Properties Of TiO2 Thin Films Research Articles

Effect of annealing temperature on the structural, optical, morphological, and photocatalytic properties of TiO2 thin films prepared by sol-gel spin-coating and electron beam physical vapor deposition

TiO2 thin films were prepared by sol-gel spin-coating (SGSC) and electron beam-physical vapor deposition (EB-PVD) methods and annealed at different temperatures (Ta ). X-ray diffraction spectroscopy (XRD) results show that the TiO2 films prepared by the SGSC method transformed from the anatase single phase to the coexistence of anatase and rutile with the increase of Ta . However, TiO2 films prepared by the EB-PVD method existed only in the anatase phase, and the crystalline strength was enhanced with the increase of Ta . Meanwhile, particles of TiO2 targets annealed at different Ta showed a rutile phase for TiO2 target particles in the EB-PVD method. The results indicate that the EB-PVD method hinders the nucleation growth and phase transformation of TiO2 films. Scanning electron microscopy and atomic force microscopy also show that the grain size and R ms of TiO2 thin films prepared by the SGSC method increased with the increase of Ta , and the grain size becomes inhomogeneous when the rutile phase is formed. Ultraviolet–visible results show that the forbidden bandwidth and light absorption capacity increase with increasing Ta . For the EB-PVD method, the grain size and surface roughness gradually increased when the Ta of the films was less than 800 °C, while annealing at 800 °C changed the direction of growth and nucleation, and also produced surface cracks; XRD verified the hypothesis that the EB-PVD method hinders the nucleation growth as well as the phase transition of the films. Weak differences in the optical absorption properties and bandgap values of the films also indicate that the EB-PVD method hinders the phase transformation of TiO2 films. Finally, the results of degradation of methylene blue (MB) under simulated visible light showed that the films prepared by the SGSC method gradually improved the photocatalytic performance with the enhancement of the crystalline strength of the anatase phase. The TiO2 films prepared by the EB-PVD method improved the photocatalytic performance with the increase of the active area.

Effect of doping on the structural, optical and electrical properties of TiO2 thin films for gas sensor

Effect of doping on the structural, optical and electrical properties of TiO2 thin films for gas sensor

Enhancing Structural Integrity, Optical Properties, and Room Temperature Formaldehyde Sensing Through Optimized Spray Deposition Rates

This study explores the impact of deposition rate on the properties of TiO2 thin films produced via spray pyrolysis, focusing on their application in gas sensors. The analysis covers structural, morphological, optical, and gas sensing characteristics of TiO2 films deposited at rates between 1 and 2.5 ml min−1. Studies show optimizing TiO2 film deposition rates at 2 ml min−1 significantly enhances formaldehyde detection, improving selectivity and achieving a rapid response of 7.52 at 20 ppm concentration. This study underscores the pivotal role of deposition rate optimization in augmenting the gas-sensing efficacy of TiO2 films, particularly for formaldehyde detection at ambient conditions. Optimal deposition rates are instrumental in enhancing sensor performance. The synergistic application of XRD and Raman spectroscopy unequivocally confirmed the presence of the TiO2 anatase phase, which is of paramount significance in gas sensing applications. FESEM furnished high-resolution insights into the surface morphology, revealing a spherical architecture. Furthermore, UV–vis spectroscopy was employed to assess the optical band gap of the films, which exhibited a decrement correlating with the rate of deposition. Notably, a deposition rate of 2 ml min−1 markedly improved the TiO2 films’ sensing performance. These insights are critical for developing cost-effective, high-performance gas sensors for cutting-edge applications.

Pre-heating Temperature Effect on Electrochromic Properties of TiO2 Thin Films

Pre-heating Temperature Effect on Electrochromic Properties of TiO2 Thin Films

Photocatalytic degradation of methylene blue by TiO2/Nd2O3 composite thin films

To improve the photocatalytic property of TiO2 thin films, the composite thin films of TiO2/Nd2O3 structure were fabricated by electron-beam physical vapor deposition method, and the photocatalytic property of the fabricated films was experimentally studied in the present work. The XRD and Raman analyses show that the TiO2/Nd2O3 films are mainly hexagonal crystalline phase of Nd2O3. The XPS analysis for the chemical state changes of Ti, O and Nd of the basic elements in the films is confirming the electron flow in the internal electric field which generated in the TiO2/Nd2O3 films. The surface morphology shows the lattice distortion which affects the changes in the energy band structure. Moreover, the formation of n-n homojunctions improved the separation efficiency of electrons and holes, and enhanced the catalytic activity. The photocatalytic performance for the methylene blue target dye shows that the sample with TiO2 thickness of 20–25 nm has better performance, high degradation efficiency and high reaction rate.

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.

Structural, Electrical and Optical Properties of Zn-Doped SrVO3 Thin Films Grown By Co-Sputtering

Due to its optical and electrical characteristics, SrVO3 is a strongly correlated metal that has received extensive research in recent years. This makes it a promising transparent conducting oxide (TCO) for a variety of optoelectronic applications. The most widely used TCO at the moment, indium tin oxide, suffers from resource depletion. By analyzing and improving these interesting properties, SrVO3 might be able to take its place [1]. Unfortunately, in order to obtain SrVO3 as a crystallized phase, non-compatible with microelectronic industry thin film growth techniques must be used. Moreover, they require specific substrates for achieving the crystalline state, such as SrTiO3, LaAlO3, and (LaAlO3)0,3(Sr2TaAlO6)0,7 (LSAT) [2]. Nevertheless, recent studies made by our groups have demonstrated that crystalline SrVO3 layers may be produced on less expensive substrates such as glass or silicon substrates, with the simple use of a TiO2 buffer layer. This recent finding is covered by a global patent [3].In the present work, we report experimental investigations on the reactively co-sputtering of SrVO3 and ZnO targets in a H-rich plasma, on Si substrates, with and without a TiO2 buffer layer, to grow transparent and conductive films. TiO2 buffer layer has been deposited on Si Substrate by Atomic Layer Deposition as reported elsewhere [4]. We looked at the effects of growth temperatures (TG) and the hydrogen rate rH (the ratio of H2 to Ar) on the thin films’ structural, electrical, and optical characteristics. XRD, high-resolution TEM, and AFM techniques were used to examine the films’ structural characteristics. The 4 probes approach, Van der Pauw measurements using a PPMS, and Hall effect measurements were used to examine the electrical properties. Finally, spectroscopic ellipsometry was used to conduct optical characterizations.The structural analysis showed that it is possible to favor the growth of crystalline SrVO3 layers on top of the TiO2 buffer layer by optimizing TG and rH (Figure 1a). In some specific conditions, a partially crystallized layer of SrVO3 was also directly deposited on a Si substrate without the use of such a buffer layer, which has never been reported in the literature and thus is encouraging for the future growth of such material on-low-cost substrate (Figure 1b). The Zn concentration in the film is only 0.15 at% because the radio-frequency (RF) power density applied to the ZnO target is much lower than the one applied to the SrVO3 target. The presence of dopants during the development process may favor the crystallization of SrVO3, which may help to explain this partial crystallization. This finding might pave the way for buffer-free complete crystallization of SrVO3 on Si substrates.When the films are grown on a TiO2 buffer layer, measurements of the physical properties have evidenced that it is possible to form thin films with optical transparency ranging from 70 to 75%, between 475 and 800 nm (Figure 1c). The thin films’ electrical resistivities at ambient temperature reach values of 1.2 × 10−3 Ohm.cm, according to electrical characterizations performed on them using the 4 probes method. Moreover, the PPMS data reveal a decrease in resistivity as a function of temperature (Figure 1d) which is the signature of semiconductor behavior. Such a feature has never been reported elsewhere and is probably due to an excess of oxygen in the layer induced 2 by the reactive growth approach. The vanadate films detailed in this paper present a sufficiently low resistivity to be used for microelectronics applications since the films produced with optimal values of rH and TG are more conductive than the undoped semiconductor films typically used as TCOs, such as ZnO and SnO2. In addition, these films feature an optical band gap, and therefore offer the opportunity to create materials with photoluminescence properties by doping them with rare earth ions for example. This is extremely promising for the design of light-emitting diodes or sensors.[1] L. Zhang et al, “Correlated metals as transparent conductors,” Nature materials, vol. 15,12 2015.[2] A. Boileau et al, “Tuning of the optical properties of the transparent conducting oxide SrVO3 by electronic correlations,” Advanced Optical Materials, vol. 7, p. 1801516, 01 2019.[3] Patent FR3113185[4] A. Jolivet et al, “Structural, optical, and electrical properties of TiO2 thin films deposited by ALD: Impact of the substrate, the deposited thickness and the deposition temperature,” Applied Surface Science, vol. 608, p. 155214, 2023. Figure 1

Development of direct current magnetron sputtered TiO[formula omitted] thin films as buffer layers for copper indium gallium diselenide based solar cells

We describe the development and characterization of direct current magnetron sputtered titanium dioxide thin films from ceramic targets mixed with metallic titanium particles. The aim of this article is to assess their suitability for the application as buffer layer in copper indium gallium diselenide (CIGSe) based solar cells. The absorber material is produced in a semi-industrial, roll-to-roll hybrid sputter co-evaporation process. A potential strategy to modify electro-optical properties of TiO2 thin films by controlling the concentration of defects, such as oxygen vacancies, is investigated by X-ray photoelectron spectroscopy (XPS), transmission/reflection spectroscopy, spectroscopic ellipsometry, and cathodoluminescence. The presence of oxygen in the plasma during the sputter deposition process has a crucial impact on the electron transport mechanism in the studied devices. The source of the changed device characteristic can be found in modified band discontinuities at the absorber–buffer interface and in an oxidized CIGSe surface, indicated by the presence of cationic selenium, as detected by XPS. We sketch a tentative band alignment diagram and outline the range of possible modifications. The harmful effect of oxygen in the plasma forces the omission of oxygen in the process and restricts the possibilities to modify the material properties of the TiO2 layers, and consequently the prospects for an application on CIGSe. Nevertheless, the results of this work depict the principal eligibility, albeit optimization on both sides of the absorber–buffer interface are inevitable for an improved cell performance.

Rapid post-annealing effect on the TiO2-based electrochromic films

The electrochromic (EC) window is a promising energy-saving smart window that can vary between three states: transparent, translucent, and opaque by applying low voltages. One of the potential EC materials is known as titanium dioxide (TiO2) due to its unique chemical and physical properties. Conventional post-annealing has been commonly employed for phase transition in EC thin films, but it suffers from drawbacks such as long treatment time and high energy consumption. Hence, in this study, TiO2 thin films were deposited on indium-doped tin oxide (ITO) and fluoride-doped tin oxide (FTO) glass substrates using a sol-gel spin coating technique, followed by a rapid post-annealing interval of 5 min at temperatures ranging from 300 to 450 °C. The optical, morphological, structural, and EC properties of TiO2 thin films were investigated. The measurement depicted that rapid post-annealing was a cost-effective and time-saving method for realising high-quality TiO2 EC thin films. Hence, this approach reduces the overall fabrication time and minimises energy consumption, rendering it an environmentally friendly process. The successful deployment of TiO2 in EC applications paves the way for integrating EC and photovoltaic technologies in energy-saving window glass applications, considering TiO2 is a crucial element in photovoltaic devices.

High Oxygen Sensitivity of TiO2 Thin Films Deposited by ALD.

The gas sensitivity and structural properties of TiO2 thin films deposited by plasma-enhanced atomic layer deposition (ALD) were examined in detail. The TiO2 thin films are deposited using Tetrakis(dimethylamido)titanium(IV) and oxygen plasma at 300 °C on SiO2 substrates followed by annealing at temperatures of 800 °C. Gas sensitivity under exposure to O2 within the temperature range from 30 °C to 700 °C was studied. The ALD-deposited TiO2 thin films demonstrated high responses to O2 in the dynamic range from 0.1 to 100 vol. % and low concentrations of H2, NO2. The ALD deposition allowed the enhancement of sensitivity of TiO2 thin films to gases. The greatest response of TiO2 thin films to O2 was observed at a temperature of 500 °C and was 41.5 arb. un. under exposure to 10 vol. % of O2. The responses of TiO2 thin films to 0.1 vol. % of H2 and 7 × 10-4 vol. % of NO2 at a temperature of 500 °C were 10.49 arb. un. and 10.79 arb. un., correspondingly. The resistance of the films increased due to the chemisorption of oxygen molecules on their surface that decreased the thickness of the conduction channel between the metal contacts. It was suggested that there are two types of adsorption centers on the TiO2 thin films surface: oxygen is chemisorbed in the form of O2- on the first one and O- on the second one.

Effect of fluoric acid concentration on the structural, optical, and photocatalytic properties of TiO2 thin films

Effect of fluoric acid concentration on the structural, optical, and photocatalytic properties of TiO2 thin films

Work function modulation and charge transport studies of 100 MeV Au7+ ions irradiated TiO2 films for optoelectronic devices

This work demonstrates the impact of 100 MeV Au7+ ion irradiation on the work function and charge-transport properties of TiO2 thin films. The sol-gel synthesized TiO2 films were irradiated by 100 MeV Au7+ ions with varying fluences from 1 × 1011 ion-cm−2 to 1 × 1013 ion-cm−2. The surface potential of these films is found to vary from 139 mV to 469 mV for pristine to ion-irradiated TiO2 thin films. This alternatively tuned the work function of the TiO2 films from −4.87 eV to −4.53 eV which may be due to the higher oxygen vacancies and surface defects created by ion irradiation. The optical transmittance and band gap of the TiO2 thin films are found to be increased after ion irradiation. Photoluminescence and Raman measurements illustrate that various irradiation-induced defect levels such as self-trapped states, oxygen vacancies, color centers, and deep-level emission defects have altered in TiO2 films after ion irradiation. Further, important electrical parameters such as the Schottky barrier height, sheet resistance, and ideality factor have been evaluated to understand the impact of ion irradiation on the charge carrier transport properties of TiO2 films by fabricating the diode in the device configuration FTO/TiO2/Ag.

Changes in Structural and Optical Properties of TiO2 Thin Films Irradiated by Various Doses of 300 keV Carbon Ions

Changes in Structural and Optical Properties of TiO2 Thin Films Irradiated by Various Doses of 300 keV Carbon Ions

Effect of sputtering temperature on optical properties of TiO2 thin films

TiO2 films with different sputtering temperature were prepared on glass and silicon substrates by magnetron sputtering. The morphology, structure, transmittance and Raman spectra of TiO2 thin films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and fluorescence spectrometer. The results show that: (1) the size and uniformity of crystalline particles are different at various sputtering temperatures, and with increasing sputtering temperature, the grain size becomes larger and the better uniformity; (2) with the increase of sputtering temperature, the transmittance of the film samples increases in the range of 200 nm-900 nm; (3) the Raman peak of the films is affected not only by the substrate material, but also by the sputtering temperature under the same substrate, the higher the sputtering temperature, the larger the Raman peak.

Characterization and photocatalytic activity of different molar ratios of TiO2 thin films prepared by Sol-Gel process

Photocatalytic application has been of large interest due to its new technology for organic pollution. Among the photocatalyst, titanium dioxide thin film is known as a photocatalyst for the elimination of organic pollutants. In this research, the structural and optical properties of TiO2 thin films prepared on glass substrates were studied, using a sol-gel (spin coating) technique. TiO2 thin films were deposited with molar ratio y between [TTIP] and [AcAc] concentration, which varied from 0.5 to 2. Photocatalytic properties of TiO2 thin films are studied by using sunlight and photodegradation of methylene blue as a water pollutant evaluated until the photocatalytic process enhances with the molar ratio. Absorbance spectra were measured using a spectrophotometer. Test results showed that the photocatalytic sunlight /TiO2 thin film is a promising method for treating wastewater. The quantity of acetylacetone in the precursor solution had no significant effect on the optical and structural properties of the TiO2 thin films. Films consisted of the anatase phase, with a band gap in the range of 3.38–3.51 eV and thickness in the range of 534–618 nm. However, the molar ratio effect on photocatalytic preperties, the best photodegradation rate reaches to 94% in y = 0.66 at t = 180 min.

Structural and Optical Properties of TiO<sub>2</sub> Thin Films prepared by the Dip-Coating Method: Effect of Thickness and Annealing Temperature

In this work, the Sol-Gel dip-coating technique is used to report the effect of thickness and annealing temperature on structural and optical properties of TiO2 thin films. To study the effect of the annealing temperature, the prepared samples were annealed at different temperatures: 300, 400, and 500 °C for 1 h. By increasing the annealing temperature, an amelioration of the crystalline quality is observed. The best crystalline quality was obtained at 500 °C. Additionally, the band gap value Eg, evaluated from transmission spectra, does not vary with the increasing of the annealing temperature. All the films with different thicknesses present crystalize in the Anatase structure, and the crystallite size value does not practically change with thickness increase. It was also found that the TiO2 film band gap value decreases with the film thickness increase, demonstrating the possibility of band gap tuning by varying the TiO2 film thickness.

Annealing effect on the physical properties of TiO2 thin films deposited by spray pyrolysis.

Titanium dioxide (TiO2) thin films were deposited on glass substrates at 350 °C using the spray pyrolysis technique. As deposited and annealed thin films were characterized by X-ray diffraction, scanning electron microscopy, UV-VIS spectroscopy, and photodetection. Unlike the as deposited samples which were amorphous, annealed samples show an anatase phase. Films were absorbent in the UV region and the band gap energy decreases from 3.78 eV to 3.4 eV with annealing. The photoresponse of TiO2 photodetectors was recorded under UV (λ1 = 365 nm, λ2 = 254 nm) and visible light illumination by reversible switching (ON/OFF) cycles using DC electrical characterization. Photosensitive properties such as reproducible photosensitivity, responsivity, and detectivity were also studied.

Preparation and characterization of titanium dioxide using PLD at various energy of pulsed laser

Because of its distinctive optical and electrical characteristics, titanium dioxide (TiO2) thin films are one of the significant and promising semiconductor materials for environmental and energy applications. The effect of the laser pulse energy of Nd:YAG on the properties of TiO2 thin film grown on silicon and quartz substrates using the laser pulse deposition technique by the crystal structure, surface area, crystalline structure, average particle size, and porosity were summarised. The nano-thin film with the optimum condition has been prepared with a pulse laser energy of 900 mJ. The optical properties have been investigated using UV–vis spectrophotometer, morphological properties have been studied using atomic force microscopy and field emission scanning electron microscopy, and structural properties have been examined using x-ray diffractometer and Raman spectrometer. The tests and measurements have shown a crystalline structure, and the distribution of the grains was regular in the film. Raman spectroscopy showed two diffraction peaks corresponding to anatase Eg and rutile Eg. This observation is typically used in dye-sensitised solar cells, separation sensor devices, and more.

Structural Investigation and Properties Of Tio2 Thin Film Prepared by Sol-Gel Spin Coating

<p>We report the structural properties of TiO<sub>2</sub> (Titanium dioxide) thin films grown using sol-gel spin coating method for temperature treatment (with temperature 50<sup>o </sup>C and without temperature) The difference in temperature is carried out to determine changes in the surface of the sample by using heating or not. Ideally, the thickness of the TiO2 layer ranges from 10-15<em><strong> </strong></em><em>μm</em>, therefore in this study it was carried out in 5 layers. Field Emission Scanning Electron Microscopy (FESEM) consist of surface morphology, Cross-section sample, and EDX images, respectively, providing the structure of the surface. The result confirm that temperature treatment can damage the surface coating, this is proven by the shape of the crack in the coating.</p>

Enhancement of mechanical, thermal and optical properties of TiO2 thin films using glancing angle deposition technique

RF Magnetron sputtering has been used to compare the mechanical, thermal, and electrical characteristics of titanium oxide (TiO2) thin films. The Glancing Angle Deposition methods (GLAD) have been implemented during the deposition of a thin film of TiO2. After annealing thin films on an ITO substrate, X-RD indicates the anatase phase, and SEM investigation confirms the deposition of TiO2 thin films and their surface morphology. The mechanical, thermal, and electrical properties of TiO2 thin films prepared by magnetron sputtering with RF supply have been investigated. Using GLAD deposition, a clear change in thermal conductivity and elastic properties has been observed. Experimental specific heat of thin film deposited at zero angles follows Debye and Einstein equation, while with GLAD deposition specific heat shows an increase in deviation as the angle of deposition increases. With a rise in inclination angle, a clear change in transmission spectra towards a higher wavelength has been observed. Following heat treatment, the optical transmission spectra of thin films with GLAD deposition confirm the formation of fringes and have been shifted towards the higher wavelength side to increase in inclination. Hence, using GLAD deposition on TiO2 plays an important role to change thermal conductivity, specific heat, elastic and electronic properties and which leads to many applications in thermal solar collectors, thermal sensors, thermo-optical switching, and sensing-based industries.