不同基底对TiO2和SiO2薄膜的光学性能的影响

采用溶胶-凝胶法分别在K9玻璃、单晶硅和石英玻璃基底上制备了纳米TiO₂和SiO₂薄膜。利用SEM、UV-Vis及反射式椭圆偏振光谱仪对薄膜的微观结构及光学特性进行了表征和分析。结果表明:3种基底中, 单晶硅基底上TiO₂和SiO₂薄膜折射率最大;在非晶态K9玻璃和石英玻璃基底上TiO₂薄膜折射率和透光率差异较大;SiO₂薄膜在非晶态基底上折射率、透光率相近;3种基底上薄膜的折射率和消光系数都有随波长增大而减小的趋势, 同时Cauchy模型能较好的描述单晶硅基底上两种薄膜在400~800 nm波段的光学性能。     

不同基底对TiO2和SiO2薄膜的光学性能的影响

采用溶胶-凝胶法分别在K9玻璃、单晶硅和石英玻璃基底上制备了纳米TiO₂和SiO₂薄膜。利用SEM、UV-Vis及反射式椭圆偏振光谱仪对薄膜的微观结构及光学特性进行了表征和分析。结果表明：3种基底中, 单晶硅基底上TiO₂和SiO₂薄膜折射率最大;在非晶态K9玻璃和石英玻璃基底上TiO₂薄膜折射率和透光率差异较大;SiO₂薄膜在非晶态基底上折射率、透光率相近;3种基底上薄膜的折射率和消光系数都有随波长增大而减小的趋势, 同时Cauchy模型能较好的描述单晶硅基底上两种薄膜在400~800 nm波段的光学性能。     

Fabrication of Sol-Gel Optical Waveguide by Hot-Dip Coating Process

The TiO₂: Sb nanoscale thin films were deposited on glass substrates by the sol–gel dip-coating method. The influence of the dopant density on the structure and the phase transformation of the thin films were investigated by X-ray diffraction (XRD) and Raman spectra. From the results of XRD, the thin films were in a majority of anatase state. The results of Raman spectra indicated that the non-doped TiO₂ thin film composed of not only anatase but also brookite phase. Dopant Sb enhances the transformation of the TiO₂ from brookite to anatase phase. After doping proper amount of Sb, the thin films show more superhydrophilicity than the non-doped TiO₂ thin film as well. The crystal size of the TiO₂ : Sb is about 13.3–20 nm calculated from the XRD patterns.     

Synthesis and characterization of chemically grown electrochromic tungsten oxide

Tungsten oxide thin films, which are cathodic coloration materials that are used in electrochromic devices, were prepared by a chemical growth method and their electrochromic properties were investigated. The thin films of WO₃ were deposited onto electrically conducting substrates: fluorine doped tin oxide coated glass (FTO) with sheet resistance of about 10 Ω/cm. Transparent, uniform and strongly adherent thin film samples of WO₃ were studied for their structural, morphological, optical and electrochromic properties. The XRD data confirmed the monoclinic crystal structure of WO₃ thin films. The direct band gap Eg for the films was found to be 2.95 eV which is good for electrochromic device application. The electrochromism of WO₃ thin film was evaluated in 0.5 M LiClO₄/propylene carbonate for Li⁺ intercalation. Electrochromic properties of WO₃ thin films were studied with the help of Cyclic Voltammetry (CV), Chronoamperometry (CA) and Chronocoulometry (CC) techniques.     

In situ spectroelectrochemical behaviour of nanocrystalline TiO2 thin films electrode fabricated by pulsed laser deposition

Nanocrystalline titanium oxide thin films have been successfully deposited on IT0 coated glass by pulsed laser ablation of metallic Ti target in 0₃/0₂ ambient gases. The intercalation of Li ions in the anatase TiO₂ film electrode is examined by cyclic voltammetry. The electrochromic behaviour of TiO₂ electrode is investigated byin-situ visible transmittance measurement, and two absorption bands at 420 and 650 nm are observed. The absorption falling and rising in color changing with excellent revisibility is relative to the insertion and deintercalation processes of Li ion. These results suggest that nanocrystalline titanium oxide films fabricated by pulsed laser deposition exhibit excellent spectroelectrochemical property. Project supported by the National Natural Science Foundation of China (Grant No. 29783001) and State Key Laboratory for Physical Chemistry of Solid Surface of Xiamen University (1997).     

Effect of heat treatment on electrochromic properties of TiO<Subscript>2</Subscript> thin films

Electrochromic titanium oxide (TiO₂) films were deposited on ITO/glass substrates by chemical solution deposition (CSD). The stock solutions were spin-coated onto substrates and then heated at various temperatures (200–500 °C) in various oxygen concentrations (0–80%) for 10 min. The effects of the processing parameters on the electrochromic properties of TiO₂ films were investigated. X-ray diffraction measurements demonstrated that the amorphous TiO₂ films were crystallized to form anatase films above 400 °C. The electrochromic properties and transmittance of TiO₂ films were measured in 1 M LiClO₄–propylene carbonate (PC) non-aqueous electrolyte. An amorphous 350 nm-thick TiO₂ film that was heated at 300°C in 60% ambient oxygen exhibited the maximum transmittance variation (ΔT%), 14.2%, between the bleached state and the colored state, with a ΔOD of 0.087, Q of 10.9 mC/cm², η of 7.98 cm²/C and x in Li _x ClO₄ of 0.076 at a wavelength (λ) of 550 nm.     

Photoelectrochemistry of indium hexacyanoferrate–titania composite films

The voltammetric and electrochromic behavior of two types of indium(III) hexacyanoferrate(II/III) (InHCF) films, potentiodynamically grown either on polycrystalline Au or on tin-doped indium oxide (ITO) support electrodes, are described. A new spectral feature was seen at ca. 475 nm for the InHCF films grown on Au under extended potential window (EPW) conditions, in addition to the dominant 420 nm feature described by previous authors. The 420 nm band is the sole electrochromic feature in films grown under restricted potential window (RPW) conditions. The InHCF films were also grown in the presence of TiO₂ particles in the deposition bath. The resultant InHCF–TiO₂ composite films showed distinctly different photoelectrochemical responses for the EPW and the RPW counterparts. X-ray phoelectron spectroscopy data showed a higher TiO₂ particle uptake for the EPW films relative to their RPW counterparts, under otherwise identical growth conditions. A second film configuration built up by InHCF derivatization of a pre-formed In–TiO₂ film, yielded decidedly inferior photoresponses. Mechanistic reasons for this are presented as is evidence for the dominance of two distinct forms of InHCF under the EPW growth conditions.     

Synthesis,structural and electrical characterization of PbS NCs in titania sol–gel films

Nanocrystals of lead sulfide were grown in TiO₂ (titania) thin films prepared by a sol-gel process. The synthetic procedure as well as the structural, optical, and electrical properties of the films are demonstrated. The structures and morphology of PbS nanocrystals were analyzed using HRTEM, SAED, AFM, HRSEM, XRD and EDAX elemental analysis technique. When the concentration of PbS in the titania matrix is 20 mol%, PbS NCs with a diameter of 2.0 nm are created. At a higher PbS concentration (> 40 mole%) in the titania matrix, PbS NCs and PbS clusters are created not only within the TiO₂ film but also on the external surface of the TiO₂ film. By increasing the PbS concentration up to 50 mol%, PbS nanocrystals of 6–8 nm in diameter are formed within the titania film and PbS clusters with a base size of about 100 nm² and a height up to about 20 nm were self assembled on the external surface of TiO₂ film. Quantum size effect and band gap energies were obtained from shifts of the absorption edge. For electrical measurements, PbS–TiO₂ films were deposited on an ITO/glass substrate, and then covered with gold contact. The electrical properties of ITO/PbS NCs–TiO₂/Au and ITO/PbS NCs–TiO₂/PbS cluster/Au structures were studied. I–V characteristics of the one layer structure are nearly linear and symmetric, while those of the two-layer structure exhibit rectifying behavior.     

Preparation and Characterization of TiO2 Thin Films by Sol-Gel Method

Titanium dioxide (TiO₂) thin films have been deposited on silicon and glass substrates by the sol-gel process using titanium iso-propoxide [Ti(O-i-C₃H₇)₄]. The bond configuration of the TiO₂ thin films was analyzed by using FTIR in the wavenumber range from 400 to 4000 cm^–1. The spectral transmittance of as-deposited TiO₂ films deposited on fused silica glass was measured in the wavelength range from 200 to 900 nm. X-ray diffraction measurements were performed to determine the crystallinity of the TiO₂ films. As-deposited films were amorphous. As the film was annealed at higher temperature, the structure was transformed from amorphous to the anatase crystalline state. The chemical composition of the deposited film was investigated using X-ray photoelectron spectroscopy (XPS). The films are essentially stoichiometric with carbon as the dominant impurity on the surface. Raman spectra show the characteristic of TiO₂ anatase phase. The electrical properties of the TiO₂ films were measured using capacitance-voltage (C-V) and current-voltage techniques. From C-V measurements, the dielectric constants were calculated to be approximately 26 for the as-deposited films and 75–82 for films annealed at 700°C in different atmosphere. For the as-deposited samples, the breakdown voltage was 2.7 MV/cm, and for an electric field of 1 MV/cm, the leakage current was 5 × 10^–5 A/cm² and the resistivity was 2.2 × 10¹⁰ -cm.     

Photovoltaic Behaviour of Titanyl Phthalocyanine Thin Films and Titania Bilayer Films

Summary: Titanyl phthalocyanine (TiOPc) thin films were prepared using evaporation and surface polymerization by ion-assisted deposition (SPIAD) in a vacuum deposition system. These films were characterized by means of ultraviolet and X-ray photoelectron spectroscopy as well as UV/Vis absorption spectroscopy. Valence band and elemental content indicated that phthalocyanine electronic and chemical structures were largely preserved during SPIAD. Further, bilayer thin films of titania (TiO₂) and SPIAD TiOPc were prepared. TiO₂ film was deposited by reactive magnetron sputtering of TiO₂ target. Study of the structured samples was focused on the optical and electrical properties of the composite films. The films were characterized by non-contact photovoltage measurements and UV-Vis spectroscopy. These results suggest there is a possibility to use these bilayer thin films in photovoltaic solar cells, however further experiments to improve conductivity of the films will be required.     

X-ray diffraction study of TiO2 thin films on mica

Thin layers of polycrystalline TiO₂ were deposited on flaky muscovite and phlogopite particles. Deposition was performed in water slurry using aqueous TiCl₄ as titanium source. The effect of heat treatments on the structure of TiO₂ thin films was investigated at different layer thicknesses. On muscovite mica the films crystallized as anatase TiO₂. On phlogopite mica the increasing layer thickness favored partial rutile formation at higher calcination temperatures, although the films could not be converted to pure rutile. The preferred orientation of the TiO₂ films was evident. The most intense reflections were measured from (004) and (105) planes. The crystallite size of TiO₂ was strongly dependent on calcination temperature and TiO₂ layer thickness. It varied between 15 and 47 nm for films deposited on phlogopite, and 15 and 57 nm for films deposited on muscovite.     

Chromogenic WPA/TiO 2 Hybrid Gels and Films

A novel low-temperature electrochromic and photochromic material in the form of gels and thin solid films composed of H₃PW₁₂O₄₀·nH₂O (WPA) incorporated in titanium oxide gel issued of Ti(OPr ⁱ )₄ with addition of acetic acid were made via the sol-gel route by the dip-coating technique. Gels in bulk and thin film forms have been studied with the help of FT-IR transmission, reflection absorption and Raman spectroscopy. Similarity of the characteristic band frequencies with pure WPA confirmed that entrapped Keggin salt is well preserved inside the gel. Photochromism of WPA/TiO₂ gels which appears after short exposure to UV (λ=366 nm) radiation is related to the excitation effect of branched alcohol leading to formation of carbonyl modes due to the alcohol transformation to aldehyde. Electrochromic properties of WPA/TiO₂ gel films were tested in aqueous 0.001M HClO₄ and 0.1M LiClO₄ electrolytes as well as in the sol-gel electrochromic device (ECD) composed of LiClO₄ doped ormolyte and Sb:Mo:SnO₂ counter electrode film with optically passive response. Slight improvement of the WPA/TiO₂ intercalation/deintercalation kinetics was obtained with the films exhibiting one order of magnitude higher electronic conductivity which were made with addition of in situ polymerized pyrrole with Fe(NO₃)₃.     

Fabrication of Ordered TiO2 Porous Thin Films by Sol-Dipping PS Template Method

Monolayer polystyrene spheres (∼400 nm) array templates were assembled orderly on clean glass substrates by dip-drawing method from emulsion of PS and porous TiO₂ thin films were prepared by using sol-dipping template method to fill TiO₂ sol into the interstices among the close-packed PS templates and then annealing to remove the PS templates. The effects of TiO₂ precursor sol concentration and dipping time in sol on the porous structure of the thin films were studied. The results showed pore size of the ordered TiO₂ porous thin film depended mainly on PS size and partly on TiO₂ sol concentration. The shrinkage of pore diameter was about 10% for 0.2 M and 20% for 0.4 M TiO₂ sol concentrations. X-ray diffraction (XRD) spectra indicated the porous thin film was anatase structure. The transmittance spectrum showed that optical transmittance of the porous thin film kept above 70% beyond the wavelength of 430 nm. Optical band-gap of the porous TiO₂ thin film (fired at 550^∘;C) was 3.12 eV.     

Preparation of the visible light responsive TiO2 thin film photocatalysts by the RF magnetron sputtering deposition method

TiO₂ thin film photocatalysts which could induce photoreactions under visible light irradiation were successfully developed in a single process by applying an ion engineering technique, i.e., the radio frequency (RF) magnetron sputtering deposition method. The TiO₂ thin films prepared at temperatures greater than 773 K showed the efficient absorption of visible light; on the other hand, the TiO₂ thin films prepared at around 573 K were highly transparent. This clearly means that the optical properties of TiO₂ thin films, which absorb not only UV but also visible light, can be controlled by the preparation temperatures of the RF magnetron sputtering deposition method. These visible light responsive TiO₂ thin films were found to exhibit effective photocatalytic reactivity under visible light irradiation (λ > 450 nm) at 275 K for the reductive decomposition of NO into N₂ and N₂O. From various characterizations, the orderly aligned columnar TiO₂ crystals could be observed only for the visible light responsive TiO₂ thin films. This unique structural factor is expected to modify the electronic properties of a TiO₂ semiconductor, enabling the efficient absorption of visible light.     

Electrochemical and Electrochromic Properties of Ni Oxide Thin Films Prepared by a Sol–Gel Method

Nickel oxide thin films, which are well known anodic coloration materials that are used in electrochromic devices, were prepared by a sol–gel method, and their electrochemical and electrochromic properties were investigated. The sol was prepared from Ni(OH)₂ powder with an average size of 7 nm, in a mixture of ethylene glycol and absolute ethanol. The films were coated on an ITO substrate using the powder, dispersed in the solution. When additive materials, acetyl acetone and glycerol, were added to the sol its hardness and adhesion properties were improved. The optimized thin film formed an amorphous, porous structure, and showed a large current density during continuous potential and pulse potential cycling. The film also was transparent and had a high coloration efficiency (33.5 cm²/C) and a rapid response time (1.0–2.5 s) during the coloring/bleaching process.     

总气压与Ar/O2流量比对直流对向靶磁控溅射TiO2薄膜光催化性能的影响

采用对向靶磁控溅射法在不同气压和Ar/O₂流量比条件下, 以氟化SnO₂ (FTO)导电玻璃为基底制备了多晶TiO₂薄膜. 台阶仪测量结果显示所制备TiO₂薄膜的平均厚度约为200 nm. 随着溅射气压的升高, TiO₂薄膜由锐钛矿与金红石混晶结构转变为纯锐钛矿结构. 分别采用场发射扫描电镜(FESEM)和原子力显微镜(AFM)分析了不同气压和Ar/O₂流量比对TiO₂薄膜表面形貌的影响, 结果显示TiO₂薄膜的表面粗糙度随溅射总气压和Ar/O₂流量比的增加而增大. 以初始浓度为100×10^-6 (体积分数)的异丙醇(IPA)气体为目标物检测所制备TiO₂薄膜的光催化性能, 并分析该气相光催化反应的机理, 在紫外照射条件下异丙醇先氧化为丙酮再被氧化为CO₂.当总溅射气压为2.0 Pa、Ar/O₂流量比为1:1时, 溅射所得TiO₂薄膜具备最优光催化活性并可在IPA降解反应中保持较高的催化活性和稳定性.     

Preparation of TiO2 Thin Film Photocatalysts by Dip Coating Using a Highly Viscous Solvent

TiO₂ thin film photocatalysts coated onto soda lime glass were prepared by a dip coating process using a highly viscous solvent. The source of the TiO₂ was tetraisopropyl orthotitanate, and -terpineol was used as the solvent. Two types of thin film preparation procedures based on dip coating (a sol-gel system and thermal decomposition system) were used to prepare the samples. TiO₂ thin films were obtained after calcination at 450°C for 1 hour. The film thickness obtained with a single dipping was proportional to the viscosity of the dip coating solutions. The obtained thin films were transparent with a thickness of 1 m. The crystal form of the obtained photocatalyst films was anatase alone. The thin films were formed with aggregated nano-sized TiO₂ single crystals (7–15 nm). The photocatalytic activity of the TiO₂ thin films, as evaluated by the photooxidation of NO (1 ppm) in dry air, was as high as our previous TiO₂ thin films prepared by the sol-gel method.     

Effect of Pt loading on the photocatalytic reactivity of titanium oxide thin films prepared by ion engineering techniques

Platinum-loaded titanium oxide thin-film photocatalysts were prepared by using an ionized cluster beam (ICB) deposition method and a RF magnetron sputtering (RF-MS) deposition method as dry processes. From the results of the photocatalytic oxidation of acetaldehyde with O₂ under UV light irradiation, small amounts of Pt loading (less than 10 nm film thickness) were found to dramatically enhance the photocatalytic reactivity. However, when TiO₂ thin films were loaded with relatively larger amounts of Pt (more than 30 nm as the film thickness), the photocatalytic reactivity became lower than for the pure TiO₂ thin films. Moreover, investigations of the ratio of Pt loaded onto the surface of the thin film catalysts by XPS measurements revealed that the small amounts of Pt loaded exist as very small clusters working to efficiently enhance the charge separation, whereas, large amounts of Pt covers the entire surface of the TiO₂ thin films, resulting in a decrease of the photocatalytic reactivity.     

Electrochromic properties of MoO<Subscript>3</Subscript> thin films derived by a sol–gel process

Molybdenum trioxide (MoO₃) films were deposited on ITO/Glass substrates by the sol–gel method using a spin-coating technique and heat treated at various temperatures under different ambient atmosphere. Effects of the process parameters on the electrochromic properties of MoO₃ films were studied using cyclic voltammetry (CV) in a propylene carbonate (PC) non-aqueous solution containing 1 M lithium perchlorate (LiClO₄). Electrochromic MoO₃ film on lithium intercalation was investigated by in-situ transmittance measurement during the CV process. The MoO₃ films showed reversible recharge ability on Li⁺/e⁻ intercalation/deintercalation. Experimental results revealed that the heat-treatment temperature, the ambient atmosphere, and the thickness will have the string influence on the electrochromic properties of MoO₃ thin films. X-ray diffraction (XRD) results show that the amorphous MoO₃ films can be obtained with the heat-treatment temperature below 300 °C in O₂ ambient atmosphere. The optimum electrochromic MoO₃ film, with a thickness of 130 nm, exhibits a maximum transmittance variation (ΔT%) of 30.9%, an optical density change (ΔOD) of 0.213, an intercalation charge (Q) of 8.47 mC/cm², an insertion coefficient x in Li _x MoO₃ was 0.21 and a coloration efficiency (η) of 25.1 cm²/C between the colored and bleached states at a wavelength (λ) of 550 nm.