Properties Of TiO2 Thin Films Research Articles

Electrical Properties of Nano-TiO<sub>2</sub> Thin Film Using Spin Coating Method

This work investigated the electrical properties of TiO2 thin film on empty glass and ITO glass by spin coating method. Highly transparent titanium oxide thin films were prepared on empty glass and Indium Tin Oxide (ITO) from a titanium (III) chloride precursor. The sheet resistance of the film prepared from both the synthesised and the commercially available TiO2 was measured by the Keithley four-point probe tester (KFPPT). A comparable sheet resistance of 10.69E + 00 Ω/sq was obtained on the ITO. The electrical conductivity of the TiO2 film on ITO glass substrate was found to be very high (3.46E + 05 Ω-1?cm-1) and comparable to that of the bare ITO glass.

Structural and optical properties of TiO2 thin films grown by sol-gel dip coating process

The mono and bi-layer TiO2 thin films have been prepared by sol-gel method on glass. X-Ray diffraction, Raman spectroscopy, atomic force microscopy, spectroscopic ellipsometry and m-lines spectroscopy techniques have been used to characterize the TiO2 films. The mono-layer film is found to be amorphous, while the bi-layer film shows the presence of anatase phase. The bi-layer film exhibits more homogeneous surface with less roughness. The thickness effect on the refractive index, extinction ceofficient, packing density and optical band gap is analysed. The waveguiding measurements of the bi-layer film exhibit single-guided TE0 and TM0 polarized modes from which we can measure the refractive index and the film thickness.

Investigation of optical, structural and morphological properties of nanostructured boron doped TiO 2 thin films

Pure and different ratios (1, 3, 5, 7 and 10%) of boron doped TiO2 thin films were grown on the glass substrate by using sol–gel dip coating method having some benefits such as basic and easy applicability compared to other thin film production methods. To investigate the effect of boron doped on the physical properties of TiO2, structural, morphological and optical properties of growth thin films were examined. 1% boron-doping has no effect on optical properties of TiO2 thin film; however, optical properties vary with > 1%. From X-ray diffraction spectra, it is seen that TiO2 thin films together with doping of boron were formed along with TiB2 hexagonal structure having (111) orientation, B2O3 cubic structure having (310) orientation, TiB0·024O 2 tetragonal structure having rutile phase (110) orientation and polycrystalline structures. From SEM images, it is seen that particles together with doping of boron have homogeneously distributed and held onto surface.

Structural, morphological and optical properties of TiO2 films prepared using aqueous sol–gel methods

The influence of the preparation conditions on the structural, morphological and optical properties of TiO2 thin films deposited on silicon substrate (Si), indium tin oxide coated glass (ITO) and alkali-free borosilicate glass (AFG), respectively is studied in this work. The X-ray diffraction analysis revealed that all TiO2 samples had a polycrystalline structure. The TiO2 films coated on Si showed a mixed phase of anatase and rutile while in the case of those on ITO and AFG only the pure anatase phase was observed. The crystallite size within the TiO2 thin films varied with the calcinations temperature, solvent lateral chain and catalyst type. The optical transmittance, band gap, reflective index and porosity were strongly affected by the annealing temperature, substrate nature and solvent.

Structural, optical and electrical properties of TiO2 thin films synthesized by sol–gel technique

The influence of annealing temperature on the structure, optical and electrical property of TiO thinfilms with (101) preferential orientation were deposited on glass substrates by sol–gel technique has beenstudied. As-deposited films were amorphous, and the XRD studies showed that the formation of anatase phasewas initiated at annealing temperature close to 400 °C. The grain size of the film annealed at 550 °C was about22 nm. The transmission spectra, recorded in the UV visible range reveal a relatively high transmissioncoefficient (~70%) in the obtained films. The transmittance data analysis indicates that the optical band gap (E)is closely related to the annealing temperature, an indirect band gap ranging from 3.43 eV to 3.04 eV wasdeduced. The electrical resistivity measurement that were carried out in function of the annealing temperature showed a sharp decrease in resistivity was found to be 0.0802 .cm.2g

Contribution of thickness dependent void fraction and TiSixOy interlayer to the optical properties of amorphous TiO2 thin films

The optical properties of TiO2 thin films prepared by electron beam evaporation were studied by spectroscopic ellipsometry and analyzed quantitatively using effective medium approximation theory and an effective series capacitance model. The refractive indices of TiO2 are essentially constant and approach to those of bulk TiO2 for films thicker than 40nm, but drop sharply with a decrease in thickness from 40 to 5.5nm. This phenomenon can be interpreted quantitatively by the thickness dependence of the void fraction and interfacial oxide region. The optical band gaps calculated from Tauc law increase with an increase of film thickness, and can be attributed to the contribution of disorder effect.

Influence of growth temperature on the structure and electrical properties of high‐permittivity TiO2 films in TiCl4‐H2O and TiCl4‐O3 atomic‐layer‐deposition processes

AbstractThe influence of the growth temperature on structure and the electrical properties of TiO2 thin films deposited from TiCl4 and H2O and from TiCl4 and O3 was investigated in the temperature range of 150–500 °C. The high‐permittivity rutile phase of TiO2 was obtained on RuO2 in both processes at 225 °C and higher substrate temperatures. The films deposited on Si contained rutile only when were deposited from TiCl4 and H2O at temperatures above 425 °C. Comparison of the films grown on RuO2 revealed superior electrical performance of those deposited from TiCl4 and O3. Although the k values ranging from 100 to 130 in the Pt/TiO2/RuO2 structures were somewhat lower for these films than for the films deposited from TiCl4 and H2O, the former process resulted in lower leakage current densities at similar capacitance effective thicknesses (CET). The leakage current density as low as 6.6 × 10−8 A cm−2 at 0.8 V and CET = 0.41 nm was obtained for films deposited from TiCl4 and O3 at 350 °C.

Tuning of optical and dielectric properties of nanoscale TiO2 using swift heavy ions

We have investigated the influence of swift heavy ion (SHI) irradiation on the optical and dielectric properties of TiO2 thin films. Films with thickness of 80–100 nm were prepared by spin coating of sol precursor onto quartz substrates and were irradiated by 100 MeV Ag7+ ions at different fluences. The pristine sample was crystallized into single TiO2 anatase phase, exhibiting better than 80% transparency in the visible region. The optical absorption edge was found to decrease with the SHI fluence. The general behavior of the dielectric constant was found to obey Drude's theory. The effect of the SHI irradiation and fluence dependence on several optical parameters such as extinction coefficient, real and imaginary parts of dielectric constants, dispersive energy and packing density has been studied.

Influence of substrate on the hydrophilicity and photocatalytic properties of TiO2 nano-layers

The influence of substrate materials on the hydrophilicity and photocatalytic properties of TiO2 thin films, prepared by the sol–gel spray pyrolysis method is investigated. In this regard, thin gold or copper films on glass, Ag-ion-exchanged glass and bare glass were used as substrates for TiO2 thin films. It is found that in comparison to other samples, a TiO2 thin film on the copper/glass substrate demonstrates the most efficient hydrophilicity property, while gold/glass substrate is the best in regards to photocatalytic behavior. The smaller band gap, larger grain size and roughness of the thin films show better photocatalyticity. In our case, we observed that, for gold/glass substrate a more condensed film causes a higher recombination rate of electron–hole pairs, which in turn decreases the hydrophilicity property of the samples.

Synthesis and characterization of Tio2 thin films doped with copper to be used in photocatalysis

In this work we studied the influence of incorporation of copper into TiO2 thin films on structural, optical and surface properties of TiO2 thin films. The as-grown TiO2 was synthesized by sol gel method using titanium isopropoxide, and the TiO2 thin films were deposited by spin coating method. TiO2 copper-doped (Cu:TiO2) was synthesized by impregnation method using Cu(NO3).H2O as source of Cu(II), the Cu:TiO2 thin films were deposited by spin coating method. The properties of the compounds obtained were evaluated by measurements of X-ray diffraction (XRD) and diffuse reflectance. The XRD results showed that Cu doping change the crystalline phase radio of the films, XRD pattern of TiO2 indicated that films grow with anatase structute, while Cu:TiO2 thin films presented a polycrystalline mixture of anatase/rutile. Reflectance analysis indicated that TiO2 presents an energy band gap of 3.25 eV and the Cu:TiO2 presents a shift-red of the band gap to 2,9 eV. The results suggest that doping with copper improved the harvesting of the TiO2 to visible radiation.

Influence of acid/base co-catalyst on the photoelectrochemical properties of TiO2 thin films in dye-sensitized solar cells

Photoelectrochemical properties of TiO2 thin films via co-catalyst sol–gel reaction for dye-sensitized solar cells (DSSCs) were investigated. Three different types of nanocrystalline TiO2 thin films were fabricated from the hydrolysis of Ti isopropoxide with various proportions of an acid/base co-catalyst. The acid/base co-catalyst with a lower proportion of base catalyst reduces particle size of the TiO2 and increases its cluster size including pore volume, which enhance short-circuit current density and open-circuit voltage of the DSSCs device by reducing charge transfer loss across the TiO2/redox electrolyte interface.

The effect of heat treatment in the reducing atmosphere on the physical properties of TiO2 thin films prepared by sol–gel method

Multilayered nanostructured TiO2 thin films were prepared by sol–gel and dipping deposition on quartz substrate followed by thermal treatment under reducing atmosphere (20 %H2–80 %Ar). Heat treatment at progressively higher temperatures caused structural, morphological, and optical changes, which were investigated by X-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy, and UV–Vis spectroscopy. The conductivities of the thin films were also measured by 4-point probe method. The XRD results showed that the calcined TiO2 thin films consist of single anatase phase which was completely transformed into rutile phase after heat treatment at 1,000 °C. The grains of films grew by intra-agglomerate densification after heat treatment at higher temperatures. The root mean square roughness of the samples was found to be in the range of 0.58–3.36 nm. The partially reduced TiO2 samples have red-shifted transmittance bands due to new energy band formed by oxygen vacancies. The electrical conductivity of the films was also enhanced after heat treatment in reducing atmosphere.

Intrinsic Nitrogen‐doped CVD‐grown TiO2 Thin Films from All‐N‐coordinated Ti Precursors for Photoelectrochemical Applications

AbstractN‐doped titanium dioxide (TiO2) thin films are grown on Si(100) and indium tin oxide (ITO)‐coated borosilicate glass substrates by metal‐organic (MO)CVD. The intrinsic doping of TiO2 thin films is achieved using all‐nitrogen‐coordinated Ti precursors in the presence of oxygen. The titanium amide‐guanidinate complex, [Ti(NMe2)3(guan)] (guan = N,N′‐diisopropyl‐2‐dimethylamidoguanidinato) has been developed to compensate for the thermal instability of the parent alkylamide [Ti(NMe2)4]. Both of these amide‐based compounds are tested and compared as precursors for intrinsically N‐doped TiO2 at various deposition temperatures in the absence of additional N sources. The structure and morphology of TiO2 thin films are characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Rutherford back scattering (RBS), nuclear reaction analysis (NRA), and secondary ion mass spectrometry (SIMS) analyses are performed to determine N content and distribution in the films. The optical and photoelectrochemical properties of TiO2 thin films on ITO substrates are also examined. N‐doped TiO2 thin films, grown from [Ti(NMe2)3(guan)] at 600 °C, exhibit the lowest optical absorption edge (3.0 eV) and the highest visible light photocurrent response. When compared to undoped TiO2, while in UV light photoconversion efficiency decreases significantly, the intrinsically N‐doped TiO2 shows enhanced photocurrents under visible light irradiation.

Effect of O2 in O2/Ar Gas Mixture on Morphological and Optical Properties of TiO2 Thin Films Deposited by DC Cylindrical Magnetron Sputtering

TiO2 films have been deposited on BK7 substrates by DC cylindrical magnetron sputtering setup in ambient temperature. The samples were fabricated at various O2/Ar reactive gas mixtures. The effects of changing O2 amount in O2/Ar reactive gas mixture on structural, morphological and optical properties of films were studied. The thickness of films was measured by surface profile meter. Thickness of films decreases with increasing the O2 amount in gas mixture. XRD studies shows that the films are amorphous. Atomic Force Microscopy was used to evaluate and compare the surface roughness and morphologies. The optical properties (transmission and reflection) of the samples were measured by UV–Vis–NIR spectrophotometer. Results show that increasing the O2 amount in O2/Ar mixture changes the surface morphologies and optical properties of films. All films exhibit a transmittance higher than 65 % in the visible region. The band gap of films was calculated from the optical measurements. The band gap of TiO2 thin films increases from 3.471 to 3.526 for different O2/Ar amounts.

Influence of terbium on structure and luminescence of nanocrystalline TiO2 thin films

Abstract In this work analysis of the structural and optical properties of TiO2 thin films doped with terbium has been described. Samples were prepared by a high energy reactive magnetron sputtering process under low pressure of oxygen plasma. X-ray diffraction results have shown that different TiO2 crystal forms have been produced, depending on the amount of Tb dopant. The undoped matrix had rutile structure with crystallites with a size of 8.7 nm, while incorporation of 0.4 at. % of Tb into the film during the sputtering process resulted in anatase structure with bigger crystallites (11.7 nm). Increasing the amount of terbium up to 2 at. % and 2.6 at. % gave rutile structure with crystallites with a size of 6.6 nm for both films. However, Raman spectroscopy has revealed that in the case of TiO2:(2 at. % Tb), except for the rutile form, the presence of fine-crystalline anatase was observed. Moreover, the lack of Raman peaks shift attests to the lack of stress in the titania lattice of all of the TiO2:Tb films. This fact indicates localization of Tb3+ ions on the surface of TiO2 nanocrystals. In the case of optical investigation, results have shown that doping with terbium has a significant influence on the properties of TiO2, but it does not decrease the high transparency of the matrix. The observed changes of the transmission characteristics were produced only due to modification of the TiO2:Tb structure. Photoluminescence measurements have shown that emission of light from TiO2:Tb films occurs when the amount of terbium is 2.6 at. %. Based on the obtained results a scheme of direct energy transfer from titanium dioxide matrix (with rutile structure) to Tb3+ ions has been proposed.

Effect of Nitrogen Doping on Optical and Photocatalytic Properties of TiO2 Thin Film Prepared by Spin Coating Process

Nitrogen-doped TiO2 thin films were prepared by spin coating on glass substrate. Different amount of nitrogen doped in TiO2 matrix was 0, 3 and 10%. As-obtained films were annealed at 400°C for 2h. The optical and photocatalytic properties of N-doped TiO2 thin films were analyzed via UV-Vis spectrophotometry. The chemical properties were investigated by Fourier transform infrared spectrometer and Raman spectroscopy. When doping TiO2 with nitrogen, its absorption spectrum is shifted to visible region resulting to the enhancement of photocatalyst properties in dye photodegradation. Raman and FTIR patterns show that N-doped TiO2 pattern is still identical to undoped TiO2 pattern resulting to unsubstitutation of nitrogen atom in Ti-O bonding.

Hydrophilic and Photocatalytic Performances of Y-Doped Titanium Dioxide Thin Films

Pure and Y-doped TiO2 thin films are prepared on glass by sol-gel method. Tetrabutyl titanate was used as Ti precursors. The chemical composition, structure and properties of TiO2 thin films are characterized by XRD, FT-IR, UV-Vis and Optical Contact Angle Measuring Instrument. Their photocatalytic performances were studied in detail by the methylene blue degradation model. The results show that the crystalline phase of Y2Ti2O7 is formed and the phase transformation from anatase to rutile is restrained when Y is doped in the TiO2 thin films. However, with the continuous increase in calcination temperature, its photocatalytic activity decreases, because the anatase will transform to the rutile. The proper amount of Y doping will cause the lattice to expand, the new defects will form and the smaller band-gap energy will be revealed. Thus, the absorption ability toward the ultraviolet can be improved, the redshift of the absorption band can also be found. As the results of it, the hydrophilicity and photocatalytic efficiency can improved. Furthermore, the photocatalytic activity increases with the hydrophilicity. When the calcination temperature of thin films is 450oC and the Y-doping is 0.3%, the main crystalline phase of the samples is the anatase, the contact angle is only 13.7o and the degradation ratio of methylene blue reached 98.84%.

Self-Cleaning Properties of Vanadium Doped TiO<sub>2</sub> Sol-Gel Derived Thin Films

In this study, vanadium doped TiO2 thin films were deposited on glass substrates using a sol-gel dip-coating process. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis spectrophotometer were used to characterize the structural, chemical and the optical properties of the thin films. The photo-catalytic activities of films were investigated by methylene blue degradation. Water contact angle on the film surfaces was measured by a water contact angle analyzer. The results indicated that vanadium doping had a significant effect on the self-cleaning properties of TiO2 thin films.

Influence of Atomic Layer Deposition Temperatures on TiO2/n-Si MOS Capacitor

This paper reports on the influence of deposition temperature on the structure, composition, and electrical properties of TiO2 thin films deposited on n-type silicon (100) by plasma-assisted atomic layer deposition (PA-ALD). TiO2 layers ∼20 nm thick, deposited at temperatures ranging from 100 to 300°C, were investigated. Samples deposited at 200°C and 250°C had the most uniform coverage as determined by atomic force microscopy. The average carbon concentration throughout the oxide layer and at the TiO2/Si interface was lowest at 200°C. Metal oxide semiconductor capacitors (MOSCAPs) were fabricated, and profiled by capacitance-voltage techniques. The sample prepared at 200°C had negligible hysteresis (from a capacitance-voltage plot) and the lowest interface trap density (as extracted using the conductance method). Current-voltage measurements were carried out with top-to-bottom structures. At −2 V gate bias voltage, the smallest leakage current was 1.22 × 10−5 A/cm2 for the 100°C deposited sample.

Structural and surface properties of TiO2 thin films doped with neodymium deposited by reactive magnetron sputtering

Thin films were deposited using modified, high energy magnetron sputtering method from Ti-Nd mosaic targets. The amount of neodymium dopant incorporated into two sets of thin films was estimated to be 0.8 and 8.5 at.%, by means of energy dispersive spectroscopy. On the basis of x-ray diffraction method, the type of crystalline structure and crystallites size were evaluated directly after the deposition process and after additional post-process annealing at 800 °C temperature. The influence of annealing on the surface properties was evaluated with the aid of atomic force microscopy. Uniformity of the dopant distribution in titanium dioxide matrix was examined with the aid of secondary ion mass spectroscopy. Additionally, using atomic force microscope, diversification and roughness of the surface was determined. Chemical bonds energy at the surface of TiO2:Nd thin films was investigated by x-ray photoelectron spectroscopy method. Wettability measurements were performed to determine contact angles, critical surface tensions and surface free energy of prepared coatings. On the basis of performed investigations it was found, that both factors, the amount of neodymium dopant and the post-process annealing, fundamentally influenced the physicochemical properties of prepared thin films.