Fe-doped TiO2 Thin Films Research Articles

Effect of Fe doping on crystalline phase, structure and photocatalytic properties of TiO2 thin films

Undoped and Fe-doped TiO2 thin films were fabricated on Si substrates using sol-gel method. XRD and Rietveld refinement results show the anatase to rutile transition in the system. SEM and AFM spectra demonstrate that the generation of agglomeration phenomena after Fe doping provides the nucleation point for the phase transition, and the difference in the Gibbs free energies of the two phases provides the driving force for the phase transition. XPS measurements verify that the formation of oxides after Fe doping contributes to the surface thermodynamic equilibrium and the possibility of the surface atomic rearrangements during the anatase to rutile phase transition. The energy band diagram illustrates at the level of electronic structure that the phase transition raises the position of the conduction band minimum of the film and the oxide of Fe that is formed becomes the charge complex center. Finally, the results of degradation of methylene blue solution under simulated visible light irradiation show that Fe doping reduces the photocatalytic ability of TiO2 films. The corresponding mechanism is proposed to explain the photocatalytic activity by which Fe3+ of larger radius replaces Ti4+ to promote the transition of the film from anatase to rutile and to act as a charge complex center.

Effect of Fe doping on the microstructure, optical and dispersion energy characteristics of TiO2 thin films prepared via spray pyrolysis technique

In this study, we have delineated the preparation and influence of Fe doping on microstructural and optical properties of the undoped and Fe-doped TiO2 thin film with different Fe concentrations (0, 2, 4, 6, and 8 at.%). The samples are prepared by a simple and cost-effective spray pyrolysis technique (SPT) using Ti(OCH2CH2CH2CH3)4 as a precursor of mother material. The effect of Fe on the microstructure and phase formation of TiO2 thin films is investigated by XRD analysis. XRD investigation depicts that the undoped product corresponds to anatase phase of TiO2 and remains uncontaminated with addition of 2 at.% Fe impurity. It is also observed that Fe introduces a phase transition from anatase to rutile after adulterating more Fe contents (4, 6 and 8 at.%). In order to study the optical characteristics, UV–vis spectroscopy has been employed, which reveals that UV absorption for the Fe incorporated TiO2 products are observed to move to a longer wavelength (red shift) and lower bandgap energy from 3.81 eV (0 at.% Fe) to 3.70 eV (8 at.% Fe) of the TiO2 thin films. The optical constants such as refractive index, complex dielectric constants, tanδ, volume energy loss (VELF) and surface energy loss (SELF) functions, dispersion parameters of synthesized titanium dioxide samples has been studied. The results of optical constant values and the dispersion enegy parameters depicts the influence of Fe on microstructural and optical transportation properties of the as prepared samples more appropriately and effectively.

Humidity sensing properties of spray deposited Fe doped TiO2 thin film

In the present work, ferrite (Fe) doped TiO2 thin films with different volume percentage (vol%) were synthesized using a spray pyrolysis technique. The effect of Fe doping on structural properties such as crystallite size, texture coefficient, microstrain, dislocation densities etc. were evaluated from the X ray diffratometry (XRD) data. XRD data revealed a polycrystalline anatase TiO2 phase for sample synthesized up to 2 vol% and mixed anatase and rutile crystalline phase for sample synthesized at 4 vol% Fe doped TiO2. The crystalline size was observed to decrease with increase in Fe dopant vol% and also other structural parameters changes with Fe dopant percentage. In the present work, electrical resistance was observed to decrease with a rise in Fe dopant vol% and temperature of the sample. Thermal properties like temperature coefficient of resistance and activation energy also showed strong correlation with Fe dopant vol%. Humidity sensing properties of the synthesized sample altered with a change in Fe dopant vol%. In the present paper, maximum sensitivity of about 88.7% for the sample synthesized with 2 vol% Fe doped TiO2 and also the lowest response and recovery time of about 52 and 3 s were reported for the same sample.

Visible light driven enhancement in photodegradation of organic dyes using FexTi1-xO2 thin films

Fe doped TiO2 thin films (Fe, 0.02, 0.03, 0.04 and 0.05 mol %) were prepared using dip coating method. Dip coating method provides thin films of self-assembly with sol gel technique. The prepared thin films were subjected to different characterization studies. The structural properties of samples were analyzed with powder X-Ray diffraction method. It is observed that Fe ion incorporation has modified the crystallite size of TiO2 particle significantly which can have effect on the wavelength of the light source required for the photocatalytic process. The surface morphological properties were investigated via FESEM and AFM techniques. The higher concentration of Fe doped TiO2 thin films exhibit the larger surface area and roughness which leads to better enhancement for catalytic properties. The optical absorption studies showed the absorption edge of doped TiO2 samples has shifted towards longer wavelength region. The catalytic efficiency of prepared samples was investigated by the degradation of organic pollutants methylene blue and Congo red dyes and the results showed enhanced chemical reaction ensued between the methylene blue and Fe TiO2 samples. Further the treated water was used to grow plant like green gram (Vigna radiata) and the growth of plant was studied. The anatase phase, narrowing band gap, acidic surface sites and large surface area of Fe doped TiO2 thin film infer the sample as an efficient photocatalyst for environmental purification.

Influence of Fe3+ ions doping on TiO2 thin films: Defect generation, d-d transition and band gap tuning for optoelectronic device applications

In this article, we have explored the influence of Fe3+ ion on the surface morphological, structural, optical and electrical properties of TiO2 thin films grown on glass substrates by thermal spray pyrolysis technique. The FESEM micrographs of the deposited TiO2 thin films reveal that the surface consists of agglomerates of small grains. The anatase and rutile phase is confirmed by XRD and Debye-Scherer (D-S), Uniform Deformation Model (UDM) and Halder-Wagner (HW) method are employed to determine the structural parameters using XRD peak profile analysis. A red shift occurs in absorption spectra and band gap decreases with Fe content. The optical parameters such as skin depth, optical static dielectric constant, Urbach energy, etc and Electron-phonon interaction are increased with increasing Fe contents, whereas steepness parameter decreases. The electrical properties are studied by Hall Effect measurements. The paramount study is useful for standardizing the Fe-doped TiO2 thin films for optoelectronic device applications.

Local structural investigations of Fe-doped TiO2 amorphous thin films

The present study deals with the local structure of amorphous TiO2 and Fe-doped TiO2 thin films deposited on Si substrate using magnetron sputtering. The absence of long range order is confirmed by grazing incidence x-ray diffraction and the short range order is studied using x-ray absorption near edge structure (XANES) measurements at Ti, Fe and O K-edges and Fe and Ti L3-edge. The XANES provides understanding about the electronic transition induced from the short range ordering and dependence of electronic hybridization of the central Ti-p orbitals with the Ti-d orbitals. The XANES measurements also show that maximum Fe doping concentration allowed to replace Ti is 2 at.% and after that separate phase starts appearing, which is consistent with simulation by ab-initio multiple scattering theory based code FEFF9. Ellipsometry measurements show gradual decrease in band-gap energy upto 2 at.% Fe doping from pristine TiO2, however a drastic decrease in band-gap energy is observed at 4 at.% or higher doping concentration due to formation of other phases.

Surface, structural and optical properties dependence of Fe-doped TiO2 films deposited onto soda–lime–glass

In this study, pure and Fe doped TiO2 thin films have been prepared via sol-gel method using the tetraethyl-orthotitanate as source of Ti and Fe(III) nitrate as a source of Fe3+ doping. XRD patterns exhibit typical peaks of TiO2 anatase phase. SEM observations confirm the nanometer grain size (below 10 nm) without a defined shape. Optical measurements indicate a transparency in the range 80–100%, it increases with Fe doping level while the energy band gap slightly decreases; 3.36 – 3.28 eV. Wettability test shows a super-hydrophilicity of Fe3+ doped TiO2 thin films and the low contact angle is founded for 0.6%Fe. However, no enhancement in photocatalytic activity of Fe doped TiO2 thin films have been achieved. This may be attributed to sodium diffusion from the substrate. The as-prepared nanostructured Fe-doped TiO2 thin films can be used as potential candidate for self-cleaning due to the super-hydrophilicity character in the visible light.

Effect of doping concentration for the properties of Fe doped TiO2 thin films applications

This paper reports the sol–gel preparation and subsequent characterization of Fe doped TiO2 thin films with different doping concentrations (1%, 3% and 5%). X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray analysis (EDX), UV–Visible analysis and Photoluminescence spectra analysis (PL) were used to characterize the prepared samples. The crystallite size of anatase phase increases from 4.76 nm to 7.61 nm when doping concentration increases from 1% to 3% and the anatase phase is transformed to brookite at the doping of 5% as the crystallite size of more than 14.82 nm. The surface morphological pictures are observing to be almost smooth and particle size dispensation of Fe doped titanium dioxide particles is non-spherical agglomeration crystallite formation. An optical band gap of 3.63 eV, 3.41 eV and 3.11 eV were obtained for the TiO2 thin films doped with 1%, 3% and 5% Fe respectively. PL analysis results the emission peaks at 347 nm for 1% Fe doped sample seems to shift slightly towards higher wavelength for 3% and 5% Fe doped samples. This may be due to reduction in bandgap because of the shallow trap state created near the absorption band edge as a result of doping.

Evaluation of electronic transport and optical response of two-dimensional Fe-doped TiO2 thin films for photodetector applications

We have carried out the structural, electronic and optical properties of Iron (Fe)-doped TiO2 thin films by sol-gel technique. The results reveal that the thin films form in a granular structure where particle-like grains cover the surface. Photophysical features of the thin films are performed by UV–vis spectrometry. The optical bandgap of undoped TiO2 thin film decreases from 3.17 eV to 3.05 eV with an increase in atomic ratios of Fe content, so the electron transfer is easier from the valence band to the conduction band. The current-voltage (I–V) and capacitance-voltage (C–V) characteristics of the undoped and Fe-doped TiO2 thin films are investigated under dark and various lighting intensities. Our results show that the photocurrents increase with increasing intensities of illumination. The photodiodes also show a decreasing capacitance with increasing frequency. From I–V and C–V plots, the photodiodes show rectifying properties and good photovoltaic behavior. Herein, the results display that the produced new Fe-doped TiO2 thin film samples can be used for photodetector applications.

Tailoring of optical, biological and magnetic properties of nanocrystalline Fe doped TiO2 thin films

Fe doped TiO2 films were synthesized by sol–gel dip coating method. The concentration of Fe3+ was varied as 1%–5% (w/w) in TiO2. X-ray diffraction showed dominating rutile phase of TiO2 along with brookite phase and hematite Fe2O3 phase. The content of the rutile phase varies depending on the Fe doping percentage. The high iron doping reduced the band gap and restrained the growth of TiO2 crystallite. All films are ferromagnetic (FM) but the films with low Fe doping percentage have a good crystallinity and a strong ferro-magnetism. Although the Fe doping has not changed the crystal structure of TiO2, but had affected its photo-catalytic and antibacterial properties. The bacteria E. coli were more vulnerable to Iron doped TiO2 when compared to the bacteria Pseudomonas. 3% Fe doped TiO2 had the best photo-catalytic activity. Fe doped TiO2 can act as a remarkable antibacterial entity against microorganisms to save from bacterial infections.

Antibacterial Activity of Visible Light-Activated TiO2 Thin Films with Low Level of Fe Doping

Development of effective antibacterial visible light-activated photocatalytic materials in industries including wastewater treatment and food industry has attracted increasing attention. In this work, Fe-doped TiO2 thin films with different doping levels on a glass substrate were prepared by the sol-gel dip-coating method. The as-prepared films were characterized by Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). Raman spectroscopy and XRD results show the crystalline phase of titanium dioxide was anatase, and the range of the crystal size for the films was 19.24–22.24 nm. XPS results indicate that iron was in the form of Fe3+ in Fe-doped TiO2 films. Regarding the antibacterial properties of TiO2 films, the order of antibacterial activity of TiO2 films was 0.1 at% Fe > 0.5 at% Fe > 1.0 at% TiO2 > bare TiO2 > 2.0 at% Fe > 3.45 at% Fe. 0.1 at% of Fe is the optimum dopant ratio related to antibacterial activity. 0.1 at% Fe-doped TiO2 film is highly efficient in inactivating E. coli under 3 h of visible light irradiation, and it remains efficient even in real dye waste water.

Structural, optical properties and photocatalytic activity of Fe3+ doped TiO2 thin films deposited by sol-gel spin coating

Nanocrystalline TiO2: Fe3+ films were deposited using a simple spin coating technique. The effect of Fe3+ on spectroscopic features and photocatalytic activity of films were studied using X-ray diffractometer (XRD), scanning electron microscope (SEM), Energy dispersive X-ray (EDX), high-resolution transmission electron microscope (HR-TEM), Raman spectrometer, UV–Vis and fluorescence spectrophotometer. The XRD of all the TiO2: Fe3+ films exhibits a decrease in the crystallite size with an increase in Fe3+ concentration. The Fe3+ doped TiO2 nanocrystals exhibited a high specific surface area. The HR-TEM images of 1% and 7% Fe doped TiO2 thin films confirmed the average particle size is about 14 and 8 nm respectively. The Raman modes of vibrations present in the TiO2:Fe3+ films also confirms the formation of the anatase phase. The optical bandgap energy of titania decreases from 3.32 to 2.57 eV. The luminescent emission intensity of TiO2: Fe3+ films decreased compare to pure titania film. Moreover, the photocatalytic activity (PCA) of TiO2:x%Fe3+ (x = 0, 1, 3, 5, 7 and 10) catalysts were determined by the decomposition of methylene blue (MB) under irradiation of visible light. The observed results revealed that the optimized Fe3+ doped TiO2 film displayed high PCA. The enhancement of PCA of the films is due to the effect of Fe doping.

Pure and Fe doped TiO2 thin films for MOSFET Technology

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Flame retardant and visible light-activated Fe-doped TiO2 thin films anchored to wood surfaces for the photocatalytic degradation of gaseous formaldehyde

Flame retardant and visible light-activated Fe-doped TiO2 thin films were anchored to wood surfaces by a facile precipitation method for the photocatalytic degradation of gaseous formaldehyde. All of the as-prepared TiO2 thin films exhibited the anatase crystal structure and grew on the wood surfaces by the aggregation of nanoparticles with diameters ranging from 11 to 16 nm. The UV–vis diffuse reflectance spectroscopy (UV–vis DRS) results showed that the presence of a small amount of iron ions in the TiO2 matrix could significantly extend the optical responses in the UV to visible region. Compared to the pure TiO2/wood samples, the Fe-doped TiO2/wood samples exhibited higher photocatalytic activities under visible light irradiation. The optimum nFe/nTi molar ratio was 2.0 at. %. The electron spin resonance (ESR) tests further confirmed that the active oxygen species of OH and O2– that were generated on the Fe-doped TiO2/wood samples under visible light irradiation are responsible for the degradation of formaldehyde. The Fe-doped TiO2 samples also exhibited high stability and reusability after 6 cycles. Additionally, the limiting oxygen index of the original wood increased from 24.8% to 33.9% after it was coated with Fe-doped TiO2 thin films, indicating a significant improvement in its flame resistance.

Iron doped TiO2 films and their photoactivity in nitrobenzene removal from water

The undoped and sol-gel Fe-doped TiO2 thin films deposited by spray pyrolysis method on glass substrates, at 373 K were prepared. The influence of Fe dopant concentration and the temperature of thermal treatment on the obtained materials has been studied using: XRD, XPS, PL and TEM techniques, and measurements of hydrophilic and photocatalytic properties. A detailed XRD analysis has established the structural changes due to the thermal treatment and the dopant concentration. For the samples with the lowest Fe content, the thermal treatment of the samples at 673 K lead to an increased super-hydrophilic performance and the best yield of nitrobenzene removal from water. In order to underline the effect of iron dopant, a comparative structural study was initiated for Fe-doped TiO2 films as prepared and the sol-gel nanopowders with the same composition presented in our previous paper. All the doped materials have also been compared with the corresponding materials in the absence of the dopant (TiO2 undoped). A mechanism of photocatalytic degradation of nitrobenzene has been proposed.

Transparent nanostructured Fe-doped TiO2 thin films prepared by ultrasonic assisted spray pyrolysis technique

Nanostructured TiO2 and Fe-doped TiO2 thin films with high transparency were deposited on glass substrate through ultrasonic-assisted spray pyrolysis technique and were used in the visible light photocatalytic degradation of MB dye. The resulting thin films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence spectroscopy, x-ray diffraction (XRD), and UV-visible absorption spectroscopy techniques. Based on Raman spectroscopy results, both of the TiO2 and Fe-doped TiO2 films have anatase crystal structure, however, because of the insertion of Fe in the structure of TiO2 some point defects and oxygen vacancies are formed in the Fe-doped TiO2 thin film. Presence of Fe in the structure of TiO2 decreases the band gap energy of TiO2 and also reduces the electron–hole recombination rate. Decreasing of the electron–hole recombination rate and band gap energy result in the enhancement of the visible light photocatalytic activity of the Fe-doped TiO2 thin film.

A detailed study on the Fe-doped TiO2 thin films induced by pulsed laser deposition route

Fe-doped TiO2 thin films are deposited both on the (100) oriented Si and glass substrates by pulsed laser deposition technique using Fe powder doped TiO2 ceramic target. The structural and optical properties of the film have been studied in detail. The degree of film crystallinity is investigated by X-ray diffraction and confirmed by Raman scattering measurements. The stoichiometry and chemical states of Fe, Ti and O are probed by X-ray photoelectron spectroscopy. The surface morphologies are observed by Scanning electron microscopy. The optical properties are studied by measuring the transmittance and the optical constants, the refractive index and the extinction coefficient. It is found that the substrate temperature is a key factor in determining the thin film structure which further influences the refractive index and the optical band gap of the film. An anatase structure emerges above 300 °C while the rutile structure appears when the substrate temperature is higher than 500 °C. Another result is that Fe exists in the deposited films as Fe3+ and the atomic concentration of Fe in the films is much lower than that in the source target.

The effect of CO2 gas adsorption on the electrical properties of Fe doped TiO2 films

CO2 has to be monitored for indoor air quality, being also an important greenhouse gas. The electrical and sensing gas properties of the undoped and Fe doped TiO2 thin films, obtained by RF sputtering, have been investigated in different CO2 atmospheres. It was observed that the response to CO2 increases by Fe doping for the lowest doped film, and then decreases, as the dopant concentration increases. An explanation was given based on multiphonon-assisted hopping model. By studying the films electrical conductivity in front of a certain CO2 atmosphere, we have qualitatively evidenced the semiconducting n-type nature of the films under study, except for the highest Fe doped film which has a p-type behavior. An important finding is that Fe doping determines the decrease of the optimum operating temperature, approaching the room temperature.

Effect of iron doping on structural and optical properties of TiO2thin film by sol–gel routed spin coating technique

Thin films of iron (Fe)-doped titanium dioxide (Fe:TiO[Formula: see text] were prepared by sol–gel spin coating technique and further calcined at 450[Formula: see text]C. The structural and optical properties of Fe-doped TiO2thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV–vis) and atomic force microscopic (AFM) techniques. The XRD results confirm the nanostructured TiO2thin films having crystalline nature with anatase phase. The characterization results show that the calcined thin films having high crystallinity and the effect of iron substitution lead to decreased crystallinity. The SEM investigations of Fe-doped TiO2films also gave evidence that the films were continuous spherical shaped particles with a nanometric range of grain size and film was porous in nature. AFM analysis establishes that the uniformity of the TiO2thin film with average roughness values. The optical measurements show that the films having high transparency in the visible region and the optical band gap energy of Fe-doped TiO2film with iron (Fe) decrease with increase in iron content. These important requirements for the Fe:TiO2films are to be used as window layers in solar cells.

Synthesis and characterization of pure and Fe doped TiO2 thin films for antimicrobial activity

Pure and Fe-doped titanium dioxide sol-gel thin films were prepared by spin coating process. Pure and Fe-TiO2 films, containing 3–6% Fe, were annealed at 450 °C for 1h. All thin films were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–vis spectroscopy. From XRD data, the dominant crystalline phase of titanium dioxide was anatase, and the range of the crystal size for the films was 19–26nm. On the other hand, antibacterial activity of pure and Fe-doped titanium dioxide against E. coli and S. aureus was evaluated by international recognized test (JIS Z 2801). The test shows incrementally increasing in antibacterial activity of the thin films when dopant ratio increased under UV light.