Surface Morphology Of TiO2 Films Research Articles

Microstructure and optical and electrical properties of TiO 2 nanotube thin films prepared by spin‐coating method

Titanium dioxide nanotubes prepared by hydrothermal method and the TiO2 films and TiO2 nanotube film were prepared by spin-coating method. The TiO2 nanotube film and a part of TiO2 film were annealed at 150°C for 1 h, while the another part of TiO2 film was annealed at 500°C. The high-resolution transmission electron microscopy analysis indicated that the TiO2 nanotubes prepared by hydrothermal method have been crystallised and the lattice plane indices corresponded to anatase {200}, and the TiO2 nanotube grown along the 〈100〉 direction. The atomic force microscopy results show that the surface morphology of the TiO2 film annealed at 150°C was smooth and uniform (0.62 nm in roughness) compared to the surface morphology of TiO2 film annealed at 500°C (roughness is 2.41 nm). For the TiO2 nanotube film, the nanotube fragments were uniformly dispersed in the base and the complete films have been prepared and the roughness was reached to 6.4 nm. The optical properties showed that the visible light transmittance of the TiO2 nanotube film was larger (larger than 95%) than the TiO2 film. The electrical properties showed that square resistance of TiO2 nanotube film was smaller than that of TiO2 film.

Micromixing-assisted preparation of TiO2 films from ammonium hexafluorotitanate and urea by liquid phase deposition based on simulation of mixing process in T-shaped micromixer

Abstract Preparation of well-ordered TiO2 films from alkaline solution by liquid phase deposition (LPD) method is still challenging owing to the fact that, in traditional mixing process, several disadvantages exist in controllable homogenous chemical reactions. In this contribution, mixing process in a porous dispersed double T-junction micromixer was designed and investigated using numerical simulation. It is obtained that high mixing intensity can be achieved by micromixer with inlet velocity of 0.6 m s−1 and microfiltration meshes 10 μm in size. A micromixing-assisted platform consisted of two syringe pumps and a micromixer was manufactured to efficiently fabricate TiO2 films via mixing of (NH4)2TiF6 and CO(NH2)2 as reactants and fluorine doped tin oxide, F: SnO2 (FTO), conducting glass substrates by LPD in alkaline solutions. The results suggest that surface morphology of TiO2 films fabricated by micromixing can be easily controlled in comparison with that of specimens prepared by traditional stirring mixing process. The dense and well-ordered TiO2 films derived from micromixing have enhanced adhesion strength, high hardness, good hydrophilic and excellent photoelectrochemical properties. Particularly, homogeneous reaction could be inhibited in micromixer and an ideal supersaturation solution would be formed via micromixing treatment, which significantly facilitates the formation of high quality TiO2 films by heterogeneous nucleation on substrate surface. These obtained achievements are expected to promote further application of TiO2 films in a variety of domains including photocatalysis and corrosion protection of metals.

Influence of post-deposition annealing and the ITO underlayer on the properties of hybrid TiO2/ITO nanocomposite for enhanced hydrogen sensing at room temperature

We report the effect of heat treatment on room temperature hydrogen sensing performance of TiO2 films prepared on ITO coated glass substrate by a novel spray deposition. Our outcomes show that the better sensitivity of the sensor strongly depends on the surface morphology of TiO2 film and the ITO under layer. All the films exhibit polycrystalline nature of tetragonal crystal structure. The average particle size of the preferential (101) peak of TiO2 was found to be 7–13nm. Heat treatment played a crucial role in the improvement of the crystal quality and energy band gap of the bilayered TiO2/ITO films. The UV spectra show shift in the absorption edge towards lower wavelength with increase in annealing temperature. XRD and Raman data suggest the phase-pure anatase creation. The sensor response was tested for hydrogen concentrations of 200–800ppm at room temperature. Predominantly, the TiO2/ITO nanocomposite annealed at 300°C exhibited more promising sensor behavior to even low concentration of 200ppm hydrogen at room temperature. The highly ordered porous nanospherical oxide structures achieved on ITO nanoclusters revealed a high sensor resistance of 85MΩ, with fast recovery of 4s. The hybrid sensor also exhibited good selectivity to H2 gas compared with other gases ethanol and acetone studied under the same operating condition.

Effect of surface morphology on wettability conversion

A hierarchical structural surface of TiO2 film with reversibly light-switchable wettability between superhydrophobicity and superhydrophilicity on metal substrate was fabricated through simply dip-coating method from TiO2 precursor solution containing TiO2 nanoparticles with the average diameter 25 nm (P25), followed by heat-treatment and modification with fluoroalkylsilane (FAS) molecules. The morphology, phase and crystallographic structure, and chemical composite of the as-prepared TiO2 film were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The wettability of TiO2 film was characterized by a drop shape analyzer. The water contact angle of superhydrophobic TiO2 film was up to 165.6°. Under UV irradiation, the water contact angle decreased and the superhydrophobic TiO2 film became superhydrophilic because of hydroxyl groups absorption on the TiO2 surface. Meanwhile, the surface morphology of TiO2 film, which resulted from the TiO2 nanoparticles added in TiO2 precursor solution, had a significant effect on the wettability conversion of TiO2 film and enhanced the switch from hydrophobicity to hydrophilicity. The wettability could be reversibly switched between superhydrophobicity and superhydrophilicity via alternation of UV exposure and dark storage.

Fabrication of Flexible Dye-Sensitized Solar Cells by Pressurization-Transfer Technique

In this study, the flexible dye-sensitized solar cell is fabricated by pressurization-transfer technique, which involves assembling TiO2 films on ITO/PEN flexible substrates via high temperature sintering. During the experiment, we change not only the film thickness and structure of TiO2 but also the dye of working electrodes. The surface morphology of TiO2 films are examined by field emission scanning electron microscopy (FE-SEM). The analyses of UV-Vis show that N3 dye could be adsorbed on the TiO2 thin films, and the TiO2 thin film with scattering layer has better absorption than that of without scattering layer. The current-voltage of the DSSC is illuminated by the solar simulator whose incident light intensity was 1000 W/m2. These results indicate that the best efficiency of flexible dye-sensitized solar cell with high-temperature sintering TiO2 film and scattering layer is 6.13%.

Morphology modification of TiO2 film by adding ammonium nitrate in precursor sol

The surface morphology of TiO2 film was modified with pore or particle by adding ammonium nitrate into TiO2 precursor sol and controlling the humidity of air during drying of dip-coated TiO2 sol film over glass substrate. Water vapor in the surrounding air condenses to the coated sol film during drying process and decreases the compatibility between the precursor and the solvent. Introduction of ammonium nitrate into the TiO2 sol causes a further increase of interfacial tension, which results in the formation of different morphologies of TiO2 film due to a phase separation between the precursor and the solvent. The formation process of pores or particles in TiO2 film is closely related to the condensation rate of water vapor. The RMS roughness of TiO2 film is significantly increased after the surface is modified with pore or particle, and can be controlled by varying the coating times. Adding NH4NO3 into the precursor sol cannot only modify the surface morphology but can also cause N element doping into the TiO2 film.

Structure and Morphology of Sol-Gel Nanocrystalline TiO<sub>2</sub> Films Coated on Glass Substrates

The Ce3+-doped and undoped nanocrystalline TiO2 films were prepared on glass substrates surface by sol-gel dip coating technique. The crystal structure and surface morphology of TiO2 films were characterized by means of X-ray diffractometer (XRD), transmission electron microscopy (TEM) and atomic force microscope (AFM). The results indicated that the Ce3+-doped TiO2 films were solely composed of the anatase phase whereas in the undoped films small amount of the rutile phase of TiO2 were present. The average crystallite size of the undoped TiO2 films was about 30nm and was decreased with Ce3+-doping in the TiO2 films. Moreover, the grains distributed more uniform and the surface roughness was smaller in the Ce3+-doped TiO2 films than in the undoped one. The action mechanism of Ce3+-doping inhibits the crystallization of the rutile phase and decreases the anatase granularity of TiO2 films is associated with its physicochemical properties, as well as ionic diffusion and valance change of Ce3+ to Ce4+ in the sintering process.

Growth of TiO<sub>2</sub> Thin Film on Glass Substrate by Air-Opened MOCVD

MOCVD was applied to deposit TiO2 thin films on glass substrates. Effects of the deposition conditions (source temperature and substrate temperature) were studied. The phase and micro- structure of the TiO2 thin films were examined by X-ray diffraction and electron microscopy, respectively. The results indicate that substrate temperature affects both the morphology and the phase of the TiO2 film, while source temperature only affects the surface morphology of TiO2 film. Highly oriented anatase film on glass substrate was obtained at a source temperature of 140 oC and a substrate temperature of 350 oC. XRD pattern shows that only the (200) peak of anatase appears under the conditions. The crystallines in the highly oriented anatase were rectangular in top view.

Blister formation in rutile TiO2(1 0 0) films by helium irradiation

Incident energy, fluence of helium ion and temperature for blister formation in rutile TiO2(100) films were investigated. Epitaxial rutile TiO2(100) films were grown on α-Al2O3(0001) substrates by pulsed laser deposition. The films were irradiated at room temperature and 95K with 4keV helium ions up to fluence range from 1.0×1016 to 2.3×1017 ions/cm2. The surface morphology of TiO2 films was observed by scanning electron microscope and atomic force microscope. Rutherford backscattering spectroscopy with channeling was used to determine the depth profile of radiation-induced damage. In the case of room temperature irradiation with fluences higher than 2×1016 ions/cm2, helium blisters with 100–200nm sizes in TiO2 films were observed. Furthermore, helium irradiation at 95K resulted in smaller size blisters (∼50nm). It is suggested that the size of blisters in TiO2(100) films is strongly affected by the temperature during the helium irradiation. The photo-induced superhydrophilicity of TiO2 films was improved by high fluence helium irradiation, which caused blister growth.

The Influence of Sol Composition on the Surface Morphology of TiO2 Films Prepared by the Sol-Gel Method

The Influence of Sol Composition on the Surface Morphology of TiO2 Films Prepared by the Sol-Gel Method

The Effect of Organic Polymer on the Surface Morphology of TiO2 Films Prepared by the Sol-Gel Method.

The Effect of Organic Polymer on the Surface Morphology of TiO2 Films Prepared by the Sol-Gel Method.

Surface Morphology of TiO2 Films Prepared by SPD Technique

Surface Morphology of TiO2 Films Prepared by SPD Technique

Atomic force microscopy observation of TiO2 films deposited by dc reactive sputtering

A bombardment of energetic particles such as secondary electrons and recoiled ions ejected from the target plane is a very useful technique for modifying the structure of the film in reactive sputtering. It leads to interesting effects such as enhancement of reactivity, adatom mobility, and atomic peening. Therefore, the state on the surface of the as-deposited film may significantly depend on the bombardment condition. So, in this study, the relationship between the bombardment condition and the surface morphology of TiO2 films has been investigated in detail. TiO2 films with a thickness of about 0.8–2.3 μm were deposited by dc reactive sputtering on glass-slide substrates. The surface roughness of films was measured with atomic-force microscopy. The roughness parameter Ra on the surface of TiO2 films depended on the energy and the number of bombarding particles. After increasing the energy and the number of bombarding particles, Ra increased from 10 to 77 nm. Consequently, it was found that the surface morphology of TiO2 films strongly affected the plasma exposure to the growing film.

Correlation between Surface Morphology and Hydrophilic/Hydrophobic Conversion of MOCVD−TiO2 Films

The relationship between hydrophilicity and surface morphology of TiO2 film was investigated. TiO2 films were deposited by MOCVD, and anatase films were crystallized. The rougher the surface of anatase film, the slower the conversion from hydrophilic to hydrophobic state. Also in some films, even the sonication could not accelerate the kinetics. However, the recovery rate to hydrophilicity under UV illumination had a reverse dependency on the surface roughness. It was assumed that the rougher TiO2 films could have a large concentration of Ti3+ generated by UV illumination on the surface, which plays a major role as adsorption sites of −OH in the water as well as in the air. Therefore, the healing kinetics of Ti3+ by oxygen in the air of a dark room could have been different among films with various surface roughnesses. Conclusively, the sustaining tendency of hydrophilic or hydrophobic properties could mainly depend on the concentration of Ti3+ by UV light, and in turn on the processing conditions of film deposition.