the slopes of the two lines in the stress versus temperature plot, the thermal expansion coefficient and the elastic modulus of Ta₂O₅ thin film are then calculated.     

SiO2 film deposition on the inner wall of a narrow polymer tube by a capacitively coupled μplasma

SiO₂ thin films were deposited on the inner wall of a narrow commercial poly(propylene) tube with inner/outer diameters of 1.0 mm/3.0 mm by plasma-enhanced chemical vapor deposition using He or Ar carrier gases and tetraethoxysilane (TEOS)/O₂ feedstock gases at high pressures from 30 kPa to atmospheric pressure and at room temperature. A glow μplasma was generated inside the tube by a radio frequency (RF 13.56 MHz) capacitively coupled discharge. X-ray photoelectron spectra and infrared spectra revealed that the inner surface of the plasma-treated tube was covered by a SiO₂ film. Scanning electron microscopy images indicated that the film produced by He/TEOS/O₂ μplasma had a smooth surface whereas the surface of the film produced by Ar/TEOS/O₂ μplasma appeared granulated. Typical deposition rates of approximately 300 nm/min were obtained by He/TEOS/O₂ μplasma at atmospheric pressure and a RF power of 11 W.