Properties Of TiO2 Thin Films Research Articles

Electronic and Optical Properties of TiO2 Thin Films: Combined Experimental and Theoretical Study

Electronic and Optical Properties of TiO2 Thin Films: Combined Experimental and Theoretical Study

Structure Characteristics of TiO2 Thin Films Prepared by DC Reactive Magnetron Sputtering at Low Pressure

Structural properties of TiO2 thin films play a main role in determine the characteristic of the thin films especially their stability and activity, the total pressure has a great influence in determine the crystallinity of the films and the orientation of the facets of their structure, especially the two facet (101) and (001), the enhancing the structure properties will cause to enhance the application efficiency of TiO2 thin films such as the dissociative adsorption of water and the solar cell. Many researcher interest to prepare the TiO2 thin film under the low range of total pressure (less than to 10 Pa) to avoid the low degree of crystalline and the mixed of two phase anatas and rutile, so in our work tend to prepare TiO2 thin films under a high total pressure (more than 10 Pa) with values (10, 20, 50 and 100) Pa and with (1:1) mixed ratio of Argon and Oxygen gases, the pattern of X-Ray diffraction revealed that the structure was polycrystalline and the phase was anatas. The intensity at 2θ ≈ 25.00°, 37.00°, 53.00° and 55.00° correspond to the diffraction from (101), (004), (105) and (211) planes respectively. The intensity and number of peaks decreased with increased the total pressure, the plane (101) could be considered as a prefential growth plane which take a high texture factor and this would decreased with increased the total pressure, the ratio of texture factor between 001 and 101 will increase with decrease the total pressure, The lattice constant and the interplanar distance displayed a greater deviation compared with the standard value at the lowest total pressure than the decrease observed with increased total pressure.

The Influence of Different Thickness on The Physical Properties of Tio2 Thin Films Prepared by Chemical Thermal Evaporation

The Influence of Different Thickness on The Physical Properties of Tio2 Thin Films Prepared by Chemical Thermal Evaporation

Photocatalytic performance of Cu-doped titania thin films under UV light irradiation

We investigated the effect of copper doping on the photocatalytic properties of TiO2 thin films. Titania thin films doped with three different copper concentrations were synthesized via radiofrequency-assisted (RF) magnetron sputtering, then annealed at 600 °C in controlled atmosphere (Ar, O2, H2 flow). The impact of the annealing in inert, oxidizing or reducing atmosphere on the crystalline and surface structure, and photocatalytic performance in the methylene blue degradation under UV light irradiation was investigated by X-ray diffraction, UV–Vis Spectroscopy, Rutherford Backscattering Spectrometry, Scanning Electron Microscopy. Annealing induced very different crystallization in different atmospheres, with strong copper out-diffusion in samples annealed in reducing atmosphere and formation of large embedded nanoparticles. The Cu-doped titania films exhibited higher photocatalytic activity than pure titania film and the best performing catalyst, treated in H2 atmosphere, suggests that the presence of embedded copper nanoparticles (both metallic and oxidized) is able to strongly enhance the photocatalytic properties of the host titania matrix. Incorporated Cu particles can act as trapped sites for generated electrons, and this leads to the reduction of carrier recombination which, ultimately, plays a significant role in the increase of photoactivity. The recyclability of the best system was ascertained by a suitable 3-cycle stability test.

Growth and Characterization of TiO2 Thin Films by PLD Technique

In this work, the structural, optical and electronic properties of TiO2 thin films grown on glass substrate by Pulse Laser Deposition (PLD) technique are presented. The stoichiometry and the oxidation degree of films were analyzed by considering the Ti 2p and O 1s core energy levels with high resolution X-Ray Photoelectron spectroscopy (XPS). The structural characteristics of the thin films have been investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) technique. The optical absorption region of growth TiO2 films were analyzed by Photoluminescence spectroscopy (PL) technique. Spin-orbit coupling splitting of Ti 2p states was measured as 5.7 eV. The characterizations promote the existence of the metal and oxygen vacancies at the surface of film. These point defects enhance the hysteretic transport properties of the TiO2 metal oxide.

Exploiting the properties of TiO2 thin films as a sensing layer on (MEMS)-based sensors for radiation dosimetry applications

In this work, we investigate the potential of exploiting TiO2 thin films as sensing layers on silicon micro-electromechanical systems for the detection of gamma radiations. All samples are exposed to gamma rays produced by 60Co, with different doses ranging from 0 kGy to 40 kGy. Properties of silicon coated with a 200-nm-thick layer of TiO2 grown at 200 °C by atomic layer deposition are studied before and after its gamma irradiation using x-ray diffraction (XRD), scanning electron microscopy, and spectroscopic ellipsometry. Atomic force microscopy (AFM) is carried out on functionalized microcantilevers to measure the resonance frequency shift (Δf 0) resulting from irradiation of the TiO2 thin film. XRD results show a change in the films from a mixture of rutile and anatase phases to an anatase phase upon irradiation. Spectroscopic ellipsometry results show a change with a fixed pattern in the film thickness, roughness, void, and optical constants with different irradiation doses. This pattern appears as Δf 0 in AFM, where the response of sensors to doses between 0 kGy and 20 kGy was linear. The values of Δf 0 are convenient to control parameters for the proposed dosimeter, which is characterized by the reproducibility and sensitivity of measurements. The maximum detectable linear effect of the proposed dosimeter was found at a dose of 20 kGy. This makes a 200-nm thin layer of TiO2 coated on a microcantilever surface, a possible candidate for dosimetry for the range lower than 20 kGy applications, such as in personal dosimeters.

Low Temperature Deposition of TiO2 Thin Films through Atmospheric Pressure Plasma Jet Processing

Titanium dioxide (TiO2) has been widely used as a catalyst material in different applications such as photocatalysis, solar cells, supercapacitor, and hydrogen production, due to its better chemical stability, high redox potential, wide band gap, and eco-friendly nature. In this work TiO2 thin films have been deposited onto both glass and silicon substrates by the atmospheric pressure plasma jet (APPJ) technique. The structure and morphological properties of TiO2 thin films are studied using different characterization techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and field emission scanning electron microscopy. XRD study reveals the bronze-phase of TiO2. The XPS study shows the presence of Ti, O, C, and N elements. The FE-SEM study shows the substrate surface is well covered with a nearly round shaped grain of different size. The optical study shows that all the deposited TiO2 thin films exhibit strong absorption in the ultraviolet region. The oleic acid photocatalytic decomposition study demonstrates that the water contact angle decreased from 80.22 to 27.20° under ultraviolet illumination using a TiO2 photocatalyst.

Optimization of structural and optical properties of sputter deposited TiO2 thin films by controlling deposition parameters

Titanium oxide (TiO2) thin films have been deposited onto highly cleaned soda lime glass substrates by DC magnetron reactive sputtering system. The Ti target with purity 99.99% is sputtered by argon gas in the sputtering chamber. Oxygen gas with purity 99.99% is introduced during the deposition process into the sputtering chamber as reactive gas for the synthesis of titanium oxide. Structural and optical properties of TiO2 thin films have been characterized by X-ray diffraction (XRD), Raman spectroscopy and UV-Vis. spectroscopy. The effect of substrate temperature and sputtering power on the optical properties of TiO2 thin films has been studied. The XRD and Raman spectroscopy of as-deposited films are used to study the structural properties of TiO2 as a function of substrate temperature and sputtered power. The structural studies show the crystalline nature of TiO2 thin films. The narrowing of energy band gap of sputtered deposited TiO2thin films was studied using UV-Vis. spectroscopy.

Enhanced Photoelectrocatalytic Degradation Activity of Titanium Dioxide Photoelectrode: Effect of Film Thickness

The present work reports synthesis of titanium dioxide (TiO2) thin films deposited from ethanolic titanium diisopropoxide bis-acetyl acetonate precursor solution by using spray pyrolysis technique. The deposition of films were carried out on both amorphous and fluorine doped tin oxide (F:SnO2) glasses. The effect of film thickness on photoelectrochemical, structural, morphological and optical properties of TiO2 thin films was studied. The photoelectrochemical performance showed highest short circuit current and open circuit voltage at the optimized thickness of the film of 0.921 μm. X-ray diffraction study revealed that the films are polycrystalline, and exhibit anatase phase having tetragonal crystal structure. The TiO2 electrodes deposited on fluorine-doped substrates were further used in the photoelectrochemical degradation of pollutants such as Methylene blue dye and benzoic acid. The degradation efficiencies were found to be 76 and 55% for the dye and benzoic acid, respectively.

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.

Optical and Structural Properties of Titanium Dioxide Papered by DC Magneto-Sputtering as a NO2 Gas Sensor

In this work, a reactive DC magnetron sputtering technique was used to prepare TiO2 thin films. The variation in argon and oxygen gases mixing ratios (4:1, 2:1, 1:1, 1:2, 1:4) was used to achieve optimal properties for gas sensing. In addition, an analysis of the optical XRD properties of TiO2 thin films is presented. High-quality and uniform nanocrystalline films were obtained at a working gas pressure of 0.25 mbar and 1:4 (Ar/O2) gas mixture. The optical properties showed a transparent thin film with uniform adherence to the substrate. The average transmission of the TiO2 films deposited on the glass substrates was higher than 95% over the range of 400 to 800 nm. The optical band gap varied from 3.84 eV to 3.93 eV as a function of oxygen/argon ratios. The XRD pattern showed that the films have an amorphous structure, which is shifted to polycrystalline with increasing oxygen to argon ratio. The sensitivity, response time, and recovery time were measured for TiO2 thin films using NO2 oxidizing gas.

An Experimental and Theoretical Study of the Impact of the Precursor Pulse Time on the Growth Per Cycle and Crystallinity Quality of TiO2 Thin Films Grown by ALD and PEALD Technique

In this paper, theoretical and experimental approaches were used to evaluate the impact of the precursor’s pulse time on the growth per cycle (GPC) and on the crystallinity quality of atomic layer deposited TiO2 thin films on Si(100) and FTO substrates. In theoretical investigation, we employ a general model that can be applied to both metal and oxidant precursors, and it is based on the Maxwell-Boltzmann velocity distribution from which the molecular flux of gases that collide with the substrate is deduced to adjust the experimental characteristics of GPC versus pulse time. This model allowed us to adjust the GPC of TiO2 films produced by thermal atomic layer deposition and by plasma-enhanced atomic layer deposition under different deposition parameters and substrates. In experimental investigation, the influence of GPC on the chemical and structural properties of TiO2 thin films was evaluated by Rutherford backscattering spectroscopy, grazing incidence x-ray diffraction and ellipsometry techniques. In thermal mode, using H2O as an oxidant precursor, the stoichiometry of TiOx films has an x value of 1.98 from the GPC saturated regardless of the metal precursor or substrate used. In addition, using O2 plasma, a super-stoichiometric film with x values from 2.02 to 2.30 is obtained. In thermal mode, the GPC saturated and film thickness are, on average, 40% higher for TiCl4 compared to TTIP precursor. Using O2 plasma, the growth per cycle saturated is approximately twice as high the thermal mode using TTIP precursor. For both atomic layer deposition modes, the crystallinity degree showed values of 50% to 80% for TiCl4 in the temperature range of 250 to 350 oC. On the other hand, for TTIP, it was below 40% in thermal mode and between 80 and 95% in plasma mode (250 oC). It was observed that the reaction rate, the diffusion coefficient and the molecular flux are inversely proportional to the temperature. These results evidenced that the crystallinity and epitaxial quality of the TiO2 film are higher for TTIP using O2 plasma. However, a better stability of the parameters analyzed for TiCl4 in the two atomic layer deposition modes was verified.

Memristive TiO2: Synthesis, Technologies, and Applications.

Titanium dioxide (TiO2) is one of the most widely used materials in resistive switching applications, including random-access memory, neuromorphic computing, biohybrid interfaces, and sensors. Most of these applications are still at an early stage of development and have technological challenges and a lack of fundamental comprehension. Furthermore, the functional memristive properties of TiO2 thin films are heavily dependent on their processing methods, including the synthesis, fabrication, and post-fabrication treatment. Here, we outline and summarize the key milestone achievements, recent advances, and challenges related to the synthesis, technology, and applications of memristive TiO2. Following a brief introduction, we provide an overview of the major areas of application of TiO2-based memristive devices and discuss their synthesis, fabrication, and post-fabrication processing, as well as their functional properties.

Synthesis of titanium oxide thin films by spray pyrolysis method and its photocatalytic activity for degradation of dyes and ciprofloxacin

Titanium oxide (TiO2) thin film was obtained using the spray pyrolysis method. The structural properties of the thin film obtained were examined by X-ray diffraction (XRD) and it was found that it also had a tetragonal structure. The morphological feature was examined with scanning electron microscopy (SEM). In addition, the optical properties of the film were examined and the forbidden energy range was calculated. Photocatalytic properties of TiO2 thin film on dyestuff and antibiotic were investigated. Methyl blue and malachite green were used in the dye degradation test of the thin film. In particular, it was found to have a high degradation of 86% after 100 minutes on malachite green. Moreover, the degradation on ciprofloxacin after 90 minutes was found as 93%. The reusability ciprofloxacin antibiotic was investigated and it was found that synthesized TiO2 thin film has excellent stability

The study of the applicability of ionizing radiation to increase the photocatalytic activity of TiO2 thin films

The paper presents the results of studying the efficiency of using ionizing radiation to modify the surface morphology and structural properties of TiO2 thin films, and the effect of ion modification on the photocatalytic activity of Rhodamine B. decomposition. Structural and morphological changes in thin films were characterized by irradiation with doses of 1014–1016 ion/cm2 using scanning electron microscopy, atomic force microscopy, energy-dispersive analysis and X-ray diffraction. Modification by ion irradiation of thin films leads to a change in grains orientation, a decrease in their size, and an increase in the active surface area. Formation of grains preferred orientation at high radiation doses is caused both by grains rotation as a result of distorting and deformation factors caused by radiation, and by grains partial fragmentation. It was shown that in the case of modified samples of thin films, not only an increase in the rate decomposition reaction constant by 2–4.5 times compared with the initial samples, but also the degree of mineralization is observed. According to the data obtained, the maximum value of mineralization as a result of photocatalytic reactions for initial films was no more than 75–76%. While for irradiated samples, this value varies from 83 to 90% depending on the irradiation dose. For modified films, an increase in crack resistance and resistance to degradation to prolonged tests of photocatalytic activity is observed.

The role of Al and Co co-doping on the band gap tuning of TiO2 thin films for applications in photovoltaic and optoelectronic devices

Titanium dioxide (TiO2) thin film samples were synthesized with the help of a thermal spray pyrolysis method. In our investigation, the effect of Al, Co co-doping on the structural, morphological, topographical, optical, and electronic properties of TiO2 thin films were investigated. The deposited films show that as-deposited samples are nanostructured and crystallite size is varied from 66 nm to 72 nm. The structural parameters are well-matched with experimental and theoretical calculations. Energy dispersive analysis of X-rays (EDAX) spectra show that all samples are in stoichiometric conditions. The surface roughness values are varying from 66 nm to 89 nm seen by atomic force microscopy (AFM) images. The Fermi energy level tuning was investigated both experimental and theoretical simulations. The study of optical properties recognized that the absorption edge of the (Al, Co)-co-doped TiO2 sample is tuned toward the low energy region compared to the pristine sample. The calculated electrical band gap energy is matched by the optical band gap energy. A combined study of the structural, morphological, topographical, optical and electronic properties of the compound suggests that Ti1-x Al0.06 CoxO2 is a suitable candidate for optoelectronic and photovoltaic applications.

Surface and photocatalytic properties of TiO2 thin films prepared by non-aqueous surfactant assisted sol-gel method

Titanium dioxide (TiO2) thin films are prepared on glass substrates using sol-gel spin coating method. Titanium tetraisopropoxide (TTIP) precursor is used to prepare TiO2 sol-gels using Ethanol solvent. Acetyl acetone (AcAc) and Acetic acid (AA) are used as modifiers and Cetyltrimethylammonium Bromide (CTAB) surfactant as pore-forming agent. A clear transparent TiO2 sol-gel is obtained without precipitation only when both AA and AcAc are present in the TiO2 sol. A worm-like structure is observed in the film at 0.1 M TTIP and changed to the flake-like structure in the film at 0.4 M TTIP. The TiO2 thin films are non-porous and porous when CTAB is below and above the concentration of 0.8 g per 0.01 mol TTIP. The critical micelle concentrationis found to exist between 0.6 to 0.8 g CTAB per 0.01 mol TTIP. Grazing Incidence X-ray diffraction and Raman analysis confirm the presence of anatase phase in the 3 and 4 times coated TiO2 thin films. The field emission scanning electron microscopy analysis shows that a highly homogeneous and uniform thin film is obtained with TiO2 sol-gel composition of 0.2 M TTIP, 0.1 M AcAc, 0.09 M AA and 1 g of CTAB per 0.01 mol TTIP. The photocatalytic activity of the TiO2 films is determined by investigating the photodegradation of methylene blue (MB) in aqueous solution. The TiO2 thin film with 110.7 nm and 145.3 nm thickness showed 42.6 % and 58.4 % degradation of MB, respectively, at 60 min of photocatalytic reaction under UV light irradiation.

The effect of Fe dopant on structural, optical properties of TiO2 thin films and electrical performance of TiO2 based photodiode

Abstract Herein, TiO2 heterojunctions were fabricated by sol gel spin coating technique as a function of Fe doping. The effect of Fe doping on the optical, structural, morphological properties of TiO2 thin films and electro-optical properties of their photodiode applications have been investigated. The XRD results have not showed peaks, which implies that the all films are amorphous. The E g values of thin films decreased with increasing Fe concentration. As result of I − V measurements of diodes under dark and light conditions, all diodes demonstrated photo characteristic behavior. The barrier height values of diodes varied between 0.68 eV and 0.70 eV. The lowest ideality factor was obtained from 2% Fe: TiO2/p-Si diode and was found to be 4.75. The highest photosensitivity of 1.53 × 104 was obtained from 6% Fe: TiO2. In addition, the C − V , G − V and R s − V measurement were taken at different frequencies and analyzed. Moreover, the obtained results showed that the performances of fabricated diodes could be governed by the Fe doping.

Machine Learning Band Gaps of Doped-TiO2 Photocatalysts from Structural and Morphological Parameters.

Titanium dioxide (TiO2) photocatalysts in the form of thin films are of great interest due to their tunable optical band gaps, Eg’s, which are promising candidates for applications of visible-light photocatalytic activities. Previous studies have shown that processing conditions, dopant types and concentrations, and different combinations of the two have great impacts on structural, microscopic, and optical properties of TiO2 thin films. The lattice parameters and surface area are strongly correlated with Eg values, which are conventionally simulated and studied through first-principle models, but these models require significant computational resources, particularly in complex situations involving codoping and various surface areas. In this study, we develop the Gaussian process regression model for predictions of anatase TiO2 photocatalysts’ energy band gaps based on the lattice parameters and surface area. We explore 60 doped-TiO2 anatase photocatalysts with Eg’s between 2.280 and 3.250 eV. Our model demonstrates a high correlation coefficient of 99.99% between predicted Eg’s and their experimental values and high prediction accuracy as reflected through the prediction root-mean-square error and mean absolute error being 0.0012 and 0.0010% of the average experimental Eg, respectively. This modeling method is simple and straightforward and does not require a lot of parameters, which are advantages for applications and computations.

Effects of Ag doping on compact TiO2 thin films synthesized via one-step sol–gel route and deposited by spin coating technique

In this paper, we present a novel one-step, easy and cost-effective method for the synthesis of Ag-doped TiO2 sol and deposition of its compact thin films by spin coating technique. The effects of dopant quantity (0–5% by weight) on structural, morphological, optical and electrical properties of TiO2 thin films have been investigated and reported. The X-ray Diffraction (XRD) spectra revealed single anatase phase having no secondary phases. The scanning electron microscopy (SEM) showed pinholes-free/compact thin films composed of spherical nanoparticles where the particle size has been demonstrated to decrease with increasing Ag doping. The atomic force microscopy (AFM) confirmed smooth and compact TiO2 thin films, however, the surface roughness tends to grow with increasing the dopant quantity. The X-ray fluorescence spectroscopy (XRF) revealed the presence of Ag mass percentage in the relevant samples, which has been demonstrated to grow with increasing the amount of dopant. The UV–Vis spectroscopy concluded the bandgap reduction of pure anatase phase of TiO2 (3.38 eV) as the Ag doping reaches to its maximum value of 5% (3.18 eV). Spectroscopic Ellipsometry has been employed to determine the thickness of thin films which was found to be in the range of ~ 100 nm, while electrical properties have been measured through DC-Hall Effect technique. It was found that the conductivity of thin films improved from 5.74 × 10–2 to 2.72 × 10–1 Ω−1 cm−1 on glass while on FTO-coated glass substrates, a higher value of 1.51 × 104 Ω−1 cm−1 was achieved.