The optical properties of Ti-doped TiO2 nanoceramic films deposited by simultaneous rf and dc magnetron sputtering

The Ti-doped TiO₂ (TiO₂:Ti) nanoceramic films were deposited by simultaneous rf magnetron sputtering of TiO₂ and dc magnetron sputtering of Ti. When dc power increased, TiO preferentially formed and the deposited films had lower O/Ti atomic ratio, especially at low substrate temperature. With the decrease of substrate temperature, the TiO₂:Ti film had relatively high optical energy gap, therefore the absorption edge showed the blue shift. The nonlinear refractive indices of TiO₂:Ti films prepared at different dc powers and substrate temperatures were measured by Moiré deflectometry, and were of the order of 10^?8 cm² W^?1. By decreasing dc power and increasing substrate temperature, TiO₂:Ti film exhibited lower surface roughness, higher linear refractive index and lower stress-optical coefficient.     

Structural and Optical Property of Titanium Oxide Film Prepared by Energy Filtering Magnetron Sputtering Technique

Titanium oxide (TiO₂) film was deposited by an improved direct current magnetron sputtering (DMS) technique. The improved technique was named as energy filtering magnetron sputtering (EFMS) technique. The phase, surface morphology, and optical property of the film were characterized by X‐ray diffraction (XRD), Raman spectrometer, scanning electron microscope (SEM), and spectroscopic ellipsometer, respectively. Results show that the TiO₂ film prepared by the EFMS technique has good crystallization of the anatase phase without subsequent annealing process. The film is denser and the grain size is smaller. The crystallite sizes of the TiO₂ films prepared by the DMS and EFMS techniques are obtained at about 17.3 and 12.5 nm. The TiO₂ film deposited by the EFMS technique has higher refractive index and larger band gap owing to the result of the quantum size effect.     

The Sintering Trajectory and Electrical Properties of Niobium‐Doped Titania Sputtering Targets

Nb‐doped TiO₂ (TNO) films, which are highly conductive and transparent, can be used as transparent conductive oxide (TCO) films. A predominant manufacturing method for TCO film is magnetron sputtering, and the material of the sputtering target affects the performance of the film. The objective of this study was to investigate the sintering densification, microstructure, and electrical properties of TNO and TiO₂ sputtering targets. The results showed that the segregation of Nb at the grain boundary in TNO helps to facilitate densification and inhibit grain growth. After 1200°C sintering, the sintered density of TNO target achieves almost 100% of the theoretical density. Moreover, the Nb₂O₅ additive greatly improves the electrical properties, decreasing the resistivity of TiO₂ from >10⁸ Ωcm to 4.6 × 10¹ Ωcm. Correlations between TNO sputtering target investigated in this study and TNO sputtered film reported in the literature are also preliminarily established. The resistivity of TNO film with an anatase structure is obviously lower than that of TNO target with a rutile structure.     

Thermal annealing induced cave in and formation of nanoscale pits in Ag–TiO2 plasmonic nanocomposite thin film

Ag–TiO₂ nanocomposite thin films on silica glass were prepared through thermal evaporation in combination with RF magnetron sputtering. Thermal annealing induced changes in the optical, morphological and structural properties of Ag–TiO₂ nanocomposites were examined using optical absorption, photoluminescence spectroscopy, Raman spectroscopy, FESEM, AFM and XRD. FESEM and AFM studies revealed cave in of the Ag–TiO₂ thin film at various places leading to the formation nanoscale pits upon thermal annealing at 600 °C. The computed average size of pits was found to be 54 nm. Raman studies indicated 600 °C annealing induced transformation of anatase phase of TiO₂ into anatase/rutile mixed phase TiO₂. Optical absorption spectra showed systematic changes due to the effects of mixed phase formation and variation in the plasmonic behavior upon annealing. PL results of the as deposited Ag–TiO₂ thin film showed peaks at 377, 402, 432 and 486 nm. PL studies of Ag–TiO₂ nanocomposites treated at different annealing temperatures revealed changes in defect concentration in TiO₂. The tentative mechanism for the creation of nanoscale pits in Ag–TiO₂ thin film through thermal annealing was proposed.     

Effects of Ti ion deposition on corrosion resistance of WE43 alloy

Ti films with different thicknesses were successfully deposited on the surface of WE43 alloy by filtered cathode vacuum arc technology, and the microscopic morphology, structural composition, and corrosion resistance of the films were studied by means of X-ray diffractometer, X-ray photoelectron spectroscopy and scanning electron microscope. The results show that when the deposition time of Ti ions is 800 s, the thickness of the Ti film is 2.35 μm, the surface of the film is dense, and there are few defects. Meanwhile, Ti800 alloy has the best corrosion resistance among the four modified alloys. It has a corrosion current density (I_corr) of 2.9 μA·cm⁻², which is about 50 times lower than that of unmodified alloy. This conclusion is also confirmed by the complete film layer of Ti800 alloy and the tight bonding with the substrate after immersion experiments. Good corrosion resistance is attributed to a dense and relatively chemically stable TiO₂/Ti structure in simulated body fluid corrosive media.     

The effects of growth conditions on the surface properties and photocatalytic activities of anatase TiO<Subscript>2</Subscript> films prepared via electrochemical anodizing and annealing methods

In the present work, nanostructured TiO₂ films were prepared by electrochemical anodization process of titanium in fluoride-containing electrolytes using an innovative approach. After anodization, the TiO₂ films were annealed at 480?°C for 2 h in air in order to acquire anatase phase transformation and increase its crystallinity. The effects of anodization voltage, electrolyte concentration and anodization time on the formation of TiO₂ films and the photocatalytic degradation of methylene blue (MB) were discussed in details. The phase structure and surface morphology of the samples characterized by means of X-ray diffraction and scanning electron microscope. The as-prepared nanostructured TiO₂ film anodized in 0.5% HF electrolyte at 15 V for 240 min showed excellent photocatalytic degradation of MB and is promising for environmental purification.     

Large-scale preparation of nanoporous TiO2 film on titanium substrate with improved photoelectrochemical performance

Fabrication of three-dimensional TiO₂ films on Ti substrates is one important strategy to obtain efficient electrodes for energy conversion and environmental applications. In this work, we found that hierarchical porous TiO₂ film can be prepared by treating H₂O₂ pre-oxidized Ti substrate in TiCl₃ solution followed by calcinations. The formation process is a combination of the corrosion of Ti substrate and the oxidation hydrolysis of TiCl₃. According to the characterizations by scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflectance spectroscopy (DRS), the anatase phase TiO₂ films show porous morphology with the smallest diameter of 20 nm and possess enhanced optical absorption properties. Using the porous film as a working electrode, we found that it displays efficient activity for photoelectrocatalytic decolorization of rhodamine B (RhB) and photocurrent generation, with a photocurrent density as high as 1.2 mA/cm². It represents a potential method to fabricate large-area nanoporous TiO₂ film on Ti substrate due to the scalability of such chemical oxidation process.     

Enhanced photocatalytic activity of Au-buffered TiO2 thin films prepared by radio frequency magnetron sputtering

Au-buffered TiO₂ thin films have been prepared by radio frequency magnetron sputtering method. The structural and morphological properties of the thin films were characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The photocatalytic activity of the samples was evaluated by the photodecomposition of methylene blue. The Au-buffer thin layer placed between the TiO₂ thin films significantly enhanced photocatalytic activity by 50%. Annealing the Au-buffered TiO₂ thin film at 600 °C decreased the film roughness, but it increased the surface area and anatase crystalline size, enhancing the photocatalytic activity.     

Structural Modification of TiO2 Nanorod Films with an Influence on the Photovoltaic Efficiency of a Dye-Sensitized Solar Cell (DSSC)

TiO₂ nanorod films have been deposited on ITO substrates by dc reactive magnetron sputtering technique. The structures of these nanorod films were modified by the variation of the oxygen pressure during the sputtering process. Although all these TiO₂ nanorod films deposited at different oxygen pressures show an anatase structure, the orientation of the nanorod films varies with the oxygen pressure. Only a very weak (101) diffraction peak can be observed for the TiO₂ nanorod film prepared at low oxygen pressure. However, as the oxygen pressure is increased, the (220) diffraction peak appears and the intensity of this diffraction peak is increased with the oxygen pressure. The results of the SEM show that these TiO₂ nanorods are perpendicular to the ITO substrate. At low oxygen pressure, these sputtered TiO₂ nanorods stick together and have a dense structure. As the oxygen pressure is increased, these sputtered TiO₂ nanorods get separated gradually and have a porous structure. The optical transmittance of these TiO₂ nanorod films has been measured and then fitted by OJL model. The porosities of the TiO₂ nanorod films have been calculated. The TiO₂ nanorod film prepared at high oxygen pressure shows a high porosity. The dye-sensitized solar cells (DSSCs) have been assembled using these TiO₂ nanorod films prepared at different oxygen pressures as photoelectrode. The optimum performance was achieved for the DSSC using the TiO₂ nanorod film with the highest (220) diffraction peak and the highest porosity.     

Spectral Selective Solar Light Enhanced Photocatalysis: TiO<Subscript>2</Subscript>/TiAlN Bilayer Films

We demonstrate that spectral selective photocatalytic multilayer films can be tailored such that they can harness the full solar spectrum for enhanced photocatalytic gas-phase oxidation of acetaldehyde. Thin films of anatase TiO₂ were deposited on a thin solar absorber TiAlN film to fabricate bilayer TiO₂/TiAlN films by dc magnetron sputtering on aluminium substrates. The structural and optical properties of the films were characterized by X-ray diffraction and Raman spectroscopy. The reaction rate and quantum yield for acetaldehyde removal was measured and an almost tenfold enhancement of the quantum yield was observed for the TiO₂/TiAlN films compared with the single TiO₂ film, on par with enhancements achieved with new heterojunction photocatalysts. The results were interpreted by a temperature-induced change of the reaction kinetics. Absorption of simulated solar light illumination resulted in a temperature increase of the TIAlN film that was estimated to be at most 126 K. We show that a concomitant temperature increase of the top layer TiO₂ by 100 K shifts the water gas-surface equilibrium from multilayer to submonolayer coverage. We propose that this is the main reason for the observed enhancement of the photocatalytic activity, whereby gas phase molecules may come in direct contact with free surface sites instead of having to diffuse through a thin water film. The implications of the results for judicious control of temperature and relative humidity for efficient gas-phase photocatalysis and exploitation of selective solar absorbing films are discussed.     

Photocatalytic functional coatings of TiO2 thin films on polymer substrate by plasma enhanced atomic layer deposition

We prepared photocatalytic TiO₂ thin films which exhibited relatively high growth rate and low impurity on polymer substrate by plasma enhanced atomic layer deposition (PE-ALD) from Ti(NMe₂)₄ [tetrakis (dimethylamido) Ti, TDMAT] and O₂ plasma to show the self-cleaning effect. The TiO₂ thin films with anatase phase and bandgap energy about 3.3 eV were deposited at growth temperature of 250 °C and the photocatalytic effects were compared with commercial Activ glass. From contact angles measurement of water droplet and photo-induced degradation test of organic liquid, TiO₂ thin films with anatase phases showed superhydrophilic phenomena and decomposed organic liquid after UV irradiation. The anatase TiO₂ thin film on polymer substrate showed highest photocatalytic efficiency after 5 h UV irradiation. We attribute the highest photocatalytic efficiency of TiO₂ thin film with anatase structure to the formation of suitable crystalline phase and large surface area.     

Synthesis of high-quality AZO polycrystalline films via target bias radio frequency magnetron sputtering

The deposition rate, transmittance and resistivity of aluminium-doped zinc oxide (AZO) films deposited via radio frequency (r.f.) sputtering change with target thickness. An effective method to control and maintain AZO film properties was developed. The strategy only involved the regulation of target bias voltage of r.f. magnetron sputtering system. The target bias voltage considerably influenced AZO film resistivity. The resistivity of the as-deposited AZO film was 9.82×10⁻⁴ Ω cm with power density of 2.19 W/cm² at target self-bias of −72 V. However, it decreased to 5.98×10⁻⁴ Ω cm when the target bias voltage was increased to −112 V by applying d.c. voltage. Both growth rate and optical band gap of AZO film increased with the absolute value of target bias voltage – growth rate increased from 10.54 nm/min to 25.14 nm/min, and band gap increased from 3.57eV to 3.71 eV when target bias voltage increased from −72 V to −112 V at r.f. power density of 2.19 W/cm². The morphology of AZO films was slightly affected by the target bias voltage. Regulating target bias voltage is an effective method to obtain high-quality AZO thin films deposited via r.f. magnetron sputtering. It is also a good choice to maintain the quality of AZO film in uptime manufacturing deposition.     

A Novel Method for Preparing V-doped Titanium Dioxide Thin Film Photocatalysts with High Photocatalytic Activity Under Visible Light Irradiation

The liquid phase deposition (LPD) method was successfully used for preparing V-doped TiO₂ thin film photocatalysts. In this simple and easily-controlled process, V-doped anatase TiO₂ thin films were directly deposited on a soda lime glass substrate placed in an aqueous solution containing Ti- and V-fluoro complex ions, followed by annealing. The thin films were analyzed by XRD, XPS, UV-vis. V⁴⁺ ions were introduced into the lattice of TiO₂ through in-situ substituting Ti⁴⁺. The absorption edge of V-doped TiO₂ films shifted to visible light region. The highly efficient photocatalytic activity was verified by the decomposition of methylene blue under visible light irradiation.     

Photocatalytic treatments on dental mirror surfaces using hydrolysis of titanium alkoxide

Anatase titanium dioxide (TiO₂) photocatalytic thin films were directly formed on glass slide and commercial dental mirror substrate surfaces by a hydrolysis of titanium alkoxide, and the hydrophilicity, the degree of oxidizing power and the transparency of the anatase TiO₂-coated substrate surfaces. The contact angles of water and the decomposition rates of methylene blue on the anatase TiO₂ photocatalytic thin films improved with the increasing duration of a tetraethyl orthotitanate (TEOT) hydrolysis, but they hardly changed for the longer duration. The reflectance of anatase TiO₂ photocatalytic thin films coated on glass slide substrate surfaces was higher as the duration of a TEOT hydrolysis increased. Similar tendencies concerning hydrophilicity and transparency were recognized in cases of commercial dental mirror substrate surfaces. A hydrolysis of titanium alkoxide obtained superhydrophilic and antibacterial treatments with excellent transparency on commercial dental mirror substrate surfaces.     

Preparation and blood compatibility of carbon/TiO2 nanocomposite

A carbon/TiO₂ nanocomposite, which consists of carbon film with various sp³C content and TiO₂ nanowire arrays, has been synthesized, in which the top surface of TiO₂ nanowire arrays prepared using hydrothermal method on fluorine-doped tin oxide glass were coated with carbon thin films. The carbon thin films with a higher, medium and lower sp³C content were deposited by pulsed magnetic filtered cathodic vacuum arc deposition, plasma-enhanced chemical vapor deposition and magnetron sputtering deposition, respectively. The surface morphology and structure of TiO₂ nanowire arrays were investigated by scanning electron microscopy, transmission electron microscope and X-ray diffraction. The sp³C content in carbon films was characterized using Raman spectroscopy. The blood compatibility of the samples including the TiO₂ nanowire arrays, carbon films and carbon/TiO₂ nanocomposite was assessed by tests of platelet adhesion in vitro. Results showed that the carbon/TiO₂ composite can effectively improve the anticoagulant function compared to the single materials. It is believed that the excellent blood compatibility of the carbon/TiO₂ nanocomposite is attributed to a joint function of surface properties adjusted by nanowire arrays and electronic structure of carbon thin films.     

Application of Optical-fiber Photoreactor for CO2 Photocatalytic Reduction

An optical-fiber photoreactor, comprised of 216 catalyst-coated fibers, was designed and assembled to transmit and spread light uniformly inside the reactor. The power loss of light transmission inside an optical fiber was calculated using beam propagation method. The optimum length of optical fiber was estimated to be near 11 cm long in order to entirely spread out light energy over surface catalyst. Vapor-phase CO₂ was photocatalytically reduced to methanol using the photoreactor under UV irradiation in a steady-state flow system. The solutions of metal-loaded titania were prepared by thermal hydrolysis method. Metal-loaded TiO₂ film was coated on optical fibers by dip-coating method. TiO₂, Cu/TiO₂ and Ag/TiO₂ films were uniformly on the fibers and their thicknesses ranged from 27 to 33 nm. The films consisted of very fine spherical particles with diameters of 10–20 nm. The XRD spectra indicated anatase phase for all films. Methanol yield increased with UV irradiative intensity. Maximum methanol rate was 4.12 μmole/g-cat h using 1.0 wt%-Ag/TiO₂ catalyst at 1.13 bar of CO₂, 0.03 bar of H₂O pressures, and 5,000 s mean residence time under 10 W/cm² UV irradiation.     

Effect of TiO2 nanoparticles on the antibacterial and physical properties of polyethylene-based film

TiO₂ nanoparticles and their application in packaging systems have attracted a lot of attention because of its antimicrobial activity. In this work, effect of TiO₂ nanoparticles on the antibacterial and physical properties of polyethylene (PE)-based film was investigated. Results indicated that the antibacterial activity of TiO₂-incorporated PE films should be due to the killing effect property of TiO₂ nanoparticles against microorganisms. The TiO₂-incorporated PE film exhibited more effective antibacterial activity for Staphylococcus aureus. The antibacterial activity to inactivate Escherichia coli or S. aureus was improved by UV irradiation. The inhibition ratio of TiO₂-incorporated PE films sample irradiated for 60 min by UV light was improved significantly, which were 89.3% for E. coli and 95.2% for S. aureus, respectively, compared to that of TiO₂-PE film without UV irradiation. The analysis of physical properties revealed that TiO₂ nanoparticles increased the tensile strength and elongation at break of PE-based film. The climate resistance of nano-TiO₂ films is greatly enhanced, compared to that of the blank PE film. Water vapor transmission increased from 18.1 to 24.6 g/m²·24 h with the incorporation of TiO₂ nanoparticles. Results revealed that PE based film incorporating with TiO₂ nanoparticles have a good potential to be used as active food packaging system.     

Corrosion resistance and photocatalytic activity evaluation of electrophoretically deposited TiO2-rGO nanocomposite on 316L stainless steel substrate

TiO₂-rGO nanocomposite coatings were obtained by electrophoretic deposition (EPD) technique of TiO₂ nanoparticles and graphene oxide (GO) on stainless steel substrate. First, GO particles were synthesized using a modified Hummers' method. GO was reduced electrochemically to form a coating in the presence of nano-sized TiO₂ particles. The influences of different parameters such as GO concentration, coupling co-electro-deposition parameters (electrophoretic duration and voltage) on thickness, surface morphology and, corrosion behavior of the as-synthesized TiO₂-rGO nanocomposite coatings were systematically surveyed. The morphology and microstructure were investigated by field emission scanning electron microscopy (FE-SEM), Raman spectra and X-ray diffraction (XRD) techniques. Atomic force microscopy (AFM) was harnessed to evaluate the topography of the as-prepared GO powder. The bonding characteristics of as-synthesized and as-reduced GO were examined after deposition, by Energy Dispersive Analysis of X-Ray (EDX) and Fourier-transform infrared spectroscopy (FT-IR). Corrosion behavior of coatings and that of the pure TiO₂ layer were evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques (by applying potentiodynamic polarization spectroscopy (PDS)). Detailed SEM studies showed that increasing EPD voltage brings about a coating with increased porosity and microcracks with higher thickness. In addition to that, the presence of rGO reduced corrosion current density (i_corr) and shifted corrosion potential (E_corr) toward more noble values in 3.5% NaCl at room temperature. Also, Analyses revealed that the optimum electrophoretically synthesized coating was obtained at GO concentration of 1 g/L, 30 V and 30 min at room temperature. The corrosion current density of the corresponding coating was remediated up to 0.2 μA cm⁻², which means an anti-corrosion ability of about 30 times compared to TiO₂-coated and bare 316L stainless steel. The results of impedance spectroscopic studies demonstrated that this coating renders as a barrier layer and resistance increased from 2.95 KΩ cm² for TiO₂-coated layer to 10.49 KΩ cm² for the optimized layer.     

Surface modification of Ti64-Alloy with silver silicon nitride thin films

Ti6Al4V (Ti64) alloys is an alpha-beta titanium alloy with good corrosion resistance, high strength-to-weight ratio, excellent physiochemical stability and good biocompatibility. However, Ti64 alloy loses its biocompatibility when it is introduced into human tissues due to possible toxic of Vanadium (V) and Aluminum (Al) ion release. Thus, modification using silver silicon nitride films onto Ti64 via magnetron sputtering technique was proposed. In this study, a set of experimental depositing AgSiN films on Ti64 alloys using different bias voltage (0, ?75, ?150 and ?200?V) were fabricated. The surface characterization and mechanical performance of the thin films with respect to bias voltage were studied using scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), nanoindentation and scratch test. Meanwhile, the biological function of the films was tested through wettability and antibacterial tests. According to the results, all thin films showed similar morphology with the highest adhesion strength (596?mN) was obtained for AgSiN thin film deposited at ?75?V. The hardness (5.5?GPa) and elastic modulus (211.0?GPa) of sample deposited at ?150?V showed an improvement for about 50% compared to the Ti64 substrate (H?=?2.75, E?=?113.8). The lowest compressive residual stress 0.06?GPa was noted for samples that have highest adhesion strength and highest thickness. In terms of biological functionality, all films showed hydrophilic property with wetting angle observed were below 90°. An inhibition zone area that observed on Bulkholderia pseudomallei (B.Psudomallei) and Escherichia coli (E.coli) were 7 and 10?mm respectively, which proved the AgSiN films as a promising candidate to be used in antibacterial applications.     

The properties of Al-doped TiO2 nanoceramic films deposited by simultaneous rf and dc magnetron sputtering

The Al-doped TiO₂ (TiO₂:Al) nanoceramic films were deposited by simultaneous rf magnetron sputtering of TiO₂ and dc magnetron sputtering of Al. The advantage of this method is that the Al content could be independently controlled. Al₂O₃ was favorable to form with decreasing Al content. The nanocrystallinity was enhanced by increasing the Al contents, because the increase of Al contents resulted in that the deposited films to be nearly stoichiometric. The morphologies of TiO₂:Al films were significantly affected by Al contents. The nonlinear refractive index of TiO₂:Al film on the glass substrate was measured by Moiré deflectometry, and was of the order of 10^?8 cm² W^?1. As Al content increased, the TiO₂:Al film had high VIS-IR transmission, high optical energy gap, high linear refractive index and low porosity.