Optical Properties Of TiO2 Films Research Articles

Effects of Electric Current on the Structural and Optical Properties of TiO2 Films

Effects of Electric Current on the Structural and Optical Properties of TiO2 Films

Synthesis, structural, photocatalytic, wettability and optical properties of TiO2 films on polymethyl methacrylate substrates

TiO2 thin films on polymethyl methacrylate (PMMA) substrates were prepared on Al foils using reactive dc magnetron sputtering followed by transformation to the PMMA substrates via chemical method. The films were prepared at different temperature preparation routes of 100, 150 and 200 °C. XRD revealed the formation amorphous structure for films prepared at 150 °C and mixed anatase/rutile crystalline phases with rutile domination at higher-temperature preparation route of 150 and 200 °C. Amorphous or homogeneous and uniform nanoparticles morphologies with particle sizes depended on the temperature preparation route were obtained for the TiO2 films. The optical properties are affected strongly by the temperature preparation route. The optical band gap values increased from 3.05 eV to 3.47 eV with increasing the temperature preparation route from 100 °C to then to 200 °C, respectively. The higher refractive index and the lower extinction coefficient were obtained for the films prepared at 200 °C. The methylene blue underwent effective photodegradation and the hydrophilicity initiated upon UV illumination. The TiO2 film prepared at 200 °C has the highest decomposition efficiency for methylene blue and the lowest water contact angle.

Impact of Cu on structural, optical, dielectric properties and antibacterial activity of TiO2 thin films

In this work, Copper-doped TiO2 thin films were synthesized on glass substrates using a sol-gel dip-coating technique with varied molar concentrations of copper precursor (1,3,5,7,9 at. wt. %). Cu affected the structural, morphological, dielectric, antibacterial, and optical properties of TiO2 films. The formation of the anatase phase was confirmed by XRD. The morphology of all synthesized thin films was spherical grains with slight aggregation. The hopping process explained dielectric characteristics that obeyed the Maxwell-Wagner model and Koop's theory. These films were ideal for high-frequency devices because of their low dielectric constant. It was observed that as Cu concentration increased, the optical band gap energy reduced, which was beneficial for improving solar cell efficiency. Cu-doped TiO2 produced the best antibacterial agent. The photocatalysts with the highest photo activities were those containing 9 wt% Cu. The increased light absorption in the UV-VIS range and the lower recombination rate of the photoinduced electron hole pair of Cu-doped TiO2 thin films were responsible for the improved photocatalytic activity. Methylene blue degraded in the presence of sunshine, making it a potential material for the treatment of water.

Surface morphology and optical properties of Ca and Mn doped TiO2 nano-structured thin films

This study was conducted to investigate the impact of Calcium (Ca) and Manganese (Mn) dopants on the optical and surface properties of Titanium dioxide (TiO2) nanomaterial. Ca and Mn doped TiO2 thin films were fabricated by sol–gel spin-coating method. By keeping the doping ratio of Ca constant, Mn was doped at the ratios of 1, 3, and 5%. The morphological, structural and optical properties of the fabricated samples were taken by Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Analysis (EDX), X-Ray Diffraction Method (XRD) and UV–VIS spectroscopy. AFM and SEM analysis revealed that the morphological properties of TiO2 changed depending on the increase in doping ratio of Mn. XRD values obtained from the samples showed that the increases of crystallite size with manganese ions doping into the TiO2 the optical band gap of the samples increased with Ca and Mn dopants. As a result of the investigations, it was determined that Mn doping has significant effects on the morphological and optical properties of TiO2 films and the produced samples can be used in transparent conductive electrode applications, optoelectronic devices, and sensor production.

Variation of structural and optical properties of TiO2 films prepared by DC magnetron sputtering method with annealing temperature

TiO2 thin films are deposited by direct current magnetron sputtering method on the silicon and quartz substrates. The effect of annealing temperature on the film properties are analysed by using X-ray diffraction (XRD), Raman scattering, atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical spectroscopy measurements. Raman and XRD results reveal that the crystal structure of the TiO2 film is strongly affected by the annealing temperature. The crystal structure of the coated film is changed from amorphous to anatase structure after annealing at 500 °C. Anatase and rutile phases of TiO2 start to coexist after annealing at 800 °C. Rutile phases of TiO2 become dominant for film annealed at 900 °C. SEM and AFM images uncover that the morphology, grain size and surface roughness of TiO2 films vary with the annealing temperature. The optical band gap decreases from 3.35 to 2.90 eV as the phase transforms from amorphous to rutile.

Atmospheric Pressure Plasma Deposition of TiO2: A Review.

Atmospheric pressure plasma (APP) deposition techniques are useful today because of their simplicity and their time and cost savings, particularly for growth of oxide films. Among the oxide materials, titanium dioxide (TiO2) has a wide range of applications in electronics, solar cells, and photocatalysis, which has made it an extremely popular research topic for decades. Here, we provide an overview of non-thermal APP deposition techniques for TiO2 thin film, some historical background, and some very recent findings and developments. First, we define non-thermal plasma, and then we describe the advantages of APP deposition. In addition, we explain the importance of TiO2 and then describe briefly the three deposition techniques used to date. We also compare the structural, electronic, and optical properties of TiO2 films deposited by different APP methods. Lastly, we examine the status of current research related to the effects of such deposition parameters as plasma power, feed gas, bias voltage, gas flow rate, and substrate temperature on the deposition rate, crystal phase, and other film properties. The examples given cover the most common APP deposition techniques for TiO2 growth to understand their advantages for specific applications. In addition, we discuss the important challenges that APP deposition is facing in this rapidly growing field.

Influence of oxygen vacancy on the response properties of TiO2 ultraviolet detectors

In this paper, the effect of sputtering distance between target and substrate (DTS) on the structural, morphological and optical properties of TiO2 films were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that crystallite size and surface morphology were strongly dependent on DTS. The X-ray photoelectron spectroscopy (XPS) results showed that obvious three peaks including C1S, Ti2p and O1s could be clearly observed and the binding energy was 285, 458 and 531 eV, respectively. For each sample, four peaks near 386, 462, 527 and 595 nm in photoluminescence (PL) spectra were observed and originated from intrinsic recombination, F center, F+ center and electrons transferred from 3d Ti3+ states to the deep levels OH−, respectively. Finally, the photoresponse properties of UV detectors based on TiO2 films were analyzed and the TiO2 UV detector prepared at a DTS of 80 mm showed high responsivity of 2.02 × 10−4 A/W and excellent photosensitivity of 32.25, also, exhibited a fast response with a rise time (τr) of 0.98 s and fall time (τf) of 3.14 s.

Effect of thermal annealing on properties of polycrystalline Titanium dioxide (TiO2) thin film prepared by simple chemical method

Titanium dioxide (TiO2) thin film prepared in a simple chemical method, on an optically flat a glass substrate. The effect of the annealing temperature on a structural and the optical properties of TiO2 films is studied systematically by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), UV–VIS spectroscopy . The XRD patterns show that the deposited films and the annealed films are polycrystalline and the average grain size of the crystallite grains ranges from 41 to 50 nm in films. AFM images reveal a regular grain distribution of grains in films and the grains in the nanoscale dimension. The UV–Vis rays results show that increase in transmittance with increase the annealing temperature, also, the energy gap decreases from 3.6 to 2.6 volts, due to the effect of quantum volume.

Preparation of high transmittance TiO2 thin films by sol-gel technique as antireflection coating

In this present work sol–gel technique with spin coating method is used to deposit Titanium dioxide thin films on glass substrates as anti-reflection coating (ARC) films. Nano crystalline TiO2 (anatase phase) is obtained after heating at 550°C for 2 h. The optical properties of TiO2 films were studied by UV-Vis absorption/reflection spectroscopy, the average transmittance of monolayer coated on glass substrates was greater than 95% in the wavelength range of 300–1000 nm.

Room temperature deposition of XRD-amorphous TiO2 thin films: Investigation of device performance as a function of temperature

In this study, TiO2 thin films were fabricated by radio frequency sputtering at room temperature in pure Ar atmosphere starting from a 6 in. TiO2 target. The thickness of the films was controlled by deposition time and the effect of Ar sputtering pressure on the characteristics of TiO2 thin films was evaluated. Surface morphology and optical properties of TiO2 films were investigated using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and UV–Vis spectrophotometry. Also, the refractive index and extinction coefficient of films were inferred by fitting spectrophotometric data. Schottky diode were fabricated by evaporation of Ni on TiO2 films. Current-voltage (I-V) measurements of Ni/TiO2 films showed that the rectifying properties of the device improves with the increasing of TiO2 film density and thickness. Therefore, the best I-V characteristic of the device was investigated depending on the temperature. Also, Ni/n-TiO2/p-Si/Al devices were fabricated to understand their transport mechanism.

Influence of interface layer on optical properties of sub-20 nm-thick TiO2 films

The sub-20 nm ultrathin titanium dioxide (TiO2) films with tunable thickness were deposited on Si substrates by atomic layer deposition (ALD). The structural and optical properties were acquired by transmission electron microscopy, atomic force microscopy and spectroscopic ellipsometry. Afterwards, a constructive and effective method of analyzing interfaces by applying two different optical models consisting of air/TiO2/TixSiyO2/Si and air/effective TiO2 layer/Si, respectively, was proposed to investigate the influence of interface layer (IL) on the analysis of optical constants and the determination of band gap of TiO2 ultrathin films. It was found that two factors including optical constants and changing components of the nonstoichiometric IL could contribute to the extent of the influence. Furthermore, the investigated TiO2 ultrathin films of 600 ALD cycles were selected and then annealed at the temperature range of 400–900 °C by rapid thermal annealing. Thicker IL and phase transition cause the variation of optical properties of TiO2 films after annealing and a shorter electron relaxation time reveals the strengthened electron–electron and electron–phonon interactions in the TiO2 ultrathin films at high temperature. The as-obtained results in this paper will play a role in other studies of high dielectric constants materials grown on Si substrates and in the applications of next generation metal-oxide-semiconductor devices.

Structure, Morphology and Optical Properties of TiO2 Films Formed by Anodizing in a Mixed Solution of Citric Acid and Sulfamic Acid

TiO2 films of 50-180 nm thickness were formed at room temperature by anodization of titanium metal in a mixture of citric acid and sulfamic acid in the potential range of 5-30 V. The films so obtained were characterized for their crystal structure, surface morphology, chemical composition and optical properties. Grazing incidence x-ray diffraction and micro-laser Raman spectroscopy measurements of the anodic films confirmed the formation of brookite phase of TiO2 at anodizing potentials of 15, 20, 25 and 30 V and amorphous structure at 5 and 10 V. Field emission scanning electron microscopy revealed non-porous microstructure of the films. Spectroscopic ellipsometry measurements evaluated the band gap of TiO2 at around 3.3 eV, whereas the refractive index of the films was found to be in the range of 2-2.35, in the visible range of spectrum.

Optical Properties of TiO2 Films Deposited by Reactive Electron Beam Sputtering

Titanium dioxide (anatase, a-TiO2) films have been prepared by electron beam sputtering of a TiO2 target in reactive atmosphere and their structural, microstructural, and optical properties were evaluated by reflection high- energy electron diffraction (RHEED) and x-ray diffraction (XRD) analyses, atomic force microscopy (AFM), and spectroscopic ellipsometry (SE). Different reflection models for determination of film optical parameters were tested and compared. The dispersive optical parameters were defined using the Tauc–Lorentz model by SE in the photon energy range of E = 1.12–4.96 eV. The films were transparent at E 3 eV. The bandgap was estimated at the level of Eg ≈ 3.44 eV.

Annealing Temperature Effect on the Physical Properties of Titanium Oxide Thin Films Prepared by the Sol-Gel Method

In this work, the low-cost sol–gel, spin-coating technique was used to grow TiO2 thin films on silicon substrates. The influence of annealing temperature on the structural, morphological, and optical properties of TiO2 films is investigated. The structural properties of the TiO2 films are investigated by Raman and Fourier transform infrared (FTIR) Spectroscopy. Morphological properties are studied by Atomic Force Microscopy (AFM). The optical properties are examined by photoluminescence (PL) and ultraviolet-visible (UV-vis) spectroscopy.

The effect of solution flow rate and substrate temperature on structural and optical properties of TiO2 films deposited by spray pyrolysis technique

Titanium dioxide thin films have been deposited on glass substrate at various solution flow rates by spray pyrolysis technique with substrate temperatures between 350°C–550°C. Samples were characterized for structural, morphological and optical properties by X-ray diffraction (XRD), scanning electron microscope (SEM) and UV–visible spectrometry. The XRD analysis of deposited TiO2 films exhibited nanocrystalline nature and preferentially oriented along [101] direction. The UV–visible transmittance results show that all thin films were transparent with an average transmittance higher than 70% in the visible region. Due to nanosized grains, the optical band gaps of the TiO2 thin films (3.35–3.68eV) were larger than the bulk TiO2 (3.2eV). The SEM analysis revealed that thickness and morphology of TiO2 films can be adjusted by rate of solution flow and substrate temperature. It seems that the process of spray pyrolysis provides an easy way to prepare either homogeneous thin and thick films.

Influence of substrate temperature and silver-doping on the structural and optical properties of TiO2 films

Evaporation of titanium together with activated oxygen is used to grow TiO2 films and simultaneously with silver to grow Ag–TiO2 films (5at.% Ag) onto sapphire substrates at three different substrate temperatures: −190, 30, and 200°C. The obtained films were characterized by X-ray powder diffraction, Raman, X-ray photoelectron, ultraviolet–visible spectroscopy, and transmission electron microscope investigations. The properties of TiO2 films varied with the substrate temperature. Amorphous, transparent TiO2 films were grown at −190°C and opaque, polycrystalline films at 200°C, respectively. Surprisingly, at room temperature black, amorphous TiO2 films are obtained which transform at 350°C into a mixture of the anatase and brookite polymorph. In the amorphous state of the TiO2 films a predefined rutile arrangement is suggested by Raman investigations, and the contraction of the lattice constant c of anatase phases (tetragonal, space group I 41/amd) depending on the substrate temperature is experimentally observed. The silver-doped TiO2 films deposited at −190 and 30°C contain Ag-particles with 2nm in size inside the TiO2 matrix, which after annealing segregate under increasing particle sizes. The silver-doping stabilizes the anatase polymorph and yields to reduced titanium species in the films especially during deposition at 30°C. The Ag–TiO2 films deposited at −190°C are transparent up to 350°C. In the undoped as well as silver-doped TiO2 films the rutile polymorph is directly formed at 200°C as main phase.

Effect of Sprayed Solution Volume on Physical Properties of Titanium Dioxide Thin Films

Titanium dioxide (TiO2) thin films were deposited on glass substrates by spray pyrolysis technique from different solution volumes. We studied the effect of sprayed solution volume on the structural, morphological and optical properties of TiO2 films. X-ray diffraction studies revealed the presence of an anatase phase with a tetragonal structure with (101) preferred orientation. The best crystallinity was obtained in the case of a sprayed solution volume of 60 ml. Also, this film had a lower average surface roughness (RMS) as measured by atomic force microscopy. Transmission and reflection optical analysis showed interference phenomena indicating a smooth reflecting surface of the film. An indirect band gap of about 3.46 eV was found, indicating a potential use of these films in solar cell devices. Based on the optical measurements, the film thickness was determined by the envelope method, which was in agreement with the scanning electron microscopy result. Wemple–Di Domenico single oscillator and Spitzer–Fan models were used to study the optical constants of the films grown from different sprayed solution volumes. Photoluminescence emission intensity was found to increase with increasing film crystallinity, and the spectra showed ultraviolet and visible emissions corresponding to intrinsic emission and trap levels within the band gap, respectively.

Influence of substrate temperature and annealing on structural and optical properties of TiO2 films deposited by reactive e-beam evaporation

The influence of deposition and post-deposition annealing parameters on the structure and optical properties of TiO2 thin films synthesized by reactive e-beam evaporation is reported. Pure Ti (99.9%) was evaporated in oxygen atmosphere to form thin films on Si (100) and glass substrates. Depositions were conducted on substrates held at room temperature and at 200–400°C heated substrates. Post-deposition annealing was done for 3h at 500°C in air. Compositional and structural studies were performed by Rutherford backscattering spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy, and optical properties were studied by ultraviolet–visible spectroscopy and analytically by pointwise unconstrained minimization approach method. It was found that both the structure and optical properties of the films are strongly influenced by the deposition and processing parameters. All deposited samples showed good stoichiometry of Ti:O ~1:2. Depending on the substrate temperature and oxygen pressure in the chamber during the deposition, anatase–rutile mixed films were obtained, and in some cases TiO and Ti2O3 phases were observed. Substrate deposition temperature appears to play the major role on the final structure of the films, while post-deposition annealing adds up for the lack of oxygen in some cases and invokes crystal grain growth of already initiated phases. The results can be interesting towards the development of TiO2 thin films with defined structure and optical properties.

Fe effect on the optical properties of TiO2:Fe2O3 nanostructured composites supported on SiO2 microsphere assemblies.

The effect of Fe ion concentration on the morphological, structural, and optical properties of TiO2 films supported on silica (SiO2) opals has been studied. TiO2:Fe2O3 films were prepared by the sol-gel method in combination with a vertical dip coating procedure; precursor solutions of Ti and Fe were deposited on a monolayer of SiO2 opals previously deposited on a glass substrate by the same procedure. After the dip coating process has been carried out, the samples were thermally treated to obtain the TiO2:Fe2O3/SiO2 composites at the Fe ion concentrations of 1, 3, and 5 wt%. Scanning electron microscopy (SEM) micrographs show the formation of colloidal silica microspheres of about 50 nm diameter autoensembled in a hexagonal close-packed fashion. Although the X-ray diffractograms show no significant effect of Fe ion concentration on the crystal structure of TiO2, the μ-Raman and reflectance spectra do show that the intensity of a phonon vibration mode and the energy bandgap of TiO2 decrease as the Fe+3 ion concentration increases.

Zr掺杂TiO2薄膜的光学性能和光催化性能

In order to study the effects of band structure and optical properties of TiO2films and Zr-doped TiO2films to its photocatalytic,TiO2films and Zr-doped TiO2films are prepared by electron beam gun evaporation on glass.The optical properties and absorption spectra of TiO2films and Zr-doped TiO2films are characterized by UV-visible spectrometry and Raman spectrometer.Analysis results show that:the anatase phase films obtained at annealing temperature of 773Kare mainly composed of TiO2,the energy band gap is decreased owing to the doped Zr,the optical absorption coefficients are increased in the region of350~450nm,a red shift of absorption band can be found,the photo catalytic activity of TiO2is enhanced.