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1.
Titanium dioxide thin films have been prepared from tetrabutyl-orthotitanate solution and methanol as a solvent by sol-gel dip coating technique. TiO2 thin films prepared using a sol-gel process have been analyzed for different annealing temperatures. Structural properties in terms of crystal structure were investigated by Raman spectroscopy. The surface morphology and composition of the films were investigated by atomic force microscopy (AFM). The optical transmittance and reflectance spectra of TiO2 thin films deposited on silicon substrate were also determined. Spectroscopic ellipsometry study was used to determine the annealing temperature effect on the optical properties and the optical gap of the TiO2 thin films. The results show that the TiO2 thin films crystallize in anatase phase between 400 and 800 °C, and into the anatase-rutile phase at 1000 °C, and further into the rutile phase at 1200 °C. We have found that the films consist of titanium dioxide nano-crystals. The AFM surface morphology results indicate that the particle size increases from 5 to 41 nm by increasing the annealing temperature. The TiO2 thin films have high transparency in the visible range. For annealing temperatures between 1000 and 1400 °C, the transmittance of the films was reduced significantly in the wavelength range of 300-800 nm due to the change of crystallite phase and composition in the films. We have demonstrated as well the decrease of the optical band gap with the increase of the annealing temperature. 相似文献
2.
T. Ando K. Masuda K. Suzuki S. Masutani H. Uchida A. Kamimoto 《Applied Surface Science》2009,255(24):9688-9690
We have investigated the control of photocatalytic behavior under deposited conditions of non-sintered target of different molar ratios with TiO2 and La2O3 from 1:0 to 1:2 for heavily La doping, and post-annealing temperature from 600 °C to 1000 °C for crystallizing by pulsed laser deposition. We have successfully crystallized heavily La-doped TiO2 films with post-annealing temperature over 800 °C and with molar ratio of TiO2:La2O3 over 1:1 on a quartz substrate. Heavily La-doped TiO2 films are observed the decomposition of methylene blue and a water-splitting reaction in photocatalytic behavior under Xe light irradiation. When stoichiometric La-doped TiO2 (TiO2:La2O3 = 1: 1) is synthesized with heat-treatment at 900 °C, the best results are obtained under photocatalytic behavior and pure La2Ti2O7 crystalline were obtained. 相似文献
3.
Indium tin oxide (ITO) and titanium dioxide (TiO2) single layer and double layer ITO/TiO2 films were prepared using reactive pulsed laser ablation deposition (RPLAD) with an ArF excimer laser for applications in dye-sensitized solar cells (DSSCs). The films were deposited on SiO2 substrates either at room temperatures (RT) or heated to 200-400 °C. Under optimized conditions, transmission of ITO films in the visible (vis) range was above 89% for films produced at RT and 93% for the ones deposited at higher temperatures. Increasing the substrate temperature from RT to 400 °C enhances the transmission of TiO2 films in the vis-NIR from about 70% to 92%. High transmission (≈90%) was observed for the double layer ITO/TiO2 with a transmission cut-off above 900 nm. From the transmission data, the energies gaps (Eg), as well as the refractive indexes (n) for the films were estimated. n ≈ 2.03 and 2.04, respectively for ITO films and TiO2 film deposited at 400 °C in the visible region. Post-annealing of the TiO2 films for 3 h at 300 and 500 °C was performed to enhance n. The refractive index of the TiO2 films increases with the post-annealing temperature. The direct band gap is 3.6, 3.74 and 3.82 eV for ITO films deposited at RT, 200, and 400 °C, respectively. The TiO2 films present a direct band gap of 3.51 and 3.37 eV for as deposited TiO2 films and when annealed at 400 °C, respectively. There is a shift of about 0.1 eV between ITO and ITO/TiO2 films deposited at 200 °C. The shift decreases by half when the TiO2 film was deposited at 400 °C. Post-annealing was also performed on double layer ITO/TiO2. 相似文献
4.
In this work, ZnO thin films covered by TiO2 nanoparticles (labeled as TiO2-ZnO thin films) were prepared by electron beam evaporation. The influence of annealing temperature on the photoluminescence property of the samples was studied. The structures and surface morphologies of the samples were analyzed by X-ray diffraction (XRD) and atomic force microscope, respectively. The photoluminescence was used to investigate the fluorescent properties of the samples. The measurement results show that the ultraviolet emission of ZnO thin films is largely enhanced after they are covered by TiO2 nanoparticles, while the green emission is suppressed. However, when the annealing temperature is relatively high (≥500 °C), the intensity of ultraviolet emission drops off and a violet emission peak along with a blue emission peak appears. This is probably connected with the atomic interdiffusion between TiO2 nanoparticles and ZnO thin film. Therefore, selecting a suitable annealing temperature is a key factor for obtaining the most efficient ultraviolet emission from TiO2-ZnO thin films. 相似文献
5.
ZnO/SiO2 thin films were fabricated on Si substrates by E-beam evaporation with thermal retardation. The as-prepared films were annealed for 2 h every 100 °C in the temperature range 400-800 °C under ambient air. The structural and optical properties were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence (PL). The XRD analysis indicated that all ZnO thin films had a highly preferred orientation with the c-axis perpendicular to the substrate. From AFM images (AFM scan size is 1 μm×1 μm), the RMS roughnesses of the films were 3.82, 5.18, 3.65, 3.40 and 13.2 nm, respectively. PL measurements indicated that UV luminescence at only 374 nm was observed for all samples. The optical quality of the ZnO film was increased by thermal retardation and by using an amorphous SiO2 buffer layer. 相似文献
6.
The article reports on correlations between the process parameters of reactive pulsed dc magnetron sputtering, physical properties and the photocatalytic activity (PCA) of TiO2 films sputtered at substrate surface temperature Tsurf ≤ 180 °C. Films were deposited using a dual magnetron system equipped with Ti (Ø50 mm) targets in Ar + O2 atmosphere in oxide mode of sputtering. The TiO2 films with highly photoactive anatase phase were prepared without a post-deposition thermal annealing. The decomposition rate of the acid orange 7 (AO7) solution during the photoactivation of the TiO2 film with UV light was used for characterization of the film PCA. It was found that (i) the partial pressure of oxygen pO2 and the total sputtering gas pressure pT are the key deposition parameters influencing the TiO2 film phase composition that directly affects its PCA, (ii) the structure of sputtered TiO2 films varies along the growth direction from the film/substrate interface to the film surface, (iii) ∼500 nm thick anatase TiO2 films with high PCA were prepared and (iv) the structure of sputtered TiO2 films is not affected by the substrate surface temperature Tsurf when Tsurf < 180 °C. The interruption of the sputtering process and deposition in long (tens of minutes) pulses alternating with cooling pauses has no effect on the structure and the PCA of TiO2 films and results in a decrease of maximum value of Tsurf necessary for the creation of nanocrystalline nc-TiO2 film. It was demonstrated that crystalline TiO2 films with high PCA can be sputtered at Tsurf ≤ 130 °C. Based on obtained results a phase zone model of TiO2 films was developed. 相似文献
7.
Aifen Tian Wei Ren Lingyan WangPeng Shi Xiaofeng ChenXiaoqing Wu Xi Yao 《Applied Surface Science》2012,258(7):2674-2678
Lead-free ferroelectric K0.5Na0.5NbO3 (KNN) thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition process. The structures, crystal orientations and electrical properties of thin films have been investigated as a function of deposition temperature from 680 °C to 760 °C. It is found that the deposition temperature plays an important role in the structures, crystal orientations and electrical properties of thin films. The crystallization of thin films improves with increasing deposition temperature. The thin film deposited at 760 °C exhibits strong (0 0 1) preferential orientation, large dielectric constant of 930 and the remnant polarization of 8.54 μC/cm2. 相似文献
8.
Dong Fang Zhiping LuoKelong Huang Dimitris C. Lagoudas 《Applied Surface Science》2011,257(15):6451-6461
Highly ordered titanium oxide (TiO2) nanotubes were prepared by electrolytic anodization of titanium electrodes. Morphological evolution and phase transformations of TiO2 nanotubes on a Ti substrate and that of freestanding TiO2 membranes during the calcinations process were studied by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction microscopy. The detailed results and mechanisms on the morphology and crystalline structure were presented. Our results show that a compact layer exists between the tubular layer and Ti substrate at 600 °C, and the length of the nanotubes shortens dramatically at 750 °C. The freestanding membranes have many particles on their tubes during calcinations from 450 to 900 °C. The TiO2 nanotubes on the Ti substrate transform to rutile crystals at 600 °C, while the freestanding TiO2 membranes retain an anatase crystal with increasing temperature to 800 °C. The photocatalytic activity of TiO2 nanotubes on a Ti substrate annealed at different temperatures was investigated by the degradation of methyl orange in aqueous solution under UV light irradiation. Due to the anatase crystals in the tubular layer and rutile crystals in the compact layer, TiO2 nanotubes annealed at 450 °C with pure anatase crystals have a better photocatalytic activity than those annealed at 600 °C or 750 °C. 相似文献
9.
The ZnO films were deposited on c-plane sapphire, Si (0 0 1) and MgAl2O4 (1 1 1) substrates in pure Ar ambient at different substrate temperatures ranging from 400 to 750 °C by radio frequency magnetron sputtering. X-ray diffraction, photoluminescence and Hall measurements were used to evaluate the growth temperature and the substrate effects on the properties of ZnO films. The results show that the crystalline quality of the ZnO films improves with increasing the temperature up to 600 °C, the crystallinity of the films is degraded as the growth temperature increasing further, and the ZnO film with the best crystalline quality is obtained on sapphire at 600 °C. The intensity of the photoluminescence and the electrical properties strongly depend on the crystalline quality of the ZnO films. The ZnO films with the better crystallinity have the stronger ultraviolet emission, the higher mobility and the lower residual carrier concentration. The effects of crystallinity on light emission and electrical properties, and the possible origin of the n-type conductivity of the undoped ZnO films are also discussed. 相似文献
10.
TiO2, which is high in refractive index and dielectric constant, plays an important role in the fields of optics and electronics. In this work, TiO2 films were prepared on glass substrates by the technique of ion beam assisted electron beam evaporation. The films were deposited at 50, 150 and 300 °C, respectively. Then the as-deposited TiO2 films were annealed at 450 °C for 1 h in vacuum atmosphere. Structures and optical properties of TiO2 films were characterized by XRD, SEM, ellipsometry and spectrophotometer. As a result, the structure and the refractive index of films were improved by both the annealing and the increasing of the deposition temperature. The UV-vis transmittance spectra also confirmed that the deposition temperature has a significant effect on the transparency of the thin films. The highest transparency over the visible wavelength region of spectra was obtained at the deposition temperature of 300 °C. The allowed direct band gap at the deposition temperature ranging from 50 to 300 °C was estimated to be in the range from 3.81 to 3.92 eV. 相似文献
11.
We used a metal-organic chemical vapor deposition (MOCVD) method to grow ZnO films on MgAl2O4 (1 1 1) substrate, and succeeded in preparing films with microstructures from well-aligned ZnO nanorods to continuous and dense films by adjusting the ratio of the input rates of oxygen and zinc sources (VI/II). At the growth temperature of 350 °C, the ZnO nanorods were formed under a low flow rate of a zinc precursor. On the other hand, continuous and dense ZnO films were formed under a high flow rate of the zinc precursor. There is a transition zone at medium zinc precursor flow rate, where nanorods transform to dense films. We proved that the height of ZnO nanorods and the thickness of ZnO dense films both increase with zinc flow rate, and are consistent with the mass-transport mechanism for ZnO growth. The XRD spectra of the sample in the transition zone show both (0 0 2) and (1 0 1) peaks, where (1 0 1) peaks are formed only in the transition zone. We consider that there are (0 0 2) and (1 0 1) ZnO grains in the early growth stage of dense ZnO films. 相似文献
12.
Tianlin Yang Shumei SongYanhui Li Yanqing XinGuiqiang Du Maoshui LvShenghao Han 《Physica B: Condensed Matter》2012,407(23):4518-4522
Aluminum doped zinc oxide (AZO) films were substitutes of the SnO2:F films on soda lime glass substrate in the amorphous thin-film solar cells due to good properties and low cost. In order to improve properties of AZO films, the TiO2 buffer layer had been introduced. AZO films with and without TiO2 buffer layer were deposited on soda lime glass substrates by r.f. magnetron sputtering. Subsequently, one group samples were annealed in vacuum (0.1 Pa) at 500 °C for 120 s using the RTA system, and the influence of TiO2 thickness on the properties of AZO films had been discussed. The XRD measurement results showed that all the films had a preferentially oriented (0 0 2) peak, and the intensity of (0 0 2) peak had been enhanced for the AZO films with TiO2 buffer layer. The resistivity of TiO2 (3.0 nm)/AZO double-layer film is 4.76×10−4 Ω cm with the maximum figure merit of 1.92×10−2 Ω−1, and the resistivity has a remarkable 28.7% decrease comparing with that of the single AZO film. The carrier scattering mechanism of TiO2 (3.0 nm)/AZO double-layer film had been described by Hall measurement in different temperatures. The average transmittance of all the films exceeded 92% in the visible spectrum. Another group samples were heat treated in the quartz tube in air atmosphere, and the effect of TiO2 thickness on thermal stability of AZO films had been discussed. 相似文献
13.
Using in situ atomic force microscope (AFM) and Raman spectroscopy, the real-time crystallization properties of Ge2Sb2Te5 films at different temperature were characterized. The given AFM topograph and phase images revealed that the structure of amorphous Ge2Sb2Te5 films began to change at a temperature of as low as 100 °C. When the temperature reached 130 °C, some crystal fragments had formed at the film surface. Heating up to 160 °C, the size of the visible crystal fragments increased, but decreased at a higher temperature of 200 °C. When the Ge2Sb2Te5 film was cooled down to room temperature (RT) from 200 °C, the crystal fragments divided into crystal grains due to the absence of heating energy. The Raman spectra at different temperature further verified the structure evolution of the Ge2Sb2Te5 film with temperature. This work is of significance for the preparation of Ge2Sb2Te5 films and the erasing of data. 相似文献
14.
Wei-an WangQian Shi Yu-ping Wang Jin-li CaoGuo-qing Liu Pan-ying Peng 《Applied Surface Science》2011,257(8):3688-3696
Iodine-doped mesoporous TiO2 (I/TiO2) was prepared by hydrothermal method, using tetrabutyl titanate as precursor, potassium iodate as iodine sources. The as-prepared I/TiO2 catalysts were characterized by UV-vis, XRD, TEM, BET, TG/DTA, XPS and photoluminescence (PL) spectroscopy. Production of OH radicals on the I/TiO2 surface was detected by the PL technique using terephthalic acid as a probe molecule. The effects of hydrothermal reaction temperature, calcination temperature and iodine doping content on the structure and properties of the catalysts were investigated. The results showed that iodine-doped TiO2 calcinated at 300 °C have good anatase crystal. The optimal hydrothermal conditions have been determined to be that reaction temperature 120 °C, calcinated temperature 300 °C and added 1.16 mmol iodine dopants. The average particle size of I/TiO2 synthesized under optimal condition (I-3 sample) is about 3.9 nm. The I-3 photocatalyst contains 100% anatase crystalline phase of TiO2. BET specific surface area of I-3 sample is184.8 m2 g−1 and is 3.67 times that of pure TiO2 (50.37 m2 g−1). Iodine in I/TiO2 catalyst mainly exists in the form of I2, and photoactivity of I/TiO2 catalyst in visible light comes from photosensitize of I2. I/TiO2 catalysis shows very high efficiency for the degradation of phenol under visible light. 相似文献
15.
The influence of titanium on the properties of zinc oxide films deposited by radio frequency magnetron sputtering 总被引:1,自引:0,他引:1
TiO2-doped zinc oxide thin films were deposited on glass substrates by radio frequency (RF) magnetron sputtering with TiO2-doped ZnO targets in an argon atmosphere. The structural properties of TiO2-doped ZnO films doped with different TiO2 contents were investigated. The experimental results show that polycrystalline TiO2-doped ZnO films had the (0 0 2) preferred orientation. The deposition parameters such as the working pressure and substrate temperature of TiO2-doped ZnO films were also investigated. The crystalline structure of the TiO2-doped ZnO films gradually improved as the working pressure was lowered and the substrate temperature was raised. The lowest electrical resistivity for the TiO2-doped ZnO films was obtained when the Ti addition was 1.34 wt%; its value was 2.50 × 10−3 Ω cm, smaller than that found in previous studies. The transmittance of the TiO2-doped ZnO films in the visible wavelength range was more than 80%. The optical energy gap was related to the carrier concentration, and was in the range of 3.30-3.48 eV. 相似文献
16.
Indium tin oxide (ITO) and titanium dioxide (TiO2) single layer and double layer ITO/TiO2 films were prepared using reactive pulsed laser ablation deposition (RPLAD) with an ArF excimer laser. The films were deposited on SiO2 substrates heated at 200 and 400 °C. ITO and TiO2 films with uniform thicknesses of about 400 and 800 nm, respectively, over large areas were prepared. X-ray diffraction (XRD) analysis revealed that the ITO films are formed of highly orientated nanocrystals with an average particle size of 10-15 nm. Atomic force microscopy (AFM) observations indicate rough ITO films surfaces with average roughness of 26-30 nm. Pores were also observed. TiO2 films deposited on the prepared ITO films result less crystalline. Annealing at 300 and 500 °C for three consecutive hours promoted formation of TiO2 anatase phase, with crystal size of ∼6-7 nm. From the scanning transmission electron microscope (STEM) images, it can be seen that the TiO2 films deposited onto the prepared ITO films present a relatively high pore sizes with an average pore diameter of ∼40 nm and excellent uniformity. In addition, STEM cross-sectional analysis of our films showed a columnar structure but no evidence of voids in the structure. Therefore, films exhibited large surface area, well suited for dye-sensitized solar cells (DSSC) applications. 相似文献
17.
Hu-Jie Jin 《Applied Surface Science》2008,254(7):2207-2210
Al-N-codoped ZnO films were fabricated by RF magnetron sputtering in the ambient of N2 and O2 on silicon (1 0 0) and homo-buffer layer, subsequently, annealed in O2 at low pressure. X-ray diffraction (XRD) spectra show that as-grown and 600 °C annealed films grown by codoping method are prolonged along crystal c-axis. However, they are not prolonged in (0 0 1) plane vertical to c-axis. The films annealed at 800 °C are not prolonged in any directions. Codoping makes ZnO films unidirectional variation. X-ray photoelectron spectroscopy (XPS) shows that Al content hardly varies and N escapes with increasing annealing temperature from 600 °C to 800 °C. 相似文献
18.
Well-aligned ZnO nanorod arrays have been successfully fabricated directly on anatase TiO2 nanoparticle films via low-temperature hydrothermal processes. The effects of the reactive time, temperature and reactant concentration on the growth of the as-prepared ZnO crystals are investigated in detail, and the possible mechanisms of crystal ZnO nanorod growth are also suggested. The results show that the low reactant concentration is in favor of the increase in the aspect ratio of crystal ZnO nanorods with weak orientation, while the long reactive time and high reactant concentration are useful to prepare well-aligned crystal ZnO nanorod arrays. Interestingly, the typically constructed composite films exhibit superhydrophilic characteristic without UV irradiation. Moreover, a strong near-ultraviolet PL band centering at about 385 nm and a weak green PL band centering at about 525 nm can appear at the room temperature. 相似文献
19.
Nadya E. Stankova Ivan G. Dimitrov Petar A. Atanasov 《Applied Surface Science》2009,255(10):5275-5279
The evolution of the crystal, the microstructural and the optical properties of pulsed-laser deposited TiO2 films, investigated by X-ray diffraction, atomic force microscopy, scanning electron microscopy, optical transmittance and m-line spectroscopy measurements are reported. The samples were grown on (0 0 1) SiO2 substrates at temperatures from 250 to 600 °C and oxygen pressures from 1 to 15 Pa. Crystalline films consisting of single anatase or anatase and rutile phases, were obtained at temperatures higher than 400 °C. A tendency toward columnar-like growth morphology was observed in the samples. Strong dependence of the optical properties on the surface roughness and the microstructure was determined. All films revealed single-mode waveguiding and optically anisotropic properties. 相似文献
20.
CoPt-TiO2 nanocomposite films were synthesized by rapid thermal annealing of CoPt/TiO2 multilayers. The effects of annealing temperature, annealing time, Ag addition and TiO2 volume fraction on the microstructures and magnetic properties of the CoPt-TiO2 nanocomposite films were studied. Results showed that the ordering degree of CoPt and coercivity of CoPt-TiO2 nanocomposites increased with annealing temperature. Increasing annealing time and Ag addition were able to increase the ordering degree and coercivity of CoPt. However, complete L10-ordering of CoPt at 550 °C annealing was not realized by increasing annealing time up to 30 min and Ag addition up to 30 vol.%. Increasing TiO2 volume fraction at 700 °C annealing did not lead to the change of ordering of CoPt. However, the grain structure of the films changed slightly when TiO2 volume fraction was larger than 56%. The coercivity of the film decreased slightly with the addition of TiO2. 相似文献