Properties Of TiO2 Thin Films Research Articles

Quartz resonator with thin TiO2 for NH3 detection

The sorption properties of TiO2 thin films are investigated, in order to detect ammonium vapor existence. For the purpose mass-sensitive quartz resonators covered by TiO2 film are used. TiO2 thin films are prepared using a new method called liquid phase deposition (LPD). By this method metal oxide layers are deposited on surfaces dipped in solutions. The layers are obtained as a result of a balance reaction, which happens between the metal fluorocomplex and metal oxide in aqueous solution. By this process substances with complex morphology are easily coated using no special equipment.The main advantage of this method is its low synthesis temperature–up to 200°C. The sorption sensitiveness of the created structure is registered by the Quartz Crystal Microbalance (QCM) method. An interval of ammonium concentration (from 100 to 10,000ppm) is investigated. A dependence is obtained between relative change of resonator frequency (Δf/f) and ammonium solution concentration.The obtained initial results show that this sort of systems could be used for creating sensor elements aiming the detection of ammonium contamination in the air.

Effect of deposition methods on the properties of photocatalyticTiO2 thin films prepared by spray pyrolysis and magnetron sputtering

Titanium dioxide thin films were deposited by DC reactive magnetron sputtering and spraypyrolysis methods onto glass and glass coated with fluorine doped tin oxide (FTO).The films were characterized by x-ray diffraction, scanning electron microscopy,atomic force microscopy and UV–visible spectroscopy. For films deposited bythe sputtering technique we have studied the effect of the total pressure of anAr–O2 mixture on the substrate properties, on the deposition rate, phase composition,crystallinity, surface morphology and on the photocatalytic properties. Also transparentTiO2 thin films have been prepared by spray pyrolysis using a low concentration of titaniumprecursor with different substrate temperatures. At higher substrate temperatures the filmswere polycrystalline in the anatase phase; at lower substrate temperatures thefilms presented an amorphous configuration. The photocatalytic properties ofTiO2 thin films were tested with the degradation methylene blue under UVlight irradiation. The higher degradation rates were reached for filmsprepared by spray pyrolysis with a substrate temperature close to400 °C, and for a high total pressure (16 mTorr) for films deposited by DC magnetron sputtering.

Properties of TiO2 Thin Films on GaAs Prepared by Metalorganic Chemical Vapor Deposition

The deposition of polycrystalline TiO2 films on GaAs substrate is studied by metalorganic chemical vapor deposition (MOCVD) with Ti(i-OC3H7)4 and O2 as the precursors in a temperature range of 280–550°C. The structure, growth rate and grain size of TiO2 films depend on the deposition temperature. The film composition was measured by dispersive X-ray spectroscopy. From capacitance–voltage and current–voltage measurements of the Al/TiO2/GaAs/Au–Zn structure, the dielectric constant can reach 64 with the leakage current of 1×10-5 A/cm2 at 0.05 MV/cm at 350°C and the refractive index of TiO2 films can reach 2.2. At 300°C, the dielectric constant and leakage current density were 43 and 1×10-5 A/cm2 at 0.05 MV/cm and the refractive index of TiO2 films can reach 2.4.

Photocatalytic Properties of TiO2 Thin Films Prepared by RF Sputtering

Titanium dioxide films were prepared by RF sputtering method on glass for various oxygen partial pressures at power 270 W. The crystal structure, photocatalytic property and the hydrophilicity of <TEX>$TiO_2$</TEX>thin film the deposition conditions were investigated. Crystallized anatase phase was observed in <TEX>$TiO_2$</TEX>film deposited at the ratio of oxygen partial pressure 10% and 20% for 2 hrs. As the increase of deposition time, the grain size and void size of <TEX>$TiO_2$</TEX>film have increased and also <TEX>$V_2$</TEX>films have been good crystallinity. The ultraviolet-visible light absorption of <TEX>$TiO_2$</TEX>films was increased with increasing of deposition time and occured chiefly at the wavelength between 280 and 340 nm. The absorption band was shifted to a longer wave length as deposition time increased. Water contact angle on the X<TEX>$TiO_2$</TEX>film of anatase structure was decreased with increasing ultraviolet illumination time and became lower than <TEX>$11^{\circ}$</TEX> from <TEX>$83^{\circ}$</TEX>. When hydrophilic <TEX>$TiO_2$</TEX>film changed by enough ultraviolet illumination was stored in the dark, the film surface gradually turned to hydrophobic state.

Optical properties of TiO2 thin films estimated by photothermal deflection spectroscopy

The optical properties of Nb doped TiO2 thin films have been investigated by using the photothermal deflection spectroscopy. The below-gap absorption of amorphous and microcrystalline TiO2 thin films is observed. The absorption coefficient in the below-gap region in microcrystalline TiO2 film decreased with thermal annealing at ∼650 °C. The origin of the below-gap absorption is discussed on the basis of the structural information.

Influence of Thickness on Oxygen-Sensing Properties of TiO2 Thin Films on Al2O3

The relationship between thickness and oxygen-sensing properties of TiO2 thin films on Al2O3 substrate is investigated. The results show that the properties of the films are influenced by both their substrate and thickness. When the thickness is less than 0.69 µm, the diffusion of Al3+ from the substrate plays the main roles in the appearance of p-type conductivity and very weak oxygen-sensing behavior. When the thickness is greater than 0.69 µm, the expected oxygen-sensing properties appear. Based on these results, the regularity of film resistance, oxygen sensitivity, response time, and consistency of these properties in relation to film thickness is investigated. The maximum oxygen sensitivity and consistency is reached at the optimal thickness of 2.3 µm.

Properties of TiO2 Thin Films on InP Substrate Prepared by Liquid Phase Deposition

The deposition of TiO2 films on InP substrate is studied by liquid phase deposition (LPD) with H2TiF6 and H3BO3 as the starting materials at the growth temperature of 75°C. The growth rate of TiO2 is about 42 Å/min. The surface morphology of the TiO2 films was mirror-like. The film stoichiometry was measured by energy dispersion spectroscopy (EDS). The refractive index of TiO2 films measured by ellipsometry reached 1.6. The structure of TiO2 is polycrystalline as determined by X-ray diffraction examination. From current–voltage measurement of the Al/TiO2/InP structure, the leakage current is 1×10-5 A/cm2 under the electric field intensity of 0.12 MV/cm.

Strutural and Optical Properties of TiO2 Thin Films Prepared by RF Reactive Magnetron Sputtering

Strutural and Optical Properties of TiO2 Thin Films Prepared by RF Reactive Magnetron Sputtering

졸-겔 침지코팅법으로 제조된 TiO2박막의 구조적.광학적 특설

졸-겔 침지코팅법으로 제조된 TiO₂박막의 구조적.광학적 특설

Effect of ZnFe 2 O 4 doping on the optical properties of TiO 2 thin films

Amorphous TiO2 thin films and ZnFe2O4-doped TiO2 composite films were deposited by radio frequency magnetron sputtering. The effect of ZnFe2O4 doping on the optical properties of TiO2 thin films was reported. Our results show that the absorption edge of TiO2 thin films and composite films exhibits a blueshift with decreasing annealing temperature. The absorption edge of composite films has moved to a visible spectrum range and a very large redshift occurs in comparison with TiO2 thin films. An enhanced photoluminescence was observed in ZnFe2O4-doped anatase TiO2 thin films at room temperature.

Structural and optical properties of TiO2 thin film and TiO2+2 wt.% ZnFe2O4 composite film prepared by r.f. sputtering

Amorphous TiO2 thin films and TiO2/ZnFe2O4 composite films were deposited by r.f. magnetron sputtering. The influence of post-deposition annealing on the structural and optical properties was studied. It was established that the anatase single phase exists between 250 and 800°C for the TiO2 thin films, and between 450 and 650°C for the composite films. The absorption edge of TiO2 thin films and composite films exhibits a blue shift with decreasing annealing temperature. The absorption edge of composite films has moved to visible spectrum range, and a very large red shift occurs in comparison with TiO2 thin films.

I-V andC-V properties of TiO2 thin film by pulsed-laser reactive deposition

TiO2 thin films have bee deposited on p-Si(111) substrates by pulsed-laser ablation of metallic Ti target in the O3 ambient. The current-voltage and capacitance-voltage of the Al/TiO2/Si capacitors are measured. The results show that the dielectric constant of thin film after being annealed at 700°C is found to be 46, and the border trap density and the interface state density at the TiO2/p-Si interface are 1.8 × 1012 cm−2 and 2 × 1012 eV1cm−2, respectively. The conduction mechanisms of asdeposited films are also discussed.

Electrical properties of TiO2 thin films formed on self-assembled organic monolayers on silicon

TiO 2 thin films were synthesized onto sulfonated self-assembled organic monolayers from Ti4+ aqueous solutions at low temperature (80 °C). The deposited TiO2 thin films were characterized using Rutherford backscattering spectroscopy and transmission electron microscopy. 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 in the range of 24–57 for the as-deposited films and 67–97 for films annealed at 400 °C. For the as-deposited samples, the breakdown voltage was 2.7 MV/cm, the leakage current was 4.5×10−6 A/cm2, the resistivity was 1–1.5×109 Ω cm, and the interface trap density ∼1×1012 cm−2 eV−1. The leakage current behavior was consistent with the Poole-Frenkel mechanism of conduction.

Effect of rapid thermal annealing on the structural and electrical properties of TiO2 thin films prepared by plasma enhanced CVD

Titanium oxide thin films were deposited on p-type Si(100), SiO2/Si, and Pt/Si substrates by plasma enhanced chemical vapor deposition using high purity Ti(O-i-C3H7)4 and oxygen. As-deposited amorphous TiO2 thin films were treated by rapid thermal annealing (RTA) in oxygen ambient, and the effects of RTA conditions on the structural and electrical properties of TiO2 films were studied in terms of crystallinity, microstructure, current leakage, and dielectric constant. The dominant crystalline structures after 600 and 800 ‡C annealing were an anatase phase for the TiO2 film on SiO2/Si and a rutile phase for the film on a Pt/Si substrate. The dielectric constant of the as-grown and annealed TiO2 thin films increased depending on the substrate in the order of Si, SiO2/Si, and Pt/ Si. The SiO2 thin layer was effective in preventing the formation of titanium silicide at the interface and current leakage of the film. TEM photographs showed an additional growth of SiOx from oxygen supplied from both SiO2 and TiO2 films when the films were annealed at 1000 ‡C in an oxygen ambient. Intensity analysis of Raman peaks also indicated that optimizing the oxygen concentration and the annealing time is critical for growing a TiO2 film having high dielectric and low current leakage characteristics.

Sol–Gel Preparation and Third-Order Nonlinear Optical Properties of TiO2 Thin Films

Abstract Rutile and anatase thin films have been prepared by the sol–gel method using Ti(OC3H7i)4. Third-order nonlinear optical properties of both TiO2 thin films have been investigated by the third-harmonic generation (THG) method and the effect of the polymorph of TiO2 on the third-order nonlinear optical susceptibility, χ(3), has been examined. The measured χ(3) values of rutile and anatase thin films were 1.4 × 10−12 and 9.7 × 10−13 esu, respectively. The χ(3) values corrected for the porosity of the film were 4.0 × 10−12 (rutile) and 2.4 × 10−12 esu (anatase), which are about 100 times as high as that of SiO2 glass used as standard sample (2.8 × 10−14 esu). The measured and corrected χ(3) values were discussed in comparision with those calculated on the basis of several models.

Influence of substrate on structural properties of TiO2 thin films obtained via MOCVD

Abstract Among the techniques developed for depositing thin films, metal-organic chemical vapor deposition is one of the most promising. In the present work, the deposition of TiO2 thin films on stainless steel, titanium, barium borosilicate glass and alumina substrates, using titanium tetraisopropoxide as a precursor, was investigated. The films were deposited at 420 °C. The resulting film phase, checked by X-ray powder diffraction, was found to be polycrystalline anatase and was oriented with the a axis perpendicular to the substrate surface, except for alumina substrates where titania films were randomly oriented. Some considerations on texture and crystallite size as a function of film thickness are reported. Annealing up to 1100 °C induced the complete anatase-rutile transformation on alumina substrates.

Process effects on structural properties of TiO2 thin films by reactive sputtering

We have been investigating the growth of crystalline titanium dioxide films at deposition temperature between room temperature and about 400 °C. The films were prepared by a dc magnetron reactive sputtering on glass and Si(100) substrates. The structural properties of the films were analyzed by x-ray diffractometry. The influence of total pressure, oxygen mole fraction in the mixture of Ar–O2, discharge current, and substrate temperature on the structural properties were studied. In addition to higher substrate temperature, low total pressure, high discharge current, and small oxygen mole fraction were shown to be preferable for growing anatase–rutile mixture films. Annealing of the films in air at 850 °C showed that anatase–rutile transformation strongly depends on the deposition temperature; the films deposited at temperature below 400 °C were converted to the anatase–rutile mixture films, and the films deposited at 400 °C to complete rutile films.

Electrical properties of TiO2 thin films prepared by the sol-gel method

A TiO2 thin film was prepared by the sol-gel method using a metal alkoxide [Ti(O-i-Pr)4 tetrasopropoxy titanium: TIPT]. The crystalline form of the film depends on the preparation conditions and the heat treatment temperature. When the ratio (γ) of H2O to TIPT is 7, the crystalline phase is formed at 400°C; when γ = 2 it is formed at 500°C. The anatase crystal structure was obtained for both γ = 2 and γ = 7. The electrical conductivity of the TiO2 film increased with the heat treatment temperature.