Properties Of TiO2 Thin Films Research Articles

Effect of Concentration Variation on Optical and Structural Properties of TiO2 Thin Films

Concentrations in weight percent (5- 25 wt %) of TiO2 films used to optimize the film formation. The TiO2 films on glass substrates successfully obtained by spin-coating process using TiO2 nanopowder as precursor. Ultraviolet-Visible (UV-Vis), Scanning Electron Microscopy (SEM) equipped with Electron Diffraction X-ray (EDX) and X-ray Diffractometer (XRD) techniques used to characterize the films. The result of electron transport material (TiO2) showed that film prepared from 15 wt % of TiO2 solution and annealed at 450 has highest transmittance at visible light region with indirect optical band gap of 3.24 eV which corresponds to wavelength of 382 nm whereas 20 wt % has indirect band gap of 2.99 nm equivalent to 414.7 nm . The chemical analysis from Electron Diffraction Spectroscopy (EDS) of the material shows titanium and oxygen present at L and K-shells, respectively. The sample crystallized with preferred orientation at (101) from XRD analysis.

Research on the influence of the filtrating electrode on the structure and optical properties of TiO2 thin films prepared by the energy filtering magnetron sputtering technique

Abstract TiO2 thin films were deposited by the energy filtrating magnetron sputtering (EFMS) technique and the traditional direct current magnetron sputtering (DMS) technique. The influence of the filtering electrode mesh number on the structure and optical properties of TiO2 thin films was investigated. The structure, surface morphology and optical properties were characterized by XRD, SEM and ellipsometric spectroscopy, respectively. Results show that the TiO2 thin films deposited by the DMS and EFMS techniques at the same deposition parameters are composed of the anatase phase exclusively. TiO2 thin films deposited at lower deposition rate by the EFMS technique have lower crystallinity, smaller particle size and smoother surface. With increasing the mesh number, the refractive index, extinction coefficient and optical band gap are larger.

Elaboration and characterization of nano-crystalline layers of transparent titanium dioxide (Anatase-TiO2) deposited by a sol-gel (spin coating) process

Thin films of titanium dioxide (TiO2) were synthesized by sol gel (spin coating) process on glass substrates. The structural, morphological, optical, and electrical properties of TiO2 thin films were examined as a function of solution concentration CS varied between 0.1 M and 0.5 M at 500°C as the annealing temperature. The elaborate samples were characterized by several characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV-VISIBLE spectroscopy and two points probe. The obtained results show that the TiO2 samples were crystallized in a tetragonal structure (anatase phase) oriented preferentially along to the (101) plane. The average grain size increases from 34.773 ± 1.738 nm to 48.674 ± 2.433 nm. The FTIR spectrum shows the presence of Ti-O and Ti-O-Ti bonds. The samples are transparent in visible and the indirect optical band gap varies from 3.09 ± 0.154 eV to 3.415 ± 0.170 eV. In addition, the electrical measurements show a minimum electrical resistivity (ρ = 0.18 ± 0.01 Ω.cm) at CS = 0.3 M .

Investigation of the Influences of Post-Thermal Annealing on Physical Properties of TiO2 Thin Films Deposited by RF Sputtering

For this study, titanium dioxide (TiO2) thin films were deposited on glass substrates at room temperature by the RF magnetron sputtering technique. The preparation parameters that offer better control and reproducibility of film fabrication were first optimized. Then, the effects of post-deposition annealing temperature at 350, 450, and 550°C on the microstructure, surface morphology, and optical properties of the prepared films were investigated using X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–Visible (UV–Vis) spectrophotometry. Interestingly, XRD analysis shows that as-deposited and annealed TiO2 film possess anatase crystal structure only with a preferential orientation along the (101) plane. The intensity of the (101) diffraction peak and crystallite size are found to increase with increasing annealing temperature, which indicates an improvement in the crystallinity of the films. Raman spectra confirm that all samples possess anatase phase and the crystallinity is enhanced with increasing thermal annealing. From the analysis of SEM and AFM images, it is revealed that the heat treatment significantly affects the morphology, grain size, and surface roughness of the TiO2 films. The UV–Vis spectroscopy analysis shows that as-deposited TiO2 thin film is highly transparent in the visible region with an average transmittance about 84%, whereas the transmission decreases slightly with an increase in annealing temperature. Moreover, the optical band gap energy shows a red shift with increasing the annealing temperature.

Effect of CdO ratios on the structural and optical properties of CdO–TiO2 nanocomposite thin films

Nanocomposite CdO–TiO2 thin films have been successfully synthesized via sol–gel and spin coating techniques. The physical properties of the prepared thin films were studied by varying the Cd:Ti ratio (0, 25, 50, 75, and 100%). The structural characterization has been performed by X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Optical transmission and reflectivity of the obtained films have been studied by UV–Vis-NIR spectroscopy. The obtained results showed that the amount of Cd into the TiO2 matrix can significantly affect the properties of TiO2 thin films; the XRD analysis revealed the appearance of new diffraction planes by increasing the of Cd:Ti ratios, a fact that was also confirmed by the Raman spectra. Effects of incorporated Cd amounts on the crystal phase, crystallite size, surface morphology were investigated. The results showed that most of Cd2+ substituted Ti4+ in the crystal lattice of TiO2 and led to the appearance of the CdTiO3 phase for thin films at a relatively low temperature, which inhibited the growth of crystallite size and suppressed the transformation from anatase to rutile of TiO2 at 450 °C. Moreover, formation of different binary and ternary nanocomposite films are justified by varying the Cd:Ti ratios. The optical analysis revealed a high transparency in the visible region, strongly affected by the different Cd:Ti ratios. Incorporated CdO initially increased the bandgap for low values of the Cd:Ti ratio, followed by a bandgap decrease for the highest one.

TiO2 thin films on Au/Ti/SiO2/textured Si substrates as high capacity anode materials for Li-ion batteries

In this paper, we investigate the structural and electrochemical properties of TiO2 thin films deposited on multilayered Au/Ti/SiO2/(100) textured-Si substrates by electron-beam evaporation technique at various substrate temperatures in the range 25 ≤ Ts ≤ 350 °C. Phase-pure and well-crystallized TiO2 thin films grown at Ts = 250 °C exhibit the typical (101) Bragg line of the tetragonal anatase structure with crystallite size of about 30 nm. The surface morphological analysis reveals the uniform growth of prismatic shaped grains (40–120 nm in size) deposited on pyramidal architectures of textured substrates. The electrochemical tests show that TiO2 thin films electrodes deposited at Ts of 250 °C deliver a specific discharge capacity of 74 μAh cm−2 μm−1 at a current density of 1 mA cm−2 with 96% capacity retention after 100 cycles. Hence, the experimental results demonstrate that TiO2 thin films can be used as anodes of planar solid-state Li-ion microbatteries.

Effect of annealing time on structural and optical proprieties of TiO2 thin films elaborated by spray pyrolysis technique for future gas sensor application

In this study we tested the effect of annealing time on some properties of titanium dioxide thin films, elaborated by the chemical technique spray pyrolysis deposited on the glass with a fixed temperature. An annealing was carried out at a temperature of 500 °C for three times 1 h, 2 h and 3 h. The structural characterization with X-ray diffraction (XRD) shows a significant increase in the crystallite size and also the preferential peak intensity of TiO2 of the anatase phase if the annealing time is decreased, the typical Scanning Electron Microscopy (SEM) image shows the morphological properties of TiO2 thin film and the optical measurement with UV–Visible spectrophotometer represent the semiconductor properties of TiO2 with an optical band gap that varies with the variation of the annealing time from 3.30 to 3.26 eV for 3 h to 2 h and from 3.26 to 3.19 eV for 2 h to 1 h.

Precursor nature and molarities effect on the optical, structural, morphological, and electrical properties of TiO2 thin films deposited by spray pyrolysis

Titanium oxide thin films were deposited by a simple and low-cost spray pyrolysis technique using two different precursors: Titanium chloride (TiCl3) and Titanium Tetra-isopropoxide (TTIP) on glass substrates. X-ray diffraction shows that most of the TiO2 thin films are amorphous in structure. The optical transmittance of the sprayed TiO2 films deposited from Titanium chloride is in the range of 80 % and for the films deposited from TTIP, it attains 90 % in the visible region. The optical band gap energies of the films deposited from TiCl3 and TTIP are about 3.5 and 3.7 eV respectively. The electrical resistivity of the films varies from 3.2*103 to 4.6*104 (Ω.cm) for the films prepared from TiCl3 precursor and 9.4*102 to 6.5*103(Ω.cm) for the films prepared from TTIP precursor.

The Effect of Various Annealing Cooling Rates on Electrical and Morphological Properties of TiO2 Thin Films

This paper presents the effect of different cooling rate after annealing on structural and electrical properties of TiO2 thin films. Titanium dioxide thin film was deposited on a silicon substrate using DC magnetron technique. After annealing TiO2 thin films at 600oC, to investigate the effect of different cooling rates on TiO2 thin films, samples were cooled down from 600oC to the room temperature under 3 different rates: 2oC/min, 6oC/min and 8oC/min. The Surface morphology, crystal structure, and electrical property of samples were characterized by atomic force measurement (AFM), X-ray diffraction (XRD) and Four-point probe (FPP) technique. It is found that the rate of decreasing temperature after annealing can affect the morphology structure and electrical resistivity of titanium dioxide. Sample with 2oC/m has the biggest grain size, and more electrical resistivity while the smallest grain size and lowest electrical resistivity belong to sample with 8oC/m cooling rate.

Effect of graphene oxide on microstructure and optical properties of TiO2 thin film

GO/TiO2 thin films have been synthesized from titanium (IV) isopropoxide (TTIP) by a sol-gel method. The films were deposited onto a glass substrate using spin coating deposition technique then were subjected to annealed process at 350 °C. The different amount of graphene oxide (GO) was added into the parent solution of sol in order to investigate the microstructure, topography, optical band gap and photocatalytic activity of the thin films. The prepared thin films were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-VIS spectrophotometry and degradation of methylene blue (MB). AFM images reveal a rougher surface of GO/TiO2 thin film than bare TiO2 thin film due to GO particles. Moreover, the SEM images showed the formation of semispherical microstructure of bare TiO2 changes to some larger combined molecules with GO addition. The UV–Vis spectrophotometer results show that with optical direct energy gap decreases from 3.30 to 3.18 eV after GO addition due to the effect of high surface roughness and bigger grain size. Furthermore, the optical results also indicated that GO improved the optical properties of TiO2 in the visible range region.

Effect of withdrawal speed on the microstructure, optical, and self-cleaning properties of TiO2 thin films

The transparent superhydrophilic TiO2 films were dip-coated on glass substrates by sol–gel method at different withdrawal speeds. The dependence of the morphological, transmittance, and self-cleaning properties of the films on withdrawal speed were investigated by scanning electron microscope (SEM), atomic force microscope (AFM), ultraviolet–visible (UV–Vis) spectrophotometer, photocatalytic degradation of a methyl blue, and water contact angle. The results indicated that the withdrawal speed had a great impact on the surface morphology, the transmittance, and self-cleaning properties of the TiO2 films. With the withdrawal speed increasing, the grains size, porosity, and RMS values of the films gradually increase, and the absorption edge shifts toward longer wavelength. These increase the radiation absorption and photocatalytic activity. The hydrophilic property enhances with the withdrawal speed increasing, due to the surface roughness and capillary force from pores between grains. All the prepared films are transparent in the visible spectrum (400–800 nm) with an average transmittance of more than 70%. Films with high transmittance (T ~ 90% at 500 nm) and good self-cleaning properties (WCA < 5°) can be obtained at high withdrawal speed.

Effect of Mn doping on the Optical and Electrical Properties of TiO2 thin film prepared by Unconventional Sol-gel route

Semi-transparent nanostructured Mn doped titanium dioxide thin films have been prepared by modified sol-gel route starting from the powder reagents. The films deposited on plane glass slides is annealed at 3500C. The characterizations of the films are done with X-ray diffraction, Scanning electron microscopy, UV-Vis spectroscopy and Hall measurement. Although annealing transformed the structure from tetragonal body centered to tetragonal primitive, the preferential growth have been reported along the (300) orientation of the diffracting planes. The optical transmittance of the film increases with annealing temperature. The optical parameters like refractive index and extinction coefficients are calculated from the transmission and reflection spectra, and the dispersion in the refractive index has been discussed in terms of single oscillator Wemple and Di Domenico model.

Investigation of growth mechanism for highly oriented TiO2 nanorods: the role of reaction time and annealing temperature

Titanium dioxide (TiO2) is a versatile and inexpensive material for extended applicability in several scientific and technological fields including photo-catalysis for industrial waste treatment, energy harvesting, and hydrogen production. In this work, we report the synthesis of TiO2 thin film using hydrothermal method and investigations on the influence of reaction time and annealing temperature on growth mechanism of the TiO2 nanorods. The synthesized TiO2 films were studied by using UV–visible spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscope and energy-dispersive X-ray spectroscopy (EDS). The XRD and Raman measurements revealed the formation of defect free and pure tetragonal TiO2 rutile phase. The TiO2 thin films show absorption band edge at around 420 nm in the UV–visible spectrum and exhibit direct band gap value of 2.9 eV. The TiO2 nanorods are demonstrated to grow randomly on the FTO substrate with changing reaction times but grow uniformly in a flower-like pattern with increasing annealing temperature. Investigation of the field emission properties of TiO2 thin films (tested as field-emitter array) estimates the turn-on and threshold field at 4.06 and 7.06 V/µm at 10 and 100 µA/cm2, respectively.Graphic

Studies on thin films of TiO2 for resistance-based sensing of ethanol vapor at room temperature

ABSTRACTWe investigate the gas sensing properties of TiO2 thin films prepared by spin coating. The presence of anatase and rutile phases in the sample was confirmed by powder X-Ray diffraction study. The thin film was characterized by FE-SEM and EDAX. The TiO2 thin films were found to have good sensitivity towards ethanol compared to other gases. The sensing studies revealed the ethanol sensing properties of the thin film at room temperature even at lower concentrations. The response and selectivity of the film were also discussed in detail.

Optical properties of TiO2 thin films deposited by DC sputtering and their photocatalytic performance in photoinduced process

TiO2 thin films were deposited by DC Sputtering varying the deposit time. These films were characterized by XRD, AFM, photoluminescence, UV–Vis, ellipsometry and XPS. The optical properties of TiO2 thin films with different thickness, influenced their photocatalytic behavior in two photoinduced process. When TiO2 thin films were irradiated with a UV light, midgap states were generated and the electrons were placed in lower energies than its band gap, favoring the photocatalytic hydrogen production and CO2 photoreduction. From PL technique analyses it was observed that electrons occupied midgap states between the bands, with lower energies than the band gap. With these results it was possible to propose an energy diagram in order to correlate with photoinduced processes results. The presence of Ti3+ species was reconfirmed by means of XPS analyses. These species could be found in the midgap states, generated by the interaction between the UV irradiation and the film surface, which contributed to the photocatalytic activity of the films. The hydrogen production was similar for all the thin films studied (33–35 μmol) associated to the presence of similar energy midgap states. In the case of CO2 photoreduction, all films produced CH2O (8951 and 6252 μmol/g) and the films with a thickness of 330 and 420 nm generated CH3OH (970 and 292 μmol/g). The extinction coefficient confirmed the XRD results for the film with greatest deposited time, which exhibited the highest crystallinity. All photocatalytic results did not show any dependence with the thin film thickness.

Investigation of the structural and optical properties of copper-titanium oxide thin films produced by changing the amount of copper

We examine how the structural, morphological and optical properties of TiO2 thin films are changed with heavily copper (Cu) content. Variations in characteristic properties of the films with 0, 12.5, 25 and 50 wt% Cu contents, grown by sol-gel dip coating method, are observed by using X-ray diffraction (XRD), Raman scattering, atomic force microscopy, energy dispersive X-ray analysis and optical spectroscopy measurements. The XRD and Raman spectra indicate that pure TiO2 film forms in the anatase structure. At high Cu concentrations, XRD results also reveal the substitution of Ti with Cu and formation of extra compound Copper-Titanium oxide. Raman measurements also show that Cu is incorporated homogeneously into TiO2 matrix up to 12.5 wt% concentration and this uniformity is distorted at higher Cu contents. In addition, optical spectroscopy measurements show that the optical band gap energy decreases from 3.26 eV to 2.05 eV with increasing Cu concentration. Furthermore, it is observed that the refractive index values obtained by means of transmittance spectra at 550 nm wavelength; increases from 2.47 to 3.39 when the Cu concentration increases from 0 to 50 wt%.

Effect of Li-doped on the crystalline phase, optical and electrical properties of TiO2 thin films

Various Li-doped TiO2 films with different doping concentration were successfully synthesized by a thermal treatment at 500 °C. With the incorporation of Li+, anatase TiO2 transformed obviously to rutile at lower temperature (500 °C) and the increasing concentration of Li+ can promote the growth of crystals. All films have good transmittance (average transmittance >75%) in the visible region, the optical band gap (Eg) of TiO2 narrowed from 3.71 eV to 3.63 eV and reached the minimum at 5.0 mol%. Moreover, an optimized carrier concentration of 6.43 * 1010 cm−3 and the resistivity of 4.06 * 105 Ω.cm were obtained after 5.0 mol% Li+ doping. Possible mechanisms for the effect of Li-doping on the carrier concentration and resistivity were discussed. In conclusion, the Li-doped TiO2 films have potential applications for solar cell.

Secondary particle properties for the ion beam sputtering of TiO2 in a reactive oxygen atmosphere

This work deals with the properties of secondary particles, i.e., sputtered target and scattered primary particles, for the ion beam sputtering of TiO2 in a reactive oxygen atmosphere. The angular and energy distributions in dependence on ion beam parameters (ion energy, ion species, or ion mass) and geometrical parameters (ion incidence angle, polar emission angle, or scattering angle) were investigated. The angular distributions of sputtered Ti particles were determined by the collection method, i.e., by growing TiO2 thin films and measuring the thickness, composition, and mass density. The distributions can be described by the superposition of an isotropic and an anisotropic part. The anisotropic part relative to the isotropic part gets more pronounced with decreasing ion energy, increasing ion incidence angle or changing the process gas from Ar to Xe. An energy-selective mass spectrometer was used to measure mass and energy distributions of secondary ions. The most prevalent species were identified to be O+, O2+, Ti+, TiO+, Ar+, and Xe+ ions. The energy distributions of Ti+ and TiO+ ions show a low-energy maximum between 10 eV and 30 eV, followed by an exponential decay. When decreasing the scattering angle, the high-energy tail extends to higher energies. O+, O2+, Ar+, and Xe+ ions show a low-energy maximum between 5 eV and 20 eV, which is followed by a sudden signal drop for scattering angles larger than 90°. For scattering angles smaller than 90°, additional peak(s) at higher energy appear, which are assigned to direct scattering and/or direct sputtering events. The experimental results are compared to calculations based on elastic collision theory and to simulations done with the Monte Carlo code SDTrimSP. The results are also discussed in relation to secondary particle properties for the reactive ion beam sputtering of Ti and to properties of TiO2 thin films grown by reactive ion beam sputter deposition with the same setup and the same parameters. Among others, it was found that sputtering of the TiO2 target exhibits less anisotropy contributions than sputtering of the Ti target.

Eco-friendly nebulized spray deposition of bifunctional anatase TiO2 thin films exhibiting multicolor switching and efficient NH3 gas sensing at room temperature

Recently, the preparation of TiO2 thin film with multifunctional properties has caused great interest among researchers for designing novel technological applications. In this aspect, an eco-friendly approach to spray deposition was employed to prepare TiO2 thin films for efficient electrochromic and room temperature gas sensing applications. The phase, morphology, topography, compositional and electrical properties of TiO2 thin films were studied by various characterization techniques. The electrochemical measurements showed that the film deposited at 350 °C exhibits excellent electrochromic properties with high coloration efficiency (240 cm2 C−1), faster response time (2.5 s) and a consistent stability up to 1000 cycles. In addition, the film deposited at 350 °C showed an efficient sensing of NH3 gas (as low as 5 ppm concentration) at room temperature operating condition. The interconnected pyramidal shaped nanoparticle network and the anatase-brookite biphasic nature enhances the electrochromic and gas sensing behavior of TiO2 films deposited at 350 °C.

Structure and Optical Properties of TiO2 Thin Films Prepared by a Sol-Gel Processing

Abstract Titanium dioxide (TiO2) thin films were deposited on CR-39 by a sol-gel dip coating route with different withdrawal speeds ranging from 250 to 350 mm/s. The TiO2 thin films were characterised by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, ellipsometry, and ultraviolet (UV)-visible (VIS)-near infrared (NIR) spectro-photometry. The role of withdrawal speed on the thickness of thin films to tailor properties of TiO2 thin films was studied. The XRD results revealed that all the films are amorphous in nature. TiO2 thin films deposited at different withdrawal speeds exhibit a decrease in transmission with an increase in speed. The direct optical band gap of the films has been estimated to be in the range 3.48–3.00 eV by UV-VIS-NIR spectro-photometry and 3.52–3.38 eV by ellipsometry. TiO2 is a potential prospect in microelectronic applications and can serve as an absorber layer for photovoltaic devices. Surface morphology is granular with an increase in grain size and an increase in withdrawal speed.