Doped Titanium Dioxide Thin Films Research Articles

Structural and optical characteristics of Cr-doped TiO2 thin films synthesized by sol-gel method

In this paper, undoped and 7 %, and 20 % chromium doped titanium dioxide thin films were synthesized on silicon and quartz substrates by utilizing the sol-gel spin coating process. The films were then annealed at 450 °C. The synthesis process and the effects of doping on the structural, optical, and vibrational properties were studied. XRD analysis showed that the undoped thin film had an anatase phase with a crystalline size of about 15.4 nm. However, as the concentration of chromium increased, the crystalline size decreased, and we obtained a mixed phase of rutile and anatase for doped films. The FTIR spectra revealed that undoped films had Ti–O bonding at 435 cm−1 and bond with stretching at 619 cm−1 wavenumbers, which decreased to 379 cm−1 and 377 cm−1 wavenumbers for 7 % and 20 % Cr doping, respectively. The optical measurements showed that the films were homogeneous and had high transmission, reaching 95 % in the visible range for the undoped thin film and 80 % for higher doping levels of chromium. These films have a remarkable level of transparency, and because of that they are highly regarded in the field of thin-film solar cells. Their optical properties make them an excellent choice for use as optical windows in these types of solar cells. As the amount of chromium in the film increases, the optical bandgap decreases from 3.23 eV to 2.26 eV. This suggests that chromium has a significant impact on the optical properties of these films, which might be helpful to researchers and professionals working in the fields of solar energy, optoelectronic devices, photocatalytic systems, gas sensors, and solar cell passivation.

Aluminum Doped Titanium Dioxide Thin Film for Perovskite Electron Transport Layer

Aluminum (Al) doped titanium dioxide thin film with different Al doping concentration (Al = 0 mol%, 1 mol%, 3 mol%, 5 mol% and 7 mol%) were deposited using solution spin coating technique and the effect of Al concentration on the structural, morphological and optical properties were examine. All samples were annealed at 450°C for 1 hour. XRD reveal that the films exhibits anatase crystal phase at (101) peak orientation. Based on the FESEM and AFM image it is found that, surface morphology of the film was significantly affected with different doping concentration. Al doped titanium dioxide with 3 mol% Al concentration shows the highest transmittance compared to others samples. Consequently, it is shown that different Al doping concentration plays vital roles in producing an optimum Al doped titanium dioxide thin films samples.

Influence of low concentration Sm doping on optical and catalytic performance of titania

The work focuses on exploring the effect of the concentration of Sm dopant (0.2–0.6 at.%) on structural, optical and photocatalytic properties of the spin coated titania based thin films annealed at different temperatures. The optical interpretation involves the influence of Sm doping on optical constants and luminescence behaviour of the samples. The comprehensive work on optical bandgap, Urbach energy and electron-phonon interaction strength was conducted for Sm doped samples. The optical band gap was found to increase with the increasing concentration of Sm, but decreased with high temperature annealing. Using ellipsometry measurement, refractive index of the samples was obtained. The orbital level information was gathered using X-Ray Photoelectron Spectroscopy (XPS) study with a special emphasis on the evolution of physico-chemical properties as function of Sm doping. The XPS study confirms the presence of Sm in the titania host material and it helped in estimating defects induced by Sm doping. The photocatalytic study of Sm doped titania thin films was carried out by using methylene blue (MB) and Rhodamine B (RhB) dye and we have found an enhanced photocatalytic activity for the 0.4 at.% Sm doped samples.

Influence of plasmon resonance on the luminescence of titanium dioxide thin films doped with rare earth ions

In this work the study of the optical properties of europium doped titanium dioxide thin films (TiO2:Eu) enhanced by gold plasmonic nanostructures are presented. Plasmonic platforms were manufactured by thermal annealing of thin film of Au, deposited on a Corning glass substrate. As a result of thermal treatment, gold spherical nanostructures with average dimensions of 50 nm were obtained. Luminescent TiO2:Eu film was deposited by RF magnetron sputtering method, from mosaic target. Morphology of gold nanostructures was investigated by SEM and TEM microscopes, while composition of oxides film was analysed by XPS methods. Luminescence properties were studied on the basis of excitation and emission spectra. Experiments have shown that such structures exhibit interesting luminescent properties and could be potential candidates for optoelectronics applications.

Spectroscopic investigation of defects in spin coated titania based thin films for photocatalytic applications

The present work focuses on Raman and photoluminescence spectroscopic study of spin coated Nd doped titania thin films annealed at 350 and 450 ​°C. For all the samples, the penetration depth of laser was evaluated to be about 300–350 ​nm. The lifetime of phonon was in the range 0.46–0.52 ps for different samples and its variation is discussed in detail. Photoluminescence (PL) spectra of Nd doped titania revealed the influence of dopant concentration on defect sites and strong emission in near infrared (NIR) region confirms Nd doping in titania matrix. The effect of Nd doping on photocatalytic behavior of titania films was studied by degrading methyl orange (MO) under UV light. The Nd doped titania thin films enhance the photocatalytic activity as compared to pristine titania. The enhancement in efficiency is correlated to the formation of surface defects.

Low concentration rare earth doping (Nd) and its effect on structural properties of titania thin films

The work focuses on investigating the influence of low concentration (0–0.6 at %) rare earth Neodymium (Nd) as dopant on structural properties of titania (TiO2) thin films. The thin films were deposited on glass substrates using spin coating method followed by thermal annealing at 350 °C and 450 °C, respectively. The surface morphology of the films was studied using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM) to check the influence of Nd dopant and annealing temperature on the grain growth. Energy Dispersive X-ray Analysis (EDAX) was used to confirm the presence of Nd dopant in Nd doped titania thin films. The chemical properties of titania doped with Nd thin films were determined through X-Ray Photoelectron Spectroscopy (XPS). The core level information of constituent elements was gathered from this measurement. A shift in high resolution spectra of Ti2p and O1s towards higher binding energies was observed on doping.

Sun light driven photocatalytic performance of Ag decorated TiO2 nanocomposite thin films by sol gel method

High performance, low cost photocatalysts are essential for water treatment applications. However the existing majority of the photocatalysts limited to Ultra violet and visible region only. Besides the fabrication of photocatalysts, there is a huge demand for low cost, recyclable and solar light trapping photocatalysts, thereby effectively remove the organic pollutants present in water. Here, we have synthesized the solar light active Ag loaded TiO2 nanocomposite thin films by sol gel method. X ray diffraction, scanning electron microscopy and UV–visible spectroscopy were applied to characterizing the product. The results show that we successfully synthesized the silver doped titanium dioxide thin films. The silver doped titanium dioxide thin films show red shift and broad absorption band in the whole UV visible region in comparison with bare titanium dioxide. The results show that the Ag-TiO2 nanocomposite exhibit best photocatalytic efficiency under direct sun-light irradiation due to increased electron transfer and charge separation. The photodegradation activities of the Ag doped TiO2 were studied with model organic pollutants. Ag doped TiO2 sample showed 98% degradation efficiency in just 70 min under sun light irradiation. Repeated cycle runs revealed that these catalysts exhibit reusability and excellent stability, able to trap solar light efficiently and suitable for degradation of many organic pollutants. The performances of the Ag-TiO2 nanocomposites indicate that, these catalysts can find potential applications in photocatalytic water treatment plants.

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.

Monitoring Photocatalytic Degradation of Plasmocorinth B with Titania Thin Films using Non‐Spectroscopic Methods

AbstractDue to its advantageous properties, titanium dioxide has been one of the most researched metal oxides and extensively used in various fields, including photocatalysis. Metal (platinum) and non‐metal (sulfur, nitrogen) doped titania thin films were prepared via a particular sol‐gel synthesis, coated onto object glasses and then thermally treated to promote TiO2 crystallization. Until now, photocatalytic activity of titania thin films has mostly been measured with different spectroscopic techniques (IR, UV‐Vis and fluorescence spectroscopy). The aim of the work presented in this article was to find alternative, non‐spectroscopic methods for photocatalytic activity measurements. To achieve this, we performed in‐situ UV‐Vis absorption spectra, conductivity (κ) and pH measurements during photocatalytic degradation of Plasmocorinth B under UV light illumination. Results have shown that there exists a linear correlation between changes in conductivity (Δκ), pH (ΔpH) values and photocatalytic activity of the samples, measured with UV‐Vis spectroscopy.

3D‐Ordered Mesoporous Chromium‐Doped Titania Thin Films: The Effect of Metal Dopant on the Microstructure, Mesoporous Symmetry, Hydrophobicity, and Surface Properties

AbstractAttention to the mesoporous metal doped titania thin films has been increased significantly due to its wide potential applications, especially in photocatalytic activities. Determining the effect of surface property, mesoporous symmetry and metal dopant in mesoporous thin films materials have rarely reported, in particular, there are essential factors determining the performance of these materials. Herein, Cr@mesoporous titania thin films prepared by the sol‐gel approach. The surface properties of the thin films, as well as crystal structure, mesoporous symmetry, hydrophobicity, and surface morphology, were deeply discussed. Power spectral density and bearing analysis were calculated using atomic force microscopy. The results confirm that the thickness of all films was completely uniform without flooding, made by randomly oriented fine grains, and mesoporous structure. The Cr particles act as a porous site eliminator and increased the lattice mismatch in mesoporous titania thin films. The surface roughness, power spectral density, bearing area, and water contact angle of the films were significantly affected by Cr content. As the Cr content is increased, the porosities shrunk together and denser films were obtained. The roughness values display that the presence of Cr increases the homogeneity and the smoothness of the thin film surface with small grain size.

Deposition and Characterization of Cobalt doped Titanium Dioxide Thin Films using Sol-gel Method

Thin films become more importance and a lot of research and studies have been done toward the improvement and achievement. In this study, the new finding of deposition Cobalt (Co) doped TiO2 thin films have been prepared by sol-gel method onto a glass substrate at room temperature for enhancement of optical properties. The effect of Co doped TiO2 thin films have been studies. The different concentration of Co was varied from 1 wt %, 2 wt % and 3 wt % dopant. The deposition of Co doped TiO2 was prepared by using sol-gel method and spin coating technique on the glass substrate. The obtained films have been annealed at 400 oC, 500 oC, and 600 oC for 2 hours and were investigated. X-ray diffraction (XRD) peaks revealed that the films exhibit showed that Co:TiO2 films are anatase crystalline structure at orientation (101). The surface morphologies of the Co:TiO2 thin films were evaluated by Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM). The calcination temperature and content of Co dopant gave a different size of particle and grain boundary. Root Mean Squared (RMS) roughness values increase by increasing the molar ratio of dopant. While, as the calcination temperature increases, the RMS also increasing. The optical properties were studied by using UV-visible spectroscopy (UV-Vis) with a wavelength range of 300 nm to 1000 nm. The calculated optical band gap decreases with increasing of Co doping.

Contribution of Drude and Brendel Model Terms to the Dielectric Function; A case of TiO2:Nb Thin Films

Parametric modeling provides a mean of deeper understanding to the properties of materials. Dielectric function is one of the key parameters which can provide information on the dielectric nature of a thin film or bulk materials. It can be obtained by modeling the material using appropriate existing, new or modified models. In our work, we utilized existing Brendel and Drude models to extract the optical constants from spectrophotometric data of fabricated undoped and niobium doped titanium oxide thin films. The individual contributions by the two models were studied to establish influence on the dielectric function. The effect of dopants on their influences was also analyzed. Results indicate a minimal contribution from the Drude term due to the dielectric nature of the undoped films. However as doping levels increase, the rise in the concentration of free electrons favors the use of Drude model.

Development of Silver Doped Titanium Oxide Thin films for Gas Sensor Applications

Gas sensors find numerous applications in fields of automotives, medical, industries and others. A number of studies focused on synthesis of silver doped titanium dioxide films with various doping concentrations of silver. The objective of the research work is to optimize gas sensing properties of Ag-TiO2 thin films using orthogonal array experimentation with different dopants, concentration, annealing temperatures and gas concentrations exposure time. Synthesis of Ag-TiO2 thin films on quartz substrates was carried out by sol-gel spin coating. TiO2 films were characterized optical, chemical and mechanical and sensing properties. Surface roughness of TiO2 Thin films are RSM 11 to 45 nm and decrease of transmittance from 74% to 45% and energy bad gap from 3.44 to 3.29 eV for variation of annealing temperature from 400 to 600 °C. Surface roughness in RSM of 15 to 67 nm and decrease in transmittance from 85 to 63 % and band gap from 3.40 to 3.28 eV from 3 to 7 layers of coating was found. Ag-TiO2 thin films showed highest sensor response of 1.247 for 300 °C annealing temperature, 0.025 atomic ratio, 5 ppm CO gas exposure. Analysis of variance showed CO gas exposure influenced sensor response by 72.95%, and annealing temperature influenced sensor response by 18.39 %. Response surface methodology showed desirability of 70.7% with maximum response value to be 1.2346.

In English

The simple and fast route of the synthesis of platinum ions doped titania thin films is designed where platinum(II) acetylacetonate is used as a perspective doping agent due to the possibility of platinum incorporation in the form of the different valence states. Additionally, the multilayered films showing the varied properties are obtained. The increase in Pt content as well as the number of layers leads to the higher absorbance and the band edge shift to the red part of the spectrum. The indirect electronic transition is suggested and the calculated band gap values are depended on the film compositions as well as the number of layers. The significant decrease in the band gap value of titania is noted for 0.5 % Pt/TiO 2 films. Pure titania and doped titania films contain anatase phase only with the average crystallite size near 14 nm. The conversion percentage of photocatalytic dichromate ions reduction is increased in the presence of three-layered 0.5 % Pt/TiO 2 films under both UV and visible light. The activity of three-layered films is higher compare to the single layered samples. The film contained 0.1 % Pt exhibited the similar activity to titania one.

Influence of silver nanoparticles on titanium oxide and nitrogen doped titanium oxide thin films for sun light photocatalysis

Decreasing recombination of photogenerated charge carriers in photocatalysts is a critical issue for enhancing the efficiency of dye degradation. It is one of the greatest challenges to reduce the recombination of photo generated charge carriers in semiconductor. In this paper, we report that there is an enhancement of photocatalytic activity in presence of Sun light, by introducing Plasmon (silver nanoparticles (Ag)) onto the titanium oxide (TiO2) and nitrogen incorporated titanium oxide (N-TiO2) films. These silver nanoparticles facilitate the charge transport and separation of charge carriers. In this paper we find that the phase transformation accurse from rutile to anatase with increase of nitrogen flow rates. The FE-SEM analysis showed the micro structure changes to dense columnar growth with increase of nitrogen flow rates. XPS studies of the N-TiO2 thin films revealed that the substitution of N atoms within the O sites plays a crucial role in narrowing the band gap of the TiO2. This enables the absorption of visible light radiation and leads to operation of the film as a highly reactive and effective photocatalysis. The synergetic effect of silver nanoparticles on TiO2 and N-TiO2 films tailored the photocatalytic acitivity, charge transfer mechanism, and photocurrent studies. The silver nanoparticle loaded N-TiO2 films showed highest degradation of 95% compare to the N-TiO2 films. The photo degradation rate constant of Ag/N-TiO2 film was larger than the N-TiO2 films.

Characterization of transparent semiconducting cobalt doped titanium dioxide thin films prepared by sol–gel process

We report the synthesis of TiO2 and Cobalt doped TiO2 (CoT) thin films by sol–gel process and the influence of dopant incorporation onto the structural, optical and electrical properties of the host lattice is analysed. The XRD analysis shows the reduction of crystal size with increasing Co dopant concentration. FESEM analysis confirmed the agglomeration of particles in CoT films upon Co doping. Vibrational modes of the anatase phase of TiO2 along with the weak intensity peaks for cobalt doped samples have been identified in Raman spectroscopy. The average transmittance of the films decreases with an increase in the surface roughness and decrease in the crystallinity of the films. Red shift in the energy gap is observed with the increase in the cobalt dopant concentration due to the defect state formation in the band gap. Surface roughness of the samples increases from 0.646 to 6.486 nm. Room temperature photoluminescence (PL) measurements confirmed the increase of F+ colour centres in cobalt doped films. I–V measurements indicate the ohmic behaviour of TiO2 films with the increase of resistivity from 2.707 × 103 to 7.699 × 103 Ω-cm for the samples with cobalt content. The increase in resistivity due to dopant incorporation is significant from its application point of view and is evaluated using grain boundary model. It was observed that by increasing cobalt doping level in TiO2 the surface trap density increases and implicitly the conductivity decreases.

Gd, I-doped TiO2 thin films coated on solid waste material: synthesis, characterization, and photocatalytic activity under UV or visible light irradiation

In this work, titanium dioxide thin films doped with different concentrations of gadolinium (Gd) and iodine (I) were synthesized using the sol–gel method and successfully coated on solid waste material (made in our lab) by dipping, resulting in the titanium dioxide thin-film-coated material (TiO2M). Then, the doped titanium dioxide thin films were characterized by X-ray diffraction (XRD), SEM, and UV–Vis spectroscopy; the optimum coating cycle was evaluated by removal rates of COD and ammonia nitrogen in raw wastewater and secondary effluent. Moreover, the photocatalytic activity was determined by degradation efficiency of methyl orange. The results showed that TiO2M had desirable reusability and the photocatalytic activity was attractive under ultraviolet light irradiation. Furthermore, it is found that the amount of dopant in TiO2 was a key parameter in increasing the photoactivity. 1% Gd-doped TiO2M exhibited the best photocatalytic activity for the degradation of methyl orange with the removal rate reaching 85.55%. The result was in good agreement with the observed smaller crystallite size and profitable crystal structure (anatase phase). Besides, the TiO2M (0.8% Gd-doped TiO2M, 1% Gd-doped TiO2M, 10% I-doped TiO2M, and 5% I–1% Gd-doped TiO2M) with desirable photocatalytic activity at ultraviolet light irradiation was selected for the visible light photocatalytic experiments with taking methyl orange as the target pollutants. The results showed that all of them exhibited the similar photocatalytic activity after 7 h of sunlight irradiation (around 90% removal effect). In general, this research developed a very effective and environmentally friendly photocatalyst for pollutant degradation.

Effect of Sn and La doping on optical and hydrophilic properties of TiO2 thin film

Sn and La co-doped TiO2 thin films were fabricated on surface of glass slide substrates. Co-doped titania thin films were prepared by a sol gel method using, TBT as a precursor. Morphology and crystallite size of the obtained co-doped thin films changed by changing the content of La. Accordingly, the doped titania thin films showed various water contact angles and optical band gaps. As, the optical band gap of the nanostructured doped titania thin films decreased with increasing in content of La from 3.4 to 2.32 eV. Moreover, the water contact angles changed from 69.0° to 13.5° by changing the content of La.

Effect of hydroxyl groups on hydrophilic and photocatalytic activities of rare earth doped titanium dioxide thin films

Rare earth (Y, La and Nd) doped TiO2 thin films were prepared on glass slides by sol-gel method. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The effects of hydroxyl groups on hydrophilic and photocatalytic activities were investigated by means of techniques such as X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared (FTIR), optical contact angle, UV-Visible spectroscopy and VIS spectroscopy. The results showed that an appropriate doping of rare earth could cause the TiO2 lattice distortion, inhibited phase transition from anatase to rutile, accelerated surface hydroxylation and produced more hydroxyl groups, which resulted in a denser surface and smaller grains (40–60 nm), and a significant improvement in the hydrophilicity and photoreactivity of TiO2 thin films. The optimal content of rare earth was between 0.1 wt.% and 0.3 wt.%. Moreover, the modification mechanism of rare earth doping was also discussed.

On the nature of niobium substitution in niobium doped titania thin films by AACVD and its impact on electrical and optical properties

Niobium doped TiO2 thin films were deposited on silica coated glass substrate using aerosol assisted chemical vapour deposition (AACVD) from hexane solution, at 500 °C.