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1

Hydrophilicity of anatase TiO2/Cr-doped TiO2 thin films with different band gaps  

International Nuclear Information System (INIS)

Based on the concept that the electron–hole separation effect caused by a different band-gap structure would improve its hydrophilicity, anatase-TiO2/Cr-doped TiO2 thin films were synthesized by DC magnetron sputtering. The optical band gaps of TiO2 thin films decreased from 3.23 to 2.95 eV with increasing Cr-doping content. Multilayer TiO2 thin films with different band gaps exhibited a superhydrophilicity under UV illumination. In particular, in anatase TiO2 (3.23 eV)/4.8% Cr-doped TiO2 (2.95 eV), the hydrophilicity, which indicated a contact angle of less than 20°, lasted for 48 h in the dark after UV illumination was discontinued. This outstanding result has rarely been reported for TiO2 thin films, which confirmed that the prominent superhydrophilicity of anatase TiO2/Cr-doped TiO2/glass could be attributed to the retardation of electron–hole recombination caused by the band-gap difference. - Highlights: ? TiO2 thin films with different band gaps exhibited a superhydrophilicity. ? Anatase TiO2/4.8% Cr-doped TiO2 showed a contact angle of less than 20°. ? The superhydrophilicity lasted for 48 h in the dark after stopping UV illumination.

2

TiO2 thin films for dyes photodegradation  

International Nuclear Information System (INIS)

The aim of the present study is to investigate the influence of the TiO2 specific surface (powder, film) on the photocatalytic degradation of methyl orange. Porous TiO2 films were deposited on transparent conducting oxide substrates by spray pyrolysis deposition. The films were characterized by X-ray diffraction (XRD), Scanning Electronic Microscopy, and the UV-Vis spectroscopy. The XRD spectra of nanoporous TiO2 films revealed an anatase, crystalline structure that is known as the most suitable structure in photocatalysis. The average thickness of the films was 260 nm and the measured band gap is 3.44 eV. The influence of the operational parameters (dye concentration, contact time) on the degradation rate of the dye on TiO2 was examined. There were calculated the kinetic parameters and the process efficiency. Using thin films of TiO2 is technologically recommended but raises problems due to lowering the amount of catalyst available for the dye degradation

3

Superhydrophilicity of TiO2 nano thin films  

International Nuclear Information System (INIS)

Full text: Among the several oxide semiconductors, titanium dioxide has a more helpful role in our environmental purification due to its photocatalytic activity, photo-induced superhydrophilicity, and as a result of them non-toxicity, self cleaning, and antifogging effects. After the discovery of superhydrophilicity of titanium dioxide in 1997, several researches have been performed due to its nature and useful applications. The superhydrophilicity property of the surface allows water to spread completely across the surface rather than remains as droplets, thus making the surface antifog and easy-to-clean. The distinction of photo-induced catalytic and hydrophilicity properties of TiO2 thin films has been accepted although, the origin of hydrophilicity property has not been recognized completely yet. TiO2 thin films on soda lime glass were prepared by the sol-gel method and spin coating process. The calcination temperature was changed from 100 to 550 C. XRD patterns show increasing the content of polycrystalline anatase phase with increasing the calcination temperature. The AFM results indicate granular morphology of the films, which particle size changes from 22 to 166 nm by increasing the calcination temperature. The RBS, EDX and Raman spectroscopy of the films show the ratio of Ti:O?0.5, and diffusion of sodium ions from substrate into the layer, by increasing the calcination temperature. The UV/Vis. spectroscopy of the films indicates a red shift by increasing the calcination temperature. The contact angle meter experiment shows that superhydrophilicity of the films depends on the formation of anatase crystal structure and diffused sodium content from substrate to the layer. The best hydrophilicity property was observed at 450 C calcination temperature, where the film is converted to a superhydrophilic surface after 10 minutes under 2mW/cm2 UV irradiation. TiO2 thin film on Si(111), Si(100), and quartz substrates needs less time to be converted to superhydrophilic surface rather than glass and polycrystalline Si substrates. Our results are consistent with the idea that UV-induced wetting of TiO2 surface is caused by the removal of hydrophobic layers of hydrocarbons by TiO2-mediated photo-oxidation, which leads to the attractive interaction of water with clean TiO2 surface. (authors)

4

Optical Properties and Surface Morphology of Nano-composite PMMA: TiO2 Thin Films  

International Nuclear Information System (INIS)

There are two nano-composite PMMA: TiO2 solutions were prepared in this research. First solution is nano-composite PMMA commercially available TiO2nanopowder and the second solution is nano-composite PMMA with self-prepared TiO2 powder. The self-prepared TiO2 powder is obtained by preparing the TiO2 sol-gel. Solvo thermal method were used to dry the TiO2 sol-gel and obtained TiO2 crystal. Ball millers were used to grind the TiO2 crystal in order to obtained nano sized powder. Triton-X was used as surfactant to stabilizer the composite between PMMA: TiO2. Besides comparing the nano-composite solution, we also studied the effect of the thin films thickness on the optical properties and surface morphology of the thin films. The thin films were deposited by sol-gel spin coating method on glass substrates. The optical properties and surface characterization were measured with UV-VIS spectrometer equipment and atomic force microscopy (AFM). The result showed that nano-composite PMMA with self prepared TiO2 give high optical transparency than nano-composite PMMA with commercially available TiO2 nano powder. The results also indicate as the thickness is increased the optical transparency are decreased. Both AFM images showed that the agglomerations of TiO2 particles are occurred on the thin films and the surface roughness is increased when the thsurface roughness is increased when the thickness is increased. High agglomeration particles exist in the AFM images for nano-composite PMMA: TiO2 with TiO2 nano powder compare to the other nano-composite solution. (author)

5

Electrochromic properties of spray deposited TiO 2-doped WO 3 thin films  

Science.gov (United States)

TiO 2-doped WO 3 thin films were deposited onto fluorine-doped tin oxide coated conducting glass substrates using spray pyrolysis technique at 525 °C. The volume percentage of TiO 2 dopant was varied from 13% to 38%. The thin film samples were transparent, uniform and strongly adherent to the substrates. Electrochromical properties of TiO 2-doped WO 3 thin films were studied with the help of cyclic voltammetry (CV), chronoamperometry (CA) and chronocoulometry (CC) techniques. It has been found that TiO 2 doping in WO 3 enhances its electrochromic performance. Colouration efficiency becomes almost double and samples exhibit increasingly high reversibility with TiO 2 doping concentrations, in the studied range.

Patil, P. S.; Mujawar, S. H.; Inamdar, A. I.; Sadale, S. B.

2005-08-01

6

PHOTOCATALYTIC PROPERTIES OF Cr DOPED TiO2–SiO2 NANOSTRUCTURE THIN FILM  

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Full Text Available Cr doped TiO2–SiO2 nanostructure thin film on glass substrates was prepared by a sol-gel dip coating method. X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS and UV-vis spectrophotometer were used to characterize the structural, chemical and optical properties of the thin film. The XRD showed that thin films contain only anatase phase. FE-SEM images illustrated that anatase average crystallite size in the pure TiO2 and Cr doped TiO2–SiO2 thin films are 15 nm and 10 nm, respectively. XPS spectra confirmed the presence of Cr3+ in the thin film. UV-vis absorption spectra indicated that absorption edge in Cr doped TiO2–SiO2 thin film shifted to the visible light region. The photocatalytic results pointed that Cr doping in TiO2–SiO2 improved decoloring rate of methyl orange in comparison to pure TiO2 thin film.

Akbar Eshaghi

2012-07-01

7

TiO2/PANI And MWNT/PANI Composites Thin Films For Hydrogen Gas Sensing  

International Nuclear Information System (INIS)

The MWNT and TiO2 doped Polyaniline (PANI) composites were synthesized by In-situ chemical oxidative polymerization method at low temperature. The MWNT/PANI and TiO2/PANI composite thin films were prepared using spin coating method onto finger type interdigited electrodes to develop the chemiresistor type gas sensor for hydrogen gas sensing application. It was observed that the MWNT and TiO2 doped PANI composite thin films show a higher response in comparision to neat PANI. The structural and morphological properties of these composite films were characterized by X-Ray differaction (XRD) pattern and sccaning electrone microscopy (SEM) respectively.

8

TiO2/PANI And MWNT/PANI Composites Thin Films For Hydrogen Gas Sensing  

Science.gov (United States)

The MWNT and TiO2 doped Polyaniline (PANI) composites were synthesized by In-situ chemical oxidative polymerization method at low temperature. The MWNT/PANI and TiO2/PANI composite thin films were prepared using spin coating method onto finger type interdigited electrodes to develop the chemiresistor type gas sensor for hydrogen gas sensing application. It was observed that the MWNT and TiO2 doped PANI composite thin films show a higher response in comparision to neat PANI. The structural and morphological properties of these composite films were characterized by X-Ray differaction (XRD) pattern and sccaning electrone microscopy (SEM) respectively.

Srivastava, Subodh; Kumar, Sumit; Agrawal, Shweta; Saxena, Arpita; Choudhary, B. L.; Mathur, Shubhra; Singh, M.; Vijay, Y. K.

2010-12-01

9

Photoinduced superhydrophilicity of TiO2 thin film with hierarchical Cu doping  

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Full Text Available Hydrophilic Cu–TiO2 thin films with a gradient in the Cu concentration were prepared on glass by layer-by-layer dip-coating from TiO2 precursors. The effects of the Cu doping on the structure and properties of TiO2 self-cleaning thin films are discussed. The Cu gradient markedly affects the hydrophilicity of the films, with the water contact angle significantly reduced compared with those of the pure or uniformly doped TiO2 thin films. This enhanced hydrophilicity is explained by the more efficient absorption of the solar light and by the reduced recombination of photoexcited electrons and holes in the TiO2 films containing a gradient of Cu dopants.

Zhifeng Liu, Yun Wang, Xinli Peng, Yabin Li, Zhichao Liu, Chengcheng Liu, Jing Ya and Yizhong Huang

2012-01-01

10

Nanostructured TiO2 thin films for field emission and sensor applications  

Science.gov (United States)

Thin films consisting TiO2 nanoparticles were synthesized by a cost effective ultrasonic spray pyrolysis technique on Si(100) and glass substrates at temperatures of 350 and 450 °C. The films were found to be anatase phase of TiO2 from GIXRD and Raman studies. Effect of substrate temperature on growth process was monitored using FESEM technique. The substrate temperature influenced the morphology of the films and also on the field emission properties. The asdeposited semi-conducting TiO2 films were investigated for the utilization of alcohol sensor at room temperature.

Raut, N. C.

2012-10-01

11

Buckle delamination of textured TiO2 thin films on mica  

International Nuclear Information System (INIS)

We present the growth of textured TiO2 thin films on muscovite mica using pulsed laser deposition. Atomic force microscopy, scanning electron microscopy, X-ray photoemission spectroscopy, and transmission electron microscopy were used to characterize the TiO2 films. Quasi-periodic wavy and comb-like buckles were observed. Below a critical thickness of about 25 nm, TiO2 films were relatively smooth, and buckles began to form when the nominal thickness of TiO2 films was larger than 25 nm. Co-existence of wavy and comb-like quasi-periodic buckles was observed when the nominal thickness of TiO2 films was larger than 100 nm. The film stress is compressive due to the competition of the tensile stress from the lattice mismatch and the growth stress. The buckle delamination occurred when the compressive stress overcome the adhesion strength of the TiO2 films on mica. A value of adhesion strength around 0.9 MPa for TiO2 on mica is obtained. The symmetric domains of buckles are assigned to the anisotropic lattice mismatch for TiO2 on mica

12

Temperature dependence of gas sensing behaviour of TiO2 doped PANI composite thin films  

International Nuclear Information System (INIS)

In the present work we have reported the effect of temperature on the gas sensing properties of TiO2 doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO2 doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO2 doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement

13

Photocatalytic properties of TiO2 thin films obtained by glancing angle deposition  

International Nuclear Information System (INIS)

Titanium dioxide (TiO2) thin films with different nanostructures such as nano-particles and separated vertical columns were grown by glancing angle deposition (GLAD) in an electron beam evaporation system. The photocatalytic properties of grown TiO2 films with different deposition angles and different annealing temperatures were evaluated by following decomposition of methyl orange under ultraviolet (UV) light irradiation. The results suggest that increased surface area due to the GLAD process could improve the photocatalytic properties of TiO2 films.

14

TiO2 thin-films on polymer substrates and their photocatalytic activity  

International Nuclear Information System (INIS)

We have developed dip-coating process for TiO2-thin film on polymer substrates (acrylonitrile-butadiene-styrene polymer: ABS, polystyrene: PS). At first, a monodispersed and transparent TiO2 nano-sol solution was prepared by the controlled hydrolysis of titanium iso-propoxide in the presence of acetylacetone and nitric acid catalyst at 80 deg. C. Powder X-ray diffraction patterns of the dried particles are indicative of crystalline TiO2 with anatase-type structure. According to the XRD and transmission electron microscopy (TEM) studies, the mean particle size was estimated to be ca. 5 nm. The transparent thin films on ABS and PS substrates were fabricated by dip-coating process by changing the processing variables, such as the number of dip-coating and TiO2 concentration in nano-sol solution. Scanning electron microscopic (SEM) analysis for the thin film samples reveals that the acetylacetone-modified TiO2 nano-sol particles are effective for enhancing the interfacial adherence between films and polymeric substrates compared to the unmodified one. Photocatalytic degradation of methylene blue (MB) on the TiO2 thin-films has also been systematically investigated

15

Obtention of TiO2 thin films by laser ablation  

International Nuclear Information System (INIS)

The thin films of TiO2 have been investigated extensively in the last years, since they have a broad variety of applications, which owing to their less usual chemical, electrical and optical properties. In this work are presented the obtained results to deposit TiO2 thin films over glass substrates utilizing the Laser ablation technique. It has been deposited thin films at different substrate temperatures and different oxygen pressures, with the purpose to study the influence of these deposit parameters in the structural characteristics of the obtained films. The structural characterization was realized through Raman spectroscopy and X-ray diffraction (XRD), the superficial morphology was verified by Scanning Electron Microscopy (SEM). The results show that the obtained films were TiO2 in rutile phase, getting this with the substrates at low temperature, its morphology shows a soft surface with some sprinkling particles and a good adherence. (Author)

16

Raman spectra of TiO2 thin films deposited electrochemically and by spray pyrolysis  

International Nuclear Information System (INIS)

In this paper we present our experimental results concerning the fabrication of TiO2 thin films by spray pyrolysis and electrochemical deposition method onto different substrates - Corning glass, Si and optical fibers. The surface morphology of the TiO2 thin films have been investigated by Atomic Force Microscopy. Raman shift spectra measurements have been done for the optical characterization of the fabricated titania thin films. The post-growth rapid photothermal processing (RPP) at temperatures of 100-800 degrees Celsius for 1-3 min have been applied. Our experimental results prove that by the application of post-growth RPP is possible to essentially improve the crystallinity of the deposited TiO2 films. (authors)

17

Preparation and Photocatalytic Activity of TiO2 Thin Films on Al Alloys  

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Full Text Available Using anodized 6061 aluminum alloy and pure aluminum as the templates, TiO2 thin films were prepared through a liquid deposition method. The TiO2 thin film fabricated on the 6061 aluminum alloy substrates appears as bamboo―like structures with holes, whereas that prepared on anodized pure aluminum substrate has one―dimensional tubular structures. The main reason is that magnesium in aluminum alloy is oxidized to form magnesium oxide which has a lower volume than that of Al2O3. The photocatalytic ability of the TiO2 films prepared on the aluminum alloy is superior to that of the films fabricated on the pure aluminum. TiO2 prepared on aluminum alloy has higher specific surface area due to its bamboo―like structures with holes, leading to better performance in the degradation of methylene blue. The photocatalytic performance of the TiO2 by the degradation of aqueous methylene blue is in accordance with the first kinetic equation. TiO2 films deposited in 0.1 mol/L (NH4) TiF6 solution obtain the best photocatalytic performance at apparent reaction rate of 0.00444/min.

CAI Qian, WANG Jin-Shu, LI Hong-Yi, LIU Shao-Lin, LI Yu-Mei

2012-06-01

18

Application of Pcvd Process to Uniform Coating of TiO2 Thin Films on Polypropylene Beads  

Science.gov (United States)

The growth of the TiO2 thin films coated on the polypropylene beads was analyzed experimentally in a rotating cylindrical plasma chemical vapor deposition (PCVD) reactor. The precursors for the thin films were generated by plasma reactions, and they deposited on the polypropylene beads to become the uniform thin films. The TiO2 thin films grow more quickly on the polypropylene beads by increasing the mass flow rate of TTIP, or the rotation speed of the reactor. The smaller number of polypropylene beads in the reactor increases the growth rate of the thin films. The high-quality TiO2 thin films can be coated on particles uniformly by using the rotating cylindrical PCVD process. The particles coated with high-quality TiO2 thin films can be applied to the removal of air and water pollutants by a photodegradation reaction of TiO2.

Kim, Dong-Joo; Pham, Hung Cuong; Kim, Kyo-Seon

19

XAS study of the local environment of impurities in doped TiO2 thin films  

CERN Document Server

In this work we present an X-ray Absorption Spectroscopy characterization of the local environment of the impurity in room temperature ferromagnetic anatase TiO2 thin films doped with Co, Ni, Cu, or Zn, deposited on LaAlO3 substrate by Pulsed Laser Deposition. It was found that there is a considerable amount of impurity atoms substituting Ti in TiO2 anatase, although the presence of metal transition monoxide clusters can not be discarded. From our results we infer that the observed room temperature ferromagnetism of the samples could be assigned to the metal transition atoms replacing Ti in TiO2 anatase.

Torres, C E R; Errico, L A; Duhalde, S; Renter'ia, M; Golmar, F; S'anchez, F H

2007-01-01

20

Preparation of titanium dioxide (Tio2) thin films by sol.gel dip coating method  

International Nuclear Information System (INIS)

Titanium dioxide (TiO2) thin films have been receiving much attention in the past as their chemical stability, high refractive index, and high dielectric constant [1], allow their use as components in optoelectronic devices, sensors, photo catalysis [2], solar cells [3], and wave guides [4]. Titanium dioxide thin films have been prepared from tetra-butylorthotitanium solution and buthanol as a solvent by sol.gel dip-coating method on an ITO substrate. The samples obtained were characterized by different experimental techniques: X-ray diffraction; Raman spectroscopy; scanning electron microscopy (SEM), optical microscopy, Photoluminescence, infrared and ultraviolet spectroscopy. The X-ray diffraction (XRD) results showed that TiO2 thin film at 300 degree C was amorphous, and transformed into the anatase.brookite at 400 degree C, the crystallite size of TiO2 thin films was increased with increasing temperature gives sizes in the range 5 to 25 nm. The observed by scanning electron microscope (SEM) shows that the coating was transparent and homogeneous without any visual cracking over a wide area, and multiple coating increased thickness, but did not affect the uniformity of the film. The film thickness varies, depending on the number of dipping iterations, between 20 (1 layer) and 153.6 nm (4 layers). The refractive index increases with increasing temperature, and the porosity of TiO2 thin films, however, shows the opposite trend

 
 
 
 
21

Room temperature ferromagnetism in vacuum-annealed TiO2 thin films  

International Nuclear Information System (INIS)

Thin films of pure TiO2 have been prepared using both spin-coating and sputter-deposition techniques on sapphire and quartz substrates. The structural characteristics of the films have been investigated in detail using Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). When annealed in vacuum, all films demonstrate room temperature ferromagnetism, while the air-annealed samples show much smaller, often negligible, magnetic moments. The magnetization of the vacuum-annealed sputtered samples depends on film thickness, with the volume magnetization decreasing monotonically with increasing thickness. Furthermore, the magnetization per unit area also decreases slightly with increasing film thickness. These results suggest that ferromagnetism in the vacuum-annealed TiO2 films is mediated by surface defects or interfacial effects, but does not arise from stoichiometric crystalline TiO2

22

Visible light catalysis of rhodamine B using nanostructured Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films.  

Science.gov (United States)

The Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) composite films are deposited using spray pyrolysis method onto glass and FTO coated substrates. The structural, morphological, optical and photocatalytic properties of Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films are studied. XRD analysis confirms that films are polycrystalline with rhombohedral and tetragonal crystal structures for Fe2O3 and TiO(2) respectively. The photocatalytic activity was tested for the degradation of Rhrodamine B (Rh B) in aqueous medium. The rate constant (-k) was evaluated as a function of the initial concentration of species. Substantial reduction in concentrations of organic species was observed from COD and TOC analysis. Photocatalytic degradation effect is relatively higher in case of the TiO(2)/Fe(2)O(3) than TiO(2) and Fe(2)O(3) thin film photoelectrodes in the degradation of Rh B and 98% removal efficiency of Rh B is obtained after 20min. The photocatalytic experimental results indicate that TiO(2)/?-Fe(2)O(3) photoelectrode is promising material for removing of water pollutants. PMID:24721593

Mahadik, M A; Shinde, S S; Mohite, V S; Kumbhar, S S; Moholkar, A V; Rajpure, K Y; Ganesan, V; Nayak, J; Barman, S R; Bhosale, C H

2014-04-01

23

Optical spectra of graded nanostructured TiO 2 chiral sculptured thin films  

Science.gov (United States)

The optical properties of graded chiral sculptured TiO 2 thin films in axial and non-axial excited states are calculated using the rigorous coupled wave analysis method (RCWA) in conjunction with the Bruggeman homogenization formalism. The filtering frequency and polarization selectivity of these graded nanostructured TiO 2 sculptured thin films showed dependence on both structural and deposition parameters. The results achieved are consistent with the experimental data [K. M. Krause and M. J. Bret, Adv. Funct. Mater. 18 (2008) 3111].

Babaei, F.; Esfandiar, A.; Savaloni, H.

2010-07-01

24

Synthesis of Structured Macroporous TiO2 Thin Films and Investigation on Their Photocatalytic Activities  

International Nuclear Information System (INIS)

Synthesis of structured macroporous TiO2 thin films on quartz substrate (macro-TiO2/Q) was performed by a dip-coating method using poly(methyl methacrylate) (PMMA) microspheres as template. Obtained TiO2 thin films kept high transparency and had anatase crystalline structure. SEM observations revealed that the macropores were uniformly formed on the film surface. The size of macropores was quite similar to the diameter of PMMA microspheres as template. In comparison to the nonporous TiO2 thin films (TiO2/Q), macro-TiO2/Q exhibited twice higher photocatalytic activity for decolorization of methylene blue in water. Decomposition of acetaldehyde in gas phase also proceeded efficiently on macro-TiO2/Q. Moreover, the surface of macro-TiO2/Q was easily hydrophilized after a short period of UV light irradiation and maintained lower water contact angle in the dark for a long period as compared to those of TiO2/Q.

25

Structural, electrical and optical properties of TiO 2 doped WO 3 thin films  

Science.gov (United States)

TiO 2 doped WO 3 thin films were deposited onto glass substrates and fluorine doped tin oxide (FTO) coated conducting glass substrates, maintained at 500 °C by pyrolytic decomposition of adequate precursor solution. Equimolar ammonium tungstate ((NH 4) 2WO 4) and titanyl acetyl acetonate (TiAcAc) solutions were mixed together at pH 9 in volume proportions and used as a precursor solution for the deposition of TiO 2 doped WO 3 thin films. Doping concentrations were varied between 4 and 38%. The effect of TiO 2 doping concentration on structural, electrical and optical properties of TiO 2 doped WO 3 thin films were studied. Values of room temperature electrical resistivity, thermoelectric power and band gap energy ( Eg) were estimated. The films with 38% TiO 2 doping in WO 3 exhibited lowest resistivity, n-type electrical conductivity and improved electrochromic performance among all the samples. The values of thermoelectric power (TEP) were in the range of 23-56 ?V/K and the direct band gap energy varied between 2.72 and 2.86 eV.

Patil, P. S.; Mujawar, S. H.; Inamdar, A. I.; Shinde, P. S.; Deshmukh, H. P.; Sadale, S. B.

2005-12-01

26

Oblique angle deposition of TiO2 thin films prepared by electron-beam evaporation  

International Nuclear Information System (INIS)

Optical, structural and photocatalytic properties of TiO2 thin films obliquely deposited on quartz glass substrate using an electron-beam evaporation method were investigated. The photocatalytic activity of the films was evaluated by photodecomposition of methylene blue. An increase in incident deposition angle increased the porosity and surface roughness of the TiO2 films. As a result, the photocatalytic activity was enhanced with incident deposition angle up to 60 deg. However, a further increase in incident deposition angle to 75 deg. reduced the photocatalytic activity due to a lack of the crystalline phase.

27

Obtenção de filmes finos de TiO2 nanoestruturado pelo método dos precursores poliméricos / Nanostructured TiO2 thin films by polymeric precursor method  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english This work focuses in optimizing setup for obtaining TiO2 thin films by polymeric precursor route due to its advantages on stoichiometric and morphological control. Precursor stoichiometry, synthesis pH, solids concentration and rotation speed at deposition were optimized evaluating thin films morpho [...] logy and thickness. Thermogravimetry and RMN were applied for precursor's characterization and AFM, XRD and ellipsometry for thin films evaluation. Results showed successful attainment of homogeneous nanocrystalline anatase TiO2 thin films with outstanding control over morphological characteristics, mean grain size of 17 nm, packing densities between 57 and 75%, estimated surface areas of 90 m²/g and monolayers thickness within 20 and 128 nm.

Daniel Grando, Stroppa; Tania Regina, Giraldi; Edson Roberto, Leite; José Arana, Varela; Elson, Longo.

1706-17-01

28

Fabrication of TiO2 nanotubes by anodization of Ti thin films for VOC sensing  

International Nuclear Information System (INIS)

Ti thin films were anodized in aqueous HF (0.5 wt.%) and in polar organic (0.5 wt.% NH4F + ethylene glycol) electrolytes to form TiO2 nanotube arrays. Ti thin films were deposited on microscope glass substrates and then anodized. Anodization was performed at potentials ranging from 5 V to 20 V for the aqueous HF and from 20 V to 60 V for the polar organic electrolytes over the temperatures range from 0 to 20 °C. The TiO2 nanotubes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). It has been observed that anodization of the deposited Ti thin films with aqueous HF solution at 0 °C resulted in nanotube-type structures with diameters in the range of 30–80 nm for an applied voltage of 10 V. In addition, the nanotube-type structure is observed for polar organic electrolyte at room temperature at the anodization voltage higher than 40 V. The volatile organic compound (VOC) sensing properties of TiO2 nanotubes fabricated using different electrolytes were investigated at 200 °C. The maximum sensor response is obtained for carbon tetrachloride. The sensor response is dependent on porosity of TiO2. The highest sensor response is observed for TiO2 nanotubes which are synthesized using aqueous HF electrolyte and have very high porosity.

29

TiO2 thin films prepared by sol - gel method  

Science.gov (United States)

There is a growing awareness that titania (TiO2) and TiO2-based oxide systems are the most promising candidates for the development of photoelectrodes for photoelectrochemical cell (PEC) for solar-hydrogen production [1]. The PEC is equipped with a single photoelectrode (photoanode) and cathode, both of which are immersed in an aqueous electrolyte. In this work we present a sol-gel method to prepare TiO2 thin films on ITO using tetraisopropoxides of titanium, acetylacetone, 1-butanol and Tween 80 as surfactant. The films were deposited on ITO coated glass slides by spray pyrolysis. UV-VIS spectra and fluorescence measurements were made for the solutions and films. X-ray diffraction was used for structural investigations and the morphology of the film was studied by Scanning Electron Microscopy.

Suciu, R. C.; Indrea, E.; Silipas, T. D.; Dreve, S.; Rosu, M. C.; Popescu, V.; Popescu, G.; Nascu, H. I.

2009-08-01

30

Uniform coating of TiO2 thin films on particles by rotating cylindrical PCVD reactor.  

Science.gov (United States)

We analyzed TiO2 thin film growth on glass particles in a rotating cylindrical plasma chemical vapor deposition (PCVD) reactor and numerically investigated the effects of several process variables on the film growth. An increase in titanium tetra-isopropoxide (TTIP) or O2 partial pressure can enhance the film growth rate on the particles because the concentration of TiO(x), which is the main precursor for thin film growth, becomes higher in the reactor. As the particle diameter decreases, the TiO(x) concentration increases and the thin film on the particles grows more quickly. The neutral-radical reaction between TTIP and O radicals for TiO(x) generation in TTIP + O2 plasmas can be important to enhance the thin film growth rate on the particles. The growth rate of TiO2 film predicted in this study was 1 approximately 20 nm/min, which is in good agreement with the published experimental results. This study suggests that a uniform TiO2 thin film on particles can be obtained by using a rotating cylindrical PCVD reactor. PMID:19916444

Kim, Dong-Joo; Baeg, Jin-Ook; Moon, Sang-Jin; Kim, Kyo-Seon

2009-07-01

31

Characterization of TiO2 Thin Films on Glass Substrate Growth Using DC Sputtering Technique  

International Nuclear Information System (INIS)

It has been fabricated and characterization a TiO2 thin films deposited on glass substrate using DC sputtering technique. Fabrication of TiO2 thin films were carried out at electrode voltage 4 kV, sputtering current 5 mA, vacuum pressure 5 x 10-4 torr, deposition time 150 minutes, and temperature of the substrate were varied from 150 -350 oC, while as a gas sputter was argon. The results was tested their micro structure using SEM, and crystal structure using XRD and found that the crystal structure of TiO2 powder before deposited on glass substrate was rutile and anatase with orientation (110) and (200) for anatase and (100) and (111) rutile structure. While the crystal structure which deposited at temperature 150 oC and deposition time 2.5 hours was anatase with orientation (001) and (200). (author)

32

Thin TiO 2 films for an electrochromic system  

Science.gov (United States)

Thin electrochromic titanium dioxide films were obtained by spray pyrolysis on glass sheets coated with SnO 2: F using titanium (IV) oxide acetylacetonate and were characterized for the morphology and chemical nature. Electrochromic coloration-bleaching reactions with a Li-ion conducting hybrid organic-inorganic electrolyte and a WO 3 coated electrochromic electrode resulted in a reversible optical properties modulation in the visible and near infrared range of the spectrum. An XPS analysis showed the presence of lower oxidized states in the films.

Zelazowska, E.; Rysiakiewicz-Pasek, E.

2009-10-01

33

Optical Spectra of Graded Nanostructured TiO2 Chiral Thin Films  

CERN Document Server

The rigorous coupled wave analysis method (RCWA) is applied to the graded chiral TiO2 thin films in axial and non-axial excited states using the Bruggeman homogenization formalism. The dependence of the filtering frequency and polarization selectivity as a function of different structural parameters, are investigated. A good agreement with experimental results reported by other researchers is achieved.

Babaei, F; Savaloni, H; 10.1016/j.optcom.2010.03.005

2010-01-01

34

Effect of Au Nanoparticles Doping on The Properties of TiO2 Thin Films  

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Full Text Available In this study, pure and gold (Au nanoparticles doped TiO2 thin films (Au/Ti = 10, 20, 30, 40 and 50 at% were prepared by sol-gel method and the impact of Au nanoparticles doping on the optical, structural and morphological properties of these thin films was examined. All thin films were characterized using ultraviolet-visible-near infrared (UV-Vis-NIR spectrophotometry, X-ray diffraction (XRD, transmission electron microscopy (TEM and atomic force microscopy (AFM. The optical band gap of the thin films increases from 3.74 eV to 3.89 eV with the increase of Au nanoparticles concentrations due to the Moss-Burstein effect. XRD results show that all thin films have cubic poly-crystal structure and the intensities of peaks of the crystalline phase increased with the increase of Au nanoparticles concentrations. The AFM results indicate that the TiO2 thin ?lms are formed from the nanoparticles and the grain size of the ?lms is changed with Au doping level. Consequently, it is shown that the structural, morphological and optical properties of the TiO2 thin ?lms could be changed by Au nanoparticles-doping. DOI: http://dx.doi.org/10.5755/j01.ms.20.1.3709

Aytaç GÜLTEK?N

2014-02-01

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Structural, optical and electrochemical properties of TiO2 thin films grown by APCVD method  

International Nuclear Information System (INIS)

Atmospheric pressure chemical vapor deposition (APCVD) of TiO2 thin films has been achieved onto glass and onto ITO-coated glass substrates, from the reaction of TiCl4 with ethyl acetate (EtOAc). The effect of the synthesis temperature on the optical, structural and electrochemical properties was studied through spectral transmittance, X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) measurements. It was established that the TiO2 films deposited onto glass substrate, at temperatures greater than 400 deg. C grown with rutile type tetragonal structure, whereas the TiO2 films deposited onto ITO-coated glass substrate grown with anatase type structure. EIS was applied as suitable method to determine the charge transfer resistance in the electrolyte/TiO2 interface, typically found in dye-sensitized solar cells.

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Magnetic and structural study of Cu-doped TiO2 thin films  

CERN Document Server

Transparent pure and Cu-doped (2.5, 5 and 10 at. %) anatase TiO2 thin films were grown by pulsed laser deposition technique on LaAlO3 substrates. The samples were structurally characterized by X-ray absorption spectroscopy and X-ray diffraction. The magnetic properties were measured using a SQUID. All films have a FM-like behaviour. In the case of the Cu-doped samples, the magnetic cycles are almost independent of the Cu concentration. Cu atoms are forming CuO and/or substituting Ti in TiO2. The thermal treatment in air promotes the CuO segregation. Since CuO is antiferromagnetic, the magnetic signals present in the films could be assigned to this Cu substitutionally replacing cations in TiO2.

Torres, C E R; Cabrera, A F; Errico, L A; Navarro, A M M; Renter'ia, M; S'anchez, F H; Duhalde, S

2007-01-01

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Fe-Doped TiO2 Thin Films for CO Gas Sensing  

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Fe-doped TiO2 thin films were prepared by the sol-gel technique on silicon substrate. The thin films were evaluated for detection of carbon monoxide (CO) gas at room temperature. The TiO2 films were characterized by x-ray diffraction (XRD) analysis, field-emission scanning electron microscopy, and ultraviolet-visible (UV) spectroscopy. The characterization revealed that, as the doping concentration was increased, the grain size decreased. XRD patterns revealed the phase transition from rutile to anatase with addition of different percentages (weight/volume) of Fe. The bandgap determined from UV spectroscopy was found to decrease with increasing Fe doping concentration. Fe doping was observed to have a significant effect on the resistivity of the doped TiO2 thin films. The gas sensing behavior of the films was studied by exposure to different concentrations of CO gas with measurement of the electrical resistance. It was observed that Fe-doped (7% weight/volume) TiO2 exhibited high sensitivity and good response/recovery on exposure to CO gas in the concentration range from 100 ppm to 900 ppm in Ar.

Kumar, Mukesh; Kumar, Dinesh; Gupta, Anil Kumar

2014-10-01

38

Self-assembly of ordered mesoporous TiO2 thin films as photoanodes for cathodic protection of stainless steel  

International Nuclear Information System (INIS)

Highlights: ? The ordered mesoporous TiO2 thin films were prepared on FTO substrates. ? The more effective photocathodic protection was observed for mesoporous TiO2 films. ? More negative photopotential was observed for 500 °C-calcined mesoporous TiO2 film. ? The larger photocurrent was observed for mesoporous TiO2 film calcined at 500 °C. - Abstract: In this paper, the ordered mesoporous TiO2 thin films that served as photoanodes for cathodic protection of SUS304 stainless steel (304SS) were prepared through the sol–gel and evaporation-induced self-assembly method. The as-prepared TiO2 thin films were calcined at 350 °C and 500 °C, and then characterized by scanning electron microscopy (SEM), the small-angle X-ray diffraction (SAXD) as well as the wide-angle X-ray powder diffraction (WAXD). Moreover, the photoelectrochemical properties of the mesoporous TiO2 thin films such as the open circuit potential (OCP), the photocurrent spectra as well as the Tafel polarization curves were also measured. The results showed that the more negative photopotential was observed for the mesoporous TiO2 films compared to the TiO2 films without mesoporous structures. Besides, the mesoporous TiO2 films calcined at 500 °C exhibited the more negative photopotential and larger photocurrent than that calcined at 350 °C. In conclusion, the mesoporous TiO2 esoporous TiO2 films could provide the effective photogenerated cathodic protection for 304SS.

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Reactive direct current magnetron sputtered TiO2 thin films with amorphous to crystalline structures  

International Nuclear Information System (INIS)

TiO2 thin films were deposited on soda-lime glass substrates by reactive direct current magnetron sputtering in a mixture of pure argon and oxygen. The influence of both the deposition time, td, and the post-annealing treatments on the films morphology, composition and structure was analyzed by scanning electron microscopy, ellipsometry, X-ray photoelectrons spectroscopy, X-ray diffraction (XRD) and Raman spectroscopy. Amorphous TiO2 was obtained for the shortest deposition time, td = 15 min. Increasing td up to 30 min, poorly crystallized anatase and rutile phases were formed together with amorphous TiO2, as was revealed by complementary XRD patterns and Raman spectra. For longer td, the growth of the anatase phase dominates that of the rutile phase. The post-annealing treatment of the films in air at 450 oC. induced the complete crystallization of the films leading to mainly anatase films for all the deposition times. All these results show the feasibility to fabricate stoichiometric TiO2 thin films with amorphous to crystalline structures by means of soft fabrication conditions: low substrate temperature and moderate annealing treatment

40

Energy transfer in the photoexcitation of Sm3+-implanted TiO2 thin films  

International Nuclear Information System (INIS)

High-quality nanocrystalline TiO2 thin films of anatase phase were prepared by using the atomic layer deposition technique and implanted with Sm3+ ions. After the annealing of the films a band-to-band optical excitation of TiO2 at low temperatures led to a broadband excitonic emission superposed by a Sm3+-specific emission series of a well-pronounced fine structure. At higher temperatures (>250 K) only the Sm3+ emission dominates. The fine structure of Sm3+ ions indicates that the Sm3+ ions occupy regular sites in the host material. The direct and indirect (retarded) channels of formation of the excitonic states were concluded from the decay kinetics of the emission spectra of Sm3+-doped TiO2. The energy transfer from the host matrix to the Sm3+ ions is demonstrated and the participation of bound excitonic states in the energy transfer process discussed

 
 
 
 
41

Structural Analysis of RF Sputtered TiO2 Thin Film on Cu Substrate for Various Annealing Temperatures  

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Full Text Available The structural parameters of RF sputtered TiO2 thin film deposited on Cu substrates was tested using XRD spectra. Prepared TiO2 thin film was polycrystalline nature with the mixture of cubic, orthorhombic and tetragonal phases. Orthorhombic phase was preferentially grown on Cu substrate. The crystallite size of the TiO2 thin film was varied depends on the orientations and overall decreased crystallite size was noticed upto 300 °C. The observed residual stress was compressive nature as dominated at all temperature other than 400°C. Crystal defects such as dislocation density was high for cubic phase of TiO2 at higher annealing temperature. Overall, the annealing temperatures influenced the structural parameters with respect to the observed orientations of TiO2 thin film on Cu substrates.

Shanmugan S

2014-08-01

42

Synthesis of photosensitive nanograined TiO2 thin films by SILAR method  

International Nuclear Information System (INIS)

Nanocrystalline TiO2 thin films are deposited by simple successive ionic layer adsorption and reaction (SILAR) method on glass and fluorine-doped tin oxide (FTO)-coated glass substrate from aqueous solution. The as-deposited films are heat treated at 673 K for 2 h in air. The change in structural, morphological and optical properties are studied by means of X-ray diffraction (XRD), selected area electron diffraction (SAED), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), transmission electron microscopy (TEM) and UV-vis-NIR spectrophotometer. The results show that the SILAR method allows the formation of anatase, nanocrystalline, and porous TiO2 thin films. The heat-treated film showed conversion efficiency of 0.047% in photoelectrochemical cell with 1 M NaOH electrolyte.

43

Pulse-induced resistive and capacitive switching in TiO2 thin film devices  

Science.gov (United States)

In this study, we exploit the non-zero crossing current-voltage characteristics exhibited by nanoscale TiO2 based solid-state memristors. We demonstrate that the effective resistance and capacitance of such two terminal devices can be modulated simultaneously by appropriate voltage pulsing. Our results prove that both resistive and capacitive switching arise naturally in nanoscale Pt/TiO2/Pt devices under an external bias, this behaviour being governed by the formation/disruption of conductive filaments through the TiO2 thin film.

Salaoru, Iulia; Khiat, Ali; Li, Qingjiang; Berdan, Radu; Prodromakis, Themistoklis

2013-12-01

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Preparation of the nano structured TiO2 thin film with dip-coating method  

International Nuclear Information System (INIS)

In this investigation, nano structured TiO2 thin films have been prepared through the Dip-coating method. The deposition solution was obtained through the hydrolysis of titanium iso-propoxide under the different range of ph. The transmission of films as an optical parameter investigated with spectrophotometer. Also the Fourier transform Infrared spectra have been used for determination of the structural phase of sample.

45

Growth and characterization of anatase phase TiO2 thin films deposited by magnetron sputtering  

International Nuclear Information System (INIS)

TiO2 thin films were deposited by DC reactive magnetron sputtering on glass substrate. The effect of various deposition conditions viz. substrate temperature, gas pressure, target to substrate distance on the crystallinity and rutile/anatase phase formation is studied in details and the deposition conditions, are optimized such that good quality crystalline anatase films can be prepared with ease. The characterization by x-ray diffraction, Raman spectroscopy and AFM is described. (author)

46

Low Loss Sol-Gel TiO2 Thin Films for Waveguiding Applications  

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Full Text Available TiO2 thin films were synthesized by sol-gel process: titanium tetraisopropoxide (TTIP was dissolved in isopropanol, and then hydrolyzed by adding a water/isopropanol mixture with a controlled hydrolysis ratio. The as prepared sol was deposited by “dip-coating” on a glass substrate with a controlled withdrawal speed. The obtained films were annealed at 350 and 500 °C (2 h. The morphological properties of the prepared films were analyzed by Scanning Electron Microscopy (SEM and Atomic Force Microscopy (AFM. The optical waveguiding properties of TiO2 films were investigated for both annealing temperature using m-lines spectroscopy. The refractive indices and the film thickness were determined from the measured effective indices. The results show that the synthesized planar waveguides are multimodes and demonstrate low propagation losses of 0.5 and 0.8 dB/cm for annealing temperature 350 and 500 °C, respectively.

Alexis Fischer

2013-03-01

47

Electron beam deposited Nb-doped TiO2 toward nanostructured transparent conductive thin films  

International Nuclear Information System (INIS)

Nb-doped TiO2 (TNO) has been widely explored as an alternative transparent conductor. TNO thin films have been fabricated by various deposition methods, and here we demonstrate fabrication by evaporation of sol–gel synthesized TNO source material. A range of NbxTi1?xO2 (x = 0, 0.03, 0.06, 0.12, 0.24) compositions were synthesized, pressed into pellets, and deposited as thin films via electron beam evaporation. The thin films were characterized for composition by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy and for crystallinity by X-ray diffraction for the different Nb contents explored. Transparency, conductivity, and Haacke transparent conductor figure of merit values are reported for the evaporated TNO films as a function of Nb content, substrate heating temperature, and post deposition annealing conditions. Glancing angle deposition (GLAD) is used to demonstrate nanostructuring of evaporated TNO based on physical shadowing. Nanostructured GLAD TNO films of increased morphological complexity can be produced using this method, and could lead to unique transparent conductor device architectures. - Highlights: ? Nb-doped TiO2 sol–gel materials were electron beam evaporated into thin films. ? Thin film Nb-content was correlated with sol–gel Nb-content. ? Transparency and conductivity were related to substrate temperature and Nb-content. ? Nanopillar Nb-doped TiO22 films were fabricated by glancing angle deposition.

48

Diffraction-aided laser-induced microstructuring of thin TiO2 films on glass  

International Nuclear Information System (INIS)

Thin films of TiO2 are deposited by magnetron sputtering on glass substrate and are irradiated by ultraviolet radiation using a KrF excimer laser. These thin films are patterned with a razor blade placed in the way of the radiation. When the fluence is in the 1250-1550 mJ/cm2 range, a regular structure appears, with controlled ablation of the films. It is shown that above a critical local fluence, the ablated depth varies linearly with the local fluence. The proportionality factor is shown to be equal to two photons per evaporated molecule

49

Structural and optical properties investigation of DC magnetron sputtered ?-TiO2 thin film  

Science.gov (United States)

Thin films of monoclinic titanium oxide phase (?-TiO2) have been grown on glass substrate using DC magnetron sputtering technique. The effect of oxygen conditions on the films stoichiometry, growth rate, structure, molecular mode of vibration and optical properties has been investigated. An improvement in stoichiometric ratio (O/Ti) has been observed with the increase of oxygen content in the synthesized chamber. XRD patterns demonstrated the polycrystalline nature of the deposited films with (2bar11) preferential orientation of ?-TiO2 phase. In the FTIR analysis, a dominant peak at 868 cm-1 wavenumbers corresponding to the longitudinal optical (LO) mode of monoclinic TiO2 phase was observed at 10% oxygen condition. It shifted to 880 cm-1 wavenumbers at higher oxygen fractions, illustrated the rise of oxygen concentration in the grown films. The influence of various oxygen conditions on transmittance/extinction coefficient, band gap and refractive index of TiO2 (B) phase is reported.

Khan, Shakil; Ahmed, Ishaq; Shah, A.

2014-10-01

50

Photocatalysis of Thin Films of TiO2 on Al2O3 Substrates  

Science.gov (United States)

Titanium dioxide (TiO2) has grown to be one of the most promising photocatalysts in recent years because of extensive applications in renewable and clean energy. The rise in demand for these new energies has driven an increase in research on metal oxides and their properties. Our interest in growing the rutile structure of TiO2 stems from its lower excitation energy (3.0 eV) when compared to anatase (3.2 eV), which indicates it has better activity in the visible portion of the spectrum. It has been shown that sapphire (Al2O3) substrates are conducive to epitaxial rutile growth. In this study, we measured the photocatalytic activity of thin films of TiO2 on r-Al2O3 (1 -1 0 2) substrates. We used PLD and MBE to grow the films, which were characterized using XPS and AFM. Photoactivity was measured via the decomposition of methyl orange on the film's surface using a UV/VIS spectrophotometer. The decomposition of this organic compound is driven by oxidation-reduction reactions on the surface of the TiO2 film. From this, we calculated the charge carrier diffusion length and compared it to that of anatase.

Turbay, David; Luttrell, Timothy; Batzill, Matthias

2013-03-01

51

Reaction of Ru(II) diazafluorenone compound with nanocrystalline TiO2 thin film.  

Science.gov (United States)

The Ru(II) compounds [Ru(bpy)(2)(mcbH)](2+) and [Ru(bpy)(2)(dafo)](2+), bpy is 2,2'-bipyridine where mcbH is 3-(CO(2)H)-2,2'-bipyridine and dafo is 4,5-diazafluoren-9-one, were synthesized, characterized, and anchored to nanocrystalline mesoporous TiO(2) thin films for excited state and interfacial electron transfer studies. X-ray crystallographic studies of [Ru(bpy)(2)(mcbH)](PF(6))(Cl) revealed a long Ru-N distance to the unsubstituted pyridine ligand of mcbH. Reaction of [Ru(bpy)(2)(dafo)](2+) with TiO(2) thin films resulted in interfacial chemistry. The IR, (1)H NMR, UV-vis, and photoluminescence spectral data indicated a room-temperature ring-opening reaction of the dafo ligand of [Ru(bpy)(2)(dafo)](2+) that ultimately yielded a carboxylate group in the 3-position of bipyridine anchored to TiO(2). Comparative reactions of [Ru(bpy)(2)(mcbH)](2+) with TiO(2) were performed and support this conclusion. In regenerative photoelectrochemical solar cells with 0.5 M LiI/0.05 M I(2) in acetonitrile, photocurrent action spectra were observed for both sensitized materials. The incident photon-to-current efficiency (IPCE) was significantly lower for Ru(bpy)(2)(dafo)/TiO(2), behavior attributed to a lower excited-state injection yield. PMID:20701276

Heuer, William B; Xia, Hai-Long; Abrahamsson, Maria; Zhou, Zhen; Ardo, Shane; Narducci Sarjeant, Amy A; Meyer, Gerald J

2010-09-01

52

Microstructure and Transport properties of epitaxial VO2 thin films on TiO2 substrates  

Science.gov (United States)

Vanadium oxides are paradigms of strongly correlated oxides and have attracted attention because of the metal insulator transitions (MIT) that several of the oxides and sub-oxides exhibit. In particular, VO2 has a metal--semiconductor transition at 340 K. This transition in VO2 combines the properties of a pure Mott Hubbard electronic transition with those of a Peierls structural transition. The Mott transition is responsible for the extreme speed of the optical switching that has been observed (faster than 100 fs). Understanding this transition and how to control it remains a challenge for both theory and experimental physics. We used a novel deposition technique, Reactive Bias Target Ion Beam Deposition, to grow 40 nm epitaxial VO2 thin films on rutile TiO2 substrates with various crystal orientations. X-ray diffraction (XRD) was used to explore the epitaxy of VO2 and we found that all VO2 thin films on TiO2 substrates showed tetragonal symmetry at room temperature due to the constrain from rutile substrates. We also characterized the metal-insulator transition of VO2 films as the function of the crystal orientation of rutile TiO2. We also characterized the anisotropy of VO2 thin films. In collaboration with Kevin West and Stuart Wolf, University of Virginia.

Lu, Jiwei

2008-10-01

53

Slurry components of TiO2 thin film in chemical mechanical polishing  

Science.gov (United States)

A chemical mechanical polishing (CMP) process was selected to smooth TiO2 thin film surface and improve the removal rate. Meanwhile, the optimal process conditions were used in TiO2 thin film CMP. The effects of silica sols concentration, slurry pH, chelating agent and active agent concentration on surface roughness and material removal rate were investigated. Our experimental results indicated that we got lower surface roughness (1.26 Å, the scanned area was 10 × 10 ?m2) and higher polishing rate (65.6 nm/min), the optimal parameters were: silica sols concentration 8.0%, pH value 9.0, active agent concentration 50 mL/L, chelating agent concentration 10 mL/L, respectively.

Bo, Duan; Jianwei, Zhou; Yuling, Liu; Chenwei, Wang; Yufeng, Zhang

2014-10-01

54

X-ray absorption and emission spectroscopy of TiO2 thin films with modified anionic sublattice  

International Nuclear Information System (INIS)

Crystallographic and optical properties as well as electronic structure of titanium dioxide thin films with modified anionic sublattice, i.e., non-stoichiometric, undoped and nitrogen doped thin films of TiO2?x and TiO2?x:N, were studied by means of X-ray diffraction, optical spectrophotometry, X-ray absorption and emission spectroscopy. We demonstrate that TiO2?x films undergo a gradual evolution of the crystallographic structure accompanied by the progressive change in interatomic distances with the preserved local symmetry and nearly unchanged effective 3d charge of Ti ions. At a certain degree of oxygen deficit an abrupt change in all the properties studied can be seen. Amorphisation, possible Ti precipitation and increased optical absorption over the visible range correlates well with a significantly higher 3d band occupancy derived from XES for TiO2?x. Thin films of TiO2?x:N demonstrate gradual evolution of the local structure and charge redistribution upon increased level of nitrogen doping. - Highlights: • Thin films of TiO2?x and TiO2?x:N were deposited by dc-pulsed reactive sputtering. • Studies with: XRD, optical spectrophotometry, XAS and XES measurements have been carried out. • TiO2?x shows preserved local symmetry and nearly unchanged effective 3d charge of Ti ions. • At certain degree of oxygen deficit in TiO2?x an abrupt change in all the properties studied is seen. • TiO2?x:N shows a gradual evolution of the local structure and charge from TiO2 to TiN

55

Luminescence properties of Sm3+-doped TiO2 thin films prepared by laser ablation  

International Nuclear Information System (INIS)

Samarium-doped anatase TiO2 (A-TiO2 : Sm3+) and rutile TiO2 (R-TiO2 : Sm3+) single phase thin films were fabricated on silicon substrates by laser ablation, resulting from the control of O2 pressures during ablation. These thin films show the Sm3+-related emissions in the visible and in the infrared wavelength regions. Visible photoluminescence (PL) and cathodoluminescence originating from the 4G5/2 ? 6HJ intra-4f transitions in Sm3+ ions were observed at room temperature. The results of the photoluminescence excitation spectroscopy measurement imply that the Sm3+ emissions are due to the indirect excitation of the Sm3+ ions through an energy transfer process from electron-hole pairs generated in the TiO2 hosts. Intense 1.2 ?m PL emissions originating from 4G5/2 ? 6F9/2 and 6F7/2 ? 6H5/2 transitions were also observed. A clear difference in the fine structure of the PL spectra between the A-TiO2 : Sm3+ and the R-TiO2 : Sm3+ thin films was observed, resulting from the difference in the Sm3+ configuration in the host crystal matrices.

56

Synthesis and characterization of TiO2 thin films coated on metal substrate  

International Nuclear Information System (INIS)

Nanostructured titanium dioxide (TiO2) thin films have been prepared on metal substrates using a facile layer-by-layer dip-coating method. The phase structure and morphologies of preparing samples were characterized by means of X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results confirm that films are highly crystalline anatase TiO2 and free from other phases of titanium dioxide. Scanning electron microscopy (SEM) shows that the nanoparticles are sintered together to form a compact structure. The electrical properties of samples were investigated by cutternt-voltage analysis, the result indicates that a rectifying junction between the nanocrystalline TiO2 film and metal substrate was formed. The photoelectrochemical characteristics recorded under 1.5 AM illumination indicates that the as-fabricated thin film electrode possesses the highest photocurrent density at 450 deg. C, which is 1.75 mA/cm2 at 0 V vs. Ag/AgCl.

57

Microanalysis of Pd and V-doped TiO2 thin films prepared by sputtering  

International Nuclear Information System (INIS)

Thin films of TiO2 doped with vanadium and palladium, prepared by the magnetron sputtering method, were studied by means of X-ray diffraction (XRD), Scanning Electron Microscopy with Energy Disperse Spectrometer (SEM-EDS) and Atomic Force Microscopy (AFM). Investigations have brought important information about microstructure due to dopant incorporation in the TiO2 host lattice. Directly after deposition thin films were XRD-amorphous and SEM investigations did not reveal details on the microstructure. Analysis of the topography of prepared thin films required application of Atomic Force Microscope. The AFM images show that as-deposited sample was dense with grain sizes varied in the range of 5.5 nm-10 nm, that indicated high quality nanocrystalline behavior. Additional annealing results in the formation of three phases in the thin film, e.g. (Ti,V)O2 - solid solution, PdO and metallic inclusions of Pd. SEM-EDS system allowed analysis of the elemental composition, especially the V one, which lines have not been evidenced in the XRD diffraction pattern. EDS maps show homogenous distribution of elements Ti, O, V, Pd in prepared thin films

58

Optical properties of TiO2 thin films deposited on polycarbonate by ion beam assisted evaporation  

International Nuclear Information System (INIS)

TiO2 thin films were deposited on polycarbonate (PC) substrate by ion beam assisted evaporation. The grain size increased with the ion anode voltage and film thickness. The TiO2 thin films had an amorphous structure. Moire deflectometry was used to measure the nonlinear refractive indices of TiO2 thin films on PC substrates. The nonlinear refractive index was measured to be of the order of 10-8 cm2 W-1 and a change in refractive index was of the order of 10-5. Dense TiO2 films exhibited high linear refractive indices, red-shift of the optical absorbance, and absorbance in the near-IR region.

59

Electrochromic investigation of sol-gel-derived thin films of TiO2-V2O5  

International Nuclear Information System (INIS)

Thin films of TiO2 and TiO2-V2O5 were obtained by dip-coating sol-gel technique. Sols were prepared from titanium ethoxide and inorganic V2O5 sol received by dissolution of vanadium pentoxide in hydrogen peroxide. Sol-gel TiO2 and TiO2-V2O5 films are deposited on conductive glass substrates. TiO2 and TiO2-V2O5 systems were characterized by FTIR and Raman spectroscopy. Optical transmittance measurements were carried out. Electrochromic characterization was recorded by cyclic voltammetry using three-electrode arrangement. All samples demonstrated electrochromic effect

60

Characteristics and properties of TiO2 thin film photocatalysts fabricated by sol-gel process  

International Nuclear Information System (INIS)

Transparent TiO2 thin films have been prepared through a sol-gel process on the surface of glass pipes and characterized by XRD, Raman, UV-Vis and XPS in this paper. Results show that the absorption of the samples calcined at 773 K is obviously stronger than that calcined at 573 K between 290 and 330 nanometer. The films heated at 573 K are still in amorphous state but show good photocatalytic activities. With the increasing of heating temperature, the photocatalytic activities of TiO2 films decrease gradually. In addition, photocatalytic activity of TiO2 films increases gradually with the increment of coating cycles. (authors)

 
 
 
 
61

Self-Cleaning Properties of Vanadium Doped TiO2 Sol-Gel Derived Thin Films  

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Full Text Available 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.

Mehrnoush Mokhtarimehr

2013-07-01

62

EFFECT OF ISOTHERMAL ANNEALING ON PROPERTIES OF TiO2 THIN FILMS TOWARDS MOS CAPACITOR APPLICATIONS  

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Full Text Available The effect of isothermal annealing on structural and electrical properties of TiO2 thin films has been investigated. The TiO2 thin films were deposited at 350 ?C using spray pyrolysis technique. The structural studies were carried out using XRD and Raman spectroscopy. The electrical characteristics were studied on the fabricated MOS structure and the parameters such as ideality factor, saturation current density and zero bias barrier height were obtained. It was found that isothermal annealing has improved the structural as well as electrical parameters of TiO2 compared to the values predicted in literature.

H D CHANDRASHEKARA

2014-04-01

63

A short literature survey on iron and cobalt ion doped TiO2 thin films and photocatalytic activity of these films against fungi  

International Nuclear Information System (INIS)

Highlights: ? Co or Fe doped TiO2 thin films were prepared by sol–gel method. ? We obtained lower Eg values for Fe-doped and Co-TiO2 thin films. ? Doping greatly affected the size and shape of the TiO2 nanoparticles. ? Photocatalytic killing effect of the doped TiO2 thin films on C. albicans and A. niger was significantly higher than undoped TiO2 thin film for short exposure periods. - Abstract: In this study, a short recent literature survey which concentrated on the usage of Fe3+ or Co2+ ion doped TiO2 thin films and suspensions were summarized. Additionally, a sol–gel method was used for preparation of the 2% Co or Fe doped TiO2 thin films. The surface of the prepared materials was characterised using scanning-electron microscopy (SEM) combined with energy dispersive X-ray (EDX) analysis and band gap of the films were calculated from the transmission measurements that were taken over the range of 190 and 1100 nm. The Eg value was 3.40 eV for the pure TiO2, 3.00 eV for the Fe-doped TiO2 film and 3.25 eV for Co-TiO2 thin film. Iron or cobalt doping at lower concentration produce more uniformed particles and doping greatly affected the size and shape of the TiO2 nanoparticles. Photocatalytic killing effect of the 2% Co doped TiO2 thin film on Candida albicans was significantly higher than Fe doped TiO2 thin film for short and long exposure periods. Doped thin films were more effective on Aspergillus niger for short exposure periods.

64

Enhanced photocatalytic activities of Ta, N co-doped TiO2 thin films under visible light  

International Nuclear Information System (INIS)

Ta, N co-doped TiO2 thin films in an anatase form were fabricated by radio-frequency (RF) magnetron sputtering method, and their photoelectrochemical and photocatalytic properties were compared to those of non-doped TiO2 and N-doped TiO2 thin films. The incident photon-to-current conversion efficiency (IPCE) spectra indicated the suppression of the isolated N 2p band formation but the enhancement hybridization of valence band with N 2p band in Ta, N co-doped TiO2, compared to N-doped TiO2. The changes in IPCE spectra in the presence of reductants, such as SCN-, Br- and I-, clearly proved that the holes produced in the N 2p band of Ta, N co-doped TiO2 under visible light had higher oxidation power than those of N-doped TiO2. Moreover, it was shown that the photocatalytic oxidation activity evaluated by the oleic acid decomposition and photoinduced hydrophilic conversion were enhanced by the Ta, N co-doping under visible light, when compared to N single doping. The enhancement of photocatalytic performances by the Ta, N co-doping under visible light was also supported by the first principle calculation, indicating the positive shift of the N 2p band in Ta, N co-doped TiO2, compared to N-doped TiO2

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Enhanced photocatalytic activity of TiO2 nano-structured thin film with a silver hierarchical configuration  

International Nuclear Information System (INIS)

of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT > TA > AA > TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO2 thin film

66

Tio2 Nanoparticles Coated With Porphyrin Dye Thin Film As Fluorescence Gas Sensor  

International Nuclear Information System (INIS)

This research explores the possibility of using fluorescence technique to detect the presence of volatile organic compounds based on a single sensing material. The material used was TiO2 nanoparticles coated with porphyrin dye. The TiO2 nanoparticles colloid is in a sol-gel form synthesized from titanium (IV) ethoxide in ethanol with addition of potassium chloride (KCl) as stabilizer. TiO2 nanoparticles were then coated with porphyrin dye, Manganese (III) 5,10,15,20 tetra (4-pyridyl)-21H, 23H porphine chloride tetrakis (meta chloride). The coated nanoparticles were deposited on quartz substrate using self-assembly through dip coating technique. The sensing properties of the thin film toward volatile organic compounds; ethanol, acetone, cyclohexane and 2-propanol were studied using luminescence spectrometer. It was found that the thin film produced different emission spectra peaks for different volatile organic compounds (VOCs). Hence, it eases chemical identification process and potentially be use as fluorescence gas sensor. (author)

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Optimization of experimental parameters in preparing multinanoporous TiO2 thin films by the anodic oxidation method  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english The anodic oxidation method has been applied to the preparation of multinanoporous TiO2 thin films. The experimental parameters, including the electrolyte nature, oxidation voltage, and oxidation time have been carefully controlled. Their influence on the structure, morphology and photocatalytic act [...] ivity of the prepared TiO2 films has been evaluated by measuring the current density. The result showed that there was a relatively wide range of preparation conditions, and the internal relationship between the structure and the photocatalytic properties of the TiO2 films was analyzed.

Gracien B., Ekoko; Joseph K-K., Lobo; Omer M., Mvele; Antoine K., Mbongo; Jérémie L., Muswema; Clarisse Z., Lefuni.

2013-08-01

68

Optimization of experimental parameters in preparing multinanoporous TiO2 thin films by the anodic oxidation method  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english The anodic oxidation method has been applied to the preparation of multinanoporous TiO2 thin films. The experimental parameters, including the electrolyte nature, oxidation voltage, and oxidation time have been carefully controlled. Their influence on the structure, morphology and photocatalytic act [...] ivity of the prepared TiO2 films has been evaluated by measuring the current density. The result showed that there was a relatively wide range of preparation conditions, and the internal relationship between the structure and the photocatalytic properties of the TiO2 films was analyzed.

Gracien B., Ekoko; Joseph K-K., Lobo; Omer M., Mvele; Antoine K., Mbongo; Jérémie L., Muswema; Clarisse Z., Lefuni.

69

Preparation of TiO2 Thin Film Photocatalyst by High-rate Low-temperature Sputtering Method  

Science.gov (United States)

After depositing an ultra-thin metallic Ti film by sputtering, we repeated the process of exposing the still active plasma gas for high-rate low-temperature deposition of a metal compound film, thereby successfully fabricating a thin film of TiO2 with photocatalytic properties. The TiO2 thin film produced using the present method exhibited approximately 15 times the deposition rate of DC reactive magnetron sputtering, yielding a crystalline structure using an unheated substrate (approximately 40°C).

Noguchi, Daisuke; Okutsu, Kana; Onitsuka, Saori; Kawano, Yoshihiko; Sei, Fumihiro

70

Characterization of sol-gel thin films of TiO2-PbO, TiO2-Bi2O3 and TiO2-CeO2 compositions  

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Single and multilayer sol-gel thin films of TiO2-PbO, TiO2-Bi2O3 and TiO2-CeO2 composition were deposited on glasses using the dip coating technique. The precursors included Ti(OPr(i))4 chemically modified by acetyl acetone and diluted in Pr(i)OH and sols of Pb(OAc)2, Bi(NO3)3 5H2O diluted in acetic acid. The TiO2-CeO2 sol was prepared by mixing Ce(NH4)2(NO3)6 in ethanol and then adding Ti(O-iso-C3H7)4. Structure texture and homogeneity of their main constituents was established b...

Aegerter, Michel A.; La Serra, Eliane R.; Martins Rodrigues, Ana Candida; Kordas, George; Moore, Glenn

1990-01-01

71

Effect of annealing temperature on the photocatalytic activity of sol-gel derived TiO2 thin films  

International Nuclear Information System (INIS)

Transparent TiO2 thin films were deposited on glass substrates by a sol-gel dip coating technique, where crystallinity can be achieved at a relatively low annealing temperature. In this sol-gel preparation technique, acetic acid was used as a catalyst. Repetitive dip coating and drying, with a single annealing has made this technique easier to prepare TiO2 thin film with desired thickness within a short period of time. The crystallographic and optical properties of TiO2 films were investigated in detail. The photocatalytic activity was evaluated by the measurement of decomposition of methanol under UV-visible irradiation. The rate of decomposition of gaseous methyl alcohol depends on the structures and surface properties of the TiO2 films. The structure of the TiO2 films, prepared at various annealing temperatures, shows different crystallinities. Although crystallinity has been observed for 300 deg. C annealing temperature, it improved with increasing annealing temperature. The average transmittances of the TiO2 films slightly decrease with the increase of the annealing temperature in the range of 900-380 nm. The optical transmission edge of the TiO2 films, annealed at different annealing temperatures shifts toward higher wavelength with higher annealing temperature. All the as-deposited TiO2 films successfully photocatalyzed methanol to CO2 and H2O, measured by Fourier transform infrared spectrometer. The decomposition efficiency of TiO2 films increased with decrease of annealing temperature. The surface morphology of all the samples was investigated by field emission scanning electron microscopy and atomic force microscopy measurements. The higher photocatalytic activity of the sample prepared at lower annealing temperature was explained by the effect of more porous structure with smaller grains and open surface morphology of the sample

72

Photocatalytic activity and stability of TiO2 and WO3 thin films  

International Nuclear Information System (INIS)

Photocatalysis represents a viable option for complete degrading the dye molecules resulted in the textile industry, up to products that do not represent environmental threats. The photocatalytic degradation of methyl orange has been investigated using TiO2, WO3 and mixed thin films. The photodegradation efficiency is examined in correlation with the experimental parameters (irradiation time, H2O2 addition and stability), along with the morphology and crystallinity data. The H2O2 addition increases the photodegradation efficiency by providing additional hydroxyl groups and further reducing the recombination of the electron–hole pairs by reacting with the electrons at the catalyst interface. To test the stability of the photocatalytic films in long time running processes, batch series of experiments were conducted using contact periods up to 9 days. The results show that the thin films maintained their photocatalytic properties confirming their stability and viability for up-scaling. Highlights: ? TiO2, WO3 and mixed thin films ? We tested the photocatalytic activity and photocatalyst stability over a period up to 9 days of continuous irradiation. ? The influence of medium pH and oxidizing agent (H2O2) was analyzed.

73

TiO2 thin film growth using the MOCVD method  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Titanium oxide (TiO2) thin films were obtained using the MOCVD method. In this report we discuss the properties of a film, produced using a ordinary deposition apparatus, as a function of the deposition time, with constant deposition temperature (90 °C), oxygen flow (7,0 L/min) and substrate tempera [...] ture (400 °C). The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and visible and ultra-violet region spectroscopy (UV-Vis). The films deposited on Si (100) substrates showed the anatase polycrystalline phase, while the films grown on glass substrates showed no crystallinity. Film thickness increased with deposition time as expected, while the transmittance varied from 72 to 91% and the refractive index remained close to 2.6.

M.I.B., Bernardi; E.J.H., Lee; P.N., Lisboa-Filho; E.R., Leite; E., Longo; J.A, Varela.

2001-07-01

74

TiO2 thin film growth using the MOCVD method  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Titanium oxide (TiO2) thin films were obtained using the MOCVD method. In this report we discuss the properties of a film, produced using a ordinary deposition apparatus, as a function of the deposition time, with constant deposition temperature (90 °C), oxygen flow (7,0 L/min) and substrate tempera [...] ture (400 °C). The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and visible and ultra-violet region spectroscopy (UV-Vis). The films deposited on Si (100) substrates showed the anatase polycrystalline phase, while the films grown on glass substrates showed no crystallinity. Film thickness increased with deposition time as expected, while the transmittance varied from 72 to 91% and the refractive index remained close to 2.6.

M.I.B., Bernardi; E.J.H., Lee; P.N., Lisboa-Filho; E.R., Leite; E., Longo; J.A, Varela.

75

TiO2 thin film growth using the MOCVD method  

Directory of Open Access Journals (Sweden)

Full Text Available Titanium oxide (TiO2 thin films were obtained using the MOCVD method. In this report we discuss the properties of a film, produced using a ordinary deposition apparatus, as a function of the deposition time, with constant deposition temperature (90 °C, oxygen flow (7,0 L/min and substrate temperature (400 °C. The films were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, atomic force microscopy (AFM and visible and ultra-violet region spectroscopy (UV-Vis. The films deposited on Si (100 substrates showed the anatase polycrystalline phase, while the films grown on glass substrates showed no crystallinity. Film thickness increased with deposition time as expected, while the transmittance varied from 72 to 91% and the refractive index remained close to 2.6.

M.I.B. Bernardi

2001-07-01

76

Preparation of TiO 2 thin films from autoclaved sol containing needle-like anatase crystals  

Science.gov (United States)

A new inorganic sol-gel method was introduced in this paper to prepare TiO 2 thin films. The autoclaved sol with needle-like anatase crystals was synthesized using titanyl sulfate (TiOSO 4) and peroxide (H 2O 2) as starting materials. The transparent anatase TiO 2 thin films were prepared on glass slides from the autoclaved sol by sol-gel dip-coating method. A wide range of techniques such as Fourier transform infrared transmission spectra (FT-IR), X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), scanning electron microscopes, X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectrum were applied to characterize the autoclaved sol and TiO 2 thin films. The results indicate that the autoclaved sol is flavescent, semitransparent and stable at room temperature. The anatase crystals of TiO 2 films connect together to form net-like structure after calcined and the films become uniform with increasing heating temperature. The surface of the TiO 2 films contain not only Ti and O elements, but also a small amount of N and Na elements diffused from substrates during heat treatment. The TiO 2 films are transparent and their maximal light transmittances exceed 80% under visible light region.

Ge, Lei; Xu, Mingxia; Fang, Haibo; Sun, Ming

2006-11-01

77

Effect of Annealing on Structure, Morphology, Electrical and Optical Properties of Nanocrystalline TiO2 Thin Films  

Directory of Open Access Journals (Sweden)

Full Text Available Semi-transparent and highly conducting nanostructured titanium oxide thin films have been prepared by sol-gel method. Thin films of TiO2 deposited on glass substrates using spin coating technique and the effect of annealing temperature (400 - 700 °C on structural, microstructural, electrical and optical properties were studied. The X-ray diffraction and Atomic force microscopy measurements confirmed that the films grown by this technique have good crystalline tetragonal mixed anatase and rutile phase structure and homogeneous surface. The study also reveals that the rms value of thin film roughness increases from 7 to 19 nm. HRTEM image of TiO2 thin film (annealed at 700 °C shows that a grain of about 50 - 60 nm in size is really aggregate of many small crystallites of around 10 - 15 nm. Electron diffraction pattern shows that the TiO2 films exhibited tetragonal structure. The surface morphology (SEM of the TiO2 film showed that the nanoparticles are fine with an average grain size of about 50 - 60 nm. The optical band gap slightly decreases from 3.26 - 3.24 eV and the dc electrical conductivity was found in the range of 10-6 to 10-5(?·cm-1 when the annealing temperature is changed from 400 to 700 °C. It is observed that TiO2 thin film annealed at 700 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.

B.T. Raut

2011-01-01

78

Photocatalytic decomposition of diclofenac potassium using silver-modified TiO2 thin films  

International Nuclear Information System (INIS)

The effects of silver insertion on the TiO2 photocatalytic activity for the degradation of diclofenac potassium were reported here. Techniques such as X-ray diffraction, scanning electron microscopy and UV-Vis spectroscopy were used to comprehend the relation between structure and properties of the silver-modified TiO2 thin films obtained by the sol-gel method. The lattice parameters and the crystallinity of TiO2 anatase phase were affected by inserted silver, and the film thickness increased about 4 nm for each 1 wt.% of silver inserted. The degradation of diclofenac potassium and by-products reached an efficiency of 4.6 mgC W-1 when the material was modified with silver. Although the first step of degradation involves only the photochemical process related to the loss of the chlorine and hydrogen atoms. This cyclization reaction leads to the formation of intermediate, which degradation is facilitated by the modified material

79

Growth of TiO2 Thin Film on Various Substrates using RF Magnetron Sputtering  

International Nuclear Information System (INIS)

The conductivity of Titanium Dioxide (TiO2) thin film fabricated using Radio Frequency (RF) Magnetron Sputtering on Silicon (Si), Indium doped--Tin Oxide (ITO) and microscope glass (M) substrates is presented in this paper. The dependant of thin film thickness and type of substrate been discussed. TiO2 was deposited using Ti target in Ar+O2(45:10) mixture at 250 W for 45, 60, 75, 90, 105 and 120 minute. Resultant thickness varies from 295 nm to 724 nm with deposition rate 6.4 nm/min. On the other hand, resistivity, Rs value for ITO substrate is between 5.72x10-7 to 1.54x10-6?.m, Si substrate range is between 3.52x10-6 to 1.76x10-5?.m and M substrate range is between 99 to 332 ?.m. The value of resistivity increases with the thickness of the thin film.

80

Preparation and Characterization of TiO2-SiO2 Thin Films  

International Nuclear Information System (INIS)

Sol-gel, is a method being used for preperation of thin films for a very long time. Its easy application process with easily available equipments that are used and the low process temperatures are the reasons for being utilized this much. A very common thin film type, TiO2-SiO2, that has been used in optical applications for a long time, is the basic structure involved in this research. In this work, the titania (TiO2) and the silica (SiO2) solutions which had been preperated seperately, were mixed with different ratios, and the differences between these mixtures that might had been occurred were investigated. The glass substrates, which had been cleaned with a special method were dipped into the mixed solutions with a constant speed which they had exactly the same while they were being withdrawned. After being dried in mid-air for a while, they were heated to 150 degree and then were dipped again. Once the number of the layers that was required is reached with reprocesses, the substrates were heated to 600 degree. The optical and the structural properties of the films deposited on the substrates were investigated. Some differences in optical properties of these films that were produced from different ratios of solutions were observed as result

 
 
 
 
81

Novel fabrication of net-like and flake-like Fe doped TiO 2 thin films  

Science.gov (United States)

New morphologies of net-like and flake-like TiO 2 thin films with different concentrations of Fe dopant were successfully fabricated by micro-arc oxidation (MAO) process of Ti plates and a subsequent chemical treatment of the as-prepared MAO-TiO 2 thin films. It was found that Fe ions can be easily introduced into the MAO-TiO 2 samples with the increase concentration of K 4(FeCN) 6·3H 2O precursor, and the amount of Fe determined the morphologies of TiO 2 thin films after chemical treatment; net-like morphology was observed with low Fe dopant, while it transformed to a flake-like one when Fe exceeds 1.7 at.%. UV-vis spectroscopy test showed that the absorption edge of the Fe ions doped TiO 2 thin films with new morphologies has an obvious red shift.

Ren, Fujian; He, Kai; Ling, Yunhan; Feng, Jiayou

2011-09-01

82

Lifetime of electrochromism of amorphous WO3-TiO2 thin films  

International Nuclear Information System (INIS)

In this paper, the degradation of the electrochromism of amorphous WO3 and WO3-TiO2 films prepared by electron-beam deposition are studied. The lifetime of the WO3-TiO2 films is five times longer than that of the WO3 films. SIMS and XPS analyses have revealed that lithium accumulates as OLi in the WO3 films, but that it cannot accumulate in the WO3-TiO2 film. Ols electron energy loss spectroscopy (EELS) spectra have indicated that the change of the electronic structure for the WO3-TiO2 film by coloration is smaller than that for the WO3 film. The increase of plasmon energy has been obtained in low loss EELS spectrum and the increase of the bond length in the WO3-TiO2 film has been measured by Raman spectrum. From these results, the number of the defect bonds as a trapping site of lithium is reduced and the bond length of W-O decreases in the WO3-TiO2 films. The authors conclude that lithium cannot accumulate in the structure of the WO3-TiO2 film and that the structure gives a prolonged lifetime to the electrochromism

83

Influence of Nb dopant on the structural and optical properties of nanocrystalline TiO2 thin films  

International Nuclear Information System (INIS)

Highlights: ? We coated Nb-doped TiO2 films on glazed porcelain via sol–gel dip coating method. ? We examined coatings by degradation of MB solution and optical light transmittance. ? Coatings show enhanced photo-catalytic activity in 1 mol% Nb. ? Nb doping inhibited the grain growth, and which are found to inhibit the anatase to rutile phase transformation. - Abstract: In this study, preparation of Nb-doped (0–20 mol% Nb) TiO2 dip-coated thin films on glazed porcelain substrates via sol–gel process has been investigated. The effects of Nb on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films was examined by atomic force microscope and X-ray photoelectron spectroscopy. XRD and Raman study showed that the Nb doping inhibited the grain growth. The photo-catalytic activity of the film was tested on degradation of methylene blue. Best photo-catalytic activity of Nb-doped TiO2 thin films were measured in the TiO2–1 mol% Nb sample. The average optical transmittance of about 47% in the visible range and the band gap of films became wider with increasing Nb doping concentration. The Nb5+ dopant presented substitutional Ti4+ into TiO2 lattice.

84

Phase determination of filtered vacuum arc deposited TiO2 thin films by optical modeling  

International Nuclear Information System (INIS)

Thin films of TiO2 were produced using filtered vacuum arc deposition. Arc currents were 275, 300, 325 A, and the oxygen pressure during deposition was 0.93 Pa. The substrates were glass microscope slides, at temperatures of 25 oC (RT), 200 oC, and 400 oC. Film thickness was in the range 100 to 250 nm, depending on the deposition conditions. Film structure and chemical composition were determined using XRD and XPS analyses, respectively. As-deposited films were amorphous, except to two samples that were found to be crystalline (deposited with 300 A, 325 A at 400 oC), and the crystalline phase was close to that of anatase. All of the films were partially crystallized by annealing in air at 450 oC for 1 h. The O:Ti atomic concentration ratio was in the range 1.6:1-2:1, independent of deposition conditions. The optical parameters, refractive index and the extinction coefficient of the films were determined using variable angle spectroscopic ellipsometry. In addition, the optical transmission of the films were determined in the UV-VIS and IR regions. The average optical transmission in the VIS spectrum was 70-85%, affected by the interference in the film with 90% maxima and 60% minima. The refractive index at ? = 550 nm was in the range 2.4 to 2.7, depending on the deposition conditions and annealing. Using the semi-empirical model of Wemple and DiDomenico for the dielectric function below the interband abielectric function below the interband absorption edge of ionic and covalent solids, the dispersion energy parameters of TiO2 (Eo, Ed) were calculated. The underlying structural order of the amorphous films was inferred by comparing the dispersion energy parameters of the amorphous films with those of crystalline TiO2. As expected, the refractive index of the amorphous films depended on the underlying phase of the film. The optical analyses indicated that the underlying phase of the amorphous films deposited on RT substrates was close to anatase, whereas the underlying phase of the amorphous films deposited on 400 oC substrates and annealed at 450 oC for 1 h consisted of both anatase and rutile. Thus, although the XRD analyses could not indicate the underlying phase of the amorphous films, it could be determined by the optical analyses.

85

Photocatalytic Functional Coating of TiO2 Thin Film Deposited by Cyclic Plasma Chemical Vapor Deposition at Atmospheric Pressure  

Science.gov (United States)

Photocatalytic TiO2 thin films were prepared with titanium tetraisopropoxide (TTIP) using cyclic plasma chemical vapor deposition (CPCVD) at atmospheric pressure. The CPCVD TiO2 films contain carbon-free impurities up to 100 °C and polycrystalline anatase phases up to 200 °C, due to the radicals and ion-bombardments. The CPCVD TiO2 films have high transparency in the visible wavelength region and absorb wavelengths below 400 nm (>3.2 eV). The photocatalytic effects of the CPCVD TiO2 and commercial sprayed TiO2 films were measured by decomposing methylene blue (MB) solution under UV irradiation. The smooth CPCVD TiO2 films showed a relatively lower photocatalytic efficiency, but superior catalyst-recycling efficiency, due to their high adhesion strength on the substrates. This CPCVD technique may provide the means to produce photocatalytic thin films with low cost and high efficiency, which would be a reasonable candidate for practical photocatalytic applications, because of the reliability and stability of their photocatalytic efficiency in a practical environment.

Kwon, Jung-Dae; Rha, Jong-Joo; Nam, Kee-Seok; Park, Jin-Seong

2011-08-01

86

Electrochromic TiO2, ZrO2 and TiO2-ZrO2 thin films by dip-coating method  

International Nuclear Information System (INIS)

Sol-gel processing of TiO2, ZrO2 and mixed Ti/Zr oxide thin films has been studied as application of these coatings in electrochromic devices. Their structural transformations as a function of annealing temperatures were analyzed by XRD and FTIR techniques. Electrochromic behavior of the three kind materials was investigated by cyclic voltammetry and the basic electrochromic characteristics were determined.

87

Layer-by-Layer TiO2/WO3 Thin Films As Efficient Photocatalytic Self-Cleaning Surfaces.  

Science.gov (United States)

New TiO2/WO3 films were produced by the layer-by-layer (LbL) technique and successfully applied as self-cleaning photocatalytic surfaces. The films were deposited on fluorine doped tin oxide (FTO) glass substrates from the respective metal oxide nanoparticles obtained by the sol-gel method. Thirty alternative immersions in pH = 2 TiO2 and pH = 10 WO3 sols resulted in ca. 400 nm thick films that exhibited a W(VI)/Ti(IV) molar ratio of 0.5, as determined by X-ray photoelectron spectroscopy. Scanning electron microscopy, along with atomic force images, showed that the resulting layers are constituted by aggregates of very small nanoparticles (LbL TiO2 films. The TiO2/WO3 thin films exhibited high hydrophilicity, which is enhanced after exposition to UV light, and they can efficiently oxidize gaseous acetaldehyde under UV(A) irradiation. Photonic efficiencies of ? = 1.5% were determined for films constituted by 30 TiO2/WO3 bilayers in the presence of 1 ppm of acetaldehyde, which are ?2 times higher than those observed for pure LbL TiO2 films. Therefore, these films can act as efficient and cost-effective layers for self-cleaning, antifogging applications. PMID:25216058

Patrocinio, Antonio Otavio T; Paula, Leonardo F; Paniago, Roberto M; Freitag, Janna; Bahnemann, Detlef W

2014-10-01

88

Photovoltaic performance improvement of dye-sensitized solar cells based on tantalum-doped TiO2 thin films  

International Nuclear Information System (INIS)

Dye-sensitized solar cells based on a tantalum (Ta)-doped TiO2 thin film prepared by the hydrothermal method show a photovoltaic efficiency of 8.18%, which is higher than that of the undoped TiO2 thin film (7.40%). The Mott-Schottky plot indicates that the Ta-doped TiO2 photoanode shifts the flat band potential positively and increases the electron density. The positive shift of the flat band potential improves the driving force of injected electrons from the LUMO of the dye to the conduction band of TiO2. Furthermore, the increased electron density caused by the Ta-doped TiO2 improves the fill factor of the solar cell. The increased electron density accelerates the transfer rate of electrons in the Ta-doped TiO2 thin films by comparison to undoped films, which is confirmed by intensity-modulated photocurrent spectroscopy measurements.

89

The enhanced conductivity and stability of AZO thin films with a TiO2 buffer layer  

Science.gov (United States)

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 ? cm with the maximum figure merit of 1.92×10-2 ?-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.

Yang, Tianlin; Song, Shumei; Li, Yanhui; Xin, Yanqing; Du, Guiqiang; Lv, Maoshui; Han, Shenghao

2012-12-01

90

Structural and morphological characterization of TiO2 thin films synthesized by spray pyrolysis technique.  

Science.gov (United States)

Thin films of nanocrystalline TiO2 were synthesized by spray pyrolysis technique in the temperature range 300 degrees C to 550 degrees C in steps of 50 degrees C. The films were coated on glass and quartz substrates by ultrasonic nebulization of titanium-oxy-acetyl acetonate followed by pyrolysis. The structure and morphology of the thin films were characterized by X-ray Diffraction (XRD), Raman Spectroscopy (RS) and Scanning Electron Microscopy (SEM), while the optical band gaps were measured by Spectroscopic Ellipsometry (SE) and UV-Visible spectroscopy. XRD investigations revealed distinct crystal structures of the films synthesized above and below 300 degrees C. While films grown at substrate temperature 300 degrees C were amorphous, those grown at 350 dgrees C and above showed tetragonal anatase crystal structure. The morphological investigations from SEM showed that the films deposited at 350 degrees C were porous and exhibited flower like morphology. The microstructures of the films grown on quartz at 450 degrees C were found to be uniform and dense. The nominal grain sizes evaluated from High Resolution SEM (HRSEM) studies were approximately 20 nm and compared well with the grain sizes calculated from XRD. The band gap values calculated from ellipsometry studies were approximately 3.7 eV and 3.95 eV for the films grown at 450 degrees C and 350 degrees C, respectively. This is in good agreement with those obtained from UV-Visible spectroscopy. PMID:19928217

Raut, N C; Mathews, Tom; Sundari, S Tripura; Sairam, T N; Dash, S; Tyagi, A K

2009-09-01

91

Titanium dioxide (TIO2) thin film and plasma properties in RF magnetron sputtering  

International Nuclear Information System (INIS)

Lately, titanium dioxide (TiO2) films with anatase crystalline property received numerous attentions as unique material properties. There are wide applications of TiO2 thin film such as for photocatalytic application in solar cell. In the present study, radio frequency (RF) magnetron sputtering technique has been used to produce high dense, homogeneously controllable film layer at low deposition temperature using titanium (Ti) target. The diameter of the Ti target is 3 inch with fixed discharge power of 400W. Magnetron sputtering plasma has been produced in high purity 99.99% Argon (Ar) and 99.99% Oxygen (O2) environment pressure ranging from 5 to 20 mTorr. The TiO2 were growth on silicon and glass substrates. Substrate temperature during deposition was kept constant at 400°C. The distance between target and substrate holder was maintain at 14 cm with rotation of 10 rotation-per-minutes. Our X-ray diffraction result, shows anatase crystalline successfully formed with characterization peaks of plane (101) at 2? = 25.28°, plane (202) at 2? = 48.05° and plane (211) at 2? = 55.06°. In addition, it is our interest to study the plasma properties and optical spectrum of Ti, Ti+ , O- , ArM and Ar+ in the chamber during the deposition process. Result of emission line intensities, electron density and temperature from optical spectroscope and Langmuir probe will be discuss further during the workshop. This works were supported by Graduateis works were supported by Graduate Incentive Scheme of Universiti Tun Hussein Onn Malaysia (UTHM) and Fundamental Research Grant Scheme of Ministry of Higher Education, Malaysia. (author)

92

Wettability conversion of colloidal TiO2 nanocrystal thin films with UV-switchable hydrophilicity.  

Science.gov (United States)

Under pulsed laser UV irradiation, thin-film coatings made of close-packed TiO2 nanorods individually coated with surfactants can exhibit a temporary increase in their degree of surface hydroxylation without any apparent photocatalytic removal of the capping molecules. This mechanism provides a basis for achieving light-driven conversion from a highly hydrophobic to a highly hydrophilic, metastable state, followed by extremely slow recovery of the original conditions under dark ambient environment. A deeper insight into the wetting dynamics is gained by time-dependent water contact-angle and infrared spectroscopy monitoring of the film properties under different post-UV storage conditions. Our study reveals that, for reversible switchability between extreme wettability excursions and long-term repeatability of such changes to be achieved, specific modifications in the polar and nonpolar components of the TiO2 films need to be guaranteed along with preservation of the original geometric arrangement of the nanocrystal building blocks. The application of moderate vacuum is found to be an effective method for accelerating the post-UV hydrophilic-to-hydrophobic conversion, thereby enabling fast and cyclic hydrophilization/hydrophobicization alternation without any detrimental signs of significant fatigue. PMID:19421480

Caputo, Gianvito; Cingolani, Roberto; Cozzoli, Pantaleo Davide; Athanassiou, Athanassia

2009-05-21

93

Structural characterisation of sprayed TiO2 films for extremely thin absorber layer solar cells  

International Nuclear Information System (INIS)

We have examined in detail the structural features of TiO2 films fabricated by spray pyrolysis. The spray solution was produced from the dissolution of Ti powder in a hydrogen peroxide and ammonium hydroxide solution. The resulting peroxo-polytitanic acid solution was diluted in water and sprayed onto heated substrates through an air-atomizing nozzle. Each sample was characterised principally by X-ray powder diffraction and scanning electron microscopy. The effect of spray solution composition and rate has been studied and a brief comparison to films produced by an alternative route ('doctor blade') provided. The films were shown to consist of almost single phase anatase and to be porous. It has been demonstrated that the growth process was uniform although the degree of preferred orientation could be controlled through the concentration of the spray solution. The lattice parameters are both shown to increase slightly with concentration and volume of solution deposited. Semi-quantitative microstructural analyses showed that the crystallites formed are consistently larger than those formed by the doctor blade process although they contain significantly more microstrain. Further, it is demonstrated that thin window layers of copper indium disulfide, also formed by spray pyrolysis, have a conformal relationship with the TiO2

94

Photo-induced hydrophilicity of TiO2-xNx thin films on PET plates  

International Nuclear Information System (INIS)

TiO2-xNx thin films were deposited on PET (polyethylene terephthalate) plates by sputtering a TiN target in a N2/O2 plasma and without heating. X-ray photoemission spectroscopy (XPS) was used to investigate the N 1s, Ti 2p core levels and the nitrogen composition in the TiO2-xNx films. The results indicate that Ti-O-N bonds are formed in the thin films. Two nitrogen states, substitution and interstitial nitrogen atoms, were attributed to peaks at 396 and 399 eV, respectively. It was observed that the nitrogen atoms occupy both the substitutive and interstitial sites in respective of the nitrogen content in the thin films. UV-VIS absorption spectroscopy of PET coated thin films shows a significant shift of the absorption edge to lower energy in the visible-light region. UV and visible-light irradiation are used to activate PET coated thin films for the development of hydrophilicity. The photo-induced surface wettability conversion reaction of the thin films has been investigated by means of water contact angle measurement. PET plates coated with TiO2-xNx thin films are found to exhibit lower water contact angle than non-coated plates when the surface is illuminated with UV and visible light. The effects of nitrogen doping on photo-generated hydrophilicity of the thin films are investigated in this work

95

Characterization of TiO2 thin films prepared by electrolytic deposition for lithium ion battery anodes  

International Nuclear Information System (INIS)

The electrolytic deposition of TiO2 thin films on platinum for lithium batteries is carried out in TiCl4 alcoholic solution and the films are subsequently annealed. The as-prepared films are amorphous TiO(OH)2·H2O, transformed into anatase TiO2 at 350 °C, and then gradually into rutile TiO2 at 500 °C. Cyclic voltammograms show oxidation and reduction peaks at 2.20 and 1.61 V, respectively, corresponding to charge and discharge plateaus at 1.98 and 1.75 V vs. Li+/Li. The specific capacity decreases with increasing current density for film of 128-nm thickness in the initial discharge. It is observed that the diffusion flux of Li+ insertion/extraction into/from TiO2 controls the reaction rate at higher current densities. Consequently, at low film thickness, high discharge capacity (per weight) is found for the initial cycle at a current density of 10 ?A cm?2. However, the capacity of prepared films in various thicknesses approach 103 ± 5 mAh g?1 after 50 cycles, since the formation of cracks for thicker films offers shorter diffusion paths for Li+. In addition, TiO2 films show electrochromic properties during lithiation and delithiation. - Highlights: ? TiO2 films have been prepared by electrolytic deposition for Li ion batteries. ? The capacity decreased with increasing film thickness at higher current denickness at higher current density. ? TiO2 films showed electrochromic properties during lithiation and delithiation.

96

Low-temperature synthesis and characterization of TiO2 and TiO2-ZrO2 photocatalytically active thin films.  

Science.gov (United States)

Transparent TiO(2) and TiO(2)-ZrO(2) (molar ratio Zr/Ti = 0.1) thin films were produced by low-temperature sol-gel processing from nanocrystalline aqueous based solutions. The structural features and compositions of the films treated at room temperature, 100 degrees C and 500 degrees C were investigated by X-ray diffraction, X-ray photoelectron spectroscopy and thermal analysis. Addition of zirconia increased specific surface area (140-230 m(2) g(-1)) and hindered the growth of anatase crystallites, exhibiting a constant size of 6-7 nm in the whole temperature range. These significant changes with respect to pure TiO(2) in anatase crystalline form did not result in significantly and systematically different photocatalytic activity, which was evaluated in terms of aqueous pollutant degradation (azo-dye in water) and self-cleaning ability (fatty contaminant deposit). The films treated at only 100 degrees C showed excellent photocatalytic activity towards azo-dye degradation. Contact angle measurements of aged and contaminated surfaces revealed a fast or sharp hydrophilicity gain under UVA illumination. Accordingly, the results of this study confirmed the potential application of advantageous low-temperature films in water treatment as well as for self-cleaning surfaces. PMID:19424539

Maver, Ksenija; Stangar, Urska Lavrencic; Cernigoj, Urh; Gross, Silvia; Cerc Korosec, Romana

2009-05-01

97

Effects of 1064 nm laser on the structural and optical properties of nanostructured TiO2 thin film  

Science.gov (United States)

TiO2 thin film has been widely used as photoelectrode in dye-sensitized solar cells. It can also be used in quantum dot synthesized solar cells. Study of its effects in different spectrum of light is important for its use in solar cells. We have reported effects of 1064 nm laser on the surface morphology, structural and optical properties of nanostructured TiO2 thin film deposited on glass substrates using sol-gel spin coating technique. Q-Switched Nd:YAG pulsed laser at various power densities is used in this study. Surface morphology of the film is investigated using X-ray diffraction (XRD) and atomic force microscopy technique. The XRD pattern of as deposited TiO2 thin film is amorphous and after laser exposure it became TiO2 anatase structure. Atomic force microscopy of the crystalline TiO2 thin film shows that the grain size increases by increasing laser power density. The calculations of the band gap are carried out from UV/Visible spectroscopy measurements with JASCO spectrometer. For laser power density of 25 MW/cm2 there is an increase in the transmission and it decreases at the value of 38 MW/cm2 and band gap decreases with increasing laser power density. Photoluminescence spectra of the crystalline TiO2 thin film indicate two broad peaks in the range of 415 and 463 nm, one for band gap peak (415 nm) and other for oxygen defect during film deposition process.

Aslam Farooq, W.; Atif, M.; Ali, Syed Mansoor; Fatehmulla, Amanullah; Aslam, M.

2014-09-01

98

Room temperature ferromagnetism in Mn doped TiO2 thin films: Electronic structure and Raman investigations  

Science.gov (United States)

In this work dc-magnetization, electronic structural, and Raman investigations of Ti1-xMnxO2 (x = 0.00, 0.05, 0.10, and 0.15) thin films deposited on fused-quartz substrate by a simple and cost effective spray pyrolysis technique have been reported. X-ray diffraction revealed the formation of pure anatase TiO2 phase devoid of elemental Mn clusters in all the Mn incorporated TiO2 films. It is established by x-ray photoelectron spectroscopic (XPS) measurements that Ti ions substituted by Mn ions in both divalent and trivalent states in the TiO2 matrix. No peak corresponding to Mn+4 could be evidenced by XPS. The Raman study has further established the formation of TiO2 in anatase structure in both pure TiO2 and Mn-doped TiO2 films. The Ti1-xMnxO2 films with x ? 0.05 exhibit ferromagnetic ordering at room temperature which arises most likely due to formation of bound magnetic polarons.

Sharma, Sudesh; Chaudhary, Sujeet; Kashyap, Subhash C.; Sharma, Shiv K.

2011-04-01

99

Self-Organized Formation of Short TiO2 Nanotube Arrays By Complete Anodization of Ti Thin Films  

Science.gov (United States)

We investigate the self-organized growth of short TiO2 nanotubes by complete anodization of Ti thin films deposited on Si substrates in ethylene glycol electrolytes with small addition of NH4F. During the anodization process, real-time inspection of the current transient is performed to anodize the Ti films completely. X-ray photoelectron spectroscopy and scanning electron microscopy are employed to characterize the resulting samples. We find that the length of the formed TiO2 nanotubes is governed by the thickness of Ti thin films independently of the tube diameter. Short TiO2 nanotubes are also found to be stable up to 550 °C in air atmosphere even after crystallization to rutile.

Okada, Masahisa; Tajima, Kazuki; Yamada, Yasusei; Yoshimura, Kazuki

100

Structural and optical properties of silver doped TiO2 thin films for solar cell applications  

Science.gov (United States)

Electron collection efficiency and hence the device performance of a dye sensitized solar cell can be increased by localized surface plasmons (LSP) produced by the thin films of 2% silver doped TiO2 photo electrode. These films of silver doped TiO2 on glass substrates are prepared by pulsed laser deposition (PLD) method and have a lowest grain size of 8-31 nm. XRD, AFM and raman studies are made to characterize the surface at various annealing temperatures and annealing time durations. The lowest grain size of 8 nm of these films developed.

Murty, V. V. S.; Dashore, Vinay

2014-09-01

 
 
 
 
101

Photodecomposition effects of graphene oxide coated on TiO2 thin film prepared by electron-beam evaporation method  

International Nuclear Information System (INIS)

Morphological, structural and photocatalytic properties of graphene oxide (GO)/TiO2 thin-film deposited on quartz substrate were investigated. The TiO2 film was prepared by electron-beam evaporation and the GO film by spin coating method. The photocatalytic activities of the GO/TiO2 film were evaluated by photodecomposition of methylene blue. There was synergistic effect between TiO2 and GO which causes a rapid photo-induced charge separation and the reduction of the recombination of electron–hole pairs under the UV–visible light irradiation. GO on TiO2 film also promotes the properties of adsorption of the dye, photon scattering probability, and interacting surface area. As a result, it leads to the enhancement of the efficiency of the photodegradation in GO/TiO2 film. - Highlights: ? Graphene oxide (GO)/TiO2 film exhibited improved charge separation and transport. ? GO/TiO2 had higher photon scattering on surface and better adsorption than the TiO2. ? Recombination of electron–hole pairs reduced under the UV–visible irradiation. ? Hydroxyl and epoxide groups in GO reduced during the photocatalytic process. ? TiO2 achieved anatase phase by electron-evaporation method.

102

Contact Angle of TiO2/SnO2 Thin Films Coated on Glass Substrate  

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Full Text Available The self-cleaning effect in terms of contact angle value and photocatalytic activity of TiO2 and TiO2/SnO2 thin films coated on glass substrate was measured. The thin films were prepared using a sol-gel dip coating technique and calcinated at a temperature of 500 °C for 2 h with a heating rate of 10 °C/min. The microstructures of the fabricated thin films were characterized by SEM and XRD techniques. The photocatalytic properties of the thin films were also tested via the degradation of methylene blue (MB solution under UV irradiation. Finally, the self-cleaning properties of the thin films were evaluated by measuring the contact angle of water droplets on the thin films with and without UV irradiation. It was found that 1 %mol SnO2/TiO2 thin films showed the highest of photocatalytic activity and provided the most self-cleaning properties.doi:10.14456/WJST.2014.21

Weerachai SANGCHAY

2014-05-01

103

Study on the Resistive Switching Behaviors of TiO2 Thin Films by Pulsed Laser Deposition  

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Full Text Available The TiO2 thin films with resistive switching behaviors were grown on Pt (111/Ti/SiO2/Si substrates by pulsed laser deposition (PLD. Scanning electrical microscope (SEM and atomic force microscope (AFM were employed to characterize the as-grown films respectively. No evident diffraction peak of TiO2 is found in X-ray diffraction (XRD pattern. The films exhibit nanocrystalline or noncrystalline. The results show that the surfaces of the films are flat, smooth and dense. The results of electrical test indicate that TiO2 thin films show a unipolar resistive switching behavior, and the high-resistance to low-resistance ratio can reach 104. The electrical conduction of the films at high resistance state is controlled by the space charge limited current mechanism, and the soft-set phenomenon is found. The formation and rupture of conducting filaments in TiO2 thin films are preliminarily analyzed.ª¤

CAO Xun,LI Xiao-Min,YU Wei-Dong,ZHANG Yi-Wen

2009-01-01

104

Waveguiding Properties of Nano-Structured TiO2 Thin Films Synthesized by Sol-Gel Process  

Science.gov (United States)

TiO2 thin films were synthesized by sol-gel process: titanium tetraisopropoxide (TTIP) was dissolved in isopropanol, and then hydrolyzed by adding a water/isopropanol mixture with a controlled hydrolysis ratio. The as prepared sol was deposited by `dip-coating' on a glass substrate with a controlled withdrawal speed. The obtained films were annealed at 350 and 500 °C (2 h). The structural, morphological and optical properties of the prepared films were analyzed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM). The optical and waveguiding properties of TiO2 films were investigated for both annealing temperatures using m-lines spectroscopy. The results show that our fabricated TiO2 waveguides are multimodes and demonstrate low propagation losses of 0.9 dB.cm-1.

Znaidi, L.; Touam, T.; Vrel, D.; Kunetsova, I. N.; Fischer, A.; Boudrioua, A.

2011-12-01

105

Sol-Gel TiO2 thin films sensitized with the mulberry pigment cyanidin  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english TiO2 films have various applications, among them solar cells and photodegradation of pollutants. In this study, we investigated TiO2 films functionalized with the organic dye cyanidin extracted from black mulberry (Morus nigra). The TiO2 was functionalized by the sol-gel method and the film was depo [...] sited on glass substrates by dip-coating. Our aim was to investigate the interaction between the semiconductor and the dye, as well as the influence of the velocity and number of deposits on the characteristics of the film. Using ultraviolet-visible spectroscopy, we observed a shift from the maximum absorption band at 545 nm for the dye’s ethanol solution to 595 nm for the film, indicating interaction of the cyanidin with the TiO2. The absorption spectra in the infrared region of the functionalized TiO2 particles showed bands characteristic of the oxide and indicated their interaction with the dye. Using profilometry and m-line techniques, we found that the films presented thicknesses in the order of 100 nm. A SEM analysis confirmed the high density of the films.

Emerson Henrique de, Faria; Alex Lemes, Marçal; Eduardo José, Nassar; Katia Jorge, Ciuffi; Paulo Sergio, Calefi.

106

Optical anisotropy of TiO2 and MgF2 thin films prepared by glancing angle deposition  

International Nuclear Information System (INIS)

In this paper, the relationship between the optical anisotropy and the columnar microstructure in TiO2 and MgF2 thin films deposited by glancing angle deposition (GLAD) and the effects of the optical anisotropy of the films on the refractive index and the microstructure are investigated. The results show that as the glancing angle increases, the column angle and the porosity of the TiO2 and the MgF2 films increase due to the shadow effects, and the refractive index decreases. The optical anisotropy of the tilted and the zigzag structures of TiO2 films reaches a maximum at a glancing angle of 60 .deg. . TiO2 films deposited during rotation of the substrate at a high glancing angle show a small anisotropy due to the symmetry of the helical microstructure. On the other hand, the anisotropy of MgF2 film deposited by using GLAD is very small, nearly isotropic, due to the low refractive index of MgF2. We found that the microstructure, as well as the refractive index of film, plays an important role in the optical anisotropy of the thin films deposited by using GLAD.

107

Investigation on surface roughness in chemical mechanical polishing of TiO2 thin film  

Science.gov (United States)

Surface roughness by peaks and depressions on the surface of titanium dioxide (TiO2) thin film, which was widely used for an antireflection coating of optical systems, caused the extinction coefficient increase and affected the properties of optical system. Chemical mechanical polishing (CMP) is a very important method for surface smoothing. In this polishing experiment, we used self-formulated weakly alkaline slurry. Other process parameters were working pressure, slurry flow rate, head speed, and platen speed. In order to get the best surface roughness (1.16 Å, the scanned area was 10 × 10 ?m2) and a higher polishing rate (60.8 nm/min), the optimal parameters were: pressure, 1 psi; slurry flow rate, 250 mL/min; polishing head speed, 80 rpm; platen speed, 87 rpm.

Bo, Duan; Jianwei, Zhou; Yuling, Liu; Chenwei, Wang; Yufeng, Zhang

2014-06-01

108

Rutherford backscattering analysis of porous thin TiO2 films  

International Nuclear Information System (INIS)

The additional energy spread due to sample porosity was implemented in the SIMNRA simulation code, version 6.60 and higher. Deviations of the path length and energy loss distributions from the ones expected from a Poisson distribution of the number of traversed pores are taken into account. These deviations are due to the interaction of pores at higher pore concentrations by overlap or blocking. The skewnesses of the energy distributions are approximated by two-piece normal distributions with identical first three moments. Propagation of porosity-induced energy spread in thick layers is taken into account. Calculated results are compared to experimental data obtained with thin TiO2 mesoporous films measured by Rutherford backscattering (RBS),transmission electron microscopy (TEM), and atmospheric poroellipsometry.

109

Influence of preparation technique on the microscopic structure and surface morphology of nanometer TiO2 thin films  

Science.gov (United States)

Nanometer TiO2 thin films are prepared by a sol-gel method and the effects of preparation technique on the microstructure and surface morphology of the obtained materials are studied using X-ray Diffraction [XRD,IR spectrum[IR], UV-VIS spectrum [UV-VIS,AFM and X-ray photoelectron spectroscopy[XPS]. The results show that the TiO2 thin films are of anatase and rutile phase structures when annealed in a temperature range from 450°C to 600°C. When heated up to 700°C, the structure of TiO2 film changed into rutile completely. In the TiO2 thin films, there is some residual carbon from the starting organometallic components and a small amount of sodium ions diffused from the glass substrates. During heat-treatment, the absorption peak of water become weak gradually and the organic groups are disappeared completely at 500°C. Optimum film layers are obtained for the UV absorbance index. AFM result shows that the rough morphology of surface [RMS] of films is about 2-3nm or so.

Hu, Xiaoyun; Fan, Jun; Li, Ting; Zhang, Dekai; Bai, Jintao; Hou, Xun

2005-02-01

110

The oxidation stability of boron nitride thin films on MgO and TiO2 substrates  

International Nuclear Information System (INIS)

The stability of BN thin film coatings (2--5 nm thick) on MgO and TiO2 substrates was investigated using transmission electron microscopy (TEM). The samples were heated in air for at least 16 hours at temperatures ranging from 773 K--1,273 K. On MgO supports, the BN thin film coating was lost by 1,073 K due to a solid state reaction with the substrate leading to formation of Mg2B2O5. No such reaction occurred with the TiO2 substrate and the BN was stable even at 1,273 K. However, the coating appeared to ball up and phase segregate into islands of near-graphitic BN and clumps of TiO2 (rutile). The oxidizing treatment appears to promote the transformation from turbostratic BN to graphitic BN

111

The properties of metal contacts on TiO2 thin films produced by reactive magnetron sputtering  

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Full Text Available The article deals with research on volt-ampere characteristics of metal contacts (Al, Cr, In, Mo, Ti on titanium dioxide thin films and influence of annealing in vacuum on their electric properties. Volt-ampere characteristics measurements were taken by three-probe method. There was established that indium contact on TiO2 thin films possessed sharply defined ohmic properties.

Brus V. V.

2010-10-01

112

CdSe-sensitized TiO2 nanotube array film fabricated by ultrasonic-assisted electrochemical deposition and subsequently wrapped with TiO2 thin layer for the visible light photoelectrocatalysis  

International Nuclear Information System (INIS)

A composite structure, TiO2 nanotube array/CdSe nanoparticle/TiO2 layer, was fabricated by inserting CdSe nanoparticles into anodized TiO2 nanotube arrays via ultrasonic-assisted cyclic voltammetry electrochemical deposition and subsequently wrapped by a TiO2 thin layer via TiCl4 hydrolysis. The films were characterized by X-ray diffraction, field emission scanning electron microscopy, energy dispersive spectroscopy and UV–vis diffuse reflectance spectroscopy. For the film used as the photoanode, linear sweep voltammetry and transient photocurrent were investigated in a three-electrode system under visible light illumination. And the photocatalytic activity was evaluated by the oxidation of glucose in the supporting electrolyte at different potential bias under visible light illumination. The results showed that CdSe nanoparticles are prone to disperse into the nanotube arrays via cyclic voltammetry electrochemical deposition under ultrasonic condition. Increasing cyclic voltammetry cycle increases the loading of CdSe on the TiO2 nanotube arrays. The CdSe-sensitized TiO2 nanotube array films exhibit a wide-absorption response in the visible light region. The TiO2 nanotube array/CdSe/TiO2 film, prepared by ultrasonic-assisted electrochemical deposition with 50 cyclic voltammetry cycles and subsequently coating a TiO2 thin layer, exhibits better protection again layer, exhibits better protection against photocorrosion of CdSe. The TiO2NTA/CdSe/TiO2 film possesses visible light photoelectrocatalytic activity on the degradation of glucose. - Highlights: ? CdSe is electrochemically deposited onto TiO2 nanotube arrays with ultrasonics. ? TiO2 thin layer overcoating on the arrays can protect CdSe from photocorrosion. ? TiO2 nanotube array/CdSe/TiO2 film possesses visible light photocatalytic activity.

113

Photoactive and self-cleaning TiO2–SiO2 thin films on 316L stainless steel  

International Nuclear Information System (INIS)

In this study, TiO2–SiO2 nanocomposite films with different amounts of SiO2 were prepared by sol–gel process and were coated onto stainless steel 316L. The effect of addition of various amount of SiO2 in the precursor solution on the photocatalysis, photo-generated hydrophilicity and self-cleaning property of TiO2 thin films was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, water contact angle measurements and UV spectroscopy. In the tested ranges of SiO2 content and sintering temperature, the highest photocatalytic activity and self-cleaning property were observed in the 15 mol% SiO2 sample sintered at 750 °C. Addition of less than 30 mol% SiO2 had a suppressive effect on the transformation of anatase to rutile and on the crystal growth of anatase in the sintering heat treatment. Phase separation occurred in the composite films for SiO2 content of 30 mol% or more. - Highlights: ? We study the effect of SiO2 addition on the photocatalysis of TiO2 films. ? By adding silica to TiO2, the photocatalysis activity of films can be improved. ? Addition of SiO2 can suppress the transformation of anatase to rutile. ? SiO2 addition prevents the growth of TiO2 grains during the sintering process.

114

Micro-arc oxidization fabrication and ethanol sensing performance of Fe-doped TiO2 thin films  

Science.gov (United States)

In-situ pure TiO2 and Fe-doped TiO2 thin films were synthesized on Ti plates via the micro-arc oxidation (MAO) technique. The as-fabricated anatase TiO2 thin film-based conductometric sensors were employed to measure the gas sensitivity to ethanol. The results showed that Fe ions could be easily introduced into the MAO-TiO2 thin films by adding precursor K4(FeCN)6·3H2O into the Na3PO4 electrolyte. The amount of doped Fe ions increased almost linearly with the concentration of K4(FeCN)6·3H2O increasing, eventually affecting the ethanol sensing performances of TiO2 thin films. It was found that the enhanced sensor signals obtained had an optimal concentration of Fe dopant (1.28at%), by which the maximal gas sensor signal to 1000 ppm ethanol was estimated to be 7.91 at 275°C. The response time was generally reduced by doped Fe ions, which could be ascribed to the increase of oxygen vacancies caused by Fe3+ substituting for Ti4+.

Ren, Fu-jian; Yu, Xiao-bai; Ling, Yun-han; Feng, Jia-you

2012-05-01

115

Substrate-controlled allotropic phases and growth orientation of TiO2 epitaxial thin films  

International Nuclear Information System (INIS)

TiO2 thin films were grown by pulsed laser deposition on a wide variety of oxide single-crystal substrates and characterized in detail by four-circle X-ray diffraction. Films grown at 873 K on (100)-oriented SrTiO3 and LaAlO3 were (001)-oriented anatase, while on (100) MgO they were (100)-oriented. On (110) SrTiO3 and MgO, (102) anatase was observed. On M-plane and R-plane sapphire, (001)- and (101)-oriented rutile films were obtained, respectively. On C-plane sapphire, the coexistence of (001) anatase, (112) anatase and (100) rutile was found; increasing the deposition temperature tended to increase the rutile proportion. Similarly, films grown at 973 K on (100) and (110) MgO showed the emergence, besides anatase, of (110) rutile. All these films were epitaxically grown, as shown by ? scans and/or pole figures, and the various observed orientations were explained on the basis of misfit considerations and interface arrangement. (orig.)

116

Substrate effects on the oxygen gas sensing properties of SnO2/TiO2 thin films  

International Nuclear Information System (INIS)

In this study, SnO2/TiO2 thin films are fabricated on SiO2/Si and Corning glass 1737 substrates using a R.F. magnetron sputtering process. The gas sensing properties of these films under an oxygen atmosphere with and without UV irradiation are carefully examined. The surface structure, morphology, optical transmission characteristics, and chemical compositions of the films are analyzed by atomic force microscopy, scanning electron microscopy and PL spectrometry. It is found that the oxygen sensitivity of the films deposited on Corning glass 1737 substrates is significantly lower than that of the films grown on SiO2/Si substrates. Therefore, the results suggest that SiO2/Si is an appropriate substrate material for oxygen gas sensors fabricated using thin SnO2/TiO2 films

117

Surface characterization of TiO2 thin films obtained by high-energy reactive magnetron sputtering  

International Nuclear Information System (INIS)

This paper presents the results of surface characterization of TiO2 thin films deposited on different substrates by the use of high-energy reactive magnetron sputtering. Structural investigations carried out by X-ray diffraction (XRD) and atomic force microscopy (AFM) have shown a strong influence of both the substrate type, and its placement in the deposition chamber (relative to the sputtering target), on the structural properties of the films. In all cases, there is evidence for pseudoepitaxial growth. XRD examination showed existence of TiO2-rutile phase with preferred (1 1 0) orientation and AFM measurements revealed nanocrystalline structure directly after deposition. X-ray photoelectron spectroscopy analysis showed that the TiO2 films have stoichiometric composition

118

Characterization and photocatalytic activity of boron-doped TiO2 thin films prepared by liquid phase deposition technique  

International Nuclear Information System (INIS)

Boron doped TiO2 thin films have been successfully deposited on glass substrate and silicon wafer at 30 deg C from an aqueous solution of ammonium hexa-fluoro titanate and boron trifluoride by liquid phase deposition technique. The boric acid was used as an F scavenger. The resultant films were characterized by XRD, EDAX, UV and microstructures by SEM. The result shows the deposited film to be amorphous which becomes crystalline between 400 and 500 deg C. The EDAX and XRD data confirm the existence of boron atom in TiO2 matrix and a small peak corresponding to rutile phase was also found. Boron doped TiO2 thin films can be used as photocatalyst for the photodegradation of chlorobenzene which is a great environmental hazard. It was found that chlorobenzene undergoes degradation efficiently in presence of boron doped TiO2 thin films by exposing its aqueous solution to visible light. The photocatalytic activity increases with increase in the concentration of boron. (author)

119

Structural and Optical Characteristics of TiO2 Nanoparticles-Containing Mesoporous Silica (SBA-15) Thin Films  

International Nuclear Information System (INIS)

The thin films of ordered mesoporous silica (SBA-15) with nanometer-sized pores have been formed on silicon substrates. It was confirmed that the pores were hexagonally ordered as the stacking of rows of pores and silica walls in the direction normal to the substrate surface. From the results of X-ray reflectivity and diffraction the pore size and wall thickness were evaluated to be ?4.8 nm and ?2.1 nm, respectively. Furthermore, titanium dioxide nanoparticles were successfully synthesized in the pores of SBA-15 thin film. X-ray photoelectron spectroscopy of SBA-15 thin film after TiO2 synthesis indicated that the nanoparticles in the pores were titanium dioxide which included a small amount of defects. The optical reflectance of TiO2-containing SBA-15 film decreased at wavelengths shorter than 350 nm as compared with that of SBA-15 film before the TiO2 synthesis, resulting in optical absorption by the TiO2 nanoparticles in the pores of SBA-15.

120

TiO2 nanoparticle thin film deposition by matrix assisted pulsed laser evaporation for sensing applications  

International Nuclear Information System (INIS)

The MAPLE technique has been used for the deposition of nanostructured titania (TiO2) nanoparticles thin films to be used for gas sensors applications. An aqueous solution of TiO2 nanoparticles, synthesised by a novel chemical route, was frozen at liquid nitrogen temperature and irradiated with a pulsed ArF excimer laser in a vacuum chamber. A uniform distribution of TiO2 nanoparticles with an average size of about 10 nm was deposited on Si and interdigitated Al2O3 substrates as demonstrated by high resolution scanning electron microscopy-field emission gun inspection (SEM-FEG). Energy dispersive X-ray (EDX) analysis revealed the presence of only the titanium and oxygen signals and FTIR (Fourier transform infra-red) revealed the TiO2 characteristic composition and bond. A comparison with a spin coated thin film obtained from the same solution of TiO2 nanoparticles is reported. The sensing properties of the films deposited on interdigitated substrates were investigated, too

 
 
 
 
121

Structural and Electrical Properties of TiO2 Thin Film Derived from Sol-gel Method using Titanium (IV Butoxide  

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Full Text Available Fabrication of titanium dioxide (TiO2 thin film on microscope glass using sol-gel method has been studied intensively. The starting materials were titanium (IV butoxide, ethanol, acetic acid, triton x-100, hydrochloric acid and deionized water. The materials were mixed together to form the sols. Then, the heat and ageing treatment was applied to form stable sols. The sols were then spin coated on the glass substrate to form the homogenous and transparent TiO2 thin film. The TiO2 thin film was coated at several layers using specific conditions. To evaluate the performance of thin film, the crystallinity of the thin film was determined by using the x-ray diffractometer  (XRD. The change on the surface morphology was observed using atomic force microscope (AFM. The electrical property of the thin film was determined by doing the current-voltage (I-V analysis on the thin film. It has been successfully shown that the anatase crystalline phase was observed when the TiO2 thin film was heated at 500°C. The roughness and the crystalline phase of TiO2 thin film changed drastically with the growth conditions. Finally, the effect of film preparation to the film resistivity also showed a critical aspect where we should take into account during the preparation of TiO2 thin film.

Isrihetty Senain

2010-12-01

122

Hydrophobic-hydrophilic conversion in microfluidic polymer channels with TiO2 thin films  

Science.gov (United States)

In this study, recoverable and maintainable hydrophilic micropatterns on polymer-based microfluidic devices were developed through liquid phase deposition of a photocatalytic TiO2. The TiO2-coated region in the microchannel could be hydrophilized through brief UV irradiation upon request. A titanium oxide film was deposited either on bare polymer substrates or on a titanium-sputtered surface using an aqueous TiCl3 solution at 80 °C. A cyclic olefin copolymer (COC) coated with the TiO2 film displayed effective photocatalytic activity, which reduced the water contact angle from 50° to less than 5°. The Ti seed layer was facilitated to pave the substrate with TiO2 grains during the liquid phase deposition. Thus, the photocatalytic effect could be achieved with less number of LPD cycles. Even after contamination from an organic solvent or photoresist, the surface became hydrophilic upon 5 min of UV irradiation. The photocatalytic effect was so stable that super-hydrophilicity of the surface could be promptly recovered after a month of storage under atmospheric conditions. A COC microchannel was fabricated with TiO2 patterns to allow for controlled delivery of the aqueous liquid without the need for external pumps or valves. A hydrogel pattern self-organized along the TiO2 pattern demonstrated a practical application of the recoverable hydrophilicity in microchannels. Functional hydrogels can easily and stably be integrated into a polymer microchannel using this approach.

Park, Hyun Jik; Kim, In Tae; Park, Sang Hui; Kim, Sang Kyung

2011-09-01

123

Polythiophene thin films electrochemically deposited on sol-gel based TiO2 for photovoltaic applications  

International Nuclear Information System (INIS)

In this work, the influence of titanium dioxide (TiO2) thin films on the efficiency of organic photovoltaic devices based on electrochemically synthesized polythiophene (PT) was investigated. TiO2 films were produced by sol-gel methods with controlled thickness. The best TiO2 annealing condition was determined through the investigation of the temperature influence on the electron charge mobility and resistivity in a range between 723 K and 923 K. The PT films were produced by chronoamperometric method in a 3-electrode cell under a controlled atmosphere. High quality PT films were produced onto 40 nm thick TiO2 layer previously deposited onto fluorine doped tin oxide (FTO) substrate. The morphology of PT films grown on both substrates and its strong influence on the device performance and PT minimum thickness were also investigated. The maximum external quantum efficiency (IPCE) reached was 9% under monochromatic irradiation (? = 610 nm; 1 W/m2) that is three orders of magnitude higher than that presented by PT-homolayer devices with similar PT thickness. In addition, the open-circuit voltage (Voc) was about 700 mV and the short-circuit current density (Jsc) was 0.03 A/m2 (? = 610 nm; 7 W/m2). However, as for the PT-homolayer also the TiO2/PT based devices are characterized by antibatic response when illuminated through FTO. Finally, the Fill Factor (FF) of these devices is low (25%), indicating that the series resistance (Rs), which is strongly dependent of the PT thickness, is too large. This large Rs value is compensated by TiO2/PT interface morphology and by FTO/TiO2 and TiO2/PT interface phenomena producing preferential paths in which the internal electrical field is higher, improving the device efficiency.

124

Formation of TiO2 Thin Films using NH3 as Catalyst by Metalorganic Chemical Vapor Deposition  

Science.gov (United States)

We have studied metalorganic chemical vapor deposition of TiO2 thin films using titanium tetra-isopropoxide [TTIP, Ti(O--C3H7)4] and NH3 as a catalyst at deposition temperatures ranging from 250 to 365°C. At deposition temperatures above 330°C, pyrolytic self-decomposition of TTIP is dominant regardless of the use of NH3, and the activation energy for TiO2 film formation is 152 kJ/mol. At deposition temperatures below 330°C, the films can be formed with the help of the catalytic activity of NH3, and the activation energy is reduced to 55 kJ/mol. TiO2 films deposited through the pyrolytic self-decomposition of TTIP have an anatase structure before and after performing post-deposition annealing in oxygen ambient for 30 min at 750°C. On the other hand, the as-deposited films formed through the catalytic reaction of TTIP with NH3 incorporate nitrogen impurities and have microcrystallites of the rutile structure within the amorphous matrix. However, the post-deposition annealing, the nitrogen impurities are completely removed from the films, and the films are converted into polycrystalline TiO2 films with the rutile structure, which have a high dielectric constant of 82 and a low leakage current.

Jung, Sung-Hoon; Kang, Sang-Won

2001-05-01

125

The role of TiO2 addition in ZnO nanocrystalline thin films: Variation of photoelectrochemical responsivity  

International Nuclear Information System (INIS)

Highlights: ? (TiO2)x-(ZnO)1-x systems with different x values were synthesized by sol-gel method. ? XRD showed a decrease in crystallinity of the systems by increasing x value. ? AFM analysis revealed the highest roughness and surface area for the system with x = 10%. ? This system showed highest photoresponse for water splitting and electrical resistance. - Abstract: In this study, the effects of TiO2 addition on the physical and photoelectrochemical properties of ZnO thin films have been investigated. The (TiO2)x-(ZnO)1-x nanocomposite thin films were dip-coated on both glass and indium tin oxide (ITO)-coated conducting glass substrates with various values of x, specifically 0, 0.05, 0.1, 0.25 and 0.5. Optical properties of the samples were studied by UV-vis spectrophotometry in the range of 300-1100 nm. The optical spectra of the nanocomposite thin films showed high transparency in the visible region. The optical bandgap energy of the (TiO2)x-(ZnO)1-x films increased slightly with increasing values of x. The crystalline structure of the nanocomposite films was investigated by X-ray diffraction, which indicated the formation of ZnO nanocrystals in the thin films with x 2 on the surfaces of the films. The photoelectrochemical properties of the samples were also characterized using a high-pressure xenon light source and KOH electrolyte. The addition of 10 mol% (x = 0.1) TiO2 to the ZnO thin films resulted in the best photoresponse in the visible region of the solar spectrum. In addition, the effect of TiO2 concentration on the electrical properties and the flat-band potential of the (TiO2)x-(ZnO)1-x system was studied by impedance spectroscopy; x = 0.1 exhibited the highest donor density and charge-transfer resistance.

126

Investigation on the nitrogen doping of multilayered, porous TiO2 thin films  

International Nuclear Information System (INIS)

N-doping is often used to improve the photocatalytic properties of TiO2 films in order to achieve visible light response. In this work, we study the effect of annealing treatment (temperature and atmosphere) on the structural and optical properties of undoped and N-doped TiO2 films by means of X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) and UV-VIS optical transmission spectroscopy. Porous five-layer TiO2 films were deposited by sol-gel method on quartz substrate and thermally treated in oxygen or NH3 flow at 500 and 600 deg. C. Significant doping effect was achieved after annealing at 600 deg. C in NH3 and a shift in optical bandgap value down to visible range (2.69 eV) was observed

127

Annealing dependence of residual stress and optical properties of TiO2 thin film deposited by different deposition methods.  

Science.gov (United States)

Titanium oxide (TiO(2)) thin films were prepared by different deposition methods. The methods were E-gun evaporation with ion-assisted deposition (IAD), radio-frequency (RF) ion-beam sputtering, and direct current (DC) magnetron sputtering. Residual stress was released after annealing the films deposited by RF ion-beam or DC magnetron sputtering but not evaporation, and the extinction coefficient varied significantly. The surface roughness of the evaporated films exceeded that of both sputtered films. At the annealing temperature of 300 degrees C, anatase crystallization occurred in evaporated film but not in the RF ion-beam or DC magnetron-sputtered films. TiO(2) films deposited by sputtering were generally more stable during annealing than those deposited by evaporation. PMID:18449260

Chen, Hsi-Chao; Lee, Kuan-Shiang; Lee, Cheng-Chung

2008-05-01

128

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

Science.gov (United States)

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.

Bouachiba, Y.; Bouabellou, A.; Hanini, F.; Kermiche, F.; Taabouche, A.; Boukheddaden, K.

2014-01-01

129

Synthesis, phase to phase deposition and characterization of rutile nanocrystalline titanium dioxide (TiO2) thin films  

International Nuclear Information System (INIS)

>2 layer between TiO2 and the substrate and the minor anatase crystalline phase of TiO2 was also identified in FTIR analysis. Grain size was found to be in the range of 100–125 nm while grain boundary was estimated to be 20 nm. Direct and indirect optical band gap was estimated to be 3.64 and 3.04 eV, respectively. A process induced self annealing of deposited film shows a strong effect on the structural, morphological and optical properties. Furthermore, low deposition rate and high vacuum allows rutile to rutile phase transformation from indigenously prepared TiO2 target to thin film.

130

Structural, morphological and local electric properties of TiO2 thin films grown by pulsed laser deposition  

International Nuclear Information System (INIS)

Titanium dioxide (TiO2) thin films were synthesized on (1 0 0) Si substrates by reactive pulsed laser deposition (PLD) technique. A frequency quadrupled Nd : YAG (? = 266 nm, ?FWHM ? 5 ns, ? = 10 Hz) laser source was used for the irradiations of metallic Ti targets. The experiments were performed in controlled oxygen atmosphere. Crystallinity, surface morphology and local electric properties of the obtained oxide thin films were investigated by x-ray diffractometry, micro-Raman spectroscopy and current sensing atomic force microscopy. An inter-relation was found between the surface morphology, the crystalline structure and the nano-scale electric properties which open the possibility of synthesizing by the PLD technique TiO2 thin films with tunable functional properties for future applications such as photocatalysts, gas sensors or solar energy converters

131

Photoluminescence of Eu-doped TiO2 thin films prepared by low pressure hot target magnetron sputtering  

International Nuclear Information System (INIS)

In this work Eu-doped TiO2 thin films prepared by reactive magnetron co-sputtering of Ti-Eu metallic target have been studied. The results of photoluminescence (PL) and its correlation with microstructure have been described. Structural properties were examined by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). XRD studies have shown that thin films consisted of TiO2-anatase and AFM images display their high quality and dense nanocrystalline structure. PL spectra, measured at room temperature, show a dominating strong red luminescence corresponding to 5D0-7F2 transition at ? 617 nm and ? 623 nm. The evolution of photoluminescence and microstructure of the thin films has been examined as they were additionally annealed in an air ambient

132

Fabrication of thin film TiO2 nanotube arrays on Co-28Cr-6Mo alloy by anodization  

Science.gov (United States)

Titanium oxide (TiO2) nanotube arrays were prepared by anodization of Ti/Au/Ti trilayer thin film DC sputtered onto forged and cast Co-28Cr-6Mo alloy substrate at 400 °C. Two different types of deposited film structures (Ti/Au/Ti trilayer and Ti monolayer), and two deposition temperatures (room temperature and 400 °C) were compared in this work. The concentrations of ammonium fluoride (NH4F) and H2O in glycerol electrolyte were varied to study their effect on the formation of TiO2 nanotube arrays on a forged and cast Co-28Cr-6Mo alloy. The results show that Ti/Au/Ti trilayer thin film and elevated temperature sputtered films are favorable for the formation of well-ordered nanotube arrays. The optimized electrolyte concentration for the growth of TiO2 nanotube arrays on forged and cast Co-28Cr-6Mo alloy was obtained. This work contains meaningful results for the application of a TiO2 nanotube coating to a CoCr alloy implant for potential next-generation orthopedic implant surface coatings with improved osseointegrative capabilities. PMID:23827596

Ni, Jiahua; Frandsen, Christine J.; Noh, Kunbae; Johnston, Gary W.; He, Guo; Tang, Tingting; Jin, Sungho

2014-01-01

133

Broad band optical characterization of sol-gel TiO2 thin film microstructure evolution with temperature  

International Nuclear Information System (INIS)

Titanium dioxide (TiO2) thin films have been produced by spin coating a titanium isopropoxide sol on silicon wafer substrates. The structural evolution of the thin films in terms of decomposition, crystallization and densification has been monitored as a function of annealing temperature from 100 to 700 oC using optical characterization and other techniques. The effect of annealing temperature on the refractive index and extinction coefficient of these TiO2 thin films was studied in the range of 0.62 to 4.96 eV photon energy (250-2000 nm wavelength) using spectroscopic ellipsometry. Thermal gravimetric analysis and atomic force microscopy support the ellipsometry data and provide information about structural transformations in the titania thin films with respect to different annealing temperatures. These data help construct a coherent picture of the decomposition of the sol-gel precursors and the creation of dense layers of TiO2. It was observed that the refractive index increased from 2.02 to 2.45 at 2.48 eV (500 nm) in sol-gel spin coated titania films for annealing temperatures from 100 oC to 700 oC.

134

Heteroepitaxial growth and structural characterization of rutile TiO2 thin films on GaN (0 0 0 1) templates prepared by pulsed laser deposition  

International Nuclear Information System (INIS)

Rutile TiO2 (1 0 0) thin films have been prepared on GaN (0 0 0 1) surfaces in the temperature range 300–600 °C by pulsed laser deposition (PLD) method. The effects of both the oxygen pressure and the substrate temperature on the properties of the TiO2 films were investigated. TiO2 thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscope (TEM). Optimum parameters have been determined for growing high-quality TiO2 thin films with a sharp interface, in which the epitaxial orientation relationship between rutile TiO2 and GaN is TiO2 [001] //GaN [112¯0]. The surface morphology of TiO2 thin films exhibited a marked dependence on the substrate temperature, and the better crystallinity of the TiO2 thin films can be obtained at lower oxygen pressure

135

A spectroscopic ellipsometry study of TiO2 thin films prepared by dc reactive magnetron sputtering: annealing temperature effect  

International Nuclear Information System (INIS)

TiO2 thin films are obtained by dc reactive magnetron sputtering. A target of titanium (99.995%) and a mixture of argon and oxygen gases are used to deposit TiO2 films on to silicon wafers (100). The crystalline structure of deposited and annealed film are deduced by variable-angle spectroscopic ellipsometry (VASE) and supported by x-ray diffractometry. The optical properties of the films are examined by VASE. Measurements of ellipsometry are performed in the spectral range O.72-3.55 eV at incident angle 75 degree. Several SE models, categorized by physical and optical models, are proposed based on the 'simpler better' rule and curve-fits, which are generated and compared to the experimental data using the regression analysis. It has been found that the triple-layer physical model together with the Cody-Lorentz dispersion model offer the most convincing result. The as-deposited films are found to be inhomogeneous and amorphous, whereas the annealed films present the phase transition to anatase and futile structures. The refractive index of TiO2 thin films increases with annealing temperature. A more detailed analysis further reveals that thickness of the top sub-layer increases, whereas the region of the bottom amorphous sub-layer shrinks when the films are annealed at 300 degree C. (authors)

136

Sputtered TiO2 thin films with NiO additives for hydrogen detection  

Science.gov (United States)

The effect of NiO additives and post-deposition treatment by rapid thermal annealing on the properties of TiO2 thin films has been studied. The structural, compositional and H2 sensing parameters have been investigated by X-ray diffraction (XRD), glow discharge optical emission spectrometry (GDOES), scanning electron microscopy (SEM) and by electrical measurements. In the range of annealing temperatures from 500 °C to 700 °C crystallization started and the structure changed from amorphous to polycrystalline. The NiO modified sensing films exhibit enhanced and improved sensing behavior to hydrogen at relatively low operating temperatures. The inversion of the conductivity type of response due to different H2 concentrations has been observed. The critical H2 concentration causing break of the p-type response to n-type response was identified. The temperature dependence of this critical concentration as a function of operating temperature was studied. Moreover, change of response type due to different annealing temperatures was achieved.

Kosc, I.; Hotovy, I.; Rehacek, V.; Griesseler, R.; Predanocy, M.; Wilke, M.; Spiess, L.

2013-03-01

137

Structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique.  

Science.gov (United States)

In this work, we report the structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique. The TiO2 film was formed on a doped fluorine tin oxide (SnO2:F, i.e., FTO) layer and used as a photo electrode in a dye solar cell (DSC). Using spectroscopic ellipsometry measurements in the 200 to 800?nm wavelengths domain, we obtain a thickness of the TiO2 film in the range of 70 to 80?nm. Characterizations by X-ray diffraction and atomic force microscopy (AFM) show a polycrystalline film. In addition, AFM investigation shows no cracks in the formed layer. Using an ultraviolet-visible near-infrared spectrophotometer, we found that the transmittance of the TiO2 film in the visible domain reaches 75%. From the measured current-voltage or I-V characteristic under AM1.5 illumination of the formed DSC, we obtain an open circuit voltage Voc?=?628?mV and a short circuit current Isc?=?22.6??A, where the surface of the formed cell is 3.14?cm2. PMID:22747886

Ghrairi, Najla; Bouaicha, Mongi

2012-01-01

138

Structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique  

Science.gov (United States)

In this work, we report the structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique. The TiO2 film was formed on a doped fluorine tin oxide (SnO2:F, i.e., FTO) layer and used as a photo electrode in a dye solar cell (DSC). Using spectroscopic ellipsometry measurements in the 200 to 800 nm wavelengths domain, we obtain a thickness of the TiO2 film in the range of 70 to 80 nm. Characterizations by X-ray diffraction and atomic force microscopy (AFM) show a polycrystalline film. In addition, AFM investigation shows no cracks in the formed layer. Using an ultraviolet-visible near-infrared spectrophotometer, we found that the transmittance of the TiO2 film in the visible domain reaches 75%. From the measured current-voltage or I-V characteristic under AM1.5 illumination of the formed DSC, we obtain an open circuit voltage V oc = 628 mV and a short circuit current I sc = 22.6 ?A, where the surface of the formed cell is 3.14 cm2.

Ghrairi, Najla; Bouaicha, Mongi

2012-07-01

139

Photocatalytic effect of the sol-gel derived nanoporous TiO2 transparent thin films  

International Nuclear Information System (INIS)

Photocatalytically active nanoporous anatase TiO2 films were deposited on glass plates by a sol-gel process conducted in the presence of polyethylene glycol (PEG). The films in different stages of the formation process were characterized by field emission scanning electron microscope, thermogravimetry-differential thermal analysis, ultraviolet-visible (UV-visible) spectroscopy and X-ray diffraction. The as-deposited TiO2/PEG composite films were smooth and dense, and were made nanoporous after the embedded PEG was thermally removed during calcination. The higher the content of PEG the larger was the resultant pore size. There were no cracks in the films common to films prepared in the presence of PEG, and the thermal stability of the films were also improved by the PEG addition. UV-visible spectroscopy showed that the calcination of PEG-TiO2 films also resulted in red shifting the absorption band of TiO2. The films were active in the photooxidation of iodide and methyl orange, and demonstrated an activity increase that scaled with the increase in the PEG content in the sol-gel preparation

140

Thickness-dependent photocatalytic performance of nanocrystalline TiO2 thin films prepared by sol-gel spin coating  

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TiO2 nanocrystalline thin films on soda lime glass have been prepared by sol-gel spin coating. The thin films were characterized for surface morphology, crystal structure, chemical composition, thickness, and transparency by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ellipsometry, and UV-vis spectrophotometry. The films prepared by titanium tetraisopropoxide (TTIP) as the precursor under pH of 3.5 ± 0.5 and with calcination temperature of 450 ?C for 3 h exhibited superior homogeneous aggregation, good optical transparency, superhydrophilicity, and reliable thickness. The effect of film thickness on the photocatalytic degradation of acid yellow 17 was investigated under UV irradiation. The photocatalytic activity was strongly correlated with the number of coatings and followed Langmuir-type kinetics. Under the same film thickness, TiO2 thin films prepared by 0.1 M TTIP exhibited more efficient photocatalytic activity than those prepared by 0.3 M TTIP. For thin films prepared by 0.1 M TTIP, the maximum specific photocatalytic activity occurred at 5 coatings with thickness of 93 ± 1 nm. A model was proposed to rationalize the dependence of the film thickness on the photocatalytic activity, which predicts the existence of an optimum film thickness.

Wu, Chung-Yi; Lee, Yuan-Ling; Lo, Yu-Shiu; Lin, Chen-Jui; Wu, Chien-Hou

2013-09-01

 
 
 
 
141

DIRECT PHOTODEPOSITION OF NANOSTRUCTURED TIO2 THIN FILMS FROM B-DIKETONATE COMPLEXES, AND THEIR PHOTOCATALYTIC BEHAVIOUR  

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Full Text Available Amorphous Titania thin films have been photochemically obtained by direct UV irradiation (254 nm of an amorphous TiO(C6H5COCHCOCH3 2 film spin-coated on Si(100 and borosilicate glass. These materials were characterized by scanning electron microscopy (SEM, X-ray diffraction spectroscopy (XRD and Auger electron spectroscopy (AES. SEM analysis showed a porous film with irregular morphology (diameter < 300 nm, whereas the XRD spectrum showed that the as-deposited film was completely amorphous and was transformed by annealing under nitrogen into polycrystalline TiO2. Subsequently, amorphous Titania deposited on borosilicate glass was used in the photocatalytic decomposition of aniline in water. The photoreaction of aniline was monitored by UV in the presence of air and nitrogen, and the product was characterized by infrared spectroscopy (IR. The results showed that aniline can be photooxidized efficiently by the TiO2/ borosilicate system in the presence of oxygen

M TEJOS

2004-12-01

142

Improved Energy Conversion Efficiency of TiO2 Thin Films Modified with Ta2O5 in Dye-Sensitized Solar Cells  

Science.gov (United States)

Tantalum-doped TiO2 thin films [(TiO2)1-x(Ta2O5)x, x=0-0.8%] were prepared on fluorine-doped tin oxide (FTO)-coated substrates by sol-gel technology for uses in dye-sensitized solar cells (DSSCs). The effects of Ta content on the growth and properties of the TiO2 thin films were investigated. The crystallization and microstructures of the thin films were examined by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller analyses. The performance of DSSCs based on Ta-doped TiO2 thin films was also studied. From the obtained results, the increases in Jsc and Voc may be due to the increased electron concentration of TiO2 thin film and the flat-band potential of the TiO2 shifted by tantalum doping, respectively. The optimum properties of DSSCs of Voc=0.68 V, Jsc=7.84 mA/cm2, FF=45.1%, and ?=2.4% were obtained using the Ta-doped TiO2 thin film with x=0.5%.

Kao, Ming-Cheng; Chen, Hone-Zern; Young, San-Lin

2013-01-01

143

Visible-light photocatalytic activity of N/SiO2–TiO2 thin films on glass  

International Nuclear Information System (INIS)

Nanocrystalline N-doped SiO2/TiO2 visible-light photocatalyst thin films were synthesized using the sol-gel method on glass substrates. The synthesized catalysts were then characterized using several analytical techniques like x-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and UV–vis absorption spectroscopy (UV–vis). The experimental results revealed that the maximum optical response of the synthesized SiO2/TiO2 thin films shifted from the ultraviolet (UV) to the visible-light region (??420?nm). The photocatalytic activity of N-doped SiO2–TiO2 photocatalyst was considerably higher than that of SiO2–TiO2, and this result was obtained with an optimal concentration of 40?mol% of N. The enhanced photocatalytic activity was attributed to the increasing surface area and forming more hydroxyl groups in the doped catalyst

144

Glancing angle synthesized indium nanoparticles covered TiO2 thin film and its structural, optoelectronic properties  

Science.gov (United States)

Surface plasmon resonance is one of the most interesting phenomena shown by noble metal nanoparticles (NPs) in nanoscale dimension. Gold, silver NPs used to show enhancement in absorption at their selective plasmon resonance frequency. But indium (In) shows broader resonance, and hence, In NPs can be employed for the purpose of wideband detection. Here, glancing angle deposition is incorporated in an e-beam chamber to obtain controlled growth of 5, 10 and 30 nm In NPs array over TiO2 thin film (TF) on ITO-coated glass plate. The 5-nm In NPs on TiO2 TF process superior performances in terms of enhanced Raman scattering and optical absorption. Optical absorption spectrophotometry shows averagely two times enhancement in absorption for 5-nm In NPs compared to bared TiO2 TF on Si substrate. The plasmonic detector (TiO2 TF/5-nm In NPs/TiO2 TF/Si) produced dark current of 0.36 µA/cm2 at 5 V, which increased to 0.51 µA/cm2 under white light illumination. The maximum 116 times photosensitivity at -2 V was calculated for the plasmonic device. The NPs-designed plasmonic device shows twofold photoresponsivity in visible region (400-650 nm) with respect to the bared TiO2TF device. The external quantum efficiency for plasmonic device was calculated to be 65 %.

Choudhuri, B.; Mondal, A.; Ganguly, A.; Saha, A. K.; Chattopadhyay, K. K.

2014-08-01

145

Localised modifications of anatase TiO 2 thin films by a Focused Ion Beam  

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A Focused Ion Beam (FIB) has been used to implant micrometer-sized areas of polycrystalline anatase TiO 2 thin films with Ga + ions using fluencies from 10 15 to 10 17 ions/cm 2. The evolution of the surface morphology was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition, the chemical modifications of the surface were followed by X-ray photoelectron spectroscopy (XPS). The implanted areas show a noticeable change in surface morphology as compared to the as-deposited surface. The surface loses its grainy morphology to gradually become a smooth surface with a RMS roughness of less than 1 nm for the highest ion fluence used. The surface recession or depth of the irradiated area increases with ion fluence, but the rate with which the depth increases changes at around 5 × 10 16 ions/cm 2. Comparison with implantation of a pre-irradiated surface indicates that the initial surface morphology may have a large effect on the surface recession rate. Detailed analysis of the XPS spectra shows that the oxidation state of Ti and O apparently does not change, whereas the implanted gallium exists in an oxidation state related to Ga 2O 3.

Surpi, A.; Göthelid, E.; Kubart, T.; Martin, D.; Jensen, J.

2010-10-01

146

Effect of polyethylene glycol additive in sol on the humidity sensing properties of a TiO2 thin film  

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We describe the effect of polyethylene glycol (PEG) addition to the precursor solution on the humidity sensing properties of a TiO2 thin film. Thin films of TiO2 were prepared by sol-gel and spin coating techniques. An increase in humidity sensitivity has been observed after the addition of PEG. This increase in sensitivity is due to smaller crystallites and pores created during the combustion of the polymer. The response and recovery time of the sensor were about 10 and 176 s, respectively. An equivalent circuit has been proposed and fitted well with the experimental data. We demonstrate that a controlled amount of polymer addition leads to the sensor being highly sensitive in the lower humidity (<40% RH) region.

Biju, Kuyyadi P.; Jain, Mahaveer K.

2007-09-01

147

Study of 44Ti grain boundary self-diffusion in thin nanocrystalline TiO2 films  

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Titanium dioxide is known for its photo-catalytic properties and enhanced corrosion resistance in aqueous environments. Due to these properties TiO2 is very attractive material for light-induced self-cleaning glass, water-cleaning and producing hydrogen from water applications. Numerous works are dedicated to the diffusion of various dopants like niobium or chromium in TiO2 but so far, none studied the self-diffusion of titanium in nanocrystalline TiO2. The grain boundary self-diffusion in thin nanocrystalline TiO2 films is investigated. The oxide films are produced using a novel deposition method from metal-organic precursors at relatively low (400-500 C) temperatures. A relaxation annealing at 800 C was performed. The diffusion was measured in temperature interval between 200 C and 600 C by means of the radiotracer technique applying the 44Ti isotope and utilizing ion beam sputtering for sectioning. The diffusion was measured at different oxygen pressures. In addition, the microstructure and its possible evaluation during diffusion annealing was investigated using TEM. The results are discussed with respect of the relationship between grain boundary self-diffusion and the synthesis pathway, the oxygen pressure and resulting microstructure of the nanoscale functional oxide films.

Straumal, Petr [Institut fuer Materialphysik, Universitaet Muenster, D-48149 Muenster (Germany); National University of Science and Technology, MISIS, 119049 Moscow (Russian Federation); Divinski, Sergiy; Wilde, Gerhard [Institut fuer Materialphysik, Universitaet Muenster, D-48149 Muenster (Germany)

2011-07-01

148

Evolution of structural and optical properties of photocatalytic Fe doped TiO2 thin films prepared by RF magnetron sputtering  

International Nuclear Information System (INIS)

Undoped and Fe doped TiO2 thin films have been prepared by RF magnetron sputtering. Pure TiO2 thin film exhibited an amorphous-like nature. With increase in iron concentration (0–0.1 at%), the films exhibited better crystallization to anatase phase . Red shift of absorption edge was observed in the UV-vis transmittance spectra . At higher Fe concentration (0.5 at%), onset of phase transformation to rutile is noticed. Photocatalytic properties of pure and 0.1 at% Fe doped TiO2 thin films were investigated by degradation of methylene blue in UV light, visible light and light from Hg vapor lamp. 70% degradation of methylene blue was observed in the presence of Fe doped film in comparison with 3% degradation in presence of pure TiO2 film when irradiated using visible light for 2 h

149

Correlation lengths, porosity and water adsorption in TiO2 thin films prepared by glancing angle deposition  

International Nuclear Information System (INIS)

This paper reports a thorough microstructural characterization of glancing angle deposited (GLAD) TiO2 thin films. Atomic force microscopy (afm), grazing-incidence small-angle x-ray scattering (GISAXS) and water adsorption isotherms have been used to determine the evolution of porosity and the existence of some correlation distances between the nanocolumns constituting the basic elements of the film’s nanostructure. It is found that the deposition angle and, to a lesser extent, the film thickness are the most important parameters controlling properties of the thin film. The importance of porosity and some critical dimensions encountered in the investigated GLAD thin films is highlighted in relation to the analysis of their optical properties when utilized as antireflective coatings or as hosts and templates for the development of new composite materials. (paper)

150

Growth of high quality rutile TiO2 thin film using ZnO buffer layer on Si(100) substrate  

International Nuclear Information System (INIS)

The TiO2 rutile thin films were grown on Si(100) substrates with ZnO buffer layer at a substrate temperature of 500 oC by radio frequency (rf) magnetron sputtering. In order to investigate the effect of buffer layer thickness on the growth of the TiO2 film, the ZnO buffer layers were deposited in the thickness range of 70-150 nm. The thickness of the TiO2 films was about 200 nm identical for all the samples. The crystal structure of the buffer layers and the TiO2 thin films was characterized by X-ray diffractometer (XRD). The XRD spectra confirmed that TiO2 rutile film with high crystalline quality was achieved on the ZnO buffer layer, which had a great relation to the improvement of the crystalline quality of the ZnO buffer layer. The surface morphologies of the TiO2 rutile thin films were evaluated by atomic force microscopy (AFM). The roughness of the TiO2 thin films became smoother as the thickness of the ZnO buffer layer increased

151

Superhydrophobic ceramic coatings enabled by phase-separated nanostructured composite TiO2-Cu2O thin films  

Science.gov (United States)

By exploiting phase-separation in oxide materials, we present a simple and potentially low-cost approach to create exceptional superhydrophobicity in thin-film based coatings. By selecting the TiO2-Cu2O system and depositing through magnetron sputtering onto single crystal and metal templates, we demonstrate growth of nanostructured, chemically phase-segregated composite films. These coatings, after appropriate chemical surface modification, demonstrate a robust, non-wetting Cassie-Baxter state and yield an exceptional superhydrophobic performance, with water droplet contact angles reaching to ˜172° and sliding angles active nature of TiO2, the chemically coated composite film surfaces display UV stability and retain superhydrophobic attributes even after exposure to UV (275 nm) radiation for an extended period of time. The present approach could benefit a variety of outdoor applications of superhydrophobic coatings, especially for those where exposure to extreme atmospheric conditions is required.

Aytug, Tolga; Bogorin, Daniela F.; Paranthaman, Parans M.; Mathis, John E.; Simpson, John T.; Christen, David K.

2014-06-01

152

An electrochemical strategy to incorporate nitrogen in nanostructured TiO2 thin films: modification of bandgap and photoelectrochemical properties  

Science.gov (United States)

We describe a simple and facile electrochemical method to introduce anionic dopants into TiO2. N-doped thin films with chemical composition TiO2-xNx, up to x = 0.23, were fabricated by anodic oxidation of a pure titanium sheet in electrolyte solutions containing ammonium ions, nitrate ions and fluoride ions enabling simultaneous nanostructuring and doping of the growing anodic oxide. Analysis by x-ray photoelectron spectroscopy (XPS) indicates that nitrogen atoms substitute for oxygen sites within the TiO2. F atoms were present in the amorphous, as-anodized samples but were resubstituted by O atoms upon annealing in oxygen at temperatures higher than 600 °C. For nitrogen doped films UV-vis spectroscopy indicates a shift in the primary absorption threshold as well as significant optical absorption in the visible wavelength range from 400 to 530 nm. The concentration of the incorporated anionic dopants, and the morphology of the doped thin film are strong functions of electrolyte chemistry and anodization time. Longer anodization periods resulted in a well-developed nanotube-array structure but smaller amounts of incorporated nitrogen. XPS depth profiling reveals the nitrogen doping to be inhomogeneous, with maximum nitrogen incorporation occurring near the oxide-electrolyte interface at the surface of the anodized film.

Shankar, Karthik; Chhay Tep, Kong; Mor, Gopal K.; Grimes, Craig A.

2006-06-01

153

Combinatorial synthesis and high-throughput evaluation of doped TiO2 thin films for the development of photocatalysts  

Science.gov (United States)

TiO2 thin films doped with various transition metals were systematically fabricated by combinatorial laser MBE technique. Alternating KrF excimer laser ((lambda) equals 248 nm) ablation of TiO2 and Ti1-x MxO2 (M equals transition metal) was employed to deposit combinatorial library of 18 samples for each dopant with different concentrations. Anatase films with c-axis orientation were grown epitaxially on SrTiO3(001) substrate while the rutile phase films with a-axis orientation were on Al2O3(0001) substrate. Solid solubility of transition metals in both the phases was determined by X-ray diffraction. The anatase phase was found to dissolve the transition metals in higher concentrations than rutile phase. The parallel evaluation of the photocatalytic activity of the doped TiO2 in combinatorial libraries was performed with respect to photo-decomposition of water in presence of a small amount of oxidizing or reducing agent which induced pH changes on the pixels. The high throughput evaluation of combinatorially deposited photocatalytic thin films was realized by adopting a potentiometric pH field effect transistor for sensing such pH changes.

Matsumoto, Yuji; Murakami, Makoto; Jin, Zhengwu; Nakayama, Akira; Yamaguchi, Tetsuo; Ohmori, Takashi; Suzuki, Eiji; Nomura, Satoshi; Kawasaki, Masashi; Koinuma, Hideomi

2000-05-01

154

Co-doped TiO2 thin films studied by magnetic resonance technique  

International Nuclear Information System (INIS)

TiO2 thin films with different Co nanoparticle content were prepared by reactive co-sputtering onto Si (100) substrates. The films thicknesses were in range of 200 to 330 nm. Electron probe microanalysis showed the Co content (x) of the Ti1-xCoxO2 samples was 2.2, 3.0, 4.4, 6.5, and 8.5 %. X-ray diffraction measurements revealed polycrystalline Rutile structure of the samples. Magnetization measurements showed hysteresis behavior for all samples with the coercive field in range of 55 - 65 Oe. The saturation magnetization at room temperature ranged from 7 emu/cm''3 (2.2 % Co) to 28 emu/cm''3 (8.5 % Co). X-band (9.5 GHz) Electron Spin Resonance measurements were performed as a function of the sample orientation and temperature. Weak ESR signals that depended on Co content were observed at room temperature. Different contributions to the room temperature spectra were attributed to super-paramagnetic cobalt particles, some ferromagnetic phase in the sample, and paramagnetic impurities in silicon substrate. Very strong temperature dependence of ESR spectra has been observed in all samples. The room temperature signals decreased with cooling, and vanished at lowest temperatures. A very broad signal appeared with cooling, dramatically intensified at about 50-80K, and then decreased at lowest temperature (10K). A kind of phase transition in the temperature behavior of the intensity was observed in the temperature range of 50-60K. We attribute this behavior to unconventional spin-glass-like ordering realized in the system. The results received are important for understanding the tunnel magnetoresistance behavior of such systems

155

Production of multicharged iron and nitrogen ions and application to enhance photo-catalytic performance in visible light region on TiO2 thin films  

International Nuclear Information System (INIS)

Multicharged iron and nitrogen ions have been produced from solid materials in a 2.45 GHz electron cyclotron resonance (ECR) ion source (TAIKO device, Toyama Prefectural University), and also large area TiO2 thin films are individually produced by reactive sputtering in an arched ECR plasma. We normally form the TiO2 thin film (?100 nm) on the Si(1 0 0) substrates. We measure the X-ray diffraction for characterization of the TiO2 crystallinity and the contact angle of distilled water for estimation of photo-catalytic performance. The crystalline TiO2 thin films are anatase and rutile phases. Fe3+ and N3+ ions were implanted into TiO2 thin films on the Si substrates in order to enhance photo-catalytic performance in visible light region. The maximum efficiency of photo-catalytic performance has been obtained at the dose of about 2 x 1015 cm-2. We compared contact angles of distilled water on the TiO2 by illuminating fluorescent light for four hours before and after implantation. Photo-catalytic performance of the TiO2 thin film in visible light region after implantation is better than that before implantation without deterioration in ultraviolet light region

156

Microstructure and optical properties of TiO2 thin films prepared by low pressure hot target reactive magnetron sputtering  

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Thin films of TiO2 were deposited onto (1 0 0) oriented silicon and glass substrates using modified magnetron sputtering method. The method, among the others, consisted in employing low pressure of reactive gas (-1 Pa), hot target (additional heating of the target) and low deposition rate (about 0.1 nm/s). X-ray diffraction, X-ray photoelectron spectroscopy and optical transmission measurements have been applied to study the influence of film thickness, substrate type and post annealing process on the microstructure, composition, and optical properties of prepared thin films. It was found that the lattice spacings were a bit smaller than those of bulk material what indicated the contraction of the thin film. Optical examinations have shown that the fundamental absorption edge was shifted toward longer wavelength region (from 330 to 351 nm) as the thickness of the film increased. It was stated that thin films of TiO2 were almost stoichiometric after additional annealing

157

Properties of TiO2 thin films and a study of the TiO2-GaAs interface  

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Titanium dioxide (TiO2) films prepared by chemical vapor deposition were investigated in this study for the purpose of the application in the GaAs metal-insulator-semiconductor field-effect transistor. The degree of crystallization increases with the deposition temperature. The current-voltage study, utilizing an Al-TiO2-Al MIM structure, reveals that the d-c conduction through the TiO2 film is dominated by the bulk-limited Poole-Frenkel emission mechanism. The dependence of the resistivity of the TiO2 films on the deposition environment is also shown. The results of the capacitance-voltage study indicate that an inversion layer in an n-type substrate can be achieved in the MIS capacitor if the TiO2 films are deposited at a temperature higher than 275 C. A process of low temperature deposition followed by the pattern definition and a higher temperature annealing is suggested for device fabrications. A model, based on the assumption that the surface state densities are continuously distributed in energy within the forbidden band gap, is proposed to interpret the lack of an inversion layer in the Al-TiO2-GaAs MIS structure with the TiO2 films deposited at 200 C.

Chen, C. Y.; Littlejohn, M. A.

1977-01-01

158

Electrical and optical properties of the hybrid TiO2 nanocrystals - MEH-PPV thin films  

International Nuclear Information System (INIS)

Recently, the conjugated polymer-inorganic nanocomposites have been increasingly studied because of their enhanced optical and electronic properties as well as their potential application in developing optoelectronic devices. In this study nanocomposite materials thin films based on poly [2-methoxy-5-(2-ethyl-hexyloxy) - 1,4- phenylene vinylene] (MEH-PPV) and nanocrystalline TiO2 (nc-TiO2) have been fabricated. The photoluminescence (PL) spectra of pure MEN-PPV and nanohybrid films have shown that the excitation at a 377 nm wavelength leads to the strongly enhanced performance in photoluminescent intensity due to the compositions of TiO2 component. Current-voltage (I-V) characteristics of multi-layer device Al/ /MEH-PPV; nc-TiO2/ /PEDOT: PSS/ /ITO/ /glass were investigated. the results show that the hybrid MEH-PPV: nc-TiO2 materials with high concentrations of TiO2 (>25 %) can be expected to be a good candidate for photovoltaic solar cell applications whereas hose with lower concentrations of TiO2 are more suitable for organic light-emitting diodes (OLEDs). (author)

159

Mechanical characterization of thin TiO2 films by means of microelectromechanical systems-based cantilevers  

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The measurement of mechanical parameters by means of microcantilever structures offers a reliable and accurate alternative to traditional methods, especially when dealing with thin films, which are extensively used in microfabrication technology and nanotechnology. In this work, microelectromechanical systems (MEMS)-based piezoresistive cantilevers were realized and used for the determination of Young's modulus and residual stress of thin titanium dioxide (TiO2) deposited by sputtering from a TiO2 target using a rf plasma discharge. Films were deposited at different thicknesses, ranging from a few to a hundred nanometers. Dedicated silicon microcantilevers were designed through an optimization of geometrical parameters with the development of analytical as well as numerical models. Young's modulus and residual stress of sputtered TiO2 films were assessed by using both mechanical characterization based on scanning profilometers and piezoresistive sensing elements integrated in the silicon cantilevers. Results of MEMS-based characterization were combined with the tribological and morphological properties measured by microscratch test and x-ray diffraction analysis.

Adami, A.; Decarli, M.; Bartali, R.; Micheli, V.; Laidani, N.; Lorenzelli, L.

2010-01-01

160

Mechanical characterization of thin TiO2 films by means of microelectromechanical systems-based cantilevers  

International Nuclear Information System (INIS)

The measurement of mechanical parameters by means of microcantilever structures offers a reliable and accurate alternative to traditional methods, especially when dealing with thin films, which are extensively used in microfabrication technology and nanotechnology. In this work, microelectromechanical systems (MEMS)-based piezoresistive cantilevers were realized and used for the determination of Young's modulus and residual stress of thin titanium dioxide (TiO2) deposited by sputtering from a TiO2 target using a rf plasma discharge. Films were deposited at different thicknesses, ranging from a few to a hundred nanometers. Dedicated silicon microcantilevers were designed through an optimization of geometrical parameters with the development of analytical as well as numerical models. Young's modulus and residual stress of sputtered TiO2 films were assessed by using both mechanical characterization based on scanning profilometers and piezoresistive sensing elements integrated in the silicon cantilevers. Results of MEMS-based characterization were combined with the tribological and morphological properties measured by microscratch test and x-ray diffraction analysis.

 
 
 
 
161

Anisotropic laser-induced damage threshold and residual stress of TiO2 sculptured thin films.  

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The residual stress and laser-induced damage threshold (LIDT) of TiO2 sculptured thin films prepared by glancing angle electron beam evaporation were studied. UV-Vis-NIR spectra and optical interferometer were employed to characterize the optical and mechanical properties, respectively. Optical microscopy and Raman spectra were used to observe damage morphology and analyze damage microstructure, respectively. It was found that the residual stress changed from compressive into tensile with increasing deposition angle. The LIDT was anisotropic with p- and s-polarization light, which was due to the anisotropic nanostructure and optical properties. Simultaneously, an optimum deposition angle for the maximum threshold of TiO2 film was about 60 degrees. The mechanism of laser-induced damage was thermal in nature. The process of thermal damage with crystallization is proved by Raman spectra. PMID:23646523

Xiao, Xiudi; Miao, Lei; Zhang, Ming; Xu, Gang; Shao, Jianda; Fan, Zhengxiu

2013-02-01

162

Chemical vapor deposition and characterization of nitrogen doped TiO2 thin films on glass substrates  

International Nuclear Information System (INIS)

Photocatalytically active, N-doped TiO2 thin films were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) using titanium tetra-iso-propoxide (TTIP) as a precursor and NH3 as a reactive doping gas. We present the influence of the growth parameters (temperature, reactive gas phase composition) on the microstructural and physico-chemical characteristics of the films, as deduced from X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultra-violet and visible (UV/Vis) spectroscopy analysis. The N-doping level was controlled by the partial pressure ratio R = [NH3]/[TTIP] at the entrance of the reactor and by the substrate temperature. For R = 2200, the N-doped TiO2 layers are transparent and exhibit significant visible light photocatalytic activity (PA) in a narrow growth temperature range (375-400 oC). The optimum N-doping level is approximately 0.8 at.%. However, the PA activity of these N-doped films, under UV light radiation, is lower than that of undoped TiO2 films of comparable thickness.

163

Determination of thermo-optic properties of atomic layer deposited thin TiO2 films for athermal resonant waveguide gratings by spectroscopic ellipsometry  

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We report on variation in the refractive index of amorphous and isotropic TiO2 thin films grown by Atomic Layer Deposition (ALD) in nano optical devices. ALD-TiO2 films of thicknesses thicknesses > 200 nm show positive TOC due to the predominance of TiO2 thickness over the very thin surface porosity region. The negative TOC of thin TiO2 films was controlled by depositing thin ALD-Al2O3 diffusion barrier films that showed impermeable behavior to block the evaporation of adsorbed water molecules on TiO2 surfaces in thermal environments. This approach turns negative sign of TOC of TiO2 thin films to positive one which is necessary to stabilize the central resonance peak of a guided mode resonance filter (GMRF). The ALD-TiO2 and ALDAl2O3 bi-layer stack was modeled by VASE analysis of spectroscopic ellipsometry using Cauchy Model to extract refractive indices at various temperatures, measured at two different angle of incidence (65° and 75°), covering a wide spectral range 380 dependent index and density of TiO2 films were calculated from ellipsometric measured data using Lorentz-Lorenz relation.

Saleem, Muhammad Rizwan; Ali, Rizwan; Honkanen, Seppo; Turunen, Jari

2014-05-01

164

Effect of electrode type in the resistive switching behaviour of TiO2 thin films  

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The influence of the electrode/active layer on the electric-field-induced resistance-switching phenomena of TiO2-based metal-oxide-metal devices (MOM) is studied. TiO2 active layers were fabricated by the reactive rf-sputtering technique and devices were made by sandwiching between several metal electrodes. Three different MOM devices were made, according with the junction type formed between the electrode and the TiO2 active layer, those where Ohmic-Ohmic, Ohmic-Schottky and Schottky-Schottky. The junction type was tested by electrical I-V measurements. It was found that MOM devices made with the Ohmic-Ohmic combination did not show any resistive switching behaviour in contrast with devices made with Ohmic-Schottky and Schottky-Schottky combinations. From a detailed analysis of the I-V curves it was found that transport characteristics are Ohmic for the low-resistance state for all the contacts combinations of the MOM devices, whereas in the high-resistance state it depends on contact combinations and can be identified as Ohmic, Schottky and Poole-Frenkel type. These conduction mechanisms in the low- and high-resistance states suggest that formation and rupture of conducting filaments through the film oxide is the mechanism responsible for the resistance switching.

165

TiO2--Ta2O5 composite thin films deposited by radio frequency ion-beam sputtering.  

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TiO2--Ta2O5 composite films were prepared by a radio frequency ion-beam sputtering deposition process, and the refractive indices and extinction coefficients of the composite films were found to be between those of the TiO2 and Ta2O5 films. The structure of the as-deposited films was amorphous, and the surface roughness was approximately 0.1 nm. The residual stress of the composite films was less than that of pure TiO2 film. The structure of the composite films after annealing was amorphous, with low surface roughness and slightly increased residual stress. The film containing 6.3% TiO2 displayed better properties than either the pure TiO2 or the pure Ta2O5 film. PMID:17151751

Lee, Cheng-Chung; Tang, Chien-Jen

2006-12-20

166

Ordered mesoporous thin films of rutile TiO2 nanocrystals mixed with amorphous Ta2O5.  

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Ordered mesoporous thin films of composites of rutile TiO2 nanocrystals with amorphous Ta2O5 are fabricated by evaporation-induced self-assembly followed by subsequent heat treatment beyond 780 degrees C. Incorporation of selected amounts of Ta2O5 (20 mol %) in the mesoporous TiO2 film, together with the unique mesoporous structure itself, increased the onset of crystallization temperature which is high enough to ensure the crystallization of amorphous titania to rutile. The ordered mesoporous structure benefits from a block-copolymer template, which stabilizes the mesostructure of the amorphous mixed oxides before crystallization. The surface and in-depth composition analysis by X-ray photoelectron spectroscopy suggests a homogeneous intermixing of the two oxides in the thin film. A detailed X-ray absorption fine structure measurement on the composite film containing 20 mol % Ta2O5 and heated to 800 degrees C confirms the amorphous nature of the Ta2O5 phase. Photocatalytic activity evaluation suggests that the rutile nanocrystals in the synthesized ordered mesoporous thin film possess good ability to assist the photodegradation of rhodamine B in water under illumination by UV light. PMID:18383238

Wu, Jin-Ming; Antonietti, Markus; Gross, Silvia; Bauer, Matthias; Smarsly, Bernd M

2008-04-01

167

The antibacterial and hydrophilic properties of silver-doped TiO2 thin films using sol-gel method  

International Nuclear Information System (INIS)

Ag-TiO2 composite thin films were deposited on glass slides by sol-gel spin coating technique. The surface structure, chemical components and transmittance spectra were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis spectrophotometer. The TiO2 thin films with silver molar ratio from 0 to 10% were tested for its antibacterial property by using Escherichia coliform (E. coli) under irradiation of UV light. The concentration of E. coli was evaluated by plating technique. The influences of different molar ratio of Ag on hydrophilicity and long-term durability of the films were also investigated by measuring the water contact angle. The results showed that the antibacterial ability was significantly improved by increasing silver content comparing with pure TiO2 thin film, and the best molar ratio of Ag was 5%. While the hydrophilicity of films increased with increasing silver content, and the best molar ratio of Ag was 1%.

168

Photocatalytic thin films of TiO2 formed by a sol-gel process using titanium tetraisopropoxide as the precursor  

International Nuclear Information System (INIS)

Thin TiO2 films were prepared with the dip-coating technique by using sols deriving from titanium tetraisopropoxide. TiO2 films were formed on glass substrates previously covered by a SiO2 layer obtained from a tetraethylortosilicate sol. The films, after a thermal treatment at 673 K, mainly consisted of TiO2 anatase. The samples were characterised by X-ray diffraction, UV-Vis spectroscopy, scanning electron microscopy and atomic force microscopy. The photoactivity of the various films was tested by using as probe reaction the photo-oxidation of 2-propanol in gas-solid regime. The photoreactivity results indicated that the TiO2 films were efficient for degrading 2-propanol under UV illumination, propanone being the only compound detected as intermediate product. Films prepared by using Degussa P25 appeared to be more photoactive, but the coating was easily detached by wiping

169

Spray pyrolysed microporous TiO2 thin films by optimisation of substrate temperature for ‘all sprayed’ solar cells  

Science.gov (United States)

Titanium dioxide thin films were deposited on glass substrate at temperatures ranging from 300 °C to 500 °C by a simple, cost effective spray pyrolysis method using commercially available TiO2 powder (Degussa P25). Analyses using scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveal the microporous nature of the films at 350 °C. X-ray diffraction (XRD) and Raman studies reveal that these films are amorphous in nature. The films were subsequently annealed at 500 °C for 2 h, resulting in crystallisation (the tetragonal anatase phase). XPS analysis was effectively used to study the chemical composition of the samples. Finally, optimized microporous TiO2 thin films were used for the fabrication of an ‘all-sprayed’ solar cell utilizing well-established CuInS2 as the absorber layer. The best device under this study has an open-circuit voltage of 409 mV and a short-circuit current density of 3.90 mA cm?2. The efficiency and fill factor were 0.61% and 38%, respectively.

Santhosh, M. V.; Deepu, D. R.; Geethu, R.; Rajeev Kumar, K.; Sudha Kartha, C.; Vijayakumar, K. P.

2014-11-01

170

Ligand coordination and spin crossover in a nickel porphyrin anchored to mesoporous TiO2 thin films.  

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The coordination and spin equilibrium of a Ni(II) meso-tetra(4-carboxyphenyl)porphyrin compound, NiP, was quantified both in fluid solution and when anchored to mesoporous, nanocrystalline TiO2 thin films. This comparison provides insights into the relative rate constants for excited-state injection and ligand field population. In the presence of pyridine, the spectroscopic data were consistent with the presence of equilibrium concentrations of a 4-coordinate low-spin S = 0 ((1)A1g) Ni(II) compound and a high-spin S = 1 ((3)B1g) 6-coordinate compound. Temperature-dependent equilibrium constants were consistently smaller for the surface-anchored NiP/TiO2, as were the absolute values of ?H and ?S. In the presence of diethylamine (DEA), the ground-state 6-coordinate compound was absent, but evidence for it was present after pulsed light excitation of NiP. Arrhenius analysis of data, measured from -40 to -10 °C, revealed activation energies for ligand dissociation that were the same for the compound in fluid solution and anchored to TiO2, Ea = 6.6 kcal/mol, within experimental error. At higher temperatures, a significantly smaller activation energy of 3.5 kcal/mol was found for NiP(DEA)2/TiO2. A model is proposed wherein the TiO2 surface sterically hinders ligand coordination to NiP. The lack of excited-state electron transfer from Ni(II)P*/TiO2 indicates that internal conversion to ligand field states was at least 10 times greater than that of excited-state injection into TiO2. PMID:23914901

Achey, Darren; Meyer, Gerald J

2013-08-19

171

Investigation of thin TiO2 films cosputtered with Si species  

International Nuclear Information System (INIS)

Titanium dioxide (TiO2) films were fabricated by cosputtering titanium (Ti) target and SiO2 or Si slice with ion-beam-sputtering deposition (IBSD) technique and were postannealed at 450 deg. C for 6 h. The variations of oxygen bonding, which included high-binding-energy oxygen (HBO), bridging oxygen (BO), low-binding-energy oxygen (LBO), and three chemical states of titanium (Ti4+, Ti3+ and Ti2+) were analyzed by X-ray photoelectron spectroscopy (XPS). The enhancement of HBO and reduction of BO in O 1s spectra as functions of SiO2 or Si amount in cosputtered film imply the formation of Si-O-Ti linkage. Corresponding increase of Ti3+ in Ti 2p spectra further confirmed the property modification of the cosputtered film resulting from the variation of the chemical bonding. An observed correlation between the chemical structure and optical properties, refractive index and extinction coefficient, of the SiO2 or Si cosputtered films demonstrated that the change of chemical bonding in the film results in the modification of optical properties. Furthermore, it was found that the optical properties of the cosputtered films were strongly depended on the cosputtering targets. In case of the Si cosputtered films both the refractive indices and extinction coefficients were reduced after postannealing, however, the opposite trend was observed in SiO2 cosputtered films. cosputtered films.

172

Preparation and characterization of Fe2O3-TiO2 thin films on glass substrate for photocatalytic applications  

International Nuclear Information System (INIS)

Fe2O3-TiO2 coatings were successfully prepared on glass slide substrates using sol-gel method for photocatalytic applications. The phase structure, thermal, microstructure and surface properties of the coatings were extensively characterized by using X-ray diffractometry (XRD), differential thermal analysis/thermograviometry (DTA/TG), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Their adhesion and absorbance properties were investigated by a scratch tester and UV-vis spectroscopy. Four different solutions were prepared by changing Fe/Ti molar ratios. Glass substrates were coated by solutions of Ti-alkoxide, Fe-chloride, glaciel acetic acid and isopropanol. The obtained gel films were dried at 300 deg. C for 10 min and subsequently heat-treated at 500 deg. C for 5 min in air. The oxide thin films were annealed at 600 deg. C for 60 min in air. The influence of Fe3+ concentration and number of layers on structure of the films was established. In addition, XRD results revealed that Fe2O3-TiO2 films composed of TiO2, Fe2Ti3O9, Ti3O5 and Fe3O4 phases. According to DTA/TG result, it was determined that endothermic and exothermic reactions were formed at temperatures between 80 and 650 deg. C due to solvent removal, combustion of carbon based materials and oxidation of Fe and Ti. SEM observations exhibited that the coating structure becomes more homogeneous depending on an increase of Fe/Ti molar ratios and thus a regular surface morphology forms with increasing Fe/Ti ratio. It was also seen that as the Fe/Ti ratio increases the surface roughness of the films increases. Critical adhesion force of thin films with Fe/Ti ratio of 0, 0.07, 0.18 and 0.73 were found to be 9, 25, 28 and 21 mN, respectively. The methylene blue solutions photocatalyzed by TiO2 based thin films shows characteristic absorption bands at 420 nm

173

Fabrication and Characterization of Hydrophilic TiO2 Thin Films on Unheated Substrates Prepared by Pulsed DC Reactive Magnetron Sputtering  

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Full Text Available TiO2 thin films were deposited on unheated silicon wafers (100 and glass slides by a pulsed DC reactive magnetron sputtering in an ultrahigh vacuum (UHV system. The effects of both an operating pressure and deposition time on film structure, surface morphology, and optical property were studied. The film structure and microstructure were characterized by grazing-incidence X-ray diffraction (GIXRD technique and transmission electron microscopy (TEM. The surface morphology was investigated by field emission scanning electron microscopy (FE-SEM. The optical property of the TiO2 thin films was determined by spectroscopic ellipsometry (SE. The water contact angle measurement was also used to determine hydrophilicity of the films after exposed to UV light. The results suggested that the TiO2 thin film at less than 40?nm was amorphous. As the thickness was increased, the mixture of anatase and rutile phases of TiO2 began to form. By reducing the operating pressure during the film deposition, the rutile phase component can also be enhanced. Both the increased film thickness and decrease operating pressure were the critical factors to improve the hydrophilicity of the TiO2 thin films.

M. Horprathum

2010-01-01

174

Gamma Radiation Monitoring Through Thin Film of ClAlPc Doped With TiO2  

International Nuclear Information System (INIS)

Chloroaluminum phthalocyanine (ClAlPc) synthesized by adopting focused microwave synthesis approach was doped with nanocrystalline TiO2 (5% by weight) and developed into the thin film sandwiched device having ITO/ClAlPc:TiO2/Ag Schottky configuration by spin coating technique covering 1 cm2 as an active area. The so fabricated device having initial dark current of the order of 0.2 5 m A was exposed to variable dose of gamma radiation ranging from lcGy to 10 Gy at a dose rate of 1 Gy/hour. The experimental observation reveals the generation of localized traps leading to structural disorder within the solid material. Doping with TiO2 enhances the surface area of the film which in tern improves sensitivity of device to wider dose rage. Exposure of the device to variable dose of gamma radiation imparts decrease in forward bias current and capacitance characteristics with increase in radiation dose. Also, absorbance characteristics of the Al Pc: TiO2 was analyzed before and after exposure to radiation which reveals that absorbance decreases with radiation dose leading to decrease in optical band gap

175

Thickness-dependent electron transport performance of mesoporous TiO2 thin film for dye-sensitized solar cells  

International Nuclear Information System (INIS)

Anatase titania (TiO2) nanocrystals with an average size of 12 nm were synthesized by combining sol–gel method and hydrothermal crystallization technology. Mesoporous TiO2 thin film electrodes (MTTFEs) were prepared by variations in layer of screen-printed TiO2 nanocrystals pastes, and dye-sensitized solar cells (DSCs) based on different thickness of MTTFEs were fabricated with dye C106. Under the irradiation of 100 mW cm?2 air mass 1.5 global (AM1.5G) sunlight, the short-circuit photocurrent density (Jsc) and overall conversion efficiency (?) was improved when the thickness of MTTFEs increased from 2.1 ?m to 9.8 ?m, and obvious decreases of the Jsc and ? were found when the film thickness was further increased over 9.8 ?m. The kinetic parameters of electron transport were investigated by the transient photoelectrical and electrical impedance measurements, and then the influence of MTTFEs thickness on electron transport performance in DSCs were further discussed. The results showed that the density of states (DOS) and recombination rate (Kr) increased with the MTTFEs thickness increasing. Furthermore, when the thickness of MTTFEs was in the range of 2.1–9.8 ?m, the electron lifetime (?n), the electron diffusion coefficient (Dn), and the electron diffusion length (Ln) of devices increased, but these parameters decreased gradually with the further increased thickness of MTTFEs, which influenced the electronic transport performance of DSCs

176

Structural investigations of TiO2:Tb thin films by X-ray diffraction and atomic force microscopy  

International Nuclear Information System (INIS)

In this work, structural investigations of TiO2 thin films doped with Tb at the amount of 0.4, 2 and 2.6 at.% have been outlined. Thin films were deposited on Si and SiO2 substrates by high energy reactive magnetron sputtering from mosaic Ti-Tb target. The influence of Tb dopant amount, post-annealing treatment and kind of applied substrate on microstructure has been discussed. Thin films were investigated by means of X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD analysis revealed the existence of crystalline TiO2 in anatase and rutile forms, depending on Tb amount in examined samples. AFM images show that as-deposited samples with 0.4 at.% concentration of terbium (anatase structure) have bigger crystallites as compared to 2% and 2.6 at.% of Tb (rutile structure). The additional annealing at 1070 K results in a mixed anatase (77%) and rutile (23%) structure

177

Apatite formation from simulated body fluid on various phases of TiO2 thin films prepared by filtered cathodic vacuum arc deposition  

International Nuclear Information System (INIS)

Hydroxyl (OH-)-free TiO2 thin films with amorphous and crystalline phases were deposited onto (100) silicon substrates using filtered cathodic vacuum arc deposition in order to investigate the in vitro apatite formation in simulated body fluid (SBF). The surface morphology, composition and structure of the TiO2 thin films were characterized. The X-ray photoelectron spectroscopy results confirmed the presence of calcium and phosphorus on all TiO2 thin film surfaces after immersion in SBF at 37 oC. Fourier transform infra red results showed the presence of carbonated apatite on the surface of these films. Amorphous structured TiO2 thin film showed poor ability to form apatite on its surface in SBF. Apatite formation was more pronounced on the surfaces of the anatase films in comparison to those of rutile. The carbonated apatite deposition rate increased significantly when the TiO2 film was illuminated with UV light prior to immersing in the SBF. In particular, the UV-treated anatase and rutile films showed increased rates of carbonated apatite formation on their surfaces in comparison to samples not treated with radiation. The increase in hydrophilicity due to UV treatment appears beneficial for the apatite growth on these surfaces.

178

Synthesis of TiO2 thin films using single molecular precursors by MOCVD method for dye-sensitized solar cells application and study on film growth mechanism  

International Nuclear Information System (INIS)

For dye-sensitized solar cells application, in this study, we have synthesized TiO2 thin films at deposition temperature in the range of 300–750 °C by metalorganic chemical vapor deposition (MOCVD) method. Titanium(IV) isopropoxide, (TIP, Ti(OiPr)4) and Bis(dimethylamido)titanium diisopropoxide, (BTDIP, (Me2N)2Ti(OiPr)2) were used as single source precursors that contain Ti and O atoms in the same molecule, respectively. Crack-free, highly oriented TiO2 polycrystalline thin films with anatase phase were deposited on Si(1 0 0) with TIP at temperature as low as 450 °C. XRD and TED data showed that below 500 °C, the TiO2 thin films were dominantly grown in the [2 1 1] direction on Si(1 0 0), whereas with increasing the deposition temperature to 700 °C, the main film growth direction was changed to [2 0 0]. Above 700 °C, however, rutile phase TiO2 thin films have only been obtained. In the case of BTDIP, on the other hand, only amorphous film was grown on Si(1 0 0) below 450 °C while a highly oriented anatase TiO2 film in the [2 0 0] direction was obtained at 500 °C. With further increasing deposition temperatures over 600 °C, the main film growth direction shows a sequential change from rutile [1 0 1] to rutile [4 0 0], indicating a possibility of getting single crystalline TiO2 film with rutile phase. This means that the precursor together with deposition temperature can be one of important parameters to influence film growth direction, crystallinity as well as crystal structure. To investigate the CVD mechanism of both precursors in detail, temperature dependence of growth rate was also carried out, and we then obtained different activation energy of deposition to be 77.9 and 55.4 kJ/mol for TIP and BTDIP, respectively. Also, we are tested some TiO2 film synthesized with BTDIP precursor to apply dye-sensitized solar cell.

179

Irradiation induced ferromagnetism at room temperature in TiO2 thin films: X-ray magnetic circular dichroism characterizations  

International Nuclear Information System (INIS)

We report on the room temperature ferromagnetism in the swift heavy ion (SHI) irradiated TiO2 thin films by x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) experiments at the O K and Ti L3,2 absorption edges. The XAS/XMCD measurements provide direct evidence of magnetic polarization of the O 2p and Ti 3d orbitals. The unquenched orbital magnetic moment within the O 2p shell is ferromagnetically coupled to the neighboring Ti moments, which illustrates the intense hybridization of the O 2p and Ti 3d orbitals induced by SHI irradiation.

180

Degradation of gas-phase trichloroethylene over thin-film TiO2 photocatalyst in multi-modules reactor  

International Nuclear Information System (INIS)

The present paper examined the photocatalytic degradation (PCD) of gas-phase trichloroethylene (TCE) over thin-film TiO2. A large-scale treatment of TCE was carried out using scale-up continuous flow photo-reactor in which nine reactors were arranged in parallel and series. The parallel or serial arrangement is a significant factor to determine the special arrangement of whole reactor module as well as to compact the multi-modules in a continuous flow reactor. The conversion of TCE according to the space time was nearly same for parallel and serial connection of the reactors.

 
 
 
 
181

Highly efficient photoelectrochemical performance of SrTiO3/TiO2 heterojunction nanotube array thin film  

International Nuclear Information System (INIS)

SrTiO3–TiO2 heterojunction thin-film nanotube arrays (SNTs, the average inner diameter is about 50 nm) was fabricated via electrochemical anodization followed by a hydrothermal treatment. The photo-to-current conversion properties and the photoelectrochemical performance for cathodic protection of carbon steel in 0.5 M of sodium chloride solution under white light illumination were investigated. The results showed that the highly ordered nanotube arrays could provide very excellent cathodic protection for carbon steel under white light irradiation.

182

ERD analysis and modification of TiO 2 thin films with heavy ions  

Science.gov (United States)

Titanium dioxide (TiO 2) films have been deposited on Si substrates using reactive magnetron sputtering. The resulting films, having a polycrystalline anatase phase with a dense columnar structure, were analysed by time-of-flight elastic recoil detection analysis (ToF-ERDA) using 40 MeV I 9+ ions. A clear decrease in the areal atomic density (atoms/cm 2) of Ti and O was observed during measurement, but the stoichiometry remained essentially constant up to a fluence of 4 × 10 13 ions/cm 2. To investigate this effect in more detail, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were applied in order to characterize the films prior to and after ion irradiation with fluences in the range of 10 10-10 13 ions/cm 2. Distinct morphological and structural changes of the polycrystalline film were observed. XRD revealed that the crystallinity of the film was gradually destroyed, and the film became amorphous at a fluence above 5 × 10 12 ions/cm 2. SEM and AFM measurements revealed topographical changes in the form of surface recession and smoothing compared to the pristine polycrystalline surface. The observed change in areal atomic density during ERD measurement is believed to be due to the combined effects of electronic sputtering, amorphization and ion hammering.

Jensen, J.; Martin, D.; Surpi, A.; Kubart, T.

2010-06-01

183

The role of energetic ion bombardment during growth of TiO2 thin films by reactive sputtering  

International Nuclear Information System (INIS)

TiO2 thin films have been deposited by several different sputtering processes: (i) dc magnetron sputtering (dcMS) employing various geometrical conditions, (ii) ion-assisted dc magnetron sputtering where additional ion bombardment of the growing films was performed with an auxiliary ECR ion source and (iii) high power impulse magnetron sputtering (HiPIMS). Films have been investigated mainly by grazing incidence x-ray diffraction and atomic force microscopy. It is shown that the highly energetic oxygen ions inherent in reactive sputtering of metal oxides are the dominant energetic species governing structure formation of TiO2 films by their kinetic impact. The trajectories of these energetic oxygen ions strongly depend on the shape of the erosion trace and hence on the age of the target, which therefore has a strong influence on structure formation. Furthermore, in a HiPIMS discharge the role of this energetic oxygen ion bombardment is strongly intensified due to the increased target voltage and the lower deposition rate compared with a dcMS discharge. It is also demonstrated that films with pure rutile structure which are stable under a post-deposition thermal treatment can be deposited under intense energetic ion bombardment at low temperatures either by HiPIMS at high peak power densities or by ion-assisted dcMS.

184

Growth and characterization of nitrogen-doped TiO2 thin films prepared by reactive pulsed laser deposition  

International Nuclear Information System (INIS)

Nitrogen-doped titanium dioxide (TiO2) thin films were grown on (001) SiO2 substrates by reactive pulsed laser deposition. A KrF* excimer laser source (? = 248 nm, ?FWHM ? 10 ns, ? = 10 Hz) was used for the irradiations of pressed powder targets composed by both anatase and rutile phase TiO2. The experiments were performed in a controlled reactive atmosphere consisting of oxygen or mixtures of oxygen and nitrogen gases. The obtained thin film crystal structure was investigated by X-ray diffraction, while their chemical composition as well as chemical bonding states between the elements were studied by X-ray photoelectron spectroscopy. An interrelation was found between nitrogen concentration, crystalline structure, bonding states between the elements, and the formation of titanium oxinitride compounds. Moreover, as a result of the nitrogen incorporation in the films a continuous red-shift of the optical absorption edge accompanied by absorption in the visible spectral range between 400 and 500 nm wavelength was observed.

185

TiO2(Fe3+) nanostructured thin films with antibacterial properties  

International Nuclear Information System (INIS)

TiO2-based nanostructured Fe3+-doped coatings have been prepared by the sol-gel method on glass substrates. The coatings were characterized by X-ray diffraction and spectroellipsometry methods. The influence of Fe3+ dopant concentration, number of coatings, and calcination temperature on the films structure was established. The antibacterial activity against E. coli, has been studied applying the so-called antibacterial-drop test. The bactericidal activity for the above bacteria cells was estimated by relative number of bacteria survived calculated from the number of viable cells which form colonies on the nutrient agar plates. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the temperature of thermal treatment and formation of anatase crystalline structure. The long thermal treatment results in rutile crystalline structure formation followed by the decrease in the antibacterial activity of the coating

186

Al2O3/TiO2 nanolaminate thin film encapsulation for organic thin film transistors via plasma-enhanced atomic layer deposition.  

Science.gov (United States)

Organic electronic devices require a passivation layer that protects the active layers from moisture and oxygen because most organic materials are very sensitive to such gases. Passivation films for the encapsulation of organic electronic devices need excellent stability and mechanical properties. Although Al2O3 films obtained with plasma enhanced atomic layer deposition (PEALD) have been tested as passivation layers because of their excellent gas barrier properties, amorphous Al2O3 films are significantly corroded by water. In this study, we examined the deformation of PEALD Al2O3 films when immersed in water and attempted to fabricate a corrosion-resistant passivation film by using a PEALD-based Al2O3/TiO2 nanolamination (NL) technique. Our Al2O3/TiO2 NL films were found to exhibit excellent water anticorrosion and low gas permeation and require only low-temperature processing (<100 °C). Organic thin film transistors with excellent air-stability (52 days under high humidity (a relative humidity of 90% and a temperature of 38 °C)) were fabricated. PMID:24712401

Kim, Lae Ho; Kim, Kyunghun; Park, Seonuk; Jeong, Yong Jin; Kim, Haekyoung; Chung, Dae Sung; Kim, Se Hyun; Park, Chan Eon

2014-05-14

187

Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium  

International Nuclear Information System (INIS)

We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO2) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy. The TiO2 thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO2 thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO2/Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33?±?0.02?eV was determined for the amorphous TiO2 thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2?eV was obtained at the TiO2/Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO2/Ge system were found to be smaller than 1?eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of ?EV(100)?>??EV(111)?>??EV(110) and a conduction band-offset relation of ?EC(110) >??EC(111)?>??EC(100). These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO2 for potential high-? dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors

188

Interfacial band alignment and structural properties of nanoscale TiO2 thin films for integration with epitaxial crystallographic oriented germanium  

Science.gov (United States)

We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO2) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy. The TiO2 thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO2 thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO2/Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33 ± 0.02 eV was determined for the amorphous TiO2 thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2 eV was obtained at the TiO2/Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO2/Ge system were found to be smaller than 1 eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of ?EV(100) > ?EV(111) > ?EV(110) and a conduction band-offset relation of ?EC(110) > ?EC(111) > ?EC(100). These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO2 for potential high-? dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors.

Jain, N.; Zhu, Y.; Maurya, D.; Varghese, R.; Priya, S.; Hudait, M. K.

2014-01-01

189

Enhanced photoelectrochemical properties of F-containing TiO 2 sphere thin film induced by its novel hierarchical structure  

Science.gov (United States)

The novel nanostructured F-containing TiO 2 (F-TiO 2) sphere was directly synthesized on the surface of Ti foil in the solution of NH 4F and HCl by one-step hydrothermal approach under low-temperature condition. The samples were characterized respectively by means of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that the F-TiO 2 sphere was hierarchical structure, which composed of porous octahedron crystals with one truncated cone, leading to a football-like morphology. XPS results indicated that F - anions were just physically adsorbed on the surface of TiO 2 microspheres. The studies on the optical properties of the F-TiO 2 were carried out by UV-vis light absorption spectrum. The surface fluorination of the spheres, the unique nanostructure induced accessible macropores or mesopores, and the increased light-harvesting abilities were crucial for the high photoelectrochemical activity of the synthesized F-TiO 2 sphere for water-splitting. The photocurrent density of the F-TiO 2 sphere thin film was more than two times than that of the P25 thin film. Meanwhile, a formation mechanism was briefly proposed. This approach could provide a facile method to synthesize F-TiO 2 microsphere with a special morphology and hierarchical structure in large scale.

Dong, Xiang; Tao, Jie; Li, Yingying; Zhu, Hong

2009-05-01

190

A Micro Oxygen Sensor Based on a Nano Sol-Gel TiO2 Thin Film.  

Science.gov (United States)

An oxygen gas microsensor based on nanostructured sol-gel TiO2 thin films with a buried Pd layer was developed on a silicon substrate. The nanostructured titania thin films for O2 sensors were prepared by the sol-gel process and became anatase after heat treatment. A sandwich TiO2 square board with an area of 350 ?m × 350 ?m was defined by both wet etching and dry etching processes and the wet one was applied in the final process due to its advantages of easy control for the final structure. A pair of 150 nm Pt micro interdigitated electrodes with 50 nm Ti buffer layer was fabricated on the board by a lift-off process. The sensor chip was tested in a furnace with changing the O2 concentration from 1.0% to 20% by monitoring its electrical resistance. Results showed that after several testing cycles the sensor's output becomes stable, and its sensitivity is 0.054 with deviation 2.65 × 10-4 and hysteresis is 8.5%. Due to its simple fabrication process, the sensor has potential for application in environmental monitoring, where lower power consumption and small size are required. PMID:25192312

Wang, Hairong; Chen, Lei; Wang, Jiaxin; Sun, Quantao; Zhao, Yulong

2014-01-01

191

A Micro Oxygen Sensor Based on a Nano Sol-Gel TiO2 Thin Film  

Directory of Open Access Journals (Sweden)

Full Text Available An oxygen gas microsensor based on nanostructured sol-gel TiO2 thin films with a buried Pd layer was developed on a silicon substrate. The nanostructured titania thin films for O2 sensors were prepared by the sol-gel process and became anatase after heat treatment. A sandwich TiO2 square board with an area of 350 ?m × 350 ?m was defined by both wet etching and dry etching processes and the wet one was applied in the final process due to its advantages of easy control for the final structure. A pair of 150 nm Pt micro interdigitated electrodes with 50 nm Ti buffer layer was fabricated on the board by a lift-off process. The sensor chip was tested in a furnace with changing the O2 concentration from 1.0% to 20% by monitoring its electrical resistance. Results showed that after several testing cycles the sensor’s output becomes stable, and its sensitivity is 0.054 with deviation 2.65 × 10?4 and hysteresis is 8.5%. Due to its simple fabrication process, the sensor has potential for application in environmental monitoring, where lower power consumption and small size are required.

Hairong Wang

2014-09-01

192

Enhanced photoelectrochemical properties of F-containing TiO2 sphere thin film induced by its novel hierarchical structure  

International Nuclear Information System (INIS)

The novel nanostructured F-containing TiO2 (F-TiO2) sphere was directly synthesized on the surface of Ti foil in the solution of NH4F and HCl by one-step hydrothermal approach under low-temperature condition. The samples were characterized respectively by means of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that the F-TiO2 sphere was hierarchical structure, which composed of porous octahedron crystals with one truncated cone, leading to a football-like morphology. XPS results indicated that F- anions were just physically adsorbed on the surface of TiO2 microspheres. The studies on the optical properties of the F-TiO2 were carried out by UV-vis light absorption spectrum. The surface fluorination of the spheres, the unique nanostructure induced accessible macropores or mesopores, and the increased light-harvesting abilities were crucial for the high photoelectrochemical activity of the synthesized F-TiO2 sphere for water-splitting. The photocurrent density of the F-TiO2 sphere thin film was more than two times than that of the P25 thin film. Meanwhile, a formation mechanism was briefly proposed. This approach could provide a facile method to synthesize F-TiO2 microsphere with a special morphology and hierarchical structure in lmorphology and hierarchical structure in large scale.

193

Determination of the melting threshold of TiO2 thin films processed by excimer laser irradiation  

International Nuclear Information System (INIS)

Processing surfaces by laser needs an understanding of the mechanisms generated by irradiation. In this work, to gain understanding of the mechanisms occurring during irradiation of TiO2 thin films by means of KrF excimer laser, we have performed infrared time resolved reflectivity measurements. This experimental investigation revealed modifications of the heating/cooling cycle as a function of the fluence (F). These modifications start appearing for a fluence value of about ?0.25 J/cm2 which is associated with the melting threshold of the film. Additionally, we have solved numerically the heat equation of the system with specific boundary conditions. From these calculations, we have established the thermal history of the film during the 25 ns irradiation pulse. The data reveal that a part of the medium liquefies around a fluence of 0.23 J/cm2 in good agreement with the experimental data.

194

Room temperature synthesis of nanocrystalline anatase sols and preparation of uniform nanostructured TiO2 thin films: optical and structural properties  

Science.gov (United States)

Transparent TiO2 thin films were deposited on soda-lime glass substrates via the sol-gel method using a nanocrystalline TiO2 sol solution prepared at room temperature employing the dip-coating method. The effects of pH on crystallinity, particle size and stability of the synthesized TiO2 sols were investigated, systematically. TiO2 thin films were thickened by means of a sequential dip-coating process. The TiO2 films were transparent and exhibited proper adherence. The effects of thickness and annealing temperature on the structural and optical properties of the thin films were evaluated. The prepared powder was crystalline without any thermal treatment. The crystallite size of the particles (anatase) was in the range 4.2-12.1 nm depending on the initial pH value. Although only the anatase phase was observed at room temperature and 400 °C, a further increase in annealing temperature up to 700 °C resulted in the formation of the rutile phase. Even at high annealing temperatures, fairly smooth and homogeneous surfaces with no cracks and pores were observed. It was demonstrated that the films were transparent in the visible region with characteristic absorption in the UV region. Band gap of the as-deposited film was estimated to be 3.34 eV and was found to decrease with increasing annealing temperature.

Hosseingholi, M.; Pazouki, M.; Hosseinnia, A.; Aboutalebi, S. H.

2011-02-01

195

Structural and optical properties of nanostructured TiO2 thin films fabricated by glancing angle deposition  

International Nuclear Information System (INIS)

TiO2 films deposited by electron beam evaporation with glancing angle deposition (GLAD) technique were reported. The influence of flux angle on the surface morphology and the microstructure was investigated by scanning electron microscopy. The GLAD TiO2 films are anisotropy with highly orientated nanostructure of the slanted columns. With the increase of flux angle, refractive index and packing density decrease. This is caused by the shadowing effect dominating film growth. The anisotropic structure of TiO2 films results in optical birefringence, which reaches its maximum at the flux angle ? = 65o. The maximum birefringence of GLAD TiO2 films is higher than that of common bulk materials. It is suggested that glancing angle deposition may offer an effective method to obtain tailorable refractive index and birefringence in a large continuous range

196

SiO2/TiO2 thin films with variable refractive index prepared by ion beam induced and plasma enhanced chemical vapor deposition  

International Nuclear Information System (INIS)

SiO2/TiO2 optical thin films with variable compositions have been prepared by ion beam induced and plasma enhanced chemical vapour deposition (IBICVD and PECVD). While the films obtained by IBICVD were very compact, the PECVD ones with a high content of Ti presented a columnar microstructure. The formation of Si-O-Ti bonds and a change in the environment around titanium from four- to six-coordinated has been proved by vibrational and X-ray absorption spectroscopies. The refractive index increased with the titanium content from 1.45 to 2.46 or 2.09 for, respectively, the IBICVD and PECVD films. Meanwhile, the band gap decreased, first sharply and then more smoothly up to the value of pure TiO2. It is concluded that the optical properties of SiO2/TiO2 thin films can be properly tailored by using these two procedures

197

Improved room temperature electron mobility in self-buffered anatase TiO2 epitaxial thin film grown at low temperature  

Science.gov (United States)

Anatase TiO2(001) epitaxial thin films were grown on LaAlO3(001) substrate self-buffered with 5-monolayer-thick insulating TiO2 by pulsed laser deposition. The use of self-buffer layer enabled the layer-by-layer growth down to 200 °C resulting in the decreased surface roughness. The carrier density of self-buffered films was controlled as a function of oxygen pressure during the growth within a range of 1019 cm?3. The electron mobility at 300 K of self-buffered film grown at the optimal condition was improved to be 18.6 cm2·V?1·s?1 in comparison with that of non-buffered TiO2 thin film <5 cm2·V?1·s?1.

Krasienapibal, Thantip S.; Fukumura, Tomoteru; Hirose, Yasushi; Hasegawa, Tetsuya

2014-09-01

198

Correlation between microstructure and optical properties of nano-crystalline TiO2 thin films prepared by sol-gel dip coating  

International Nuclear Information System (INIS)

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 deg. C, and into the anatase-rutile phase at 1000 deg. C, and further into the rutile phase at 1200 deg. 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 deg. 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.

199

Silver enhanced TiO2 thin films: photocatalytic characterization using aqueous solutions of tris(hydroxymethyl)aminomethane.  

Science.gov (United States)

The photocatalytic activity in aqueous solutions of TiO2 and Ag enhanced TiO2 sol-gel produced films was characterized using tris(hydroxymethyl)aminomethane (Tris) under black light (365 nm) and the observed differences in efficiency were further investigated by O2 adsorption studies using the same probe. Hydrogen abstracting species, such as hydroxyl radicals formed upon photocatalysis, are able to abstract hydrogen from Tris. This reaction leads to the formation of formaldehyde which was detected and quantified through a modified version of the Hantzsch reaction. It was found that the Ag enhanced TiO2 film increased the apparent quantum yield from 7% to 12%, partly as a result of a Schottky barrier formation at the metal-semiconductor interface and partly as the sensitizing effect of Ag nanoparticles extends the visible light absorption, which through electron transfer processes enable an efficient charge separation in the TiO2 by attracting acceptor species more efficiently than pure TiO2. The O2 adsorption studies in this paper showed that the Ag enhanced TiO2 film has a stronger adsorption affinity than pure TiO2 towards O2, which make the reduction of O2 more efficient with a subsequent enhanced electron-hole lifetime. It was also found that the Ag enhanced TiO2 film had a poorer adsorption affinity for Tris than the pure TiO2 film, which is a consequence of fewer available surface adsorption sites due to the Ag coverage at 64% which agrees well with the obtained adsorption equilibrium constants (K(LH(TiO2)) = 615 M(-1) and K(LH(Ag-TiO2)) = 320 M(-1)). PMID:24107998

Diesen, Veronica; Dunnill, Charles W; Österberg, Elin; Parkin, Ivan P; Jonsson, Mats

2014-01-01

200

Chemical bath deposition of thin TiO2-anatase films for dielectric applications  

International Nuclear Information System (INIS)

Titania thin films were prepared on bare Si and Pt/Ti/SiO2/Si substrates by chemical bath deposition (CBD) from solutions of a titanium peroxo complex and subsequent calcinations at 350 and 700 deg. C, respectively. The CBD process allowed deposition on both uncoated and metal-coated Si substrates with the same deposition rate. Optimization of the annealing process yielded uniform and crack-free nanocrystalline anatase films. The influence of the film thickness, irradiation of visible light, measuring frequency, temperature and substrate on the dielectric properties will be discussed in the paper. Films with a final thickness of about 600 nm showed comparably high relative permittivity of 31.8 on silicon and of 52.7 on Pt/Ti/SiO2/Si substrates, respectively. The present route provides anatase thin films with higher dielectric constants than classical sol-gel routes and is therefore a promising candidate for potential applications in large scale integration

 
 
 
 
201

Optical and morphological characterization of photocatalytic TiO2 thin films doped with silver  

International Nuclear Information System (INIS)

Silver-doped titanium dioxide thin films were deposited on glass substrates by the sol-gel process. Undoped films and films doped with 1 and 3 mol% Ag were annealed at 100 or 500 oC. The optical and morphological properties of the films were analyzed by optical absorption spectroscopy and scanning electron microscopy. Additionally, the films were evaluated for their ability to degrade methylene blue. It was found that the photocatalytic activity is barely sensitive to silver doping for films annealed at 100 oC, whereas the effect of silver resulted in enhanced photocatalytic activity for films annealed at 500 oC. For the latter annealing temperature, the photocatalytic activity increased with increasing Ag doping concentration.

202

Influência do tipo de ácido e tempo de envelhecimento na atividade fotocatalítica de filmes finos de TiO2 / Type of acid and ageing effect influence on photocatalytic activity of TiO2 thin films  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english TiO2 thin films were prepared by the sol-gel method using different acids (HCl and HAc), with a parallel evaluation of the gel ageing effects on the film properties. After the thermal treatments, the resulting materials were characterized through gravimetric analysis, UV-VIS spectrophotometry (from [...] which optical parameters such as band gap was derived), XRD, morphological surface analysis (AFM) and photocatalytic activity. The majority of the obtained thin films parameters were similar independent of the acid type and the ageing time of the gel. Nevertheless, a visible effect of the surface morphology properties on the films and their photocatalytic activity was observed.

Liana Key Okada, Nakamura; Jorge Moreira, Vaz.

203

The effects of film thickness on the optical properties of TiO2-SnO2 compound thin films  

International Nuclear Information System (INIS)

In this work, TiO2-SnO2 compound thin films was synthesized by the sol-gel technique, and the effects of film thickness on the optical and structural properties of these thin films were investigated. Optical constants such as the refractive index, extinction coefficient, dielectric constant and third-order optical nonlinear susceptibility were determined from the measured transmittance spectra in the wavelength range 300-1500 nm using the envelope method. Meanwhile, the dispersion behavior of the refractive index was studied in terms of the single-oscillator Wemple-DiDomenico (W-D) model, and the physical parameters of the refractive index dispersion parameter and the dispersion energy were found. Furthermore, the optical band gap values were calculated by the W-D model and the Tauc model, respectively. It is observed that the values obtained from the W-D model are in quite good agreement with those determined from the Tauc model. Important changes in optical and dielectric constants were observed by means of variation in film thickness. To examine the structure of the thin films, x-ray diffraction (XRD) methods were used. Combined with XRD analysis, the observed variations in both the refractive index and optical band gap are directly correlated with the structural evolution of the composite TiO2-SnO2 thin films. The most significant results of the present study are that the thickness of the film can be used to modify the oss of the film can be used to modify the optical, structural and dielectric properties of TiO2-SnO2 thin films.

204

Photoactivity and hydrophilic property of SiO2 and SnO2 co-doped TiO2 nano-composite thin films  

Directory of Open Access Journals (Sweden)

Full Text Available SiO2 and SnO2 co-doped TiO2 nano-composite thin films were prepared by sol-gel method. The effects of film thicknessand amount of SiO2 and SnO2 co-doping into TiO2 nano-composite films on phase presence, crystallite size, photocatalyticreaction and hydrophilicity were investigated. Thickness of 3-coating layers (238 nm seems to provide the highest photocatalyticactivity. The crystallinity of anatase phases, crystallite sizes and photocatalytic reactions of SiO2 and SnO2 co-dopedTiO2 films decrease with an increase in SiO2 content. It was found that more amount of SiO2 addition seems to inhibit graingrowth and the formation of anatase phase; especially when it was synthesized at temperature less than 600°C. The photocatalyticreaction seems to decrease with an increase in SiO2 doping when the concentrations of SnO2 in the composite films are fixed. It was apparent that 1SiO2/1SnO2/TiO2 composite film exhibits the highest photoactivity. Suitable amounts of SiO2and SnO2 doping into the TiO2 composite films tend to enhance the hydrophilic property of the films. It was also apparentthat the 3SiO2/3SnO2/TiO2, 5SiO2/5SnO2/TiO2 and 10SiO2/3SnO2/TiO2 composite films exhibit super hydrophilic characteristicsunder UV irradiation for 30 min.

Lek Sikong

2010-08-01

205

Thin Sol-Gel TiO2 Films Prepared by Inkjet Printing – Photoelectrochemical Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study reports the structural and electrochemical properties of the deposited TiO2 layers prepared by means of the templated sol-gel method by the inkjet printing. The layer morphology and material properties were in detail investigated by optical microscopy, SEM, AFM as well as Raman spectroscopy and XRD analysis. The photo-excitation properties of the TiO2 layers and the ability of their photocurrent generation were studied by electrochemical methods.

Morozova?, Magdalena

2011-01-01

206

Sol-gel synthesis, characterization and optical properties of mercury-doped TiO2 thin films deposited on ITO glass substrates  

International Nuclear Information System (INIS)

The Hg-doped and undoped nano-crystalline TiO2 films on ITO glass substrates surface and polycrystalline powders were prepared by sol-gel dip coating technique. The crystal structure and surface morphology of TiO2 were characterized by means of X-ray diffractometer (XRD), atomic force microscope (AFM), spectrophotometer, Fourier-transform infrared (FTIR), and spectroscopic ellipsometry (SE). The results indicated that the powder of TiO2, doped with 5% Hg in room temperature was only composed of the anatase phase whereas in the undoped powder exhibits an amorphous phase were present. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 400 oC. The average crystallite size of the undoped TiO2 films was about 8.17 nm and was increased with Hg-doping in the TiO2 films. Moreover, the grains distributed more uniform and the surface roughness was greater in the Hg-doped TiO2 films than in the undoped one. Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range (1.95-2.49) and the porosity is in the range (47-2.8). The coefficient of transmission varies from 60 to 90%. SE study was used to determine the annealing temperature effect on the optical properties in the wavelength range from 0.25 to 2 ?m and the optical gap of the Hg-doped TiO2 thin films.

207

Sol-gel synthesis, characterization and optical properties of mercury-doped TiO 2 thin films deposited on ITO glass substrates  

Science.gov (United States)

The Hg-doped and undoped nano-crystalline TiO 2 films on ITO glass substrates surface and polycrystalline powders were prepared by sol-gel dip coating technique. The crystal structure and surface morphology of TiO 2 were characterized by means of X-ray diffractometer (XRD), atomic force microscope (AFM), spectrophotometer, Fourier-transform infrared (FTIR), and spectroscopic ellipsometry (SE). The results indicated that the powder of TiO 2, doped with 5% Hg in room temperature was only composed of the anatase phase whereas in the undoped powder exhibits an amorphous phase were present. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 400 °C. The average crystallite size of the undoped TiO 2 films was about 8.17 nm and was increased with Hg-doping in the TiO 2 films. Moreover, the grains distributed more uniform and the surface roughness was greater in the Hg-doped TiO 2 films than in the undoped one. Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range (1.95-2.49) and the porosity is in the range (47-2.8). The coefficient of transmission varies from 60 to 90%. SE study was used to determine the annealing temperature effect on the optical properties in the wavelength range from 0.25 to 2 ?m and the optical gap of the Hg-doped TiO 2 thin films.

Mechiakh, R.; Ben Sedrine, N.; Chtourou, R.

2011-08-01

208

Preillumination of TiO2 and Ta2O5 photoactive thin films as a tool to tailor the synthesis of composite materials.  

Science.gov (United States)

Illumination of TiO 2 thin films with UV light is known to induce the transformation of the surface of this material from partially hydrophobic into fully hydrophilic. The present work shows that this transformation is accompanied by other effects that may be used to control the synthesis of composite materials. For this purpose, TiO 2 and Ta 2O 5 transparent thin films with a columnar structure and open pores were prepared by electron evaporation at glancing angles. Transparent TiO 2 thin films with micropores (i.e., pores smaller than 2 nm) prepared by plasma enhanced chemical vapor deposition (PECVD) were also used. All these films became hydrophilic upon UV illumination. Rhodamine 6G and Rhodamine 800 dyes were irreversibly adsorbed within the columns of the TiO 2 and Ta 2O 5 thin films by immersion into a water solution of these molecules. Isolated and aggregated molecules of these two dyes were detected by visible absorption spectroscopy. The infiltration adsorption efficiency was directly correlated with the acidity of the medium, increasing at basic pHs as expected from simple considerations based on the concepts of the point of zero charge (PZC) in colloidal oxides. The infiltration experiments were repeated with columnar TiO 2 and Ta 2O 5 thin films that were subjected to preillumination with UV light. It was found that this treatment produced a modification in the type (isolated or aggregated) and amount of dye molecules incorporated into the pores. Moreover, the selective adsorption of a given dye in preilluminated areas of the films permitted the lithographic coloring of the films. Preillumination also controls the UV induced deposition of silver on the surface of the microporous TiO 2 thin films. It was found that the size distribution of the formed silver nanoparticles was dependent on the preillumination treatment and that a well-resolved surface plasmon resonance at around 500 nm was only monitored in the preilluminated films. A model is proposed to account for the effects induced by UV preillumination on the TiO 2 and Ta 2O 5 oxide surfaces. The possibilities of this type of light treatment for the tailored synthesis of nanocomposite thin films (i.e., dye-oxide, metal nanoparticles-oxide) are highlighted. PMID:18642860

Sánchez-Valencia, Juan R; Borrás, Ana; Barranco, Angel; Rico, Victor J; Espinós, Juan P; González-Elipe, Agustín R

2008-09-01

209

TiO2:polymer bulk-heterojunction thin films made from a miscible new carbazole based TiO2 precursor with poly(N-vinylcarbazole) for enhanced charge transfer properties  

International Nuclear Information System (INIS)

TiO2:polymer bulk-heterojunctions (BHJ) have been elaborated from hydrolysis-condensation reactions of a TiO2 precursor in contact to the surrounding air humidity in a polymer thin film. A new precursor: tetrakis(9H-carbazole-9-yl-ethyl-oxy) titanium [Ti(OeCarb)4], has been synthesized as a TiO2 precursor to form a blend with Poly(N-vinylcarbazole) (PVK) which is the archetype of non-conjugated photoconducting polymer with strong electron-donor properties. This new precursor is expected to enhance the materials miscibility because of the chemical structure of the ligand close to the PVK repetitive unit and to inhibit premature hydrolysis by a strong steric hindrance. Commercial titanium isopropoxide [Ti(iOPr)4] was used as a reference to study the influence of the chemical structure of the precursor on BHJ properties. Photoluminescence studies have shown charge transfer enhancement when Ti(OeCarb)4 is used. In order to understand this ligand effect, photoluminescence (PL) responses were correlated with surface chemical composition (XPS) and topography (AFM) of thin films. Results have shown that Ti(OeCarb)4 allows a better miscibility between TiO2 and PVK. The lower reactivity of Ti(OeCarb)4 to hydrolysis and its chemical structure close to the repetitive unit structure of the polymer are believed to play a main role in the BHJ property improvement

210

The effects of film thickness on the optical properties of TiO2-SnO2 compound thin films  

Science.gov (United States)

In this work, TiO2-SnO2 compound thin films was synthesized by the sol-gel technique, and the effects of film thickness on the optical and structural properties of these thin films were investigated. Optical constants such as the refractive index, extinction coefficient, dielectric constant and third-order optical nonlinear susceptibility were determined from the measured transmittance spectra in the wavelength range 300-1500 nm using the envelope method. Meanwhile, the dispersion behavior of the refractive index was studied in terms of the single-oscillator Wemple-DiDomenico (W-D) model, and the physical parameters of the refractive index dispersion parameter and the dispersion energy were found. Furthermore, the optical band gap values were calculated by the W-D model and the Tauc model, respectively. It is observed that the values obtained from the W-D model are in quite good agreement with those determined from the Tauc model. Important changes in optical and dielectric constants were observed by means of variation in film thickness. To examine the structure of the thin films, x-ray diffraction (XRD) methods were used. Combined with XRD analysis, the observed variations in both the refractive index and optical band gap are directly correlated with the structural evolution of the composite TiO2-SnO2 thin films. The most significant results of the present study are that the thickness of the film can be used to modify the optical, structural and dielectric properties of TiO2-SnO2 thin films.

Sönmezo?lu, Sava?; Arslan, Aysun; Serin, Tülay; Serin, Necmi

2011-12-01

211

Influence of the growth parameters on TiO2 thin films deposited using the MOCVD method / Influência dos parâmetros de crescimento em filmes finos de TiO2 depositados pelo método MOCVD  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A síntese de filmes finos de TiO2 por meio do método MOCVD é descrita. Foi estudada a influência de parâmetros de deposição usados durante o crescimento nas características estruturais obtidas. Foram combinados diferentes temperaturas do banho organometálico, tempo de deposição, temperatura e tipo d [...] o substrato. A forte influência destes parâmetros na microestrutura final dos filmes foi estudada por meio de diferentes técnicas: microscopia eletrônica de varredura associada com espectroscopia eletrônica de dispersão de raios X, microscopia de força atômica e difração de raios X. Abstract in english In this work we report the synthesis of TiO2 thin films by the Organometallic Chemical Vapor Deposition (MOCVD) method. The influence of deposition parameters used during the growth in the obtained structural characteristics was studied. Different temperatures of the organometallic bath, deposition [...] time, temperature and type of the substrate were combined. Using Scanning Electron Microscopy associated to Electron Dispersive X-Ray Spectroscopy, Atomic Force Microscopy and X-ray Diffraction, the strong influence of these parameters in the thin films final microstructure was verified.

M. I. B., Bernardi; E. J. H., Lee; P. N., Lisboa-Filho; E. R., Leite; E., Longo; A. G., Souza.

212

Influence of the growth parameters of TiO2 thin films deposited by the MOCVD method / Influência dos parâmetros de crescimento de filmes finos de TiO2 depositados pelo método MOCVD  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A síntese de filmes finos de TiO2 foi feita pelo método de deposição química do vapor de organometálicos (MOCVD). Foi estudada a influência de parâmetros de deposição usados durante o crescimento, nas características estruturais finais. Foi feita uma combinação de vários parâmetros experimentais: te [...] mperatura do banho do organometálico, tempo de deposição, e temperatura e tipo do substrato. A forte influência destes parâmetros na microestrutura final do filme foi analisada por microscopia eletrônica de varredura com espectroscopia de raios X dispersiva de elétrons, microscopia de força atômica e difração de raios X. Abstract in english The synthesis of TiO2 thin films was carried out by the Organometallic Chemical Vapor Deposition (MOCVD) method. The influence of deposition parameters used during growth on the final structural characteristics was studied. A combination of the following experimental parameters was studied: temperat [...] ure of the organometallic bath, deposition time, and temperature and substrate type. The high influence of those parameters on the final thin film microstructure was analyzed by scanning electron microscopy with electron dispersive X-ray spectroscopy, atomic force microscopy and X-ray diffraction.

M. I. B., Bernardi; E. J. H., Lee; P. N., Lisboa-Filho; E. R., Leite; E., Longo; A. G., Souza.

213

Photocatalytic removal of hazardous Ponceau S dye using Nano structured Ni-doped TiO2 thin film prepared by chemical method  

Science.gov (United States)

Many attempts have been made by researchers for the removal of various dyes using nano structured Ni-doped TiO2; however, removal of `hazardous Ponceau S dye' using nano structured Ni-doped TiO2 has been not studied yet. In the present work, environmental application of Nano structured Ni doped TiO2 has been studied. Nano structured Ni-doped TiO2 thin films were deposited by the chemical method on a glass substrate. The prepared thin film was characterized by XRD, SEM, and EDX. The crystal size calculated from XRD is about 26.2 nm. The SEM analysis reveals nano spherical morphology of average particle size about 92 nm. The optical analysis was carried by using UV-visible spectroscopy. The band gap estimated from absorbance spectra for thin film was around 3.5 eV, making suitable Ni-doped TiO2 for photocatalytic removal of hazardous Ponceau S dye. In photocatalytic application different parameters like dye concentration, contact time, pH, UV light and sunlight were optimized for the removal of Ponceau S dye, respectively. The change in chemical oxygen demand after photo catalytic treatment was also studied.

Marathe, Sunil D.; Shrivastava, Vinod S.

2014-05-01

214

Influences of the iron ion (Fe3+)-doping on structural and optical properties of nanocrystalline TiO2 thin films prepared by sol-gel spin coating  

International Nuclear Information System (INIS)

Titanium dioxide (TiO2) thin films doping of various iron ion (Fe3+) concentrations were deposited on silicon (Si) (100) and quartz substrates by sol-gel Spin Coating technique followed by a thermal treatment at 600 deg. C. The structure, surface morphology and optical properties, as a function of the doping, have been studied by X-ray diffractometer (XRD), Raman, ultraviolet-visible (UV-vis) and Spectroscopic Ellipsometry (SE). XRD and Raman analyzes of our thin films show that the crystalline phase of TiO2 thin films comprised only the anatase TiO2, but the crystallinity decreased when the Fe3+ content increased from 0% to 20%. During the Fe3+ addition to 20%, the phase of TiO2 thin film still maintained the amorphous state. The grain size calculated from XRD patterns varies from 29.3 to 22.6 nm. The complex index and the optical band gap (Eg) of the films were determined by the spectroscopic ellipsometry analysis. We have found that the optical band gap decreased with an increasing Fe3+ content.

215

Modifications in structural and electronic properties of TiO2 thin films using swift heavy ion irradiation  

International Nuclear Information System (INIS)

We report on the structural and electronic properties of swift heavy ion (SHI) irradiated pristine TiO2 thin films, deposited by radio frequency magnetron sputtering on sapphire substrates. The high resolution x-ray diffraction and Raman measurements show a structural phase transition from anatase to admixture of brookite and rutile phases of TiO2 with increasing SHI fluence followed by a significant distortion in the TiO6 octahedra. The modification in the electronic structure stimulated by SHI irradiation has been investigated using x-ray absorption (XAS) experiments at the O K and Ti L3,2 absorption edges. The O K edge spectra clearly indicate the splitting of the pre-edge spectral features having t2g and eg symmetry bands due to structural disorder/distortion induced by irradiation. The intensity of the SHI generated components at the O K edge increases monotonically, which can be correlated to the modification in unoccupancies associated with O 2 p orbitals hybridized with Ti 3 d states. The XAS spectra at the Ti L3,2 edge further authenticate that SHI creates a controlled structural disorder/distortion in the TiO6 octahedra.

216

Effect of compressed TiO2 nanoparticle thin film thickness on the performance of dye-sensitized solar cells  

Science.gov (United States)

In this study, dye-sensitized solar cells (DSSCs) were fabricated using nanocrystalline titanium dioxide (TiO2) nanoparticles as photoanode. Photoanode thin films were prepared by doctor blading method with 420 kg/cm2 of mechanical compression process and heat treatment in the air at 500°C for 30 min. The optimal thickness of the TiO2 NP photoanode is 26.6 ?m with an efficiency of 9.01% under AM 1.5G illumination at 100 mW/cm2. The efficiency is around two times higher than that of conventional DSSCs with an uncompressed photoanode. The open-circuit voltage of DSSCs decreases as the thickness increases. One DSSC (sample D) has the highest conversion efficiency while it has the maximum short-circuit current density. The results indicate that the short-circuit current density is a compromise between two conflict factors: enlargement of the surface area by increasing photoanode thickness and extension of the electron diffusion length to the electrode as the thickness increases.

Tsai, Jenn Kai; Hsu, Wen Dung; Wu, Tian Chiuan; Meen, Teen Hang; Chong, Wen Jie

2013-11-01

217

Origin of significant visible-light absorption properties of Mn-doped TiO2 thin films  

International Nuclear Information System (INIS)

It is highly desirable to induce significant red-shift in the optical absorption edges of TiO2 phases so that this class of low-cost and environmentally friendly materials can be used as effective optical absorbing materials in novel photovoltaic cells with long-term sustainability or smart photo-catalysts beyond the ultraviolet range. This work focuses on studying the mechanisms of Mn-induced red-shift by combining theoretical modeling with advanced structural and spectroscopic characterization of doped thin films, aiming to provide fundamental guidance for effective doping through enhanced understanding of doping chemistry resulting from the interplay between doping atoms and defects. It is shown that Mn atoms doped into the Ti lattice sites are associated with oxidation valency higher than +3, resulting in maximized effectiveness in modifying the band structure to achieve remarkable optical red-shifting. The presence of oxygen vacancies reduces the Mn valency and its red-shifting effect, but their detrimental effect in bringing about localized defect levels is reduced owing to their association with Mn atoms, making Mn doping highly promising in activating various visible light functionalities of TiO2.

218

Study of the photocatalytic activity of nanocrystalline S, N-codoped TiO2 thin films and powders under visible and sun light irradiation  

Science.gov (United States)

Homogeneous and transparent sulfur and nitrogen (S, N)-codoped TiO2 nanocrystalline thin films were deposited on glass substrates by sol gel dip coating method using thiourea (Tu) as a source of sulfur and nitrogen. The surface structure of the films was modified by addition of different concentrations of polyethylene glycol (PEG) into the TiO2 sol. The equal powders of pure and modified TiO2 were also prepared to compare of their photocatalytic activity with films. The films and powders were characterized by different techniques like diffuse reflectance UV-Vis spectroscopy (DRS), X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX). DRS exhibited a shift in optical absorption wavelength to visible region and XRD analysis showed that only the anatase TiO2 formed in both of film and powder. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) as a model. The modified TiO2 films and powders showed excellent visible-light photocatalytic ability for the degradation of MO under both irradiation of visible and sun light. So that, up to 96% MO can be decomposed in sun light only within 3 h in the presence of a modified TiO2 film consist of Tu/TiO2 molar ratio of 0.45 and 0.9 g PEG. On the other hand, MO solution was discolored completely under sun light in 75 min in the presence of the modified TiO2 powder.

Behpour, Mohsen; Atouf, Vajiheh

2012-06-01

219

Study of the photocatalytic activity of nanocrystalline S, N-codoped TiO2 thin films and powders under visible and sun light irradiation  

International Nuclear Information System (INIS)

Homogeneous and transparent sulfur and nitrogen (S, N)-codoped TiO2 nanocrystalline thin films were deposited on glass substrates by sol gel dip coating method using thiourea (Tu) as a source of sulfur and nitrogen. The surface structure of the films was modified by addition of different concentrations of polyethylene glycol (PEG) into the TiO2 sol. The equal powders of pure and modified TiO2 were also prepared to compare of their photocatalytic activity with films. The films and powders were characterized by different techniques like diffuse reflectance UV-Vis spectroscopy (DRS), X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX). DRS exhibited a shift in optical absorption wavelength to visible region and XRD analysis showed that only the anatase TiO2 formed in both of film and powder. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) as a model. The modified TiO2 films and powders showed excellent visible-light photocatalytic ability for the degradation of MO under both irradiation of visible and sun light. So that, up to 96% MO can be decomposed in sun light only within 3 h in the presence of a modified TiO2 film consist of Tu/TiO2 molar ratio of 0.45 and 0.9 g PEG. On the other hand, MO solution was discolored completely under sun light in 75 min in the presence of the modified TiO2 powder.

220

The effect of aeration and solar intensity power on photocatalytic degradation of textile industrial wastewater using TiO2 thin film  

International Nuclear Information System (INIS)

Solar photo catalytic degradation of the textile industry wastewater using TiO2 thin films was studied. This experiment was performed to investigate the effect of aeration and solar intensity power on decreasing of Chemical Oxygen Demand (COD). A serpentine flow photo catalytic reactor was developed for this purpose. TiO2 thin films photo catalyst supported on the stainless steel 304 substrates were prepared using sol-gel dip coating method. The results of thin films were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffractometer (XRD). XRD result showed that the prepared thin films gave the anatase crystallite formation whilst SEM demonstrated the macro pores were formed. Finally, the aeration and solar intensity power factors are considered to be responsible for the photo catalytic degradation. (Author)

 
 
 
 
221

Initial stages of TiO 2 thin films MOCVD growth studied by in situ surface analyses  

Science.gov (United States)

In situ chemical surface analyses using X-ray photoelectron spectroscopy (XPS) were performed to understand the initial stages of TiO 2 thin-film MOCVD growth. Deposits on Si (1 0 0), a few nanometres thick, were obtained at a fixed temperature of 650 °C and for two different pressures, 2.9 and 0.05 mbar, using titanium tetraisopropoxide (TTIP) as precursor. Pressure lowering led to a higher deposit growth rate. Reduction of titanium with respect to stoichiometric titanium dioxide and oxidation of the wet-cleaned silicon substrate are observed from decomposition of the Ti 2p and Si 2p peaks. The formation of a TiSi xO y mixed oxide is also pointed out and confirmed by the presence of a characteristic component in the O 1 s peak.

Brevet, A.; Peterlé, P. M.; Imhoff, L.; Marco de Lucas, M. C.; Bourgeois, S.

2005-02-01

222

Effect of substrate temperature on the optical and the electrochromic properties of sputtered TiO2 thin films  

International Nuclear Information System (INIS)

Titanium oxide films (TiO2) were deposited on ITO-coated glass substrates at different substrate temperatures by using an RF reactive magnetron sputtering in an Ar/O2 atmosphere, and their electrochromic properties and stability by repeated coloring and bleaching cycles were investigated for counterelectrode applications. The electrochemical properties of the TiO2 films as counterelectrodes showed weak dependences on the substrate temperature. The optical band gap of the film increased from 3.30 eV to 3.40 eV when the substrate temperature was increased from room temperature to 500 .deg. C. The cyclic durability of the TiO2 films deposited at a substrate temperature of 200 .deg. C was found to be the most stable and was suitable for counterelectrode applications when the films were subjected to 1000 cycles between -2 V and +2 V in a 1-M solution of LiClO4.

223

Correlation between structure and semiconductor-to-metal transition characteristics of VO2/TiO2/sapphire thin film heterostructures  

International Nuclear Information System (INIS)

This study focuses on the role of strain and thin film epitaxy on the semiconductor-to-metal transition (SMT) characteristics of single crystalline VO2 thin films. The VO2/TiO2 heterostructures of controlled orientations were epitaxially grown on m-cut, r-cut and c-cut sapphire substrates. Detailed structural investigations were performed using high-resolution X-ray diffraction (2?–? and ? scans) and high-resolution transmission electron microscopy techniques to correlate SMT properties with microstructural characteristics. Monoclinic (M1) VO2 thin films with (1 0 0), (0 0 1) and (2¯01) out-of-plane orientations were grown on TiO2(1 0 1)/r-sapphire, TiO2(1 0 0)/c-sapphire and TiO2(0 0 1)/m-sapphire platforms, respectively. The in-plane alignments across the interfaces were established to be [0 1 0](1 0 0)VO2||[0 1 0](1 0 1)TiO2, [1 0 0](0 0 1)VO2||[0 0 1](1 0 0)TiO2 and [010](2¯01)VO2?[010](001)TiO2 for r-sapphire, c-sapphire and m-sapphire substrates, respectively. We were able to tune the SMT temperature of VO2 epilayers from ?313 K to 354 K (bulk Tc ? 340 K). The SMT characteristics were interpreted based upon the residual strain in the VO2 lattice, particularly along the c-axis of tetragonal VO2. This research introduces the VO2-based single crystalline heterostructures as a potential candidate for a wide range of applications where different transition temperatures are required

224

Strategies to prepare TiO2 thin films, doped with transition metal ions, that exhibit specific physicochemical properties to support osteoblast cell adhesion and proliferation.  

Science.gov (United States)

Metal ion doped titanium oxide (TiO2) thin films, as bioactive coatings on metal or other implantable materials, can be used as surfaces for studying the cell biological properties of osteogenic and other cell types. Bulk crystallite phase distribution and surface carbon-oxygen constitution of thin films, play an important role in determining the biological responses of cells that come in their contact. Here we present a strategy to control the polarity of atomic interactions between the dopant metal and TiO2 molecules and obtain surfaces with smaller crystallite phases and optimal surface carbon-oxygen composition to support the maximum proliferation and adhesion of osteoblast cells. Our results suggest that surfaces, in which atomic interactions between the dopant metals and TiO2 were less polar, could support better adhesion, spreading and proliferation of cells. PMID:24582228

Dhayal, Marshal; Kapoor, Renu; Sistla, Pavana Goury; Pandey, Ravi Ranjan; Kar, Satabisha; Saini, Krishan Kumar; Pande, Gopal

2014-04-01

225

Surface-enhanced Raman scattering of amorphous TiO2 thin films by gold nanostructures: Revealing first layer effect with thickness variation  

Science.gov (United States)

In this paper, amorphous titanium dioxide (TiO2) thin films have been deposited on a commercially available Klarite substrate using the sol-gel process to produce surface-enhanced Raman scattering (SERS). The substrate consists of square arrays of micrometer-sized pyramidal pits in silicon with a gold coating. Several thin TiO2 layers have been deposited on the surface to study the influence of film thickness. Ultimately, we obtained information on SERS of an amorphous TiO2 layer by gold nanostructures, whose range is less than a few nanometers. Mechanisms responsible for the enhancement are the product of concomitant chemical and electromagnetic effects with an important contribution from plasmon-induced charge transfer.

Degioanni, S.; Jurdyc, A.-M.; Bessueille, F.; Coulm, J.; Champagnon, B.; Vouagner, D.

2013-12-01

226

Undoped and Cr-doped TiO2 thin films obtained by spray pyrolysis  

International Nuclear Information System (INIS)

Undoped and chromium doped titanium oxide thin films were fabricated by spray pyrolysis by using a solution of titanium tetrachloride and ethyl alcohol. The films have been deposited on heated glass substrates at 373 K. After annealing for 90 min at 723 K, the initially amorphous films became polycrystalline with a predominant anatase structure and average crystallite sizes depending on dopant (Cr) concentration. The repartition of chromium impurities in the matrix of titanium oxide films, analyzed by electron paramagnetic resonance and X-ray photoelectron spectroscopy showed that the entrance of chromium into the anatase structure is mainly achieved by substitution. A decrease in unit cell parameters ratio (c/a) with the increase of chromium content sustains this assertion. The wetting properties of the titanium oxide films were evaluated from contact angle measurements between de-ionized water and films surface during- and post-irradiation with UV light. The correlation between the concentration of the dopant, film structure, surface morphology and wettability characteristics is discussed.

227

Effect of solution contents on the evolution of microstructure and photoluminescence of laser-annealed rutile TiO2 thin films  

International Nuclear Information System (INIS)

Highlights: •The titanium dioxide (TiO2) material has attracted great attentions to wide applications. •The microstructure and photoluminescence (PL) of TiO2 are related to annealing methods. •The laser-annealed rutile TiO2 films were prepared using various sol gel solutions. •The tetraisopropyl orthotitanate content is the primary factor affecting rutile formation. •The PL emission of our rutile TiO2 can be extended from ultraviolet to visible range due to residual organics. -- Abstract: The titanium dioxide (TiO2) material has attracted great attentions because of its wide application in photocatalyst and optoelectronics devices. The microstructure and photoluminescence behavior of TiO2 thin films are related to the fabrication and annealing methods. In this article, the amorphous titanium oxide thin films were prepared by sol gel process with a mixture of tetraisopropyl orthotitanate, acetonylacetone, distilled water and alcohol at various molar ratios and then spin-coated on the p-Si(1 0 0) substrate. Subsequently, the CO2 laser irradiation at a power of 1.5 W was utilized for annealing treatment to form crystalline rutile TiO2 instead of conventional furnace annealing. The evolution of microstructure, bonding and photoluminescence (PL) of TiO2 films were characterized by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy, Fourier transform infrared spectrometer and PL spectrometer. GIXRD showed that the crystalline phase of TiO2 after 1.5 W laser annealing was rutile. The PL spectra of annealed films covered broad wavelengths of 350–800 nm which extends conventional ultraviolet range. They can be deconvoluted into three peaks at about 411, 441 and 534 nm which were attributed to the lattice emission, deep-level emissions from oxygen vacancies and defect states from bonding of extra impurities of Ti, O and C in rutile TiO2 together with residual organics. The relationship between the process parameters, microstructure, bonding and PL behavior were further discussed and established

228

Bactericidal activity of copper-deposited TiO2 thin film under weak UV light illumination.  

Science.gov (United States)

The bactericidal activity of copper-deposited titanium dioxide thin film (Cu/TiO2) was investigated under very weak ultraviolet (UV) light illumination. To elucidate the roles of the film photocatalyst and the deposited copper in the bactericidal activity, cells from a copper-resistant Escherichia coli (E. coli) strain were utilized. A decrease in survival rate was not observed with the copper-resistant cells under dark conditions, but when illuminated with a very weak UV intensity of 1 microW/cm2, the survival rate decreased, suggesting photocatalytic bactericidal activity. The decay curve of survival on the Cu/TiO2 film under very weak UV light illumination consisted of two steps, similar to the survival change of normal E. coli on TiO2 films under rather strong UV illumination. The first step is due to the partial decomposition of the outer membrane in the cell envelope by a photocatalytic process, followed by permeation of the copper ions into the cytoplasmic membrane. The second step is due to a disorder of the cytoplasmic membrane caused by the copper ions, which results in a loss of the cell's integrity. These processes explain why the Cu/TiO2 film system shows an effective bactericidal activity even under very weak UV light illumination. PMID:14594392

Sunada, Kayano; Watanabe, Toshiya; Hashimoto, Kazuhito

2003-10-15

229

Effects of high-temperature postannealing on magnetic properties of Co-doped anatase TiO2 thin films  

Science.gov (United States)

The origin of ferromagnetism in cobalt-doped anatase TiO2 (Co: TiO2 ) has been quite controversial due to the possible formation of Co nanoparticles. Recently, Shinde claimed that high-temperature postannealing (i.e., at 900 °C) should incorporate Co ions into the TiO2 matrix even from Co-clustered samples, thus proposing a new method to obtain intrinsic diluted magnetic semiconductors using Co: TiO2 [Phys. Rev. B 67, 115211 (2003)]. In order to verify this intriguing possibility, we investigated the effects of high-temperature annealing on the magnetic and structural properties of two kinds of Co-doped anatase TiO2 samples, one prepared by Co ion implantation and another by pulsed laser deposition with a Co-doped polycrystalline target. After postannealing under oxygen pressure of 1.0×10-6Torr at 900 °C, we observed drastic changes in the magnetic properties of both kinds of films. Although the Co nanoclusters, formed during the implantation, seemed to disappear inside the film, we found the formation of large clusters composed of metallic Co on the surface of the film using transmission electron microscopy. After annealing the samples prepared by pulsed laser deposition, similar large Co clusters were found at the interface. The results from x-ray-absorption near-edge spectroscopy and x-ray magnetic circular dichroism measurements on the postannealed film also demonstrated that the observed ferromagnetism in our films should come from Co metal.

Kim, D. H.; Yang, J. S.; Kim, Y. S.; Noh, T. W.; Bu, S. D.; Baik, S.-I.; Kim, Y.-W.; Park, Y. D.; Pearton, S. J.; Kim, J.-Y.; Park, J.-H.; Lin, H.-J.; Chen, C. T.; Song, Y. J.

2005-01-01

230

Studies of LPCVD and anodised TiO2 thin films and their photoelectrocatalytic photochemical properties for destruction of organic effluents  

International Nuclear Information System (INIS)

TiO2 thin films prepared by CVD and anodisation methods and their applications for the photoelectrocatalytic and photocatalytic destruction of organic effluents are described in this thesis. The theoretical background of CVD, photoelectrocatalysis (PEC) and photocatalysis (PC) is introduced in Chapter 1. This chapter also contains an intensive literature review about TiO2 thin film preparation, mainly by CVD, and about PEC and PC destruction of organic effluents by TiO2 thin films. The experimental methods, which include CVD reactors, PEC cells and film characterisation and chemical analysis, are described in Chapter 2. The results for TiO2 films deposited by LPCVD on SnO2 coated glass using either TTIP or TTB precursors in the presence of O2, with or without water as a reagent, are discussed in Chapter 3 for a small CVD reactor and Chapter 4 for a large reactor. The effects of precursor, water and annealing on the crystal structure of the films have been investigated and compared. It was found that phase transition temperatures for changes from amorphous to anatase and anatase to rutile with TTIP were higher than those obtained with TTB. Water also had an effect by decreasing the temperature for depositing crystalline films. The other kind of TiO2 films prepared by anodisation of titanium mesh was studied and the results are presented in Chapter 5. PEC or PC destruction of MPA, RDX and 4-CP have been studied using TiO2 thin film anodes in small and large PEC reactors which are described in Chapter 6 and Chapter 7, respectively. PC destruction rates of organics are found to be improved significantly with an applied potential; i.e. by a PEC process. The effects of film properties, such as film crystallinity, thickness and film type on the PEC and PC efficiencies have been investigated. It was found that the different behaviour of films in PEC processes probably was due to surface effects rather than internal electric field differences. The extent of PEC and PC destruction of organics for CVD films was higher than for anodised films. The thesis concludes with an overall summary of the results and some suggestions for future work (Chapter 8). (author)

231

Investigation of structural, optical and photocatalytic properties of mesoporous TiO 2 thin film synthesized by sol-gel templating technique  

Science.gov (United States)

TiO 2 surfactant-templated nanostructured thin film was fabricated by supramolecular templating technique using TiCl 4 and P-123 as raw material and surfactant, respectively. The film was produced by Sol-gel dip coating procedure due to its simple technique as well as relatively low cost. Characterization of the product was carried out by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface areas, thermogravimetry-differential scanning calorimetry (TG-DSC) and UV-vis absorption spectroscopy. The as-prepared TiO 2 film showed a quasi hexagonal mesostructure, and a further increase in the meso-scale order was observed after calcination. The prepared TiO 2 film had a high surface area of 124 m 2 g -1. The film was 2-?m thick and had a closely packed of anatase particles. The direct and indirect band gap of the film was estimated from UV-vis spectroscopy data to be 4.16 and 3.69 ev, respectively. The photocatalytic activity of the prepared TiO 2 film was evaluated by Congo Red degradation. The film had excellent photocatalytic efficiencies and more than 80% Congo Red was decolorized in 60 min.

Janitabar-Darzi, S.; Mahjoub, A. R.; Nilchi, A.

2009-12-01

232

An In-situ Real-Time Optical Fiber Sensor Based on Surface Plasmon Resonance for Monitoring the Growth of TiO2 Thin Films  

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Full Text Available An optical fiber sensor based on surface plasmon resonance (SPR is proposed for monitoring the thickness of deposited nano-thin films. A side-polished multimode SPR optical fiber sensor with an 850 nm-LD is used as the transducing element for real-time monitoring of the deposited TiO2 thin films. The SPR optical fiber sensor was installed in the TiO2 sputtering system in order to measure the thickness of the deposited sample during TiO2 deposition. The SPR response declined in real-time in relation to the growth of the thickness of the TiO2 thin film. Our results show the same trend of the SPR response in real-time and in spectra taken before and after deposition. The SPR transmitted intensity changes by approximately 18.76% corresponding to 50 nm of deposited TiO2 thin film. We have shown that optical fiber sensors utilizing SPR have the potential for real-time monitoring of the SPR technology of nanometer film thickness. The compact size of the SPR fiber sensor enables it to be positioned inside the deposition chamber, and it could thus measure the film thickness directly in real-time. This technology also has potential application for monitoring the deposition of other materials. Moreover, in-situ real-time SPR optical fiber sensor technology is in inexpensive, disposable technique that has anti-interference properties, and the potential to enable on-line monitoring and monitoring of organic coatings.

Wen-Ching Shih

2013-07-01

233

Reliability of ultra-thin titanium dioxide (TiO2) films on strained-Si  

International Nuclear Information System (INIS)

Ultra-thin high-k titanium oxide (equivalent oxide thickness ? 2.2 nm) films have been deposited on strained-Si/relaxed-Si0.8Ge0.2 heterolayers using titanium tetrakis iso-propoxides (TTIP) as an organometallic source at low temperature (2 gate dielectric during constant current (CCS) and voltage stressing (CVS) has been investigated. Normalized trapping centroid and trapped charge density variation with injected fluences have been investigated and also empirically modeled. Oxide lifetime is predicted using empirical reliability model developed. Dielectric breakdown and reliability of the dielectric films have been studied using constant voltage stressing. A high time-dependent dielectric breakdown (TDDB, tbd > 1000 s) is observed under high constant voltage stress

234

Sol-gel preparation of TiO2-ZrO2 thin films supported on glass rings: Influence of phase composition on photocatalytic activity  

International Nuclear Information System (INIS)

In order to optimize the characteristics of TiO2-ZrO2 thin films supported on glass for the photocatalytic removal of VOCs, acidic sols of different composition (ZrO2, TiO2 and Ti-Zr mixed oxides) have been prepared using metal alkoxides as starting materials. The photoactive oxides were deposited on 'Raschig rings' of borosilicate glass using a dip-coating technique. The phase composition of the thin films was controlled during the sol preparation stage to produce either (1) Ti0.9Zr0.1O2 solid solutions, or (2) ZrO2/TiO2 binary metal oxides (10% and 20% molar content of Zr). The particle size of the different sols was measured by photon correlation spectroscopy, and the xerogels were characterized by XRD, N2 adsorption isotherms, and TG-DTA, so as to monitor the modifications induced by the thermal treatments. Raman spectroscopy was used to determine the crystalline structure of the supported TiO2-ZrO2 oxides, which in all cases corresponded to the anatase phase. The band gap of the thin films was estimated from the UV-vis spectra, and none of them differed significantly from that of unmodified TiO2. The photoactivity of the coated glass 'Raschig rings' was measured for the oxidation of acetone and methylcyclohexane vapors using, respectively, total recycle and single pass plug flow photoreactors. The results obtained indicate that, for the same Zr content, the photoactivity of the films containing binary metal oxides is slightly higher than that of the solid solution. In contrast, specific surface area seems to have little influence on the performance of the thin films

235

Preparation of TiO2/SnO2 thin films by sol-gel method and periodic B3LYP simulations.  

Science.gov (United States)

Titanium dioxide (TiO2) thin films are grown by the sol-gel dip-coating technique, in conjunction with SnO2 in the form of a heterostructure. It was found that the crystalline structure of the most internal layer (TiO2) depends on the thermal annealing temperature and the substrate type. Films deposited on glass substrate submitted to thermal annealing until 550 °C present anatase structure, whereas films deposited on quartz substrate transform to rutile structure at much higher temperatures, close to 1000 °C, unlike powder samples where the phase transition takes place at about 780 °C. When structured as rutile, the oxide semiconductors TiO2/SnO2 have very close lattice parameters, making the heterostructure assembling easier. The SnO2 and TiO2 have their electronic properties evaluated by first-principles calculations by means of DFT/B3LYP. Taking into account the calculated band structure diagram of these materials, the TiO2/SnO2 heterostructure is qualitatively investigated and proposed to increase the detection efficiency as gas sensors. This efficiency can be further improved by doping the SnO2 layer with Sb atoms. This assembly may be also useful in photoelectrocatalysis processes. PMID:24824227

Floriano, Emerson A; Scalvi, Luis V A; Saeki, Margarida J; Sambrano, Julio R

2014-08-01

236

Prediction of TiO2 thin film growth on the glass beads in a rotating plasma chemical vapor deposition reactor.  

Science.gov (United States)

We calculated the concentration profiles of important chemical species for TiO2 thin film growth on the glass beads in the TTIP + O2 plasmas and compared the predicted growth rates of thin films with the experimental measurements. The film thickness profile depends on the concentration profile of TiO(OC3H7)3 precursors in the gas phase because TiO(OC3H7)3 is the main precursor of the thin film. The TTIP concentration decreases with time, while the TiO(OC3H7)3 concentration increases, and they reach the steady state about 2 approximately 3 sec. The growth rate of TiO2 film predicted in this study was 9.2 nm/min and is in good agreements with the experimental result of 10.5 nm/min under the same process conditions. This study suggests that a uniform TiO2 thin film on particles can be obtained by using a rotating cylindrical PCVD reactor. PMID:20358924

Kim, Dong-Joo; Kim, Kyo-Seon

2010-05-01

237

Solar photocatalytic degradation of gaseous formaldehyde by sol-gel TiO2 thin film for enhancement of indoor air quality  

International Nuclear Information System (INIS)

Solar photocatalytic degradation of formaldehyde in the gaseous phase has been investigated. The tested photoreactor is made of a borosilicate glass tube with the inner surface coated with a sol-gel TiO2 thin film. In a pseudo-first-order Langmuir-Hinshelwood (L-H) model, the maximum reaction rate constant obtained is 0.148 min-1 under an exposure to sunlight with solar UVA irradiance of 1.56 mW/cm2. The solar photolysis effect is found to be negligible. It is also found that the sol-gel TiO2 thin film has a lower apparent photonic efficiency of solar photocatalysis than a Degussa P25 TiO2 coating. However, for the photonic efficiency taking into account the absorbed and scattered photons only and, in other words, excluding the transmitted photons, the thin film has a higher value. Based on a total of 28 measured data, an empirical-correlation equation has been developed to express the reactant residue with respect to the solar UVA irradiance and exposure time. A reasonable agreement between the correlation and experimental data is obtained. The findings of this investigation can be applied to design optimization of a honeycomb photoreactor made up of TiO2-coated glass tubes or polygonal cells. (author)

238

Optical-Refractometric Synthesis of Transmission Spectra and Optical Parameters of 0.5TiO2*0.5Nd2O3 Thin Films  

Directory of Open Access Journals (Sweden)

Full Text Available An original method for determining the optical parameters of thin films with the optical-refractometric synthesis of their transmission spectra is suggested. The proper choice of dispersion relation for refractive indices is substantiated. Experimental studies and computer simulations are performed for the quartz-glass optical element with 0.5TiO2*0.5Nd2O3 film. The advantages of the suggested method are discussed.

I.P. Studenyak

2003-09-01

239

Effects Of Tin Doping On Ethanol And Isopropyl Alcohol Sensing Properties Of Sol-Gel Derived TiO2 Thin Films  

International Nuclear Information System (INIS)

In this work, ethanol and isopropyl alcohol sensing properties of Sn-doped TiO2 thin films were investigated. Sn-doped titanium dioxide (TiO2) films were prepared by sol-gel dipping technique using titanium (IV) n-butoxide and tin (IV) chloride pentahydrate as starting materials. The starting materials were dissolved in ethanol separately. Mixture of the solutions was stirred for 1 h. Sn-doped and undoped TiO2 thin films were deposited onto glass substrate patterned with interdigitated electrodes (IDT) by a sol-gel dipping process. Final curing were performed at 820 K in air for 2 h. The structure of the films was studied by X-ray diffraction. Sn:Ti ratio (wt.) was kept between the values of 5% and 11%. Response characteristics of the films were determined in the gas concentrations range of 10%-30%. Gas concentrations were controlled by mass flow controller. Gas sensing characteristics were obtained by recording the current values of the films versus time as a function of gas concentration at the temperatures of 300 and 525 K. The results showed that sensitivity of the films increases with increasing tin doping. We can conclude that tin doping to SnO2 films improve the sensing parameters.

240

Raman spectroscopy of TiO2 thin films formed by hybrid treatment for biomedical applications.  

Science.gov (United States)

The paper presents the results of the investigations of the surface layer obtained after application of the combined hybrid method of oxidation in a fluidized bed (FB) and deposition of the oxide coating by PVD technique. The material used in the study was Ti Grade 2. The process of diffusive saturation was carried out in a fluidized-bed reactor at the temperature of 640°C for 8h in air while the top oxide layer was obtained through PVD method - magnetron sputtering using TiO2 target and argon atmosphere with the pressure of 3×10(-2)mbar and the distance between the substrate to the target of 60mm. In order to determine changes in the properties that occur as a result of modification of the Ti surface, the following examinations were carried out by SEM-EDX, X-ray diffraction methods, Raman spectroscopy, Glow Discharge Optical Spectroscopy (GDOS) and Secondary Ion Mass Spectrometry (SIMS). The coatings obtained were characterized by zonal structure comprising the solution zone of Ti?(O) and oxide zone of TiO2 with modifications of rutile and anatase, depending on the oxidation method. It was found that formation of oxide layers using the hybrid method (FB+PVD) leads to limitation of defects in the oxide layer after fluidized-bed thermal treatment and obtaining a uniform, tight coating with improved corrosion properties which are important from the biomedical standpoint. PMID:25037440

Lubas, M; Jasinski, J J; Sitarz, M; Kurpaska, L; Podsiad, P; Jasinski, J

2014-12-10

 
 
 
 
241

Structural and morphological properties of TiO2thin films prepared by spray pyrolysis  

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Full Text Available En el presente trabajo la técnica de roc?o pirol?tico fue empleada para producir pel?culas delgadas de TiO2 sobre substratos de cuarzo y silicio cristalino (Si. Generado por ultrasonido, un aerosol de di-isopropoxido de titanio fue usado como precursor en los depósitos. El proceso de cristalización como función de los parámetros de deposito fue estudiado por difracción de rayos-X (XRD, espectroscop?a Rama (RS, microscopia de fuerza atómica (AFM y espectroscop?a óptica de transmisión (TS. Los resultados demuestran que la técnica de roc?o pirol?tico puede producir pel?culas con superficies planas y buenas propiedades cristalinas. Cuando la temperatura de depósito es menor a 400±C, la pel?cula crece con una superficie suave (rugosidad»5 ° A pero en una fase amorfa; sin embargo a temperaturas iguales a 400±C o mayores las pel?culas cristalizan en la fase anatasa aun cuando la rugosidad se incrementa hasta un valor que depende del espesor. Después de un tratamiento térmico a 750±C, las muestras depositadas sobre Si muestran una transicion parcial a la fase rutilio del TiO2con orientación preferencial (111; sin embargo, las pel?culas depositadas sobre cuarzo no muestran tal transicion.

N. Castillo

2004-01-01

242

Co distribution in ferromagnetic rutile Co-doped TiO$_2$ thin films grown by laser ablation on silicon substrates  

CERN Document Server

Pure rutile Co-doped TiO$_2$ films were fabricated successfully by the conventional pulsed laser deposition technique on silicon substrates from a ceramic target. Under the right fabrication conditions, Co concentration in the films could be almost the same as in the synthesized target, and films under various conditions all are ferromagnetic well above room temperature. Even though Rutherford backscattering spectroscopy measurements show that Co atoms seem to be mostly localized near the surface of the films and less exist in deeper levels, other experimental evidences show that the ferromagnetism does not come from Co segregations but from the Co-doped TiO$_2$ matrix. Rutile Ti$_1-x$Co$_x$O$_2$ thin films grown by a very simple technique on low-price silicon substrates showing Curie temperature (TC) above 400 K appear to be very attractive to applications.

Hong, N H; Prellier, W; Hassini, A; Hong, Nguyen Hoa; Sakai, Joe; Hassini, Awatef

2003-01-01

243

Nanostructured columnar heterostructures of TiO2 and Cu2O enabled by a thin-film self-assembly approach: Potential for photovoltaics  

International Nuclear Information System (INIS)

Graphical abstract: Display Omitted Highlights: ? Material self-assembly in phase-separated oxides is exploited. ? Three-dimensionally nanostructured epitaxial films are grown using sputtering. ? Films are composed of well-ordered oriented nanopillars of n-type TiO2 and p-type Cu2O. ? Observed interfaces at adjacent TiO2–Cu2O columns are nearly atomically distinct. ? Absorption profile of the composite film captures a wide range of the solar spectrum. -- Abstract: Significant efforts are being devoted to the development of multifunctional thin-film heterostructures and nanostructured material architectures for components with novel applications of superconductivity, multiferroicity, solar photocatalysis and energy conversion. In particular, nanostructured assemblies with well-defined geometrical shapes have emerged as possible high efficiency and economically viable alternatives to planar photovoltaic thin-film architectures. By exploiting phase-separated self-assembly, here we present advances in a vertically oriented two-component system that offers potential for future development of nanostructured thin film solar cells. Through a single-step deposition by magnetron sputtering, we demonstrate growth of an epitaxial, composite film matrix formed as self-assembled, well ordered, phase segregated, and oriented nanopillars of n-type TiO2 and p-type Cu2O. The composite films were structurally characterized to atomic resolution by a variety of analytical tools, and evaluated for preliminary optical properties using absorption measurements. We find nearly atomically distinct TiO2–Cu2O interfaces (i.e., needed for possible active p–n junctions), and an absorption profile that captures a wide range of the solar spectrum extending from ultraviolet to visible wavelengths. This high-quality materials system could lead to photovoltaic devices that can be optimized for both incident light absorption and carrier collection.

244

Optimizing preparation of the TiO2 thin film reactor using the Taguchi method  

International Nuclear Information System (INIS)

In this study, titanium dioxide thin film was prepared using the modified chemical vapor deposition. The parameters employed to control the preparation of the catalyst include the temperature of water bath, the Ti(OC3H7)4/H2O ratio, the flow rate of carrier gas, the oxidation temperature, the oxidation time, the calcination temperature, the rotating speed of furnace, and the speed of geared motor. The orthogonal arrays in the design of experimental method proposed by Taguchi were adopted to conduct the multiple-factor experiment. The conversion rate of salicylic acid in the aqueous or heterogeneous phase photocatalysis experiment was employed to identify the optimal conditions for assembly. The results indicated that a higher conversion ratio of the organic substance could be achieved under catalytic oxidation temperature of 400 oC, calcination temperature of 550 oC, and spraying speed of 30 rpm and the optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm-2 on salicylic acid at concentration of 250 mg L-1 by both agitation and aeration processes (dissolved oxygen level = 8.2 mg O2 L-1) at pH 5, which could achieve optimal hydroxyl radical yield of 5.1 x 10-17 M.

245

The fabrication of visible light responsive Ag-SiO2 co-doped TiO2 thin films by the sol–gel method  

International Nuclear Information System (INIS)

In this study we have successfully deposited Ag-SiO2 co-doped TiO2 thin films on glass substrates by the sol–gel method. After being coated by a dip coating method, the film was transparent, smooth and had strong adhesion on the glass surface. The deposited film was characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV–Vis), a scanning electron microscope (SEM) and atomic force microscope (AFM) to investigate its crystallization, transmittance and surface structure. The antifogging ability is explained by the contact angle of water on the surface of the glass substrates under visible-light. The obtained results show that Ag-SiO2 co-doped TiO2 film has potential applications for self cleaning and anti-bacterial ceramic tiles

246

Effects of dip-coating speed and annealing temperature on structural, morphological and optical properties of sol-gel nano-structured TiO2 thin films  

Science.gov (United States)

We reported material characterization of the nano-structured TiO2 thin films prepared by the sol-gel dip-coating process on glass substrates. The dependence of the structural, morphological and optical properties of the synthesized films on the fabrication parameters such as withdrawal velocity and annealing temperature were investigated by the techniques of X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-visible spectrophotometry. The results indicate that for the TiO2 films annealed at 500 °C there exhibits (1 0 1) XRD peak corresponding to the anatase phase of TiO2. The latter is consistent with the recorded Raman signal observed at 142 cm-1 (Eg mode) and 391 cm-1 (B1g mode), respectively. From the analyses made on the SEM micrographs and AFM images, it was revealed that the morphology and surface roughness of the thin films would depend on the withdrawal speed and the heat treatment temperature. The UV-visible spectroscopy analyses show that all the films were transparent in the visible region with an average transmittance of more than 70%. With an increase on the dip-coating speed from 1 cm/min to 3 cm/min, we observed a spectral red shift of the absorption edge from 3.76 eV to 3.71 eV, indicating a decrease in the bandgap energy (Eg) of the films.

Touam, Tahar; Atoui, Mohamed; Hadjoub, Ilhem; Chelouche, Azeddine; Boudine, Boubekeur; Fischer, Alexis; Boudrioua, Azzedine; Doghmane, Abdellaziz

2014-09-01

247

Optical and crystallisation behaviour of TiO2 and V/TiO2 thin films prepared by plasma and ion beam assisted methods  

International Nuclear Information System (INIS)

This paper reports the synthesis of TiO2 and V/TiO2 thin films, prepared by plasma enhanced and ion beam induced chemical vapour deposition procedures. Thin films with different contents of vanadium from a few to some tenth percents of this element have been prepared. Vanadium oxide thin films were also prepared for comparison. Morphological, structural and chemical characterisation of the samples was carried out by means of several techniques including scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Optical properties of these samples were studied by ellipsometry and ultraviolet-visible absorption spectroscopy. It has been shown that the absorption threshold of V/TiO2 thin films shifts continuously towards the visible by increasing the V content. On the basis of this behaviour it is proposed the use of these thin films as optical filters in the UV-vis region of the spectrum. In the 'as prepared' samples vanadium is homogeneously distributed within an amorphous Ti-O structure. After annealing in air at T>673 K, both segregation of vanadium as vanadium oxide and crystallisation of the TiO2 into the rutile structure take place. It is realised that infrared spectroscopy can be a complementary technique of XRD to determine the crystallisation behaviour of the samples. The observed structural modifications are accompanied by a change in the light absorption properties of the films that can now be interpreted as due to the superposition of the absorption spectra of TiO2 and vanadium oxide. In the ion beam assisted films, only slight changes in their refraction index (n) are found as a function of the vanadium content and/or the annealing treatments. The changes were greater for the less compact films obtained by plasma deposition, indicating that the main parameter controlling the value of n is the density of the films

248

Photoelectric properties of TiO2-ZrO2 thin films prepared by sol-gel method.  

Science.gov (United States)

Acidic sols of TiO2, ZrO2 and Ti-Zr mixed oxide precursors were prepared. The sols were then smeared on quartz substrate and annealed at 650 degrees C for 2 hour to form polycrystalline oxide films. XRD, SEM, UV-visible absorption spectra and XPS were carried out to characterize the films. It was found that the crystalline phase of pure titania is an anatase and pure zirconia is a tetragonal. The binary oxides show the anatase phase at the molar ratio of Ti:Zr = 2.73:1, which means that solid solution was formed. The absorption edge of the TiO2-ZrO2 binary oxides showed obvious blue shift as the Zr ratio increased. The results obtained indicate that the band gap of the binary oxides could be adjusted from 3.2 eV (TiO2) to 7.8 eV (ZrO2) by varying the molar ratio of Ti and Zr. Au interdigitated electrodes were produced by planar technology and MSM (metal-semiconductor-metal) structure UV detector based on TiO2-ZrO2 binary oxides was fabricated. Obvious photoelectric response was observed. PMID:22413339

Zhang, Haifeng; Ruan, Shengping; Feng, Caihui; Xu, Baokun; Chen, Weiyou; Dong, Wei

2011-11-01

249

Vibrational relaxation dynamics of catalysts on TiO2 Rutile (1 1 0) single crystal surfaces and anatase nanoporous thin films  

International Nuclear Information System (INIS)

Highlights: • Investigated vibrational relaxation dynamics of a CO2-reduction catalyst on TiO2 surfaces. • IR pump-vibration sum-frequency generation probe spectroscopy on Rutile (1 1 0) surface. • IR-pump/IR probe transient absorption spectroscopy on nano-crystalline thin films. • CO stretching modes show a ultrafast population equilibration followed by population decay. - Abstract: Time-resolved vibrational sum frequency generation (VSFG) spectroscopy has been used to investigate the vibrational relaxation dynamics of the rhenium bipyridyl CO2-reduction catalyst Re(CO)3Cl(dcbpy) [dcbpy = 4,4?-dicarboxy-2,2?-bipyridine] adsorbed onto the (1 1 0) surface of a Rutile TiO2 single crystal. IR pump-VSFG probe spectra of the a?(1) CO stretching mode indicate a ultrafast population equilibration between three CO stretching modes followed by their population relaxation via intramolecular vibrational energy transfer. Similar vibational relaxation dynamics was also observed for the same complex on anatase TiO2 nanocrystalline thin films measured by IR pump-IR probe transient absorption spectroscopy. The relaxation dynamics of ReCOA on TiO2, in DMF solution, and immobilized on Au through alkane thiol linkers were compared to examine possible effects of adsorbate-TiO2 interaction

250

Corrosion behavior of TiO2–NiO nanocomposite thin films on AISI 316L stainless steel prepared by sol–gel method  

International Nuclear Information System (INIS)

TiO2–NiO nanocomposite thin films were deposited on the 316L stainless steel using sol–gel method by a dip coating technique. Different techniques such as differential thermal analysis, thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy and scanning probe microscopy were carried out in order to characterize the structure of the coatings. The corrosion resistance of the coatings was evaluated by using Tafel polarization and electrochemical impedance spectroscopy tests of uncoated and coated specimens in a 3.5% NaCl solution at room temperature. It was found that to obtain desirable structure in coatings, the coatings should be calcined at 600 °C for one and half hour. NiTiO3, anatase and rutile were the phases obtained in different calcination conditions in air atmosphere. The results of corrosion tests indicated that with increasing the dipping times from 2 to 4, the corrosion current density first decreases but when increasing the dipping times to 6, it increases. Also the corrosion current density decreased from 186.7 nA.cm?2 (uncoated steel) to 34.21 nA.cm?2 (80%TiO2–20%NiO) and corrosion potential increased from ? 150.2 mV (uncoated steel) to ? 107.3 mV (67%TiO2–33%NiO). - Highlights: ? TiO2–NiO thin films were deposited on the 316L stainless steel using sol–gel method. ? Different compositions, annealing times and temperatures resulted in various phases. ? Films having different compositions showed various surface morphologies. ? Films having a composition of 80%TiO2–20%NiO showed a good corrosion protection.

251

Thin-film photo-catalytic TiO2 phase prepared by magnetron sputtering deposition, plasma ion implantation and metal vapor vacuum arc source  

International Nuclear Information System (INIS)

This study utilizes three methods, magnetron sputtering deposition (MSD), plasma ion implantation (PIII), and metal vapor vacuum arc (MeVVA), to prepare a thin-film TiO2. The formation of stoichiometrical TiO2-polymorphs as a layer is regularly relevant to the characteristic of the photo-catalytic effect. TiO2-polymorphs created at the outermost surface and initiated by efficient photons are still capable to produce superficial hydroxyl groups for subsequent photo-catalytic reactions. The MSD-treated surface with the majority of TiO2-anatase (101) surface is presently photo-catalytic. The PIII or MeVVA treatment results in an ion-implanted layer of different Ti / O ratios along with the detecting depths, whereas the Ti and O elements in TiO2 phase at the outermost surface of the layer can be distinguished. Although the PIII- or MeVVA-treated surface is relatively insignificant in photo-catalytic reactions assessed by water droplet contact angle, the consumption of methylene blue in water and antibacterial test, it is still potential to adjust their surface chemistry by improving the quality of the ion-implanted layer, roughening the contact surface area, and increasing the efficiency to regenerate the photo-catalytic reactions. In addition, the ion implantation methods do not alter the size and dimension of a substrate that is a great advantage to employ them for various advanced applications

252

Non-adiabatic small polaron hopping conduction in Nb-doped TiO2 thin film  

International Nuclear Information System (INIS)

Transport properties of Nb-doped titanium oxide (TiO2) thin film, obtained by a RF sputtering technique, have been investigated by means of the electrical conductivity and the Seebeck coefficient as a function of temperature (13-425 K). At high temperatures (T>325 K), temperature dependent behaviors of the electrical conductivity and the Seebeck coefficient confirm that the transport mechanism is the non-adiabatic small polaron hopping type. An excellent agreement between the theoretical and the experimental values of non-adiabatic polaron hopping energy (WH?0.3 eV) is obtained. The conductivity follows the Mott's variable range hopping conduction (VRH) at the temperature range of 200-325 K, while it exhibits a temperature-independent behavior at low temperatures (T<200 K). Various physical parameters of the present sample such as polaron radius, effective dielectric constant, polaron hopping energy, density of states at the Fermi level, polaron band width and polaron coupling constant are determined using small polaron hopping model.

253

Excellent resistive switching property and physical mechanism of amorphous TiO2 thin films fabricated by a low-temperature photochemical solution deposition method  

Science.gov (United States)

High-performance resistive switching Pt/TiO2/Pt memory cells were fabricated. The amorphous TiO2 active layer was prepared by using a low-temperature photochemical solution deposition method-a simple preparation process combining first chemical solution deposition of the TiO2 film layer and subsequent ultraviolet (UV) irradiation treatment. The obtained Pt/TiO2/Pt memory cells exhibited excellent resistive switching parameters, such as centralized distribution of set and reset voltages, stable current values at high and low resistance states, and long retention time. The conductive mechanisms of high resistance state and low resistance state were Schottky emission and Ohmic conduction, respectively. The X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy characterization of the TiO2 thin films indicated that the UV irradiation treatment can lead to decomposition of the residual organics and the formation of enhanced metal-oxide bonds in the thin films. On the basis of the analysis of current-voltage characteristics and the temperature dependence of resistance, we explained the resistive switching phenomenon for Pt/TiO2/Pt devices by using the model of formation/rupture of conductive filaments. Our study also suggested that the simple photochemical solution deposition method can be used for preparing some other oxide thin films with good resistive switching properties at low processing temperature which is promising to be extended to flexible resistive switching devices.

Zou, Lilan; Hu, Wei; Xie, Wei; Chen, Ruqi; Qin, Ni; Li, Baojun; Bao, Dinghua

2014-08-01

254

Crystalline nanoporous metal oxide thin films by post-synthetic hydrothermal transformation: SnO2 and TiO2  

Science.gov (United States)

Nanostructured and nanoporous metal oxide thin films are rarely accessible by standard synthetic approaches but highly desired for many applications, e.g. as electrodes, transparent conducting coatings, sensors or surface catalysts. Template based sol-gel chemistry combined with post-synthetic hydrothermal treatment allows now the synthesis of nanocrystalline mesostructured porous thin films of metal oxides, e.g. tin oxide and titania. Even in cases where the crystallization cannot be induced highly stable thin films can be achieved, e.g. niobium oxide thin films. We demonstrate how the size of the nanocrystallites influences and stabilizes the mesostructure at temperatures as low as 100 °C and thereby in the case of titania or tin dioxide even prevents it from deterioration at higher temperatures up to 400-600 °C.Nanostructured and nanoporous metal oxide thin films are rarely accessible by standard synthetic approaches but highly desired for many applications, e.g. as electrodes, transparent conducting coatings, sensors or surface catalysts. Template based sol-gel chemistry combined with post-synthetic hydrothermal treatment allows now the synthesis of nanocrystalline mesostructured porous thin films of metal oxides, e.g. tin oxide and titania. Even in cases where the crystallization cannot be induced highly stable thin films can be achieved, e.g. niobium oxide thin films. We demonstrate how the size of the nanocrystallites influences and stabilizes the mesostructure at temperatures as low as 100 °C and thereby in the case of titania or tin dioxide even prevents it from deterioration at higher temperatures up to 400-600 °C. Electronic supplementary information (ESI) available: Methods-detailed description of applied synthesis and characterization methods, Fig. S1-XRD wide angle data for titania after psHT and calcination, Fig. S2-XPS spectra of mesoporous titania thin films, Fig. S3-nitrogen physisorption measurements of Nb2O5 (A), TiO2 (B), SnO2 (C) thin films scratched of wafers, Fig. S4-PSD from EP measurements of Nb2O5 (A), TiO2 (B), SnO2 (C) thin films, and Fig. S5-photo of glass slides with thin films of Nb2O5 (A), TiO2 (B), SnO2 (C), empty (D) for transparency comparison. See DOI: 10.1039/c0nr00079e

Shao, Shaofeng; Dimitrov, Momtchil; Guan, Naijia; Köhn, Ralf

2010-10-01

255

Photocatalytic Degradation of Glyphosate in Water by N-Doped SnO2 /TiO2 Thin-Film-Coated Glass Fibers.  

Science.gov (United States)

Photocatalytic degradation of glyphosate contaminated in water was investigated. The N-doped SnO2 /TiO2 films were prepared via sol-gel method, and coated on glass fibers by dipping method. The effects of nitrogen doping on coating morphology, physical properties and glyphosate degradation rates were experimentally determined. Main variable was the concentration of nitrogen doping in range 0-40 mol%. Nitrogen doping results in shifting the absorption wavelengths and narrowing the band gap energy those lead to enhancement of photocatalytic performance. The near optimal 20N/SnO2 /TiO2 composite thin film exhibited about two- and four-folds of glyphosate degradation rates compared to the undoped SnO2 /TiO2 and TiO2 films when photocatalytic treatment were performed under UV and solar irradiations, respectively, due to its narrowest band gap energy (optical absorption wavelength shifting to visible light region) and smallest crystallite size influenced by N-doping. PMID:25169246

Kongsong, Peerawas; Sikong, Lek; Niyomwas, Sutham; Rachpech, Vishnu

2014-11-01

256

On the optical properties of Ag+15 ion beam irradiated TiO2 and SnO2 thin films  

CERN Document Server

In this study, the effects of 200 MeV Ag+15 ion irradiation on the optical properties of TiO2 and SnO2 thin films prepared by RF magnetron sputtering technique were investigated. These films were characterized by the UV-vis spectroscopy and it was observed that with increase in irradiation fluence the transmittance for the TiO2 films systematically increases while that for SnO2 decreases. Absorption spectra of the irradiated samples showed a minor changes in indirect bandgap from 3.44 to 3.59 eV for TiO2 while that for SnO2 significant modifications in the direct bandgap from 3.92 to 3.6 eV were observed on increasing irradiation fluence. The observed modifications in the optical properties of both TiO2 and SnO2 systems with irradiation can be attributed to controlled structural disorder/defects in the system.

Thakur, Hardeep; Thakur, P; Sharma, K K; Singh, Abhinav Pratap; Kumar, Yogesh; Kumar, Ravi; Chae, Keun Hwa

2011-01-01

257

Preparation and optical properties of mesoporous TiO2 thin films by a two-step sol-gel technique  

International Nuclear Information System (INIS)

This paper concerns the preparation of mesoporous titania nanopowders and thin films for use in next generation photoelectrochemical solar cells. We have recently developed a novel method for preparing mesoporous TiO2 powders using a Two-Step Sol-gel method (TSS). These materials have crystalline domains characteristic of anatase. The first step of the process involves the hydrolysis of titanium isopropoxide in a basic aqueous solution mediated by neutral surfactant. The solid product resulting from Step-1 is then treated in acidified ethanol solution containing a titanium precursor to yield anatase TiO2. The resultant powder exhibits a high surface area and large pore volume with uniform mesopores. Slurries made from the resultant powder of Steps 1 and 2 have been used to produce thin titania films on glass slides. The optical and structural properties of these films have been compared to the films made of a commercial titania (Degussa P25, BASF). We will discuss these properties with respect to the possible use of such mesoporous titania films as the wide band gap semiconductor in dye-sensitized nanocrystalline TiO2 solar cells

258

Effect of deposition methods on the properties of photocatalytic TiO2 thin films prepared by spray pyrolysis and magnetron sputtering  

International Nuclear Information System (INIS)

Titanium dioxide thin films were deposited by DC reactive magnetron sputtering and spray pyrolysis methods onto glass and glass coated with fluorine doped tin oxide (FTO). The films were characterized by x-ray diffraction, scanning electron microscopy, atomic force microscopy and UV-visible spectroscopy. For films deposited by the sputtering technique we have studied the effect of the total pressure of an Ar-O2 mixture on the substrate properties, on the deposition rate, phase composition, crystallinity, surface morphology and on the photocatalytic properties. Also transparent TiO2 thin films have been prepared by spray pyrolysis using a low concentration of titanium precursor with different substrate temperatures. At higher substrate temperatures the films were polycrystalline in the anatase phase; at lower substrate temperatures the films presented an amorphous configuration. The photocatalytic properties of TiO2 thin films were tested with the degradation methylene blue under UV light irradiation. The higher degradation rates were reached for films prepared by spray pyrolysis with a substrate temperature close to 400 deg. C, and for a high total pressure (16 mTorr) for films deposited by DC magnetron sputtering

259

Site-specific and patterned growth of TiO2 nanotube arrays from e-beam evaporated thin titanium film on Si wafer.  

Science.gov (United States)

Growth of TiO(2) nanotubes on thin Ti film deposited on Si wafers with site-specific and patterned growth using a photolithography technique is demonstrated for the first time. Ti films were deposited via e-beam evaporation to a thickness of 350-1000 nm. The use of a fluorinated organic electrolyte at room temperature produced the growth of nanotubes with varying applied voltages of 10-60 V (DC) which remained stable after annealing at 500 °C. It was found that variation of the thickness of the deposited Ti film could be used to control the length of the nanotubes regardless of longer anodization time/voltage. Growth of the nanotubes on a SiO(2) barrier layer over a Si wafer, along with site-specific and patterned growth, enables potential application of TiO(2) nanotubes in NEMS/MEMS-type devices. PMID:22948670

Chappanda, Karumbaiah N; Smith, York R; Misra, Mano; Mohanty, Swomitra K

2012-09-28

260

Site-specific and patterned growth of TiO2 nanotube arrays from e-beam evaporated thin titanium film on Si wafer  

International Nuclear Information System (INIS)

Growth of TiO2 nanotubes on thin Ti film deposited on Si wafers with site-specific and patterned growth using a photolithography technique is demonstrated for the first time. Ti films were deposited via e-beam evaporation to a thickness of 350–1000 nm. The use of a fluorinated organic electrolyte at room temperature produced the growth of nanotubes with varying applied voltages of 10–60 V (DC) which remained stable after annealing at 500?°C. It was found that variation of the thickness of the deposited Ti film could be used to control the length of the nanotubes regardless of longer anodization time/voltage. Growth of the nanotubes on a SiO2 barrier layer over a Si wafer, along with site-specific and patterned growth, enables potential application of TiO2 nanotubes in NEMS/MEMS-type devices. (paper)

 
 
 
 
261

Structure of glancing incidence deposited TiO(2) thin films as revealed by grazing incidence small-angle X-ray scattering.  

Science.gov (United States)

For the first time, grazing incidence small-angle X-ray scattering (GISAXS) analysis is used to characterize the morphology of TiO(2) thin films grown by glancing angle physical vapor deposition (GLAD). According to cross-section scanning electron microscopy (SEM) images, the films consist of near isotilted TiO(2) columns of different length and width depending on film thickness. The obtained GISAXS patterns show a characteristic asymmetry with respect to the incidence plane, which is associated with the tilted geometry of the TiO(2) columns. The patterns also show the existence of two populations of columns in these GLAD-TiO(2) films. The population of the thinnest columns appears related to the first grown layer and is common for all the films investigated, while the second population of columns grows with the thickness of the films and has been related to wider columns formed by shadowing at the expense of the initially formed columns. PMID:20491135

González-García, Lola; Barranco, Angel; Páez, Adela Muñoz; González-Elipe, Agustín R; García-Gutiérrez, Mari-Cruz; Hernández, Jaime J; Rueda, Daniel R; Ezquerra, Tiberio A; Babonneau, David

2010-07-12

262

Antifungal activity of Ag:hydroxyapatite thin films synthesized by pulsed laser deposition on Ti and Ti modified by TiO2 nanotubes substrates  

Science.gov (United States)

Hydroxyapatite (HA) is a widely used biomaterial for implant thin films, largely recognized for its excellent capability to chemically bond to hard tissue inducing the osteogenesis without immune response from human tissues. Nowadays, intense research efforts are focused on development of antimicrobial HA doped thin films. In particular, HA doped with Ag (Ag:HA) is expected to inhibit the attachment of microbes and contamination of metallic implant surface. We herewith report on nano-sized HA and Ag:HA thin films synthesized by pulsed laser deposition on pure Ti and Ti modified with 100 nm diameter TiO2 nanotubes (fabricated by anodization of Ti plates) substrates. The HA-based thin films were characterized by SEM, AFM, EDS, FTIR, and XRD. The cytotoxic activity was tested with HEp2 cells against controls. The antifungal efficiency of the deposited layers was tested against the Candida albicans and Aspergillus niger strains. The Ti substrates modified with TiO2 nanotubes covered with Ag:HA thin films showed the highest antifungal activity.

Erakovi?, S.; Jankovi?, A.; Ristoscu, C.; Duta, L.; Serban, N.; Visan, A.; Mihailescu, I. N.; Stan, G. E.; Socol, M.; Iordache, O.; Dumitrescu, I.; Luculescu, C. R.; Jana?kovi?, Dj.; Miškovic-Stankovi?, V.

2014-02-01

263

Photo-assisted electrochemical copper removal from cyanide solutions using porous TiO2 thin film photo-anodes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english TiO2 porous films were prepared on ITO coated glass slides by the sol-gel dip-coating method assisted with Polyethylene glycol (PEG). The films were used as photo-anodes in the photo-assisted electrolytic removal of cuprous ions in cyanide media. These were characterized by SEM, UV-Visible spectrosc [...] opy and XRD. The PEG modified films were free of cracks and developed a porous structure after heat treatment at 500 ºC, due to the thermal decomposition of the structure associated PEG. It was demonstrated that the photo-assisted electrochemical reduction of copper is promoted by the use of modified TiO2 films as photo-anodes, thanks to the greater surface area given by the PEG decomposition. However, the film thickness was found to be a critical factor in the process, to such an extent that films composed of 5 layers were completely inefficient, meaning that despite the open porosity, multilayered films acted as a barrier within the photo-electrolytic process.

Álvaro A., Ramírez-Santos; Próspero, Acevedo-Peña; Elcy M., Córdoba.

2014-02-01

264

Photo-assisted electrochemical copper removal from cyanide solutions using porous TiO2 thin film photo-anodes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english TiO2 porous films were prepared on ITO coated glass slides by the sol-gel dip-coating method assisted with Polyethylene glycol (PEG). The films were used as photo-anodes in the photo-assisted electrolytic removal of cuprous ions in cyanide media. These were characterized by SEM, UV-Visible spectrosc [...] opy and XRD. The PEG modified films were free of cracks and developed a porous structure after heat treatment at 500 ºC, due to the thermal decomposition of the structure associated PEG. It was demonstrated that the photo-assisted electrochemical reduction of copper is promoted by the use of modified TiO2 films as photo-anodes, thanks to the greater surface area given by the PEG decomposition. However, the film thickness was found to be a critical factor in the process, to such an extent that films composed of 5 layers were completely inefficient, meaning that despite the open porosity, multilayered films acted as a barrier within the photo-electrolytic process.

Álvaro A., Ramírez-Santos; Próspero, Acevedo-Peña; Elcy M., Córdoba.

265

Microstructure characterization of sol-gel prepared MoO3-TiO2 thin films for oxygen gas sensors  

International Nuclear Information System (INIS)

Binary metal-oxide MoO3-TiO2 films have been prepared using the sol-gel technique. The thin films were annealed at several temperatures including 400, 450, 500, 550, and 600 deg. C for 1 h. The morphology, crystalline structure, and chemical composition of the films have been analyzed using scanning electron microscopy (SEM) and atomic force microscopy, x-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), and x-ray photoelectron spectroscopy (XPS) techniques. The SEM analysis showed that there are two different sizes of grains in the films annealed at temperatures of 400, 450, 500, and 550 deg. C. One grain type is small with 20-100 nm; the other is a large grain type several micrometers in length. The XRD analysis revealed that the films annealed at 400 deg. C were a mixture of orthorhombic and hexagonal MoO3 phases. The films annealed at 450 deg. C showed an increase in the hexagonal phase. A preferential orientation growth along the (100) plane of the hexagonal phase and the (010) plane of the orthorhombic phase has been found in both samples. RBS and XPS analysis showed that the films were stoichiometric. When the annealing temperature was increased beyond 500 deg. C, the concentration ratio of MoO3-TiO2 decreased due to the evaporation of MoO3. For the study of the electrical and gas sensing properties, the films were deposited on sapphire substrates with interdigital electrodes o substrates with interdigital electrodes on the frontside and a Pt heater on the backside. The MoO3-TiO2 thin films are sensitive to oxygen gas. The film has exhibited the O2 response (S=Rg/Rb) of 2.1, 8.1, and 80 for 120, 1000, and 10 000 ppm concentration of O2, respectively

266

Templated synthesis of porous TiO2 thin films using amphiphilic graft copolymer and their use in dye-sensitized solar cells  

International Nuclear Information System (INIS)

Porous TiO2 thin films have been prepared using an amphiphilic graft copolymer, i.e. poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(oxyethylene methacrylate) (P(VDF-co-CTFE)-g-POEM) as a structure-directing agent via the sol-gel process. The graft copolymer was synthesized via atom transfer radical polymerization using CTFE units as an initiating site and designed to have a hydrophobic P(VDF-co-CTFE) domain and a hydrophilic POEM domain. Fourier transform-infra red spectroscopy indicated that a hydrophilic titania precursor was selectively incorporated into hydrophilic POEM domains. In-situ formation and morphologies of porous TiO2 thin films were confirmed by ultraviolet-visible spectroscopy, X-ray diffraction, transmission electron microscopy and thermogravimetric analysis. The resultant porous TiO2 films with 10-25 nm in size were used as a photoelectrode for solid-state dye-sensitized solar cells, exhibiting energy conversion efficiency of 2.8% at 100 mW/cm2.

267

Damage performance of TiO 2 /SiO 2 thin film components induced by a long-pulsed laser  

Science.gov (United States)

In order to study the long-pulsed laser induced damage performance of optical thin films, damage experiments of TiO 2/SiO 2 films irradiated by a laser with 1 ms pulse duration and 1064 nm wavelength are performed. In the experiments, the damage threshold of the thin films is measured. The damages are observed to occur in isolated spots, which enlighten the inducement of the defects and impurities originated in the films. The threshold goes down when the laser spot size decreases. But there exists a minimum threshold, which cannot be further reduced by decreasing the laser spot size. Optical microscopy reveals a cone-shaped cavity in the film substrate. Changes of the damaged sizes in film components with laser fluence are also investigated. The results show that the damage efficiency increases with the laser fluence before the shielding effects start to act.

Wang, Bin; Dai, Gang; Zhang, Hongchao; Ni, Xiaowu; Shen, Zhonghua; Lu, Jian

2011-09-01

268

TiO2 and Al2O3 ultra thin nanolaminates growth by ALD; instrument automation and films characterization  

Directory of Open Access Journals (Sweden)

Full Text Available We report on the development of a fully operational atomic layer deposition (ALD system. This system is computer controlled and can deposit multilayered systems without user intervention. We describe the design of manifold, reaction chamber and exhaust. Additionally we give some features of the automatization software and electronics. To evaluate the ALD performance we used as precursor trymethyl aluminum (TMA and tetrakis (dimethylamino titanium (TDMAT to deposit Al2O3 and TiO2, respectively, in nanolaminated film structures. The thicknesses and composition of the films are precisely controlled, as determined by spectroscopic ellipsometry, and the nanolaminates have a sharp interface as indicated by Auger depth profile.

H. Tiznado

2012-01-01

269

Photocatalytic performance of Sn-doped and undoped TiO2 nanostructured thin films under UV and vis-lights  

International Nuclear Information System (INIS)

Sn-doped and undoped nano-TiO2 particles have been synthesized by hydrotermal process without solvent at 200 deg. C in 1 h. Nanostructure-TiO2 based thin films have been prepared on glass substrate by spin-coating technique. The structure, surface morphology and optical properties of the thin films and the particles have been investigated by element analysis and XRD, SEM, BET and UV-vis-NIR techniques. The photocatalytic performance of the films were tested for degradation of Malachite Green dye in solution under UV and vis-lights. The results showed that (a) hydrothermally synthesized nano-TiO2 particles are fully anatase crystalline form and are easily dispersed in water, (b) the coated surfaces have nearly super-hydrophilic properties and (c) the doping of transition metal ion efficiently improved the photocatalytic performance of the TiO2 thin film

270

Significant enhancement of yellow-green light emission of TiO2 thin films using Au localized surface plasmons: effect of dielectric MgO spacer layer thickness.  

Science.gov (United States)

TiO2/MgO/Au composite thin films with different MgO spacer layer thicknesses (0-41 nm) were fabricated on c-sapphire substrates by sputtering and pulsed laser deposition. Through optimizing the thickness of MgO spacer layer, which can effectively prevent nonradiative Förster resonant energy transfer and charge transfer between Au and TiO2, defect-related yellow-green light emission of TiO2 thin film was greatly enhanced - 12 times. The enhancement mechanism is attributed to the efficient increase of luminescence efficiency of deep levels in TiO2 induced by resonant coupling between localized surface plasmons in Au nanoparticles and electron-hole pairs in defect-related levels of TiO2. PMID:24734627

Zhang, Cen; Liu, Weizhen; Xu, Haiyang; Ma, Jiangang; Liu, Yichun

2014-05-01

271

Enhanced performance in organic light-emitting diodes by sputtering TiO2 ultra-thin film as the hole buffer layer  

International Nuclear Information System (INIS)

Organic light-emitting diodes were prepared using titanium oxide (TiO2) ultra-thin film by RF magnetron sputtering as the hole buffer layer. The device configuration is ITO/TiO2/N-N'-diphenyl-N-N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine/tris (8-quinolinolato)-aluminum/LiF/Al. The maximum luminous efficiency for the 1.2 nm TiO2 device is increased by approximately 46% (6.0 cd/A), in comparison with that of the control device (4.1 cd/A). The atomic force microscopy shows that with the insertion of TiO2 buffer layer, the roughness of ITO surface decreases, which is favorable to improve the device luminance and increase the device lifetime. The mechanism behind the enhanced performance is that the TiO2 layer enhances most of the holes injected from the anode and improves the balance of the hole and electron injections.

272

Semiconductor TiO2-Ga2O3 thin film gas sensors derived from particulate sol-gel route  

International Nuclear Information System (INIS)

rds all CO and NO2 concentrations operated at 200 deg. C. The response magnitude of 13.7 and 4.3 with response times of 30 s and 108 s were achieved for TG11 sensor towards 400 ppm CO and 10 ppm NO2, respectively. Furthermore, calibration curves revealed that TiO2-Ga2O3 sensors follow the power law (S = A[gas] B) (where S is sensor response, coefficients A and B are constants and [gas] is gas concentration) for the two types of gases, and they have excellent capability for the detection of low gas concentrations (25 ppm CO and 0.5 ppm NO2). The maximum response of TiO2-Ga2O3 sensors towards CO and NO2 was measured at 450 and 400 deg. C, respectively. The sensor response decreased with increasing film annealing temperature owing to sintering of the particles. The response magnitude and response time of the sensors obtained in this work is superior to TiO2-based sensors reported in previous studies

273

On the optical, structural, and morphological properties of ZrO2 and TiO2 dip-coated thin films supported on glass substrates  

International Nuclear Information System (INIS)

This article reports the optical and morphological properties of dip-coated TiO2 and ZrO2 thin films on soda-lime glass substrates by metal-organic decomposition (MOD) of titaniumIV and zirconiumIV acetylacetonates respectively. Thermogravimetric and differential thermal analysis (DTA-TG) were performed on the precursor powders, indicating pure TiO2 anatase and tetragonal ZrO2 phase formation. Phase crystallization processes took place in the range of 300-500 deg. C for anatase and of 410-500 deg. C for ZrO2. Fourier Transform Infrared Spectroscopy (FT-IR) was used to confirm precursor bidentate ligand formation with keno-enolic equilibrium character. Deposited films were heated at different temperatures, and their structural, optical and morphological properties were studied by grazing-incidence X-ray Diffraction (GIXRD) and X-Ray Photoelectron Spectroscopy (XPS), Ultraviolet Visible Spectroscopy (UV-Vis), and Atomic Force Microscopy (AFM) respectively. Film thinning and crystalline phase formation were enhanced with increasing temperature upon chelate decomposition. The optimum annealing temperature for both pure anatase TiO2 and tetragonal ZrO2 thin films was found to be 500 deg. C since solid volume fraction increased with temperature and film refractive index values approached those of pure anatase and tetragonal zirconia. Conditions for clean stoichiometric film formation with an average roughness value of 2 nm are discussed in terms of material binding energies indicated by XPS analyses, refractive index and solid volume fraction obtained indirectly by UV-Vis spectra, and crystalline peak identification provided by GIXRD

274

Atomic layer deposition, characterization, and growth mechanistic studies of TiO2 thin films.  

Science.gov (United States)

Two heteroleptic titanium precursors were investigated for the atomic layer deposition (ALD) of titanium dioxide using ozone as the oxygen source. The precursors, titanium (N,N'-diisopropylacetamidinate)tris(isopropoxide) (Ti(O(i)Pr)3(N(i)Pr-Me-amd)) and titanium bis(dimethylamide)bis(isopropoxide) (Ti(NMe2)2(O(i)Pr)2), exhibit self-limiting growth behavior up to a maximum temperature of 325 °C. Ti(NMe2)2(O(i)Pr)2 displays an excellent growth rate of 0.9 Å/cycle at 325 °C while the growth rate of Ti(O(i)Pr)3(N(i)Pr-Me-amd) is 0.3 Å/cycle at the same temperature. In the temperature range of 275-325 °C, both precursors deposit titanium dioxide in the anatase phase. In the case of Ti(NMe2)2(O(i)Pr)2, high-temperature X-ray diffraction (HTXRD) studies reveal a thickness-dependent phase change from anatase to rutile at 875-975 °C. X-ray photoelectron spectroscopy (XPS) indicates that the films have high purity and are close to the stoichiometric composition. Reaction mechanisms taking place during the ALD process were studied in situ with quadrupole mass spectrometry (QMS) and quartz crystal microbalance (QCM). PMID:24896967

Kaipio, Mikko; Blanquart, Timothee; Tomczak, Yoann; Niinistö, Jaakko; Gavagnin, Marco; Longo, Valentino; Wanzenböck, Heinz D; Pallem, Venkateswara R; Dussarrat, Christian; Puukilainen, Esa; Ritala, Mikko; Leskelä, Markku

2014-07-01

275

Evidence of room temperature ferromagnetism in argon/oxygen annealed TiO2 thin films deposited by electron beam evaporation technique  

Science.gov (United States)

TiO2 thin films deposited by electron beam evaporation technique annealed in either O2 or Ar atmosphere showed ferromagnetism at room temperature. The pristine amorphous film demonstrates anatase phase after annealing under Ar/O2 atmosphere. While the pristine film shows a super-paramagnetic behavior, both O2 and Ar annealed films display hysteresis at 300 K. X-ray photo emission spectroscopy (XPS), Raman spectroscopy, Rutherford's backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) were used to refute the possible role of impurities/contaminants in magnetic properties of the films. The saturation magnetization of the O2 annealed film is found to be higher than the Ar annealed one. It is revealed from shifting of O 1s and Ti 2p core level spectra as well as from the enhancement of high binding energy component of O 1s spectra that the higher magnetic moment is associated with higher oxygen vacancies. In addition, O2 annealed film demonstrates better crystallinity, uniform deposition and smoother surface than that of the Ar annealed one from glancing angle X-ray diffraction (GAXRD) and atomic force microscopy (AFM). We conclude that although ferromagnetism is due to oxygen vacancies, the higher magnetization in O2 annealed film could be due to crystallinity, which has been observed earlier in Co doped TiO2 film deposited by pulsed laser deposition (Mohanty et al., 2012 [10]).

Mohanty, P.; Kabiraj, D.; Mandal, R. K.; Kulriya, P. K.; Sinha, A. S. K.; Rath, Chandana

2014-04-01

276

Brookite TiO2 thin film epitaxially grown on (110) YSZ substrate by atomic layer deposition.  

Science.gov (United States)

Epitaxial brookite TiO2 (B-TiO2) film was deposited on (110) yttria-stabilized zirconia (YSZ) substrate using plasma-enhanced atomic layer deposition, and its structural, optical, and gas sensing properties were investigated. As-deposited TiO2 film was a pure brookite and (120) oriented. The determined in-plane orientation relationships were [21?0]B-TiO2//[1?10]YSZ and [001]B-TiO2 //[001]YSZ. The B-TiO2 film showed ?70% transmittance and the optical band gap energy was 3.29 eV. The B-TiO2 film-based gas sensor responded to H2 gas even at room temperature and the highest magnitude of the gas response was determined to be ?150 toward 1000 ppm of H2/air at 150 °C. In addition, B-TiO2 sensor showed a high selectivity for H2 against CO, EtOH, and NH3. PMID:25007217

Kim, Dai-Hong; Kim, Won-Sik; Kim, Sungtae; Hong, Seong-Hyeon

2014-08-13

277

Photocatalytic performance of Sn-doped TiO2 nanostructured thin films for photocatalytic degradation of malachite green dye under UV and VIS-lights  

International Nuclear Information System (INIS)

Sn-doped and undoped nano-TiO2 particles have been synthesized by hydrotermal process without acid catalyst at 225 deg. C in 1 h. Nanostructure-TiO2 based thin films, contain at different solid ratio of TiO2 in coating, have been prepared on glass surfaces by spin-coating technique. The structure, surface morphology and optical properties of the thin films and the particles have been investigated by element analysis and XRD, BET and UV/VIS/NIR techniques. The photocatalytic performance of the films was tested for degradation of malachite green dye in solution under UV and VIS-lights. The results showed that the hydrothermally synthesized nano-TiO2 particles are fully anatase crystalline form and are easily dispersed in water, the coated surfaces have nearly super-hydrophilic properties and, the doping of transition metal ion efficiently improved the photocatalytic performance of the TiO2 thin film. The results also proved that malachite green is decomposed catalytically due to the pseudo first-order reaction kinetics

278

Perovskite Solar Cell with an Efficient TiO2 Compact Film.  

Science.gov (United States)

A perovskite solar cell with a thin TiO2 compact film prepared by thermal oxidation of sputtered Ti film achieved a high efficiency of 15.07%. The thin TiO2 film prepared by thermal oxidation is very dense and inhibits the recombination process at the interface. The optimum thickness of the TiO2 compact film prepared by thermal oxidation is thinner than that prepared by spin-coating method. Also, the TiO2 compact film and the TiO2 porous film can be sintered at the same time. This one-step sintering process leads to a lower dark current density, a lower series resistance, and a higher recombination resistance than those of two-step sintering. Therefore, the perovskite solar cell with the TiO2 compact film prepared by thermal oxidation has a higher short-circuit current density and a higher fill factor. PMID:25166513

Ke, Weijun; Fang, Guojia; Wang, Jing; Qin, Pingli; Tao, Hong; Lei, Hongwei; Liu, Qin; Dai, Xin; Zhao, Xingzhong

2014-09-24

279

Schottky junction/ohmic contact behavior of a nanoporous TiO2 thin film photoanode in contact with redox electrolyte solutions  

Directory of Open Access Journals (Sweden)

Full Text Available The nature and photoelectrochemical reactivity of nanoporous semiconductor electrodes have attracted a great deal of attention. Nanostructured materials have promising capabilities applicable for the construction of various photonic and electronic devices. In this paper, a mesoporous TiO2 thin film photoanode was soaked in an aqueous methanol solution using an O2-reducing Pt-based cathode in contact with atmospheric air on the back side. It was shown from distinct photocurrents in the cyclic voltammogram (CV that the nanosurface of the mesoporous n-TiO2 film forms a Schottky junction with water containing a strong electron donor such as methanol. Formation of a Schottky junction (liquid junction was also proved by Mott–Schottky plots at the mesoporous TiO2 thin film photoanode, and the thickness of the space charge layer was estimated to be very thin, i.e., only 3.1 nm at ?0.1 V vs Ag/AgCl. On the other hand, the presence of [Fe(CN6]4? and the absence of methanol brought about ohmic contact behavior on the TiO2 film and exhibited reversible redox waves in the dark due to the [Fe(CN6]4?/3? couple. Further studies showed that multiple Schottky junctions/ohmic contact behavior inducing simultaneously both photocurrent and overlapped reversible redox waves was found in the CV of a nanoporous TiO2 photoanode soaked in an aqueous redox electrolyte solution containing methanol and [Fe(CN6]4?. That is, the TiO2 nanosurface responds to [Fe(CN6]4? to give ohmic redox waves overlapped simultaneously with photocurrents due to the Schottky junction. Additionally, a second step photocurrent generation was observed in the presence of both MeOH and [Fe(CN6]4? around the redox potential of the iron complex. It was suggested that the iron complex forms a second Schottky junction for which the flat band potential (Efb lies near the redox potential of the iron complex.

Masao Kaneko

2011-02-01

280

Schottky junction/ohmic contact behavior of a nanoporous TiO2 thin film photoanode in contact with redox electrolyte solutions  

Science.gov (United States)

Summary The nature and photoelectrochemical reactivity of nanoporous semiconductor electrodes have attracted a great deal of attention. Nanostructured materials have promising capabilities applicable for the construction of various photonic and electronic devices. In this paper, a mesoporous TiO2 thin film photoanode was soaked in an aqueous methanol solution using an O2-reducing Pt-based cathode in contact with atmospheric air on the back side. It was shown from distinct photocurrents in the cyclic voltammogram (CV) that the nanosurface of the mesoporous n-TiO2 film forms a Schottky junction with water containing a strong electron donor such as methanol. Formation of a Schottky junction (liquid junction) was also proved by Mott–Schottky plots at the mesoporous TiO2 thin film photoanode, and the thickness of the space charge layer was estimated to be very thin, i.e., only 3.1 nm at ?0.1 V vs Ag/AgCl. On the other hand, the presence of [Fe(CN)6]4? and the absence of methanol brought about ohmic contact behavior on the TiO2 film and exhibited reversible redox waves in the dark due to the [Fe(CN)6]4?/3? couple. Further studies showed that multiple Schottky junctions/ohmic contact behavior inducing simultaneously both photocurrent and overlapped reversible redox waves was found in the CV of a nanoporous TiO2 photoanode soaked in an aqueous redox electrolyte solution containing methanol and [Fe(CN)6]4?. That is, the TiO2 nanosurface responds to [Fe(CN)6]4? to give ohmic redox waves overlapped simultaneously with photocurrents due to the Schottky junction. Additionally, a second step photocurrent generation was observed in the presence of both MeOH and [Fe(CN)6]4? around the redox potential of the iron complex. It was suggested that the iron complex forms a second Schottky junction for which the flat band potential (E fb) lies near the redox potential of the iron complex. PMID:21977423

Ueno, Hirohito; Nemoto, Junichi

2011-01-01

 
 
 
 
281

Synthesis and characterization of C-doped TiO2 thin films for visible-light-induced photocatalytic degradation of methyl orange  

Science.gov (United States)

C-TiO2 thin films were synthesized by a modified sol-gel route based on the self-assembly technique exploiting Tween80 (T80) as a pore directing agent and carbon source. The effect of calcination time on the photocatalytic activity of C-doped TiO2 catalyst was studied. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transforms infrared (FTIR), UV-vis diffuse reflectance spectroscopy, and photoluminescence spectra (PL). The XRD results showed that C-TiO2 sample calcined at 400 °C for various times exhibited anatase phase and no other crystal phase was identified. C-TiO2 exhibited a shift in an absorption edge of samples in the visible region than that of conventional or reference TiO2. The XPS results showed an existence of C in the TiO2 catalysts and C might be existed as COTi group. Moreover, the C-TiO2 thin film calcined at 400 °C for 30 min showed the lowest PL intensity due to a decrease in the recombination rate of photogenerated electrons and holes under UV light irradiation. Also the photocatalytic activity of synthesized catalyst was evaluated by decomposition of methyl orange (MO) under visible light irradiation. The results showed that the optimum preparations of C-TiO2 thin films were found to be under calcination temperature of 400, calcination time of 30 min, and with preparation 9 layers film.

Hassan, Mohamed Elfatih; Cong, Longchao; Liu, Guanglong; Zhu, Duanwei; Cai, Jianbo

2014-03-01

282

Facile solution-controlled growth of CuInS2 thin films on FTO and TiO2/FTO glass substrates for photovoltaic application  

International Nuclear Information System (INIS)

This paper reports on the preparation of two thin films (CuInS2/FTO and CuInS2/TiO2/FTO) by a facile solvothermal method and their photovoltaic properties. Instrumental measurements including X-ray diffraction (XRD), inductively coupled plasma emission spectroscopy (ICP), scanning electron microscopy (SEM), and UV-vis spectra have been used to characterize the obtained CuInS2 thin films. The results show that the CuInS2 films deposited on fluorine-doped tin oxide-coated (FTO) conductive glass substrates are composed of nanoplates and microspheres. The thickness of the CuInS2/FTO films can be adjusted from 1 ?m to 8 ?m by controlling the solution concentration of the reactants. While, the prepared 10 ?m-thick CuInS2 film on the TiO2 film substrate consists of nanoplates. The UV-vis absorption spectra reveal that the CuInS2 thin films have a strong absorption around 400-850 nm and the band-gap energy is tunable in the range of 1.45-1.61 eV with the variation of Cu/In ratio from 1.20 to 0.90. Furthermore, two types of thin film solar cells, which have an effective area of 0.25 cm2 and possess separately the top-down composition of Ag/CdS/CuInS2/FTO and FTO/TiO2/CuInS2/Au, were fabricated after heat-treatment to evaluate their photovoltaic properties and the corresponding conversion efficiency is 0.33% and 0.29% under AM 1.5 irrncy is 0.33% and 0.29% under AM 1.5 irradiation (100 mW cm-2), respectively.

283

Surface characterization of poly(methylmethacrylate) based nanocomposite thin films containing Al2O3 and TiO2 nanoparticles  

International Nuclear Information System (INIS)

Poly(methylmethacrylate) (PMMA) based nanocomposite electron beam resists have been demonstrated by spin coating techniques. When TiO2 and Al2O3 nanoparticles were directly dispersed into the PMMA polymer matrix, the resulting nanocomposites produced poor quality films with surface roughnesses of 322 and 402 nm respectively. To improve the surface of the resists, the oxide nanoparticles were encapsulated in toluene and methanol. Using the zeta potential parameter, it was found that the stabilities of the toluene/oxide nanoparticle suspensions were 7.7 mV and 19.4 mV respectively, meaning that the suspension was not stable. However, when the TiO2 and Al2O3 nanoparticles were encapsulated in methanol the zeta potential parameter was 31.9 mV and 39.2 mV respectively. Therefore, the nanoparticle suspension was stable. This method improved the surface roughness of PMMA based nanocomposite thin films by a factor of 6.6 and 6.4, when TiO2 and Al2O3 were suspended in methanol before being dispersed into the PMMA polymer.

284

Experimental evidence of a UV light-induced long-range electric field in nanostructured TiO2 thin films in contact with aqueous electrolytes.  

Science.gov (United States)

Nanostructured TiO(2) thin-film electrodes of controlled thickness were obtained by immobilization of TiO(2) powder (Degussa P25) on SnO(2):F (FTO)-coated glasses by electrophoresis. The photocurrent-potential characteristics of the electrodes in contact with an indifferent aqueous electrolyte, for both front--and backside UV illumination, show the existence of a macroscopic electric field in the electrode region near the FTO substrate. This electric field, which is only photoinduced in the presence of water (it does not appear in TiO(2) dye-sensitized solar cells under visible illumination), apparently disappears when an efficient hole scavenger, like methanol, is added to the aqueous electrolyte. It is attributed to a nonhomogeneous spatial accumulation of photogenerated holes at surface-bound OH radicals resulting from the photooxidation of chemisorbed water molecules. The influence of film thickness and UV illumination mode (front- and backside) on the photoinduced electric field is analyzed by solving the transport equations for diffusion and drift of electrons. PMID:16852255

Lana-Villarreal, T; Bisquert, J; Mora-Seró, I; Salvador, P

2005-05-26

285

TiO2 and Al2O3 ultra thin nanolaminates growth by ALD; instrument automation and films characterization  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in english We report on the development of a fully operational atomic layer deposition (ALD) system. This system is computer-controlled and can deposit multilayered systems without user intervention. We describe the design of manifold, reaction chamber and exhaust. Additionally we give some features of the aut [...] omatization software and electronics. To evaluate the ALD performance we used as precursor trymethyl aluminum (TMA) and tetrakis (dimethylamino) titanium (TDMAT) to deposit Al2O3 and TiO2, respectively, in nanolaminated film structures. The thicknesses and composition of the films are precisely controlled, as determined by spectroscopic ellipsometry, and the nanolaminates have a sharp interface as indicated by Auger depth profile.

H., Tiznado; D., Domínguez; W. de la, Cruz; R., Machorro; M., Curiel; G., Soto.

2012-12-01

286

Low-temperature atomic layer deposition of TiO2, Al2O3, and ZnO thin films  

International Nuclear Information System (INIS)

We studied low-temperature atomic layer deposition (LT-ALD) of TiO2, Al2O3, and ZnO thin films at temperatures down to room temperature, mainly focusing on the growth characteristics and the film's properties. Here, two kinds of ALD deposition systems were introduced. Initially, for the thermal ALD (T-ALD) process using a commercial ALD system, a very long purging time of up to ?300 s was required to entirely evacuate the remaining H2O vapors at room temperature due to the large volume and the complicated inner structure of the commercial ALD chamber. For the realization of LT-ALD with a short process time, a plasma-enhanced ALD (PE-ALD) process using O2 plasma was employed, which enabled us to effectively remove the residual reactants at temperatures down to room temperature. As another method, we specifically designed a homemade ALD system with a small volume and a simple inner structure, thereby being able to use T-ALD to synthesize TiO2, Al2O3, and ZnO thin films by using H2O with very short H2O purging times even at room temperature, which reveals that the chamber size and design are the critical factors enabling LT-ALD with a short process time. The LT-ALD processes produced highly-pure Al2O3, TiO2, and ZnO films without any C and N impurities by complete elimination of ligands and exhibited excellent conformality in 3-dimensional nanoscale via holes.

287

Real-time identification of the evolution of conducting nano-filaments in TiO2 thin film ReRAM.  

Science.gov (United States)

Unipolar resistance switching (RS) in TiO2 thin films originates from the repeated formation and rupture of the Magnéli phase conducting filaments through repeated nano-scale phase transitions. By applying the Johnson-Mehl-Avrami (JMA) type kinetic model to the careful analysis on the evolution of transient current in a pulse-switching, it was possible to elucidate the material specific evolution of the Magnéli phase filament. This methodology was applied to the two types of TiO2 films grown by plasma-enhanced atomic layer deposition (PEALD) and sputtering. These two samples have structurally and electrically distinctive properties: PEALD film exhibited high variability in switching parameters and required an electroforming while sputtered film showed higher uniformity without distinct electroforming process. The JMA-type kinetic analysis of the RS behaviors revealed that the rejuvenation of the filament is accomplished by repeated one-dimensional nucleation followed by a two-dimensional growth in PEALD samples, whereas one-dimensional nucleation-free mechanism dominates in sputtered films. PMID:24309421

Song, Seul Ji; Seok, Jun Yeong; Yoon, Jung Ho; Kim, Kyung Min; Kim, Gun Hwan; Lee, Min Hwan; Hwang, Cheol Seong

2013-01-01

288

Photocatalytic Antibacterial Performance of Glass Fibers Thin Film Coated with N-Doped SnO2/TiO2  

Science.gov (United States)

Both N-doped and undoped thin films of 3SnO2/TiO2 composite were prepared, by sol-gel and dip-coating methods, and then calcined at 600°C for 2 hours. The films were characterized by FTIR, XRD, UV-Vis, SEM, and XPS, and their photocatalytic activities to degrade methylene blue in solution were determined, expecting these activities to correlate with the inactivation of bacteria, which was confirmed. The doped and undoped films were tested for activities against Gram-negative Escherichia coli (E. coli) and Salmonella typhi (S. typhi), and Gram-positive Staphylococcus aureus (S. aureus). The effects of doping on these composite films included reduced energy band gap, high crystallinity of anatase phase, and small crystallite size as well as increased photocatalytic activity and water disinfection efficiency. PMID:24693250

Sikong, Lek; Niyomwas, Sutham; Rachpech, Vishnu

2014-01-01

289

Photocatalytic antibacterial performance of glass fibers thin film coated with N-doped SnO2/TiO2.  

Science.gov (United States)

Both N-doped and undoped thin films of 3SnO2/TiO2 composite were prepared, by sol-gel and dip-coating methods, and then calcined at 600 °C for 2 hours. The films were characterized by FTIR, XRD, UV-Vis, SEM, and XPS, and their photocatalytic activities to degrade methylene blue in solution were determined, expecting these activities to correlate with the inactivation of bacteria, which was confirmed. The doped and undoped films were tested for activities against Gram-negative Escherichia coli (E. coli) and Salmonella typhi (S. typhi), and Gram-positive Staphylococcus aureus (S. aureus). The effects of doping on these composite films included reduced energy band gap, high crystallinity of anatase phase, and small crystallite size as well as increased photocatalytic activity and water disinfection efficiency. PMID:24693250

Kongsong, Peerawas; Sikong, Lek; Niyomwas, Sutham; Rachpech, Vishnu

2014-01-01

290

Preparation and Electrical Properties of TiO2/SnO2 Nanocrystalline Films  

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Full Text Available The effect of SnO2 nanocrystalline coatings on the performance of dye-sensitized solar cells (DSSC based on TiO2-nanoparticle photoanode was studied. The TiO2-nanoparticle photoanode was prepared by screen-printing technique, and the SnO2 nanocrystalline films were coated on TiO2 nanoparticles by soaking TiO2 photoanodes in SnO2 solution with different concentrations or different time. SEM images indicate SnO2 nanocrystalline films have smaller surface grains than the TiO2 nanocrystalline films. The electrical properties of the films indicate that SnO2 thin films growing on the TiO2 films by soaking TiO2 films in 0.4 mol /L SnO2 solution for 50 min play a positive role on the structure and performance of the TiO2 films, and the conversion efficiency of the solar cell with TiO2/SnO2 photoanode is about 7% higher than that of TiO2 films.

CUI Xu-Mei, ZUO Cheng-Yang, LAN De-Jun, WANG Jun

2013-11-01

291

Annealing of TiO2 Films Deposited on Si by Irradiating Nitrogen Ion Beams  

International Nuclear Information System (INIS)

Thin TiO2 films were deposited on Si at a temperature of 600 deg. C by an ion beam assisted deposition (IBAD) method. The TiO2 films were annealed for 30 min in Ar at temperatures below 700 deg. C. The as-deposited TiO2 films had high permittivities such 200 ?o and consisted of crystallites that were not preferentially oriented to the c-axis but had an expanded c-axis. On the annealed TiO2 films, permittivities became lower with increasing annealing temperature, and crystallites were oriented preferentially to the (110) plane

292

Influence of reactive sputtering process parameters on the structure and properties of TiO2 thin films  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In der jüngsten Vergangenheit haben dünne Titandioxid-Schichten (TiO2) erhebliche Aufmerksamkeit auf sich gezogen: Sie wurden zu einem wichtigen Bereich in der Forschung seitdem die Möglichkeit der Wasseraufbereitung durch Photokatalyse an der TiO2-Oberfläche entdeckt wurde. TiO2 ist ein Oxid mit einer weiten Bandlücke, das sich durch hohe chemische Stabilität, mechanische Härte und optische Durchlässigkeit, wie auch durch einen hohen Brechungsindex auszeichnet. Deshalb wird es in ein...

El-hamshary, Azza Amin

2011-01-01

293

Characterization of sol-gel thin films of TiO2-PbO, TiO2-Bi2O3 and TiO2-CeO2 compositions  

Science.gov (United States)

Single and multilayer sol-gel thin films of Ti02-PbO, Ti02-Bi203 and Ti02-CeO2 composition were deposited on glasses using the dip coating technique. The precursors included Ti(OPri)4 chemically modified by acetyl acetone and diluted in PriOH and sols of Pb(OAc)2, Bi(NO3)3 5H20 diluted in acetic acid. The Ti02-Ce02 sol was prepared by mixing Ce NH2 (NO3 )6 in ethanol and then adding Ti (O-iso-C3H7 )4. Structure texture and homogeneity of their main constituants was established by XRD, XPS,SIMS and SEM-EDX techniques as a function of heat treatments.

Aegerter, Michel A.; La Serra, Eliane R.; Martins Rodrigues, Ana C.; Kordas, George; Moore, Glenn A.

1990-11-01

294

Research on TiO2-Based Photocatalyst Thin Film and Its Application in a Pilot-Scale Supply Water Treatment System  

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Full Text Available In order to utilize the abundant natural sunlight in Hochiminh City for energy-saving purpose, the application of TiO2-based photocatalyst thin film coated on ceramic beads in a pilot-scale supply water treatment system of 2 m3/day was studied in this present work. The photocatalyst thin film was prepared by sol-gel and spray coating methods. The derived photocatalyst thin film presented high BET specific surface area of more than 160 m2/g while it also maintained good crystallinity. These superior physicochemical properties of the photocatalyst were well consistent with its strong photoactivity in the pilot-scale supply water treatment system. Groundwater after passed through ferric removal and sandfilter systems was treated in the pilot-scale supply water treatment system using the photocatalyst thin film. The COD, TOC and coliform removal efficiencies were measured at 63%, 51% and 100%, respectively by using the above system under natural sunlight in Hochiminh City.

The-Vinh Nguyen

2009-01-01

295

TiO2/methylcellulose nanocomposite films for photocatalytic applications  

Science.gov (United States)

TiO2/methylcellulose (MeC) nanocomposite films were obtained by wet-chemical techniques using MeC and/or additives (acetylacetone, polyethylene glycol and Triton X-100). Thin films were obtained by spin-coating the colloidal suspensions on conductive indium tin oxide (ITO) glass, followed by a heat-treatment. The effect of MeC and additives on TiO2 nanoparticles dispersion was investigated by FTIR microscopy and X-ray diffraction (for structural and morphological properties), UV-VIS absorption spectroscopy and spectrofluorimetry (for optoelectronic properties) and wet technique adhesion test (for mechanical integrity). The composite film with methylcellulose and additives has good integrity and better adhesion to ITO substrate, without losing its photocatalytic activity. The results of these experiments showed that such nanocomposite films are interesting candidate for applications in the field of photocatalytic degradation of organic pollutants.

Rosu, M. C.; Suciu, R. C.; Dreve, S. V.; Silipas, T. D.; Bratu, I.; Indrea, E.

2012-02-01

296

DIRECT PHOTODEPOSITION OF NANOSTRUCTURED TIO2 THIN FILMS FROM B-DIKETONATE COMPLEXES, AND THEIR PHOTOCATALYTIC BEHAVIOUR  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english Amorphous Titania thin films have been photochemically obtained by direct UV irradiation (254 nm) of an amorphous TiO(C6H5COCHCOCH3) 2 film spin-coated on Si(100) and borosilicate glass. These materials were characterized by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD) an [...] d Auger electron spectroscopy (AES). SEM analysis showed a porous film with irregular morphology (diameter

M, TEJOS; G.E., BUONO-CUORE; F.R., DÍAZ; M.A., DEL VALLE; J, PALOMARES.

2004-12-01

297

Fabrication of TiO2 Colloidal Crystal Films and Characterization of Their Photocatalytic Properties  

Energy Technology Data Exchange (ETDEWEB)

We have studied hydrolysis of organic alkyltitanate compounds and optimized reaction condition for synthesis of monodisperse titania (TiO2 colloidal particles with controlled size from nanometer to submicron. The synthesized TiO2 colloidal particles were further surface-modified with hydrophobic silane coupling agent. With the monodisperse hydrophobic particles, we fabricated TiO2 colloidal crystal thin films through transferring self-assembled colloidal crystal monolayer from water surface onto solid substrates. The TiO2 colloidal crystal films exhibit enhanced interaction with visible light. Consequently, in comparison with plain TiO2 particle thin film, the thin film with colloidal crystal structure shows enhanced photocatalytic activity, as evaluated through photodegradation of organic dye methyl orange in solution under simulated solar light.

Huang, Wei [Zaozhuang University, People' s Republic of China; Wang, Feng [Zaozhuang University, People' s Republic of China; Wang, Wei [ORNL

2011-01-01

298

Optical and structural properties of nanocrystalline anatase (TiO2) thin films prepared by non-aqueous sol-gel dip-coating  

International Nuclear Information System (INIS)

Anatase (TiO2) thin films were grown by non-aqueous sol-gel dip-coating using titanium (IV) n-butoxide as precursor and 1-butanol as solvent. High withdrawal speed of 4.7 mm/s in dip-coating resulted in defect free films of 100 nm average film thickness after subsequent heat treatments. According to scanning electron microscope and X-ray diffraction measurements, the films consisted of nanocrystalline anatase with 30 nm mean crystallite size. Refractive index n(?) and extinction coefficient k(?) were determined over the wavelength range from 200 to 1650 nm. The optical band gap of the film material was approximately 3.2 eV. The results showed very similar optical characteristics to those that are accomplished with chemically more reactive aqueous sol-gel processes. Furthermore, it was found that in addition to porosity, coordination number of Ti atoms to nearest oxygen neighbors is likely to have a significant role in explaining differences of optical properties between bulk anatase and thin film materials of the present work.

299

Nanoassembled thin film gas sensors. III. Sensitive detection of amine odors using TiO2/poly(acrylic acid) ultrathin film quartz crystal microbalance sensors.  

Science.gov (United States)

Quartz crystal microbalance (QCM) gas sensors based on the alternate adsorption of TiO(2) and polyacrilic acid (PAA) were developed for the sensitive detection of amine odors. Individual TiO(2) gel layers could be regularly assembled with a thickness of approximately 0.3 nm by the gas-phase surface sol-gel process (GSSG). The thickness of the poly(acrylic acid) (PAA) layer is dependent on its molecular weight, showing different thicknesses of approximately 0.4 nm for PAA(25) (Mw 250,000) and 0.6-0.8 nm for PAA(400) (Mw 4,000,000). The QCM sensors showed a linear response to ammonia in the concentration range 0.3-15 ppm, depending on the deposition cycle of the alternate TiO(2)/PAA layer. The ammonia binding is based on the acid-base interaction to the free carboxylic acid groups of PAA and the limit of detection (LOD) of the 20-cycle TiO(2)/PAA(400) film was estimated to be 0.1 ppm when exposed to ammonia. The sensor response was very fast and stable in a wide relative humidity (rH) range of 30-70%, showing almost the same frequency changes at a given concentration of ammonia. Sensitivity to n-butylamine and ammonia was higher than to pyridine, which is owing to the difference of molecular weight and basicity of the amine analytes. The alternate TiO(2)/PAA(400) films have a highly effective ability to capture amine odors, and the ambient ammonia concentration of 15 ppm could be condensed up to approximately 20,000 ppm inside the films. PMID:20170084

Lee, Seung-Woo; Takahara, Naoki; Korposh, Sergiy; Yang, Do-Hyeon; Toko, Kiyoshi; Kunitake, Toyoki

2010-03-15

300

Carrier recombination-incited substrate vibrations after pulsed UV-laser photolysis of TiO2 thin single-crystal plate and nanoparticle films.  

Science.gov (United States)

Photo-induced carrier generation and recombination have been regarded as important steps in understanding the photocatalytic reactions on the surfaces of semiconductors such as TiO2. During the investigation of a photocatalytic water-splitting reaction on the surface of semiconductor TiO2 (rutile) single-crystal plate and sintered-nanoparticle (anatase) films coated on a CaF2 plate, a pulsed 355 nm laser was used for band-gap excitation and a continuous-working, mid-infrared laser as the probe to trace the kinetics of the photogenerated electrons. Fast oscillations with periods of 10-50 ?s were observed. We demonstrated experimentally that these oscillations are neither from the nonlinear carrier recombination dynamics nor surface chemical reactions; instead, they are caused by the thermal-induced flexural vibrations initiated by the fast carrier recombination in the light-absorbing area. The observed oscillations can be well accounted for by thermal stress-induced flexural vibrations of the substrates due to rapid charge recombination, and the observed oscillation frequencies match the flexural vibration frequencies predicted by the Kirchhoff-Love thin-plate theory. Light-interference effect caused by the beam reflecting off the surfaces of the substrate and windows, which can amplify the oscillation signals, is also discussed. Several approaches are proposed to minimize or eliminate the interference from the substrate vibration in the transient kinetic measurement when a coherent laser is used as the probe beam. PMID:23643039

Zhu, Ming; Zhu, Gangbei; Weng, Yuxiang

2013-05-01

 
 
 
 
301

Influence of TiO2 nanoparticles on the optical and structural properties of PPV thin films converted at low temperatures  

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Full Text Available In this work we studied the optical properties of poly(p-phenylene vinylene (PPV produced by the thermal conversion of a precursor polymer blended with a synthetic dye (Reactive Black 5. The production of PPV by this method decreases the overall time and cost of the process. We observed that the introduction of the dye resulted in an additional absorbance band near 550–700 nm, which can be beneficial to the photon harvesting capacity of the polymer if it is used as the donor material in a photovoltaic device. We studied how the optical and structures properties of this blend change when different quantities of TiO2 nanoparticles are introduced. For that, thin films were produced by the cast deposition of pre-PPV:dye:TiO2. The scanning electronic microscopic images showed that the inorganic semiconductor form large agglomerates of approximately 200 nm, indicating a very rough surface where the dye can be adsorbed. The analysis of photoluminescence and Raman peaks indicated a reduction of the mean conjugation length of the polymer chains in the presence of TiO2 nanoparticles.

B. Rostirolla

2013-08-01

302

Spectroscopic ellipsometry characterization of amorphous and crystalline TiO2 thin films grown by atomic layer deposition at different temperatures  

Science.gov (United States)

TiO2 thin films of widely different structural and morphological characteristics were grown on Si (1 0 0) substrates using Atomic Layer Deposition (ALD) by varying the substrate temperature (Ts) in a wide range (50 °C ? Ts ? 400 °C). Spectroscopic ellipsometry (SE) measurements were carried out to investigate the effect of growth temperature on the optical properties of the films. Measured SE data were analyzed by considering double layer optical model for the sample together with the single oscillator Tauc-Lorentz dispersion relation. Surface roughness was taken into consideration due to the columnar growths of grains in crystalline films. The refractive index was found to be increased from amorphous (Ts ? 150 °C) to the nanocrystalline films (2500 absorption edge were found to be strongly correlated with the single oscillator Wemple-DiDomenico (WD) model. The increase in dispersion energy parameter in WD model from disordered amorphous to the more ordered nanocrystalline films was found to be associated with the increase in the film density and coordination number.

Saha, D.; Ajimsha, R. S.; Rajiv, K.; Mukherjee, C.; Gupta, M.; Misra, P.; Kukreja, L. M.

2014-10-01

303

Effect of dehydration rate on non-hydrolytic TiO2 thin film processing: Structure, optical and photocatalytic performance studies  

International Nuclear Information System (INIS)

Highlights: ? Clear transparent TiO2 thin film prepared using non aqua sol-gel processing. ? The complexing agents plays significant role in the rate of dehydration due to hydrolysis. ? Faster dehydration significantly affects visible light transmittance and other properties. ? Diethanoalamine plays significant role in the crystallization and phase transformation. - Abstract: The influence of complexing agent diethanolamine (DEA) on the rate of dehydration due to hydrolysis in titania thin films prepared by non-aqua sol-gel process was investigated. The formation of complex with titanium precursor controls the rate of hydrolysis over wide range of temperature. The rate of hydrolysis with respect to complex formation and firing temperate was studied by using thermogravimetry and differential thermal analysis (TG-DTA). The role of complexing agent in the crystallization of anatase and phase transformation to rutile was studied by X-ray diffraction (XRD). Effect of complexing agent on the optical transmittance in the visible range was monitored by ultraviolet-visible absorption spectroscopy. Photocatalytic performance of the titania films was measured using methylene blue (MB) as the model contaminant. Mechanical characteristics such as hardness and adhesion of the film were rated by using scratch tests as per ASTM standards.

304

Low temperature deposition of TiO 2 thin films on polyvinyl alcohol fibers with photocatalytical and antibacterial activities  

Science.gov (United States)

Fine particles of photoactive anatase-type TiO 2 coated polyvinyl alcohol (PVA) fibers (TiO 2/PVA) were prepared successfully via a simple dip-coating method. Tetrabutyl orthotitanate (TBOT) was hydrolyzed in presence of hydrolysis control agent tetrabutylammonium hydroxide (TBA)OH and the TiO 2 fine particles were crystallized under microwave (MW) irradiation. The X-ray diffraction (XRD) and selected-area electron diffraction (SAED) analyses indicated that the fine particles obtained with MW irradiation have much higher crystallinity with a single phase anatase compared with the non-MW-treated solution. The continuous layers of titania were found on PVA fibers by the scanning electron microscopy (SEM) analysis. The fibers with anatase coatings showed high photocatalytic property on the photodegradation of methylene blue (MB) and high antibacterial activity.

Liuxue, Zhang; Xiulian, Wang; Peng, Liu; Zhixing, Su

2008-01-01

305

Low temperature deposition of TiO2 thin films on polyvinyl alcohol fibers with photocatalytical and antibacterial activities  

International Nuclear Information System (INIS)

Fine particles of photoactive anatase-type TiO2 coated polyvinyl alcohol (PVA) fibers (TiO2/PVA) were prepared successfully via a simple dip-coating method. Tetrabutyl orthotitanate (TBOT) was hydrolyzed in presence of hydrolysis control agent tetrabutylammonium hydroxide (TBA)OH and the TiO2 fine particles were crystallized under microwave (MW) irradiation. The X-ray diffraction (XRD) and selected-area electron diffraction (SAED) analyses indicated that the fine particles obtained with MW irradiation have much higher crystallinity with a single phase anatase compared with the non-MW-treated solution. The continuous layers of titania were found on PVA fibers by the scanning electron microscopy (SEM) analysis. The fibers with anatase coatings showed high photocatalytic property on the photodegradation of methylene blue (MB) and high antibacterial activity

306

Photocatalytic degradation of methylene blue using undoped and Ag-doped TiO2 thin films deposited by a sol-gel process: Effect of the ageing time of the starting solution and the film thickness  

International Nuclear Information System (INIS)

Undoped and Ag-doped TiO2 thin films were deposited on glass substrates by the sol-gel method. A novel propose to prepare the solution is the use of titanium monohydrate oxyacetyl acetonate as the starting reagent. The effect of the ageing time of the starting solution as well as the number of coatings on the photocatalytic degradation of methylene blue (MB) was studied. The variation of the absorption spectra shows the degradation of MB dissolved in water, as a result of the reaction produced on the surface of the films, and promoted by ultraviolet irradiation during 5 h. The results show an optimum photocatalytic activity, in the order of 35%, presented in the 5-immersion Ag-doped TiO2 thin films, deposited from 7- and 14-day aged solutions. On the other hand, the Ag-doped TiO2 films deposited at different coatings show small changes in the photocatalytic activity. Morphological studies show the presence of silver particles on the film surface, due to the different number of coatings, affecting the photocatalytic performance.

307

Enhancement of NMP Degradation Under UV Light by Nitrogen-Doped TiO2 Thin Films Using a Design of Experiment  

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Full Text Available Doping nitrogen within TiO2 is an effective way to enhance visible light photocatalysis due to a direct electron excitation from the N2p states within the band gap. However, nitrogen doping is not always efficient for UV photocatalytic activity. Here, different structures of N-doped TiO2 (TiOxNy have been prepared by reactive RF (13.56 MHz magnetron sputtering. The morphological, optical, structural, and photocatalytic properties of the films have been studied in order to investigate the competitive effect of the morphology and the chemical composition on the efficiency of the photocatalytic activity. The variation of surface wettability of the film over time in the dark and under visible and UV irradiation was also studied. The reduction in wettability by dark storage can be explained by the adsorption of hydrocarbon contamination on the thin film’s surface. Additionally, from water contact angle experiments, it was found that these films developed hydrophilic properties upon UV and visible illumination. The photoinduced change in the contact angle of water was due to the removal of hydrocarbon contamination on the surface and also the photo-oxidation of the water droplet. Samples prepared at high pressure gave the best photocatalytic activity, even though the deposition rate was lower at higher pressures (lower film thicknesses, due to the high specific surface area and the optimal presence of TiOxNy crystals in the lattice. However, at low pressure, the TiN crystals became more predominant, and acted as recombination centers for the photo-generated charge carriers. A design of experiments was used in order to optimize the deposition parameters to have the best photocatalytic activity. The high photocatalytic activity under UV light was found to be due to the introduction of discrete energy levels within the band gap, the increased sample wettability, and the higher specific surface area. However, the post annealing process did not effect the activity under UV irradiation. Using the response surface methodology, RSM, based on a design of experiment, DOE, we are able to achieve a good understanding of the complex processes involved in the deposition of the thin films and their effect on the photocatalytic activity.

F. Arefi-Khonsari

2011-01-01

308

Thermal formation of silicon-doped TiO2 thin films with enhanced visible light photoelectrochemical response  

Energy Technology Data Exchange (ETDEWEB)

Si-doped TiO{sub 2} thin films were fabricated by annealing titanium metal sheet embedded in SiO{sub 2} powders and characterized by X-ray photoemission spectroscopy (XPS) and photoelectrochemical measurements. The results showed that the content of silicon in the doped films was proportional to the annealing time and temperature. Enhanced visible light response, more negative flat band potential and higher carrier density were demonstrated by the electrochemical measurement. The technique proposed in this paper can be also applicable to fabricate other doped TiO{sub 2} based on the corresponding oxide bath.

Sun, Mingxun; Zhang, Xiao-Yan; Li, Jing; Cui, Xiao-Li; Lin, Yuehe

2012-03-01

309

Li-N doped and codoped TiO2 thin films deposited by dip-coating: Characterization and photocatalytic activity under halogen lamp  

Science.gov (United States)

Li-, N-doped and codoped TiO2 powders and thin films, deposited on glass substrate using dip-coating method and Ti(OBu)4 as precursor, were prepared and their structural properties were investigated using grazing angle X-ray diffraction (GXRD), Raman spectroscopy, time resolved luminescence, X-ray photoelectron spectroscopy (XPS), ground state diffuse reflectance absorption and scanning electron microscopy (SEM). Unlike the powder samples, thin films with the same composition and calcination temperature exhibited lower crystallinity degree along with the prevalence of the anatase phase. Ground state diffuse reflectance absorption studies carried on the nanopowders have shown that both the Li and N dopants led to an increase of the band gap. XPS studies revealed differences in the binding energy of N in the presence and in the absence of Li, which was explained in terms of a modification in the chemical environment of N when Li is introduced. The photocatalytic activity of the ensuing film toward the degradation of aromatic amine pollutant revealed a huge enhancement upon doping with N or codoping with N and Li. This behavior is probably provide by a charge-transfer-complex mechanism in which neither the photocatalyst nor the organic compounds absorbs visible light by itself. The improvement in the photocatalytic properties occurred simultaneously with the increase of the lifetime of the charge carriers whenever N and Li were introduced at a level 2%.

Hamden, Z.; Boufi, S.; Conceição, D. S.; Ferraria, A. M.; do Rego, A. M. Botelho; Ferreira, D. P.; Ferreira, L. F. Vieira; Bouattour, S.

2014-09-01

310

Controlling the orientation of ZnO nanorod arrays using TiO2 thin film templates dip-coated by sol-gel  

International Nuclear Information System (INIS)

The oriented ZnO nanorod arrays have been synthesized on a silicon wafer that coated with TiO2 films by aqueous chemical method. The morphologies, phase structure and the photoluminescence (PL) properties of the as-obtained product were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffractometer (XRD), transmission electron microscope (TEM) and PL spectrum. The nanorods were about 100 nm in diameter and more than 1 ?m in length, which possessed wurtzite structure with a c axis growth direction. The room-temperature PL measurement of the nanorod arrays showed strong ultraviolet emission. The effect of the crystal structure and the thickness of TiO2 films on the morphologies of ZnO nanostructures were investigated. It was found that the rutile TiO2 films were appropriate to the oriented growth of ZnO nanorod arrays in comparison with anatase TiO2 films. Moreover, flakelike ZnO nanostructures were obtained with increasing the thickness of anatase TiO2 films

311

Structural and electrochromic properties of TiO2 thin films prepared by metallorganic chemical vapor deposition  

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Titanium dioxide thin films were deposited by Metallorganic Chemical Vapor Deposition at substrate temperatures ranging from 250 oC to 450 oC over soda lime glass and indium tin oxide coated glass substrates. X-ray diffraction studies show that films have a crystalline anatase structure at all the deposition temperatures. Particle size decreases and texture changes with the increase in substrate temperature. X-ray photoelectron spectroscopy confirms the appearance of a new well resolved state in the core level of Ti 2p spectrum shifted by 1.16 eV to lower binding energy due to the reduction of Ti+4 to Ti+3 upon litheation. Chronoamperometery, cyclic voltammetery and in situ UV-Vis spectrophotometeric studies were carried out on the prepared samples. Particle size and crystallinity control the electrochromic performance. The 350 oC film shows the highest ion storage capacity and the highest optical modulation along with an appreciable band gap broadening.

312

Epitaxial growth of TiO2 thin films on SrTiO3, LaAlO3 and yttria-stabilized zirconia substrates by electron beam evaporation  

International Nuclear Information System (INIS)

Epitaxial anatase, rutile and mixed (brookite and anatase) TiO2 thin films have been obtained by reactive electron beam evaporation. Anatase TiO2 thin films have been prepared on LaAlO3 (LAO) and SrTiO3 (STO) substrates of (100) and (110) orientation. The epitaxial relationship between anatase films (A) and (110) LAO/STO substrates is (012) A vertical bar vertical bar (110) LAO/STO, [100] A vertical bar vertical bar [001] LAO/STO. The anatase films were transformed into a cubic structure similar to TiO when in situ exposed to an electron beam. On the other hand, TiO2 thin films with a mixture of epitaxial anatase and brookite grains have been grown on (100)-oriented yttria-stabilized zirconia (YSZ) at a substrate temperature of 600 deg. C while the pure rutile phase has been obtained at a substrate temperature of 900 deg. C on (100) YSZ. The crystalline structure and surface morphology of the thin films were investigated by X-ray diffraction, transmission electron microscopy and atomic force microscopy. The crystallographic reason for the epitaxy between anatase films and perovskite substrates is discussed

313

Methylene blue photoelectrodegradation under UV irradiation on Au/Pd-modified TiO2 films  

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In this work TiO2 thin films were modified with gold/palladium (Au/Pd) bimetallic paticles by sputtering method. TiO2 films were deposited on ITO (SnO2:In) by Doctor Blade method and post-anneling. The properties of the films were studied through measurements of XRD (X-ray diffraction) and AFM (atomic force microscopy). The degradation of methylene blue was studied by UV-irradiated pure TiO2 and Au/Pd-modified TiO2 in aqueous solution. Langmuir-Hinshelwood model was used to obtain kinetic information. Photocatalytic study indicated that Au/Pd-modified TiO2 photocatalytic activity was better than TiO2 pure; the best half-life time for Au/Pd-modified TiO2 in photodegradation was 2.8 times smaller than TiO2 pure; finally the efficiency in methylene blue photodegradation was improved from 23% to 43% when Au/Pd-modified TiO2 films were used.

314

Synthesis and growth mechanism of thin-film TiO2 nanotube arrays on focused-ion-beam micropatterned 3D isolated regions of titanium on silicon.  

Science.gov (United States)

In this paper, the fabrication and growth mechanism of net-shaped micropatterned self-organized thin-film TiO2 nanotube (TFTN) arrays on a silicon substrate are reported. Electrochemical anodization is used to grow the nanotubes from thin-film titanium sputtered on a silicon substrate with an average diameter of ~30 nm and a length of ~1.5 ?m using aqueous and organic-based types of electrolytes. The fabrication and growth mechanism of TFTN arrays from micropatterned three-dimensional isolated islands of sputtered titanium on a silicon substrate is demonstrated for the first time using focused-ion-beam (FIB) technique. This work demonstrates the use of the FIB technique as a simple, high-resolution, and maskless method for high-aspect-ratio etching for the creation of isolated islands and shows great promise toward the use of the proposed approach for the development of metal oxide nanostructured devices and their integration with micro- and nanosystems within silicon-based integrated-circuit devices. PMID:23957211

Hamedani, Hoda Amani; Lee, Simon W; Al-Sammarraie, Abdulkareem; Hesabi, Zohreh R; Bhatti, Asim; Alamgir, Faisal M; Garmestani, Hamid; Khaleel, Mohammad A

2013-09-25

315

Investigation of the antibacterial effects of silver-modified TiO2 and ZnO plasmonic photocatalysts embedded in polymer thin films.  

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Nanosilver-modified TiO2 and ZnO photocatalysts were studied against methicillin-resistant Staphylococcus aureus on the surface and against naturally occurring airborne microorganisms. The photocatalysts/polymer nanohybrid films were prepared by spray coating technique on the surface of glass plates and on the inner surface of the reactive light source. The photoreactive surfaces were activated with visible light emitting LED light at ??=?405 nm. The optical properties of the prepared photocatalyst/polymer nanohybrid films were characterized by diffuse reflectance measurements. The photocatalytic properties were verified with the degradation of ethanol by gas chromatography measurements. The destruction of the bacterial cell wall component was examined with transmission electron microscope. The antibacterial effect of the photocatalyst/polymer nanohybrid films was tested with different methods and with the associated standard ISO 27447:2009. With the photoreactive coatings, an extensive disinfectant film was developed and successfully prepared. The cell wall component of S. aureus was degraded after 1 h of illumination. The antibacterial effect of the nanohybrid films has been proven by measuring the decrease of the number of methicillin-resistant S. aureus on the surface and in the air as the function of illumination time. The photocatalyst/polymer nanohybrid films could inactivate 99.9 % of the investigated bacteria on different thin films after 2 h of illumination with visible light source. The reactive light source with the inner-coated photocatalyst could kill 96 % of naturally occurring airborne microorganisms after 48 h of visible light illumination in indoor air sample. The TEM results and the microbiological measurements were completed with toxicity tests carried out with Vibrio fischeri bioluminescence bacterium. PMID:24497305

Tallósy, Szabolcs Péter; Janovák, László; Ménesi, Judit; Nagy, Elisabeth; Juhász, Adám; Balázs, László; Deme, István; Buzás, Norbert; Dékány, Imre

2014-10-01

316

Ultrathin-layer chromatography on SiO(2), Al(2)O(3), TiO(2), and ZrO(2) nanostructured thin films.  

Science.gov (United States)

We explored four different inorganic oxides and determined their merits in miniaturized planar chromatography. Despite progression of chromatographic techniques over several decades, such alternatives to traditional planar silica gel stationary phases have not been fully evaluated. Glancing angle deposition(GLAD) provided an excellent platform for engineering nanostructured thin films in these materials for ultrathin-layer chromatography (UTLC). Separations of carotenoids and synthetic food dyes were used to investigate the attributes of SiO(2), Al(2)O(3), TiO(2), and ZrO(2)GLAD UTLC media. These anisotropic high surface area thin films possessed similar channel-like features but different chromatographic properties.TiO(2)and ZrO(2)media were especially interesting since analyte retention could be modified through sim-ple oxidation heat treatments and UV irradiation. Generally, oxidation reduced analyte retention while UV exposure increased retention. Changes in retention factor as large as ?hRF? 40 (for Acid Red 14 on titanium oxide) were achieved. Food dye mixtures were applied using consumer inkjet printers as per the Office Chromatography concept and separation performance was quantified using advanced video instrumentation designed for miniaturized plates. Enhanced time-resolved UTLC methods were used to calculate figures of merit from recorded dye separation videos. Small theoretical plate heights (inorganic oxide thin films were also successfully hyphenated with electrospray ionization mass spectrometry for the first time. This investigation demonstrates the utility of alternative inorganic oxide GLADUTLC media and probes avenues of expanding the capabilities of miniaturized planar chromatography. PMID:24354005

Wannenmacher, Julia; Jim, Steven R; Taschuk, Michael T; Brett, Michael J; Morlock, Gertrud E

2013-11-29

317

TiO2/Au/TiO2 multilayer thin films: Novel metal-based transparent conductors for electrochromic devices  

International Nuclear Information System (INIS)

Transparent conductors based on Au films, with thicknesses in the 2.6 8 nm, as seen from electron microscopy, electrical resistance, and spectrophotometric transmittance and reflectance. Optical data for uniform films were given a consistent interpretation within the Drude model. Optimized TiO2/Au/TiO2 films, with a luminous transmittance of 80%, were found to have good electrochemical durability and may be useful for applications in electrochromic devices.

318

Structural, magnetic and optical properties of Ni-doped TiO2 thin films deposited on silicon(1 0 0) substrates by sol–gel process  

International Nuclear Information System (INIS)

Highlights: •Ni doping decreases the activation energy for the anatase-to-rutile transformation. •With increasing Ni content, the reversible ferromagnetism is found. •Sharp decrease of the EOBG at low Ni content is mainly related to phase composition. -- Abstract: Ni-doped TiO2 films were deposited on Si(1 0 0) substrates by sol–gel technique. X-ray photoelectron spectroscopy analysis suggests that the valence of Ni ion is in +2 and oxygen vacancies increase with increasing Ni content. X-ray diffraction measurements indicate that Ni doping catalyzes the anatase-to-rutile transformation (ART) of TiO2 films, which is due to the decrease of the ART activation energy. The reversible ferromagnetism of the samples with Ni fraction is found, which is due to an anatase-to-rutile junction destroying an F-center bound magnetic polaron. Optical properties of Ni-doped TiO2 films were studied by the ellipsometric spectra. With increasing Ni content, the optical band gap of TiO2 films is decreased from 3.56 to 3.34 eV, which may be related to phase composition and impurity band

319

Structure of epitaxial (Fe,N) codoped rutile TiO2 thin films by x-ray absorption  

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Homoepitaxial thin films of Fe:TiO2 and (Fe,N):TiO2 were deposited on rutile(110) by molecular beam epitaxy. X-ray absorption near edge spectroscopy (XANES) spectra were collected at the Ti L-edge, Fe L-edge, O K-edge, N K-edge, and Ti K-edge. No evidence of structural disorder associated with a high concentration of oxygen vacancies is observed. Substitution of Fe for Ti could not be confirmed, although secondary phase Fe2O3 and metallic Fe can be ruled out. The similarity of the N K-edge spectra to O, and the presence of a strong x-ray linear dichroism (XLD) signal for the N K-edge, indicates that N is substitutional for O in the rutile lattice, and is not present as a secondary phase such as TiN. Simulations of the XANES spectra qualitatively confirm substitution, although N appears to be present in more than one local environment. Neither Fe:TiO2 nor (Fe,N):TiO2 exhibit intrinsic room temperature ferromagnetism, despite the presence of mixed valence Fe(II)/Fe(III) in the reduced (Fe,N):TiO2 film.

Kaspar, Tiffany C.; Ney, A.; Mangham, Andrew N.; Heald, Steve M.; Joly, Yves; Ney, V.; Wilhelm, F.; Rogalev, A.; Yakou, Flora; Chambers, Scott A.

2012-07-23

320

Poly(vinyl chloride)-g-poly(2-(dimethylamino)ethyl methacrylate) graft copolymers templated synthesis of mesoporous TiO2 thin films for dye-sensitized solar cells  

International Nuclear Information System (INIS)

A poly(vinyl chloride) (PVC) main chain was grafted with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) containing a quaternary amine group using atom transfer radical polymerization. The successful synthesis of a PVC-g-PDMAEMA graft copolymer was confirmed by Fourier transform infrared, nuclear magnetic resonance, thermogravimetric analysis, and transmission electron microscopy. The PVC-g-PDMAEMA graft copolymer was used as a structure-directing agent (SDA) for the fabrication of a mesoporous thin film containing a titanium dioxide (TiO2) layer. To control the porosity of the resultant inorganic layer, the ratio of SDA to TTIP as well as the concentration of the sol–gel was varied. The structure and porosity of the mesoporous film were characterized by XRD and SEM analysis. The mesoporous TiO2 film fabricated on the FTO surface was used as a photoanode for the dye-sensitized solar cell (DSSC). DSSC performance was the greatest when using TiO2 film with a higher porosity and lower interfacial resistance. The highest energy conversion efficiency reached 3.2 % at 100 mW/cm2, which was one of the highest reported values for a quasi-solid-state DSSC with 600-nm-thick TiO2 film.

 
 
 
 
321

Ultrafast dynamics of the indoline dye D149 on electrodeposited ZnO and sintered ZrO2 and TiO2 thin films.  

Science.gov (United States)

The ultrafast photoinjection and subsequent relaxation steps of the indoline dye D149 were investigated in detail for a mesoporous electrodeposited ZnO thin film and compared with experiments on sintered TiO(2) and ZrO(2) thin films, all in contact with air, using pump-supercontinuum probe (PSCP) transient absorption spectroscopy in the range 370-770 nm. D149 efficiently injects electrons into the ZnO surface with time constants from ?70 fs (time-resolution-limited) up to 250 fs, without the presence of slower components. Subsequent spectral dynamics with a time constant of 20 ps and no accompanying change in the oscillator strength are assigned to a transient Stark shift of the electronic absorption spectrum of D149 molecules in the electronic ground state due to the local electric field exerted by the D149?(+) radical cations and conduction band electrons in ZnO. This interpretation is consistent with the shape of the relaxed PSCP spectrum at long times, which resembles the first derivative of the inverted steady-state absorption spectrum of D149. In addition, steady-state difference absorption spectra of D149?(+) in solution from spectroelectrochemistry display a bleach band with distinctly different position, because no first-order Stark effect is present in that case. Interference features in the PSCP spectra probably arise from a change of the refractive index of ZnO caused by the injected electrons. The 20 ps component in the PSCP spectra is likely a manifestation of the transition from an initially formed bound D149?(+)-electron complex to isolated D149?(+) and mobile electrons in the ZnO conduction band (which changes the external electric field experienced by D149) and possibly also reorientational motion of D149 molecules in response to the electric field. We identify additional spectral dynamics on a similar timescale, arising from vibrational relaxation of D149?(+) by interactions with ZnO. TiO(2) exhibits similar dynamics to ZnO. In the case of ZrO(2), electron injection accesses trap states, which exhibit a substantial probability for charge recombination. No Stark shift is observed in this case. In addition, the spectroelectrochemical experiments for D149?(+) in dichloromethane and acetonitrile, which cover the spectral range up to 2000 nm, provide for the first time access to its complete D(0)? D(1) absorption band, with the peak located at 1250 and 1055 nm, respectively. Good agreement is obtained with results from DFT/TDDFT calculations of the D149?(+) spectrum employing the MPW1K functional. PMID:23070060

Oum, Kawon; Lohse, Peter W; Flender, Oliver; Klein, Johannes R; Scholz, Mirko; Lenzer, Thomas; Du, Juan; Oekermann, Torsten

2012-11-28

322

Formation of efficient dye-sensitized solar cells by introducing an interfacial layer of long-range ordered mesoporous TiO2 thin film.  

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Long-range ordered cubic mesoporous TiO 2 films with 300 nm thickness were fabricated on fluorine-doped tin oxide (FTO) substrate by evaporation-induced self-assembly (EISA) process using F127 as a structure-directing agent. The prepared mesoporous TiO 2 film (Meso-TiO 2) was applied as an interfacial layer between the nanocrystalline TiO 2 film (NC-TiO 2) and the FTO electrode in the dye-sensitized solar cell (DSSC). The introduction of Meso-TiO 2 increased J sc from 12.3 to 14.5 mA/cm (2), and V oc by 55 mV, whereas there was no appreciable change in the fill factor (FF). As a result, the photovoltaic conversion efficiency ( eta) was improved by 30.0% from 5.77% to 7.48%. Notably, introduction of Meso-TiO 2 increased the transmittance of visible light through the FTO glass by 23% as a result of its excellent antireflective role. Thus the increased transmittance was a key factor in enhancing the photovoltaic conversion efficiency. In addition, the presence of interfacial Meso-TiO 2 provided excellent adhesion between the FTO and main TiO 2 layer, and suppressed the back-transport reaction by blocking direct contact between the electrolyte and FTO electrode. PMID:18922027

Kim, Yong Joo; Lee, Yoon Hee; Lee, Mi Hyeon; Kim, Hark Jin; Pan, Jia Hong; Lim, Goo Il; Choi, Young S; Kim, Kyungkon; Park, Nam-Gyu; Lee, Chongmu; Lee, Wan In

2008-11-18

323

Using the voids. Evidence for an antenna effect in dye-sensitized mesoporous TiO2 thin films.  

Science.gov (United States)

Composite structures of Ru(bpy)(2)(4,4'-(PO(3)H(2))(2)bpy)(2+) surface bound to nanocrystalline TiO(2) with an overlayer of Ru(bpy)(3)(2+) ion exchanged into Nafion, FTO|nanoTiO(2)-[Ru(bpy)(2)(4,4'-(PO(3)H(2))(2)bpy)](2+)/Nafion,Ru(bpy)(3)(2+) (FTO = fluorine-doped tin oxide), have been prepared and characterized. Steady-state emission and time-resolved lifetime measurements demonstrate that energy transfer occurs from Nafion,Ru(bpy)(3)(2+*) to adsorbed Ru(bpy)(2)(4,4'-(PO(3)H(2))(2)bpy)(2+) with an efficiency of ?0.49. Energy transfer sensitizes photoinjection by the adsorbed metal-to-ligand charge transfer (MLCT) excited state by an "antenna effect." PMID:20712329

Hoertz, Paul G; Goldstein, Anna; Donley, Carrie; Meyer, Thomas J

2010-11-18

324

Effect of oxygen partial pressure on the structural and electrical properties of DC sputtered (Ta2O5)0.85(TiO2)0.15 thin films on Si  

Science.gov (United States)

Thin films of (Ta2O5)0.85(TiO2)0.15) were deposited on p-Si (100) by DC reactive magnetron sputtering at various oxygen partial pressures in the range 3×10-2 - 9×10-2 Pa and annealed in air for 1 hour at 700°C. The structural properties of the (Ta2O5)0.85(TiO2)0.15 films were studied and the electrical properties of Al/ (Ta2O5)0.85(TiO2)0.15 gate stacks formed on p-Si substrates were systematically investigated. The leakage current density of the films deposited at 3×10-2 Pa was 6.97×10-6 A/cm2 (at a gate bias voltage of 1.5 V) and it was decreased to 1.75×10-8 A/cm2 with the increase of oxygen partial pressure to 9×10-2 Pa. The current conduction mechanism of the (Ta2O5)0.85(TiO2)0.15 films was analyzed and compared with mechanisms of Poole-Frenkel and Schottky emissions.

Uthanna, S.; Sekhar, M. Chandra

2012-06-01

325

Preparation of regularly structured nanotubular TiO2 thin films on ITO and their modification with thin ALD-grown layers  

International Nuclear Information System (INIS)

Nanotubular titanium dioxide thin films were prepared by anodization of titanium metal films evaporated on indium tin oxide (ITO) coated glass. A facile method to enhance the adhesion of the titanium film to the ITO glass was developed. An optimum thickness of 550 nm for the evaporated titanium was found to keep the film adhered to ITO during the anodization. The films were further modified by growing amorphous titania, alumina and tantala thin films conformally in the nanotubes by atomic layer deposition (ALD). The optical, electrical and physical properties of the different structures were compared. It was shown that even 5 nm thin layers can modify the properties of the nanotubular titanium dioxide films. (paper)

326

Investigation of a broadband TiO2/SiO2 optical thin-film filter for hybrid solar power systems  

International Nuclear Information System (INIS)

Highlights: ? We present a new optical filter to get optimal performance of PV power system. ? The experimental results of the filter fabrication match well with numerical design. ? The measured results of a typical Si cell show efficiency increase using the filter. ? A proposed model for hybrid PV–TEG system demonstrates the benefits of the filter. -- Abstract: Using the technology of spectral selectivity to integrate different solar power generators in a hybrid system is a feasible way to improve the optical-electric efficiency. This paper presents an 82-layer broadband optical interference thin-film filter matching with crystalline silicon photovoltaic cells, which using TiO2 and SiO2 as fabrication materials and can be used in hybrid solar power systems like photovoltaic–thermoelectric generator (PV–TEG) systems. The design, optimization and fabrication process of the filter is described, high reflectance from 400 nm to 1100 nm as well as high transmittance from 1100 nm to 2500 nm over the broadband of solar spectrum are obtained. The classical electron beam evaporation plant is used to fabricate the filter. Four different incidence angles’ optical performances of the sample filter are measured which agree well with the numerical simulation results. The electrical characteristics of a typical Silicon photovoltaic cell using the fabricated sample filter are measured. An average efficiency increase of 3.24% for the solar cell with respect to the solar energy it receives can be obtained due to the filter. A calculation model for a hybrid PV–TEG system using this thin-film filter is proposed and the benefits of the filter for hybrid solar power systems are demonstrated.

327

Morphology control of cathodically deposited TiO2 films  

International Nuclear Information System (INIS)

This work demonstrates that the microstructure of TiO2 film can be designed and controlled by adjusting the temperature and cycle number of cathodic deposition in a solution containing TiCl3 and NaNO3. The redox interactions between TiCl3 and NO3- are investigated by in situ ultraviolet-visible (UV-vis) absorption spectroscopy. Linear sweep voltammetry (LSV) is employed to study the NO3- reduction and to clarify the deposition behavior of TiO2 in the designed plating solution. The decrease in TiO2 deposition rate with the TiO2 thickness may be due to the poor electron conductivity of TiO2 depressing the generation rate of OH- from the NO3- reduction. The morphology and size of TiO2 aggregates are strongly influenced by varying the deposition temperature from 5 to 50 oC and a maximal rate of TiO2 deposition is obtained at 25-35 oC. TiO2 deposited at 25 oC is the roughest with a roughness factor (Ra) of ca. 67 nm. This study provides a useful method to control the morphology and deposition rate of TiO2 film for practical photoelectrochemical applications.

328

Superhydrophilic and Wetting Behavior of TiO2 Films and their Surface Morphologies  

International Nuclear Information System (INIS)

TiO2 films, showing superhydrophilic behavior, are prepared by electron beam evaporation. Atomic force microscopy and the contact angle measurement were performed to characterize the morphology and wetting behavior of the TiO2 films. Most studies attribute the wetting behavior of TiO2 surfaces to their physical characteristics rather than surface chemistry. These physical characteristics include surface morphology, roughness, and agglomerate size. We arrange these parameters in order of effectiveness. Surface morphologies are demonstrated to be the most important. TiO2 films with particular morphologies show superhydrophilic behavior without external stimuli, and these thin films also show stable anti-contamination properties during cyclical wetting and drying. (cross-disciplinary physics and related areas of science and technology)

329

Substrate and Fe-doping effects on the hydrophilic properties of TiO2 thin films  

International Nuclear Information System (INIS)

Titanium dioxide films are known for their hydrophilic and photocatalytic characteristics. Increasing specific surface area and doping can enhance their photocatalytic activity and hydrophilicity. We report here results regarding the enhancement of the photocatalytic properties of titania by both controlling surface morphology and the anatase/rutile ratio. The samples were deposited on glass, indium tin oxide covered glass, and SrTiO3 by sputtering and laser ablation techniques. Film structure and surface morphology were investigated by X-ray diffraction and atomic force microscopy. Film hydrophilicity was assessed from contact angle measurements during- and post-irradiation with UV light. The contact angle data are discussed in terms of the synergic effects of surface morphology, structure and composition of the films

330

Deposition of a thin film of TiOx from a titanium metal target as novel blocking layers at conducting glass/TiO2 interfaces in ionic liquid mesoscopic TiO2 dye-sensitized solar cells.  

Science.gov (United States)

In dye-sensitized TiO2 solar cells, charge recombination processes at interfaces between fluorine-doped tin oxide (FTO), TiO2, dye, and electrolyte play an important role in limiting the photon-to-electron conversion efficiency. From this point of view, a high work function material such as titanium deposited by sputtering on FTO has been investigated as an effective blocking layer for preventing electron leakage from FTO without influencing electron injection. X-ray photoelectron spectroscopy analysis indicates that different species of Ti (Ti4+, Ti3+, Ti2+, and a small amount of Ti0) exist on FTO. Electrochemical and photoelectrochemical measurements reveal that thin films of titanium species, expressed as TiOx, work as a compact blocking layer between FTO and TiO2 nanocrystaline film, improving Voc and the fill factor, finally giving a better conversion efficiency for dye-sensitized TiO2 solar cells with ionic liquid electrolytes. PMID:17165966

Xia, Jiangbin; Masaki, Naruhiko; Jiang, Kejian; Yanagida, Shozo

2006-12-21

331

A corrosion-resistance superhydrophobic TiO2 film  

Science.gov (United States)

A superhydrophobic TiO2 film with water contact angle greater than 170° on Hastelloy substrate was fabricated through simply dip-coating method from TiO2 precursor solution containing TiO2 nanoparticles with the average diameter 25 nm, followed by heat-treatment and modification with fluoroalkylsilane (FAS) molecules. The as-obtained sample was characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and water contact angle measurement respectively. Moreover, the dynamic light scattering (DLS) size distribution of TiO2 aggregated particles in the TiO2 precursor solution containing P25 particles was evaluated by Laser Particle Sizer. It is found that the TiO2 nanoparticles in TiO2 precursor solution play a crucial role to form high superhydrophobicity. Simultaneously, the superhydrophobic TiO2 film still showed great superhydrophobicity after corroded with strong acid or alkali solutions and protected the substrate from corrosion which should be critical to the potential application in industry.

Hu, Yawei; Huang, Siya; Liu, Shan; Pan, Wei

2012-07-01

332

Nanocrystalline SnO2-TiO2 thin film deposited on base of equilateral prism as an opto-electronic humidity sensor  

Science.gov (United States)

Present paper reports the synthesis of SnO2-TiO2 nanocomposite, its characterization and performance as opto-electronic humidity sensor. Nanocrystalline SnO2-TiO2 film was deposited on the base of an equilateral prism using a photo resist spinner and the as prepared film was annealed at 200 °C for 2 h. The crystal structure of the prepared film was investigated using X-ray diffraction (XRD). Minimum crystallite size of the material was found 7 nm. Surface morphology of the film was investigated by Scanning electron microscope (SEM LEO-0430, Cambridge). SEM image shows that the film is porous. Differential scanning calorimetry (DSC) of as synthesized material shows two exothermic peaks at about 40 and 110 °C, respectively which are due to the evaporation of chemical impurities and water. Further the prepared film was investigated through the exposure of humidity and relative humidity (%RH) was measured directly in terms of modulation in the intensity of light recorded on a digital power meter. The maximum sensitivity of sensor was found 4.14 ?W/%RH, which is quite significant for sensor fabrication purposes.

Yadav, B. C.; Verma, Nidhi; Singh, Satyendra

2012-09-01

333

Photocatalysis and characterization of the gel-derived TiO2 and P-TiO2 transparent thin films  

International Nuclear Information System (INIS)

The gel-derived TiO2 and P-TiO2 transparent films coated on fused-SiO2 substrates were prepared using a spin-coating technique. Effects of phosphorus dopants and calcination temperature on crystal structure, crystallite size, microstructure, light transmittance and photocatalytic activity of the films were investigated. By introducing P atoms to Ti-O framework, the growth of anatase crystallites was hindered and the crystal structure of anatase-TiO2 could withstand temperature up to 900 deg. C. The photocatalytic activities of the prepared films were characterized using the characteristic time constant (?) for the photocatalytic reaction. The titania film with a smaller ? value possesses a higher photocatalytic ability. After exposing to 365-nm UV light for 12 h, the P-TiO2 films calcined between 600 deg. C and 900 deg. C can photocatalytically decomposed ? 84 mol% of the methylene blue in water with corresponding ? ? 7.1 h, which were better than the pure TiO2 films prepared at the same calcination temperature.

334

Processing and characterization of TiO2 film prepared on glass via pulsed laser deposition  

International Nuclear Information System (INIS)

Nanocrystalline titanium dioxide films with anatase structures were prepared on glass by pulsed laser deposition. Our results demonstrated that deposition temperature and oxygen pressure were important parameters in optimization of the microstructure and conductivity of TiO2 anatase film. The conductivity of the TiO2 film increased as the substrate temperature increased. It did not, however, increase further even though the depositions were performed above 600 deg. C. It was also confirmed that the conductivity showed a unique dependence on ambient oxygen pressure, which demonstrated the significant influence of oxygen pressure on the carrier concentration in thin oxide films

335

TiN and TiO2:Nb thin film preparation using hollow cathode sputtering with application to solar cells  

International Nuclear Information System (INIS)

Titanium nitride (TiN) is well known for its excellent conductivity, inertness, and good optical reflectivity at long wavelengths. These properties make it a potential IR-reflective back contact material suitable for ultrathin Cu(In,Ga)Se2 (CIGS) solar cells. Using a pulsed power, 12 cm linear hollow cathode source fitted with Ti targets and with N2 as the reactive gas, TiN films were deposited on Mo-coated glass. The static deposition rate was 50 nm/min for a sputtering power of only 500 W. The high deposition rate indicates the advantage of the reactive environment, hollow cathode sputtering method, i.e., the reactive gas is excluded from the target. Electrical, optical, and physical properties of the films were measured. Resistivities in the range of 50-60 ?? cm were achieved. Reflectance and x-ray diffraction measurements were conducted, and the effects of deposition parameters such as substrate bias and substrate temperature were studied. The optical emission from N and Ti atoms in the plasma was also studied. CIGS solar cells were successfully fabricated on TiN and a conversion efficiency of 12.3% was achieved. Transparent and moderately conductive TiO2 films doped with Nb were also prepared. The electrical and optical properties of these films are reported, and the reflectance of a-Si solar cells was reduced via incorporation of a TiO2:Nb layer

336

The fabrication of nanocomposite thin films with TiO2 nanoparticles by the layer-by-layer deposition method for multifunctional cotton fabrics  

Science.gov (United States)

A multilayer nanocomposite film composed of anatase TiO2 nanoparticles was fabricated on cationically modified woven cotton fabrics by the layer-by-layer molecular self-assembly technique. For cationic surface charge, cotton fabrics were pre-treated with 2,3-epoxypropyltrimethylammonium chloride (EP3MAC) by a pad-batch method. Attenuated total reflectance Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to verify the presence of deposited nanolayers. Photocatalytic activities of the nanocomposite films were evaluated through the degradation of red wine pollutant. Nano-TiO2 deposition enhanced the protection of cotton fabrics against UV radiation in comparison with the untreated cotton fabrics. Air permeability and whiteness value analysis was performed on the fabrics before and after the treatment with TiO2 nanoparticles by the layer-by-layer deposition method. Tensile strength tests of the warp and weft yarns were performed to evaluate the effect of solution pH value changes during the alternate dipping procedures. For the first time the durability of the effect of the self-assembled multilayer films on the cotton fabric functional properties was analyzed after 10 and 20 washing cycles at 40 °C for 30 min.

Ugur, ?ule S.; Sarii?ik, Merih; Hakan Akta?, A.

2010-08-01

337

Flexible InGaZnO thin film transistors using stacked Y2O3/TiO2/Y2O3 gate dielectrics grown at room temperature  

International Nuclear Information System (INIS)

In this Letter, we report a low operation voltage and high mobility flexible InGaZnO thin-film transistor (TFT) using room-temperature processed Y2O3/TiO2/Y2O3 gate dielectric. The flexible IGZO TFT showed a low threshold voltage of 0.75 V, a small sub-threshold swing of 137 mV/decade, a good field effect mobility of 32.7 cm2/V s, and a large Ion/Ioff ratio of 1.7 x 106. The low operation voltage, small sub-threshold swing and high mobility could be ascribed to the combination of high-? TiO2 and large band gap Y2O3, which provide the potential to meet the requirements of low-temperature and low-power portable electronics. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

338

Time-dependent absorption of TiO2 optical thin films under pulsed and continuous wave 790??nm laser irradiation.  

Science.gov (United States)

The time-dependent absorption at 790 nm of TiO2 films prepared by ion-beam sputtering (IBS) and electron-beam evaporation (EBE) was measured. The pump source was a Ti:sapphire oscillator that was operated in CW and pulsed (50 fs) modes. The absorption coefficient of the IBS film under CW illumination was 8??cm-1, independent of time and power. Under pulsed illumination, there was evidence of three-photon absorption, and the total absorption increased 10-fold over time at the highest measured irradiance. The absorption of the EBE film had higher initial absorption (?24??cm-1) and increased under both CW and pulsed illumination with time. An electron state model based on band-to-band excitation and electron trapping is presented that explains the observed results. The implications for laser-induced damage of oxide coatings are discussed. PMID:24513825

Zhang, Xuerong; Emmert, Luke A; Rudolph, Wolfgang

2013-12-01

339

Photoelectrochemical characterization and photocatalytic properties of mesoporous TiO 2 / ZrO 2 films  

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Full Text Available Optically transparent, crack-free mesoporous titania and zirconia-doped titania thin film photocatalysts were fabricated by sol-gel technique, using nonionic amphiphilic block copolymer Pluronic P123 as template. The structural and optical properties of these films were characterized using SEM, low-angle XRD, and UV/Vis spectroscopy, hexane adsorption investigation. Band gap energy and the position of flatband potentials were estimated by photoelectrochemical measurements. Enhancing of photocatalytic activity of zirconia-doped films relative to pure TiO 2 originates from an anodic shift of the valence band edge potential. Catalytic activity of mesoporous TiO 2 and TiO 2 / ZrO 2 ( 5 –50% of ZrO 2 films in the processes of Cr VI to Cr III photoreduction and 2,4-dinitroaniline photooxidation correlates with crystalline size and growth with increasing of specific surface area of the samples.

2006-01-01

340

Photoelectrochemical characterization and photocatalytic properties of mesoporous TiO2/ZrO2 films  

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Full Text Available Optically transparent, crack-free mesoporous titania and zirconia-doped titania thin film photocatalysts were fabricated by sol-gel technique, using nonionic amphiphilic block copolymer Pluronic P123 as template. The structural and optical properties of these films were characterized using SEM, low-angle XRD, and UV/Vis spectroscopy, hexane adsorption investigation. Band gap energy and the position of flatband potentials were estimated by photoelectrochemical measurements. Enhancing of photocatalytic activity of zirconia-doped films relative to pure TiO2 originates from an anodic shift of the valence band edge potential. Catalytic activity of mesoporous TiO2 and TiO2/ZrO2 (5–50% of ZrO2 films in the processes of CrVI to CrIII photoreduction and 2,4-dinitroaniline photooxidation correlates with crystalline size and growth with increasing of specific surface area of the samples.

Olga Linyucheva

2006-02-01

 
 
 
 
341

Microwave irradiation as an alternative source for conventional annealing: a study of pure TiO2, NiTiO3, CdTiO3 thin films by a sol-gel process for electronic applications  

International Nuclear Information System (INIS)

The lower temperature and shorter timescale for microwave irradiation may be ascribed to the activating and facilitating effect of microwaves on solid-phase diffusion. Using the microwave-heating process, it is possible to achieve enhanced mechanical properties such as greater hardness, improved scratch resistance, and structure texturing. In the present investigation, thin films of pure TiO2 and their respective perovskite-structured thin films, namely NiTiO3 and CdTiO3, have been prepared by simple and cost-effective sol-gel processing on Si(100) substrates and subjected to irradiation with different microwave powers for 10 min. X-ray diffraction (XRD), scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) techniques have been employed to characterize the structural, morphological and elemental composition of the films. It is evident that there is a dramatic change in the structural and morphological properties of the films irradiated in microwaves compared to conventional annealing at high temperature. A plausible mechanism for the formation of the anatase phase of TiO2 and perovskite structures with a rhombohedral phase formation at low microwave powers has also been discussed. This new innovative microwave heating could open a door for advanced technologies to cut process costs in the post-treatment of materials

342

Growth of TiO2 nanosheet-array thin films by quick chemical bath deposition for dye-sensitized solar cells  

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Rutile TiO2 nanofilms, which were composed of many nanosheet-array domains with different orientations, were synthesized directly on fluorine-doped SnO2 conductive glass (FTO) substrates by a chemical deposition method in a short time in this paper. The average thickness of the nanosheets is about 10 nm; the nanosheets in each domain were parallel to each other and perpendicular to the substrate. The size and profile of the domains have a good correspondence to those of the FTO grains of the substrate, indicating a coherent nucleating and epitaxial growing nature of the films. The nanosheets split gradually and finally developed into nanofibers on prolonging the growing time to 20 h. Dye-sensitized solar cells, which were fabricated with the films, present an open-circuit voltage of 0.63 V and a short-circuit current of 7.02 mA/cm2, respectively.

Zhu, Hu; Yang, Junyou; Feng, Shuanglong; Liu, Ming; Zhang, Jiansheng; Li, Gen

2011-11-01

343

Double light-scattering layer film based on TiO2 hollow spheres and TiO2 nanosheets: Improved efficiency in dye-sensitized solar cells  

International Nuclear Information System (INIS)

Highlights: ? A novel TiO2 double-layer composite film is successfully fabricated. ? The TiO2-hollow spheres overlayer exhibited intense scattering ability. ? The TiO2-nanosheets underlayer can enlarge the contact area and increase the contact points between TiO2 photoelectrode and FTO glass. ? TiO2-double light-scattering layer film cells have the maximum conversion efficiency. -- Abstract: A novel TiO2 double light-scattering layer (TiO2-DLL) film consisting of TiO2 hollow spheres (TiO2-HS) as overlayer and TiO2 nanosheets (TiO2-NS) as underlayer was designed as the photoelectrode of dye-sensitized solar cells (DSSCs). The photoelectric conversion performances of DSSCs based on TiO2-HS film, TiO2-NS film, and TiO2-DLL film were investigated. It was found that the TiO2-DLL film cell achieved the highest conversion efficiency and reached up to a maximum value of 5.08%, which is 23.3% higher than that of TiO2-HS film cell (? = 3.62%) and 8.3% higher than that of TiO2-NS film cell (? = 4.31%) under identical film thickness at a constant irradiation of 100 mW cm?2. The enhanced efficiency of TiO2-DLL film can be attributed to its relatively high specific surface area and enhanced light-scattering capability. Furthermore, the TiO2-NS underlayer ensures good electronic contact between TiO2 film and the F-doped tin oxide (FTO) conducting glass

344

Fiber texturing in nano-crystalline TiO2 thin films deposited at 150 °C by dc-reactive sputtering on fiber-textured [0?0?0?1] ZnO?:?Al substrates  

International Nuclear Information System (INIS)

TiO2 thin films were deposited at an effective surface temperature of 150 °C by dc-reactive magnetron sputtering on ZnO?:?Al oriented substrates having a fiber texture along the [0?0?0?1] axis, and studied by transmission electron microscopy and x-ray diffraction analyses. The substrate texturing was used to tailor the TiO2 structure in such a way that a porous matrix made of anatase nano-grains (10 nm in diameter) is formed instead of an amorphous layer (as observed at 150 °C on glass). Additionally, we demonstrate that, by adding an ex situ 200 °C annealing, the anatase domains also gain a fiber texture with the axes aligned to that of the substrate. The TiO2/AZO structural coupling is expected to play a crucial role for the carrier transport through the interface as required in dye-sensitized solar cells. Moreover, the low temperatures used render the process compatible with commonly used plastics substrates.

345

TiO2/polyaniline nanocomposite films prepared by magnetron sputtering combined with plasma polymerization process  

International Nuclear Information System (INIS)

Radiofrequency plasma polymerization in combination with direct current reactive magnetron sputtering is utilized for the synthesis of TiO2/plasma polymerized aniline nanocomposite thin films. In the composite film, X-ray diffraction measurements reveal formation of nanocrystalline rutile TiO2 of crystallite size 3.6 nm. Due to continuous bombardment of plasma species during simultaneous magnetron sputtering and plasma polymerization, the precursors of polymerization are broken and few functional groups are retained in the composite film. The plasma polymerized aniline has the direct optical band gap of 3.55 eV and the nanocrystalline rutile TiO2 is wide gap semiconductor with indirect gap of 3.20 eV which suggests the existence of an energy barrier at the interface in the composite form. The ac conductivity of composite film shows significant improvement as compared to plasma polymerized aniline film and sputtered rutile TiO2 film. The composite film may find potential application as antistatic coatings.

346

Enhanced photocatalysis by coupling of anatase TiO2 film to triangular Ag nanoparticle island  

Science.gov (United States)

In order to overcome the low utilization ratio of solar light and high electron-hole pair recombination rate of TiO2, the triangular Ag nanoparticle island is covered on the surface of the TiO2 thin film. Enhancement of the photocatalytic activity of the Ag/TiO2 nanocomposite system is observed. The increase of electron-hole pair generation is caused by the enhanced near-field amplitudes of localized surface plasmon of the Ag nanoparticles. The efficiently suppressed recombination of electron-hole pair caused by the metal-semiconductor contact can also enhance the photocatalytic activity of the TiO2 film. PMID:22548875

2012-01-01

347

Enhance of electrical properties of resistive switches based on Sr0.1Ba0.9TiO3 and TiO2 thin films by employing a Ni-Cr alloy as contact  

International Nuclear Information System (INIS)

We have investigated the electric-field-induced resistance-switching phenomena of ReRAM cells based on Sr0.1Ba0.9TiO3 and TiO2 thin films fabricated by rf-sputtering technique. Thin films were sandwiched between Pt, Ti and nichrome bottom electrode and Cu top electrode. The I-V measurements at room temperature are non-linear and hysteretic. Cells based on Sr0.1Ba0.9TiO3 present a unipolar resistance-switching phenomenon and it is symmetric with respect to the voltage polarity, while cells based on TiO2 have a bipolar resistance-switching with asymmetric behavior. From the I-V measurements we demonstrated that the nichrome enhances the resistance-switching characteristics of the cells. A reduction of the voltage needed to achieve the HRS-LRS and LRS-HRS transitions are found and a very clear transition between these states is accomplished, in comparison with ReRAM cells fabricated with Pt and Ti electrodes, whose voltage values are large and no clear transitions are presented. This improvement in resistance-switching behavior can be explained due to O2 vacancies formed in the interface because higher affinity for oxygen of nickel and chromium.

348

The influence of TiO2 powder and film on the photodegradation of methyl orange  

International Nuclear Information System (INIS)

Recent investigation has showed that the semiconductor nano-powder or thin film, such as titanium dioxide suspended in water, can utilize ultraviolet light for photocatalytic oxidation of organic pollutants, such as dyes. The photocatalytic activity of TiO2 (powder or thin film) was tested in the reaction of photodegradation of methyl orange (MO). The effect of the initial concentration of dye, the pH, the amount and the type of TiO2 have been investigated. The films were prepared by doctor blade technique, and were annealed in air at various temperatures ranging from 300 to 500 deg. C. The thermal treatment increases the surface roughness of thin films. The best film (without fissures), with higher pores and small grains (150 nm) was the annealed one at 500 deg. C. The correlation between the measured contact angle and the films roughness estimated from atomic force microscopy (AFM) shows that a low contact angle (wetting behavior) corresponds to a higher porosity (a fractured structure, rich in edges and corners), and consequently to high surface energy. Kinetic analyses indicate that the photodegradation rates of dyes can usually be approximated as first-order kinetics for degradation mechanisms. Adsorption is a prerequisite for the TiO2-assisted photodegradation, and the extent of degradation has been discussed in terms of the Langmuir-Hinshelwood model. Thin-film coating of photocatalyst may solve the problems of leaching and sepaay solve the problems of leaching and separation. At a low concentration of MO (0.0125 mM) the efficiency of MO photodegradation is comparable in the case of thin film and powder of TiO2

349

Photocatalytic performance of Fe-, Ni-, or Cu-ion implanted TiO2 films under UV light, visible light and sunlight irradiation  

Science.gov (United States)

TiO2 thin films were fabricated on microscope glass slides by sol-gel method. Then Fe, Ni or Cu ions were implanted in the films. XRD, XPS and UV-Vis spectrophotometer technologies were used to characterize the films. The results of photodegradation of methyl orange in aqueous solution demonstrate: (1) the films are of visible light response photocatalytic activity; (2) under UV light and sunlight excitation, all the films present less efficient than pure TiO2 film. The photodegradation effects of transition metal ion implanted TiO2 thin films were discussed.

Qin, L. Z.; Liang, H.; Liao, B.; Liu, A. D.; Wu, X. Y.; Sun, J.

2013-07-01

350

Photocatalytic performance of Fe-, Ni-, or Cu-ion implanted TiO2 films under UV light, visible light and sunlight irradiation  

International Nuclear Information System (INIS)

TiO2 thin films were fabricated on microscope glass slides by sol–gel method. Then Fe, Ni or Cu ions were implanted in the films. XRD, XPS and UV–Vis spectrophotometer technologies were used to characterize the films. The results of photodegradation of methyl orange in aqueous solution demonstrate: (1) the films are of visible light response photocatalytic activity; (2) under UV light and sunlight excitation, all the films present less efficient than pure TiO2 film. The photodegradation effects of transition metal ion implanted TiO2 thin films were discussed

351

Langmuir--Schaefer films of Nafion with incorporated TiO(2) nanoparticles.  

Science.gov (United States)

An easy method of incorporating TiO(2) nanoparticles into Nafion perfluorinated ionomer is proposed. Ultrathin films of Nafion were prepared by employing the Langmuir-Schaefer (LS) technique. The pressure-area isotherm study of a Langmuir monolayer of Nafion at the air-water interface on different concentrations of NaCl as the subphase allowed us to find the best experimental conditions for the deposition of stable Langmuir-Schaefer films. Incorporation of TiO(2) nanoparticles was performed by dipping Nafion LS films in a solution of TiO(2) nanoparticles. The uniformity of the TiO(2) incorporation was detected by UV-visible spectroscopy. The morphology of the Nafion, Nafion/TiO(2) nanoparticles thin films, and the changes due to the annealing procedure were investigated by atomic force microscopy. Interestingly, the AFM investigation showed that Nafion and Nafion/TiO(2) LS films have thermal stability up to 600 degrees C. PMID:15620299

Bertoncello, Paolo; Notargiacomo, Andrea; Nicolini, Claudio

2005-01-01

352

Thin Films  

Science.gov (United States)

Titanium dioxide (TiO2) thin films were synthesized on glass substrates by spray pyrolysis. The effect of solution flow rate on the physical properties of the films was investigated by use of x-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy (AFM), and spectrophotometry techniques. XRD analysis revealed the tetragonal anatase phase of TiO2 with highly preferred (101) orientation. AFM images showed that grain size on top of TiO2 thin films depended on solution flow rate. An indirect band gap energy of 3.46 eV was determined by means of transmission and reflection measurements. The envelope method, based on the optical transmission spectrum, was used to determine film thickness and optical constants, for example real and imaginary parts of the dielectric constant, refractive index, and extinction coefficient. Ultraviolet and visible photoluminescence emission peaks were observed at room temperature. These peaks were attributed to the intrinsic emission and to the surface defect states, respectively.

Naffouti, Wafa; Nasr, Tarek Ben; Mehdi, Ahmed; Kamoun-Turki, Najoua

2014-11-01

353

Secondary ion mass spectrometry and X-ray photoelectron spectroscopy investigation on chemical vapor deposited CeO(2-)ZrO(2)-TiO(2) thin films.  

Science.gov (United States)

Mixed CeO(2)-ZrO(2) systems have attracted widespread interest for their use in three-way catalyst (TWC) technology for automotive exhaust conversion to non-toxic products. In this work, CeO(2)-ZrO(2) thin films were deposited, via chemical vapor deposition, in order to obtain nanoscale materials with a high surface-to-volume ratio, with precise control of system properties. The addition of TiO(2) as buffer layer was also investigated. Cordierite was chosen as substrate, being the usual refractory material for catalytic mufflers. The multilayers were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). In particular, the combination of SIMS and XPS allowed us to investigate both surface and in-depth chemical composition, studying also film-intermixing phenomena induced by annealing processes. PMID:12717775

Barison, Simona; Barreca, Davide; Battiston, Giovanni A; Daolio, Sergio; Fabrizio, Monica; Gerbasi, Rosalba; Tondello, Eugenio

2003-01-01

354

Preparation of TiO2-SnO2 Solid Solution Film by Ion Beam Sputtering  

Science.gov (United States)

Thin film of rutile-type TiO2-SnO2 solid solution was successfully prepared by reactive ion beam sputtering without postannealing. The crystallinity of the film was highly dependent on the temperature of the substrate. The (101)-oriented film with rutile structure was obtained at substrate temperatures higher than 300°C.

Okamura, Takeshi; Seki, Yoji; Sagawa, Nobukazu

1992-02-01

355

Density, thickness and composition measurements of TiO2 -SiO2 thin films by coupling X-ray reflectometry, ellipsometry and electron probe microanalysis-X  

International Nuclear Information System (INIS)

Mixed TiO2 -SiO2 thin films were deposited by aerosol atmospheric CVD method by using di-acetoxi di-butoxi silane (DADBS) and Ti tetra-butoxide as precursors. By varying the deposition temperatures between 470 and 600 deg. C and the ratios between the Si and Ti precursors (Si/Ti) from 2 up to 16, films with different compositions and thicknesses were deposited. The coupled analysis of the results of different characterisation methods was used in order to determine the variation of the composition, the thickness and the density of the films. First EPMA measurements were performed at different acceleration voltages with a Cameca SX50 system. By analysing, with specific software, the evolution of the intensity ratio I x/I std versus the voltage, the composition and the mass thickness (product of density by the thickness) were determined. In order to measure independently the density, X-ray reflectometry experiments were performed. By analysing the value of the critical angle and the Kiessig fringes, the density and the thickness of the layers were determined. The refractive index and the thickness of the films were also measured by ellipsometry. By assuming a linear interpolation between the index value of the pure SiO2 and TiO2 films, the film composition was deduced from the refractive index value. XPS measurements were also performed in order to obtain an independent value of the composition. A good agrndent value of the composition. A good agreement between the ways to measure the density is obtained

356

Photocatalytic and superhydrophilicity properties of N-doped TiO2 nanothin films  

International Nuclear Information System (INIS)

Pure TiO2 and nitrogen doped titanium dioxide (N-TiO2) thin films were prepared by sol-gel method through spin coating on soda lime glass substrates. TiCl4 and urea were used as Ti and N sources in the sol. XRD results showed nitrogen doping has retarded anatase to rutile phase transformation. The doping also leads to a decrease in roughness of the samples from 4 nm (TiO2) to 1 nm (N-TiO2). However, surface analysis by statistical methods reveals that both surfaces have self-affine structure. Optical band gap of thin films was shifted from 3.65 eV (TiO2) to 3.47 eV (N-TiO2). Hydrophilic conversion and photocatalytic degradation properties of thin films were investigated and exhibited that N-TiO2 thin film has more preferable hydrophilicity and photocatalytic properties under UV illumination.

357

Enhanced photocurrent from generated photothermal heat in indium nanoparticles embedded TiO2 film  

Science.gov (United States)

We have demonstrated the synthesis of indium (In) nanoparticle (NP) arrays on TiO2 thin film (TF) using glancing angle deposition technique. The deposited In NPs are of the order of 4-10 nm in size. Optical absorption measurements depict 2.5 times enhanced absorption for In-NPs/TiO2-TF compared to TiO2 TF. The plasmonic device shows a turn on voltage at ˜3.0 and ˜1.0 V under dark and 30 min illumination, respectively. The device current increases from 1.6 to 6.5 mA/cm2 (+5 V) with enhanced temperature for 1-30 min continuous light exposures. The plasmonic device shows eight-fold enlarged photoresponsivity (+2.3 V) compared to the TiO2 TF based device.

Choudhuri, B.; Mondal, A.; Dhar, J. C.; Singh, N. K.; Goswami, T.; Chattopadhyay, K. K.

2013-06-01

358

Effect of annealing treatment on electrical and optical properties of Nb doped TiO2 thin films as a TCO prepared by sol-gel spin coating method  

Science.gov (United States)

Anatase niobium doped TiO2 thin films (Ti0.94Nb0.06O2) were prepared on quartz substrates by sol-gel spin coating technique and various initial concentrations ([Ti + Nb] in the solution) of 0.1 M and 0.4 M. All the films dried at 100 °C and then the annealing treatment performed by three different procedures. The influence of different annealing processes and total metal concentrations was studied on crystallinity, transparency, conductivity and morphology of thin films by XRD, EDX, FT-IR and UV-vis transmittance spectroscopy, four point probe, AFM and SEM images. It was found that two-step annealing procedure under vacuum is a more proper way to increase the conductivity of TNO thin films compared to one-step annealing process. Two-step method exhibited the minimum resistivity of 4.4 ? cm and the transparency of about 50% in the visible region with 36 nm thickness.

Fallah, Milad; Zamani-Meymian, Mohammad-Reza; Rahimi, Rahmatollah; Rabbani, Mahboubeh

2014-10-01

359

Inactivation of algal blooms in eutrophic water of drinking water supplies with the photocatalysis of TiO2 thin film on hollow glass beads.  

Science.gov (United States)

Photocatalytic inactivation of algae, Anabaena, Microcystis, and Melosira, was carried out with TiO2-coated Pyrex hollow glass beads under the illumination of UV light (370 nm wavelength). After being irradiated with UV light in the presence of the TiO2-coated Pyrex glass beads, Anabaena and Microcystis, known as typical cyanobacteria, lost their photosynthetic activity, and the string of Anabaena cells and the colonies of Microcystis cells were completely separated into individual spherical ones. In the case of Melosira, which is a typical diatom, however, somewhat lower photocatalytic inactivation efficiency was obtained, which was believed to be due to the presence of the inorganic siliceous wall surrounding the cells of Melosira. The TiO2-coated hollow glass beads could successfully be employed for the practical application in a eutrophicated river under sunlight. More than 50% of the chlorophyll-a concentration could be reduced by the action of TiO2 photocatalysis. PMID:16445183

Kim, S-C; Lee, D-K

2005-01-01

360

Epitaxial Growth of TiO2-SnO2 Solid Solution Film by Reactive Ion Beam Sputtering  

Science.gov (United States)

Epitaxial thin film of rutile-type TiO2-SnO2 solid solution has been successfully prepared. The film was fabricated on a sapphire (01\\bar{1}2) substrate by the reactive ion beam sputtering method using a TiO2-SnO2 ceramic target. The crystallinity of the film was dependent on the substrate temperature. The (101)-oriented film was grown at temperatures higher than 300°C. An epitaxial film was obtained by heat-treatment at temperatures higher than the miscibility gap.

Okamura, Takeshi; Seki, Yoji; Sagawa, Nobukazu

1992-07-01

 
 
 
 
361

Highly sensitive fast-response UV photodetectors based on epitaxial TiO2 films  

International Nuclear Information System (INIS)

Epitaxial TiO2 thin films were fabricated on LaAlO3 single crystal substrates by RF magnetron sputtering. Ag electrodes were then evaporated on the TiO2 thin films to form metal-semiconductor-metal photoconductive detectors. The TiO2 photodetector exhibited a maximum photoresponse of 3.63 A W-1 at 310 nm with a sharp cutoff wavelength at 380 nm. The ultraviolet (UV)-visible response rejection ratio (R310 nm/R390 nm) was about three orders of magnitude. The photocurrent response of the detectors scaled linearly with the applied bias and the incident light intensity. The dark current was only 0.14 nA at 10 V bias. A transient photovoltage with a rise time of ?8 ns and a full-width at half-maximum of ?90 ns was observed when the photodetector was under the irradiation of a 308 nm XeCl laser with 25 ns duration. The excellent performances of high responsivity and ultrahigh response speed suggest that the presented TiO2 detectors have promising potential in UV photodetection.

362

Effect of 79 MeV Br ion irradiation on the surface features of rutile TiO2 thin film  

Science.gov (United States)

In this study, rutile titanium dioxide thin films deposited on Si (100) substrates by DC magnetron sputtering are irradiated by 79 MeV Br ions. Though each Br ion is expected to amorphize the medium along its path, the film remains crystalline even at the highest fluence of irradiation. The evolution of surface of the films with Br ion fluence is studied using atomicforce microscopy. The films were found to smoothen under dense electronic excitation of Br ions. The irregular shape grain of the pristine films convert to circular shape at a fluence of 1 × 1013 Br ions cm-2. Power spectral density (PSD) analysis of the AFM images indicates that irradiation induced smoothing of the surfaces is governed by the surface diffusion process.

Rath, H.; Dash, P.; Som, T.; Dash, B. N.; Singh, U. P.; Kanjilal, D.; Mishra, N. C.

2012-07-01

363

Effect of a TiO2 Buffer Layer on the Properties of ITO Films Prepared by RF Magnetron Sputtering  

Directory of Open Access Journals (Sweden)

Full Text Available Sn-doped In2O3 (ITO thin films were prepared by radio frequency magnetron sputtering without intentionalsubstrate heating on bare glass and TiO2-deposited glass substrates to investigate the effect of a TiO2 buffer layer onthe electrical and optical properties of ITO films. The thicknesses of TiO2 and ITO films were kept constant at 5 and100 nm, respectively. As-deposited ITO single layer films show an optical transmittance of 75.9%, while ITO/TiO2 bilayeredfilms show a lower transmittance of 76.1%. However, as-deposited ITO/TiO2 films show a lower resistivity(9.87×10-4 ?cm than that of ITO single layer films. In addition, the work function of the ITO film is affected by the TiO2buffer layer, with the ITO/TiO2 films having a higher work-function (5.0 eV than that of the ITO single layer films. Theexperimental results indicate that a 5-nm-thick TiO2 buffer layer on the ITO/TiO2 films results in better performancethan conventional ITO single layer films.

Daeil Kim

2013-10-01

364

Thermal properties of TiO2 films fabricated by atomic layer deposition  

Science.gov (United States)

Thin, amorphous, high index, dense, low scattering & absorption (low extinction coefficient) and optical grade TiO2 films of various thicknesses are prepared by Atomic layer deposition (ALD) technique and investigated in terms of thermo-optic coefficient (dn/dT) and temperature dependent density (d?/dT). The d?/dT and d?/dT are calculated by modeling ellipsometric experimental data by developing appropriate optical model such as Cauchy Model. The modeled data was further modeled with Lorentz-Lorenz relation under least-square approach. The dn/dT of TiO2 films shows negative values for thin and positive values for relatively thicker films and reveals no significant changes in dn/dT and d?/dT when film thickness increases more than ~ 200 nm. The coefficient values are calculated for a wavelength range of 380-1800 nm. The average values of (dn/dT)60nm= -4.2 ± 0.7 × 10-5°C-1 and (d?/dT)60nm= -6.6 ± 1.1 × 10-5gcm-3 °C-1 at wavelength of 640 nm. The reported coefficients values are measured and calculated for TiO2 film of thickness t = 60 nm and described in detail.

Rizwan Saleem, Muhammad; Honkanen, Seppo; Turunen, Jari

2014-06-01

365

Up-conversion luminescence application in Er3+: TiO2 thin film prepared by dip coating sol-gel route  

International Nuclear Information System (INIS)

Sol-gel derived nano-crystalline titanium dioxide films doped with 1 up to 5% Er3+ ions were prepared by dip coating sol-gel method. The coating sol was obtained by hydrolysis of Ti(OC4H9)4 in ethanol/HCI solution. The FT-Raman and the X-ray diffraction (XRD) were carried out to determine the crystal structure of the prepared samples. The morphology SEM and the cross-sectional of the film were used to characterize the microstructure and the thickness of the prepared film. It is shown that relative homogeneous, crack-free and transparent film was achieved via dipping process at 500 deg C. After the excitation with laser diode at wavelength 808 nm, visible (Vis) and infrared (IR) up-conversion emissions were evidenced in the thin film samples under investigation. The up-conversion was found to depend strongly on the Er3+ ion concentrations. The visible emission was found to be at 540, 560, 590 and 640 nm for thin film. They are attributed to intra-4f transition of Er3+ ions and assigned to the (2H11/2 + 4S3/2) and 4F9/2, which are populated through excited state absorption (ESA) for 808 nm excitation. (author)

366

The resistive switching in TiO2 films studied by conductive atomic force microscopy and Kelvin probe force microscopy  

Directory of Open Access Journals (Sweden)

Full Text Available The resistive switching characteristics of TiO2 thin films were investigated using conductive atomic force microscopy (CAFM and Kelvin probe force microscopy (KPFM. The as-prepared TiO2 thin films were modulated into higher and lower resistance states by applying a local electric field. We showed that the resistive switching results from charge injection and release assisted by electro-migration of oxygen ions. An integrated model combined with filamentary and interfacial effects was utilized to elucidate the experimentally observed phenomenon.

Yuanmin Du

2013-08-01

367

Optical, electrical and dielectric properties of TiO 2-SiO 2 films prepared by a cost effective sol-gel process  

Science.gov (United States)

Titanium dioxide (TiO 2) and silicon dioxide (SiO 2) thin films and their mixed films were synthesized by the sol-gel spin coating method using titanium tetra isopropoxide (TTIP) and tetra ethyl ortho silicate (TEOS) as the precursor materials for TiO 2 and SiO 2 respectively. The pure and composite films of TiO 2 and SiO 2 were deposited on glass and silicon substrates. The optical properties were studied for different compositions of TiO 2 and SiO 2 sols and the refractive index and optical band gap energies were estimated. MOS capacitors were fabricated using TiO 2 films on p-silicon (1 0 0) substrates. The current-voltage ( I- V) and capacitance-voltage ( C- V) characteristics were studied and the electrical resistivity and dielectric constant were estimated for the films annealed at 200 °C for their possible use in optoelectronic applications.

Vishwas, M.; Rao, K. Narasimha; Gowda, K. V. Arjuna; Chakradhar, R. P. S.

2011-12-01

368

Influence of process parameters on the growth of pure-phase anatase and rutile TiO2 thin films deposited by low temperature reactive magnetron sputtering  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english In this work is investigated the optimal conditions for deposition of pure- phase anatase and rutile thin films prepared at low temperatures (less than 150ºC) by reactive dc magnetron sputtering onto well- cleaned p- type Si substrates. For this, the variation of deposition plasma parameters as subs [...] trate- to- target distance, total gas pressure, oxygen concentration, and substrate bias were studied and correlated with the characteristics of the deposited films. The XRD analysis indicates the formation of pure rutile phase when the substrate is biased at voltages between - 200 and - 300 V. Pure anatase phase is only attained when the total pressure is higher than 0.7 Pa. Moreover, it's noticeable a strong dependence of surface roughness with parameters studied.

H., Toku; R.S., Pessoa; H.S., Maciel; M., Massi; U.A., Mengui.

2010-09-01

369

Influence of process parameters on the growth of pure-phase anatase and rutile TiO2 thin films deposited by low temperature reactive magnetron sputtering  

International Nuclear Information System (INIS)

In this work is investigated the optimal conditions for deposition of pure-phase anatase and rutile thin films prepared at low temperatures (less than 150 deg C) by reactive dc magnetron sputtering onto well-cleaned p-type Si substrates. For this, the variation of deposition plasma parameters as substrate-to-target distance, total gas pressure, oxygen concentration, and substrate bias were studied and correlated with the characteristics of the deposited films. The XRD analysis indicates the formation of pure rutile phase when the substrate is biased at voltages between -200 and -300 V. Pure anatase phase is only attained when the total pressure is higher than 0.7 Pa. Moreover, it is noticeable a strong dependence of surface roughness with parameters studied. (author)

370

Influence of process parameters on the growth of pure-phase anatase and rutile TiO2 thin films deposited by low temperature reactive magnetron sputtering  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english In this work is investigated the optimal conditions for deposition of pure- phase anatase and rutile thin films prepared at low temperatures (less than 150ºC) by reactive dc magnetron sputtering onto well- cleaned p- type Si substrates. For this, the variation of deposition plasma parameters as subs [...] trate- to- target distance, total gas pressure, oxygen concentration, and substrate bias were studied and correlated with the characteristics of the deposited films. The XRD analysis indicates the formation of pure rutile phase when the substrate is biased at voltages between - 200 and - 300 V. Pure anatase phase is only attained when the total pressure is higher than 0.7 Pa. Moreover, it's noticeable a strong dependence of surface roughness with parameters studied.

H., Toku; R.S., Pessoa; H.S., Maciel; M., Massi; U.A., Mengui.

371

Enhanced performance of dye-sensitized solar cell via surface modification of mesoporous TiO2 photoanode with electrodeposited thin TiO2 layer  

International Nuclear Information System (INIS)

Highlights: ? TiO2-modified photoanode composed of compact underlayer and efficient electron transport network was fabricated directly by anodic electrodeposition in an aqueous TiCl3 electrolyte. ? The electrodeposited thin TiO2 layer could bridge gaps between TiO2 nanoparticles and improve the electrical contact at the FTO/TiO2 interface, leading to an efficient electron transport. ? The electrodeposited compact TiO2 layer could cover the exposed surface area of FTO to the electrolyte, which contributes to the suppression of the charge recombination. ? We demonstrated that the TiO2-modified photoanode significantly enhances the photovoltaic properties of the DSSC compared to the bare photoanode. - Abstract: Surface modification of porous TiO2 photoanode with a thin compact TiO2 layer was carried out by means of anodic electrodeposition in an aqueous TiCl3 electrolyte. Results indicated that the electrodeposited thin TiO2 layer could bridge gaps between TiO2 nanoparticles and improve the electrical contact at the FTO (fluoride-doped tin oxide)/TiO2 interface, leading to an efficient electron transport. In addition, the thin compact TiO2 layer could cover the exposed surface area of FTO to the electrolyte, which contributes to the suppression of the charge recombination. The surface treatment of mesoporous TiO2 photoanode via aqueous electrochemical route is an effective way to improve the performance of DSSC (dye-sensitized solar cell), which could increase the short-circuit current density, and reduce the dark current density compared to DSSCs with bare and TiCl4-treated TiO2 photoanodes. The photoelectron conversion efficiency of DSSC was increased from 7.3 to 8.2% after employing the TiO2-modified photoanode.

372

Influence of High-energy electron-beam on photocatalytic activity of TiO2 films on carbon-fiber deposited by atomic layer deposition  

International Nuclear Information System (INIS)

High-energy electron-beam with energy of 1 MeV was used for modifying surface structure of TiO2 thin films on carbon fiber prepared by using atomic layer deposition under atmospheric pressure. TiO2 nanoparticles (?20 nm) on carbon fiber underwent structural modification of the surface upon electron-beam treatment, resulting in enhanced photocatalytic activity. In contrast, a thicker film of TiO2 did not show such changes in surface structure and photocatalytic activity by electron-beam treatment. We demonstrate that electron-beam can be used for modifying surface structure of photocatalysts consisting of nanoparticles for improvement of their activity. - Highlights: ? Electron-beam was used for modifying surface of TiO2 on carbon fiber. ? TiO2 with various structures were prepared by atomic layer deposition. ? Photocatalytic activity of TiO2/carbon was enhanced by e-beam.

373

Unusual photoelectric behaviors of Mo-doped TiO2 multilayer thin films prepared by RF magnetron co-sputtering: effect of barrier tunneling on internal charge transfer  

Science.gov (United States)

Mo-doped TiO2 multilayer thin films were prepared by RF magnetron co-sputtering. Microstructures, crystallite parameters and the absorption band were investigated with atomic force microscopy, X-ray diffraction and ultraviolet-visible spectroscopy. Internal carrier transport characteristics and the photoelectric property of different layer-assemble modes were examined on an electrochemical workstation under visible light. The result indicates that the double-layer structure with an undoped surface layer demonstrated a red-shifted absorption edge and a much stronger photocurrent compared to the uniformly doped sample, signifying that the electric field implanted at the interface between particles in different layers accelerated internal charge transfer effectively. However, a heavily doped layer implanted at the bottom of the three-layer film merely brought about negative effects on the photoelectric property, mainly because of the Schottky junction existing above the substrate. Nevertheless, this obstacle was successfully eliminated by raising the Mo concentration to 1020 cm-3, where the thickness of the depletion layer fell into the order of angstroms and the tunneling coefficient manifested a dramatic increase. Under this circumstance, the Schottky junction disappeared and the strongest photocurrent was observed in the three-layer film.

Yan, B. X.; Luo, S. Y.; Mao, X. G.; Shen, J.; Zhou, Q. F.

2013-01-01

374

Hydrogenated TiO2 film for enhancing photovoltaic properties of solar cells and self-sensitized effect  

International Nuclear Information System (INIS)

Hydrogenated TiO2 film was obtained by annealing TiO2 film at 350?°C for 2?h with hydrogen, and TiO2 films were prepared by screen printing on fluorine-doped tin oxide glass. Structural characterization by X-ray diffraction and electron microscopy did not show obvious difference between hydrogenated TiO2 film and pristine TiO2 film. Through optical and electrochemical characterization, the hydrogenated TiO2 film showed enhanced absorption and narrowed band gap, as well as reduced TiO2 surface impedance and dark current. As a result, an obviously enhanced photovoltaic effect was observed in the solar cell with hydrogenated TiO2 as photoanode without adding any dye due to the self-sensitized effect of hydrogenated TiO2 film, which excited electrons injecting internal conduction band of TiO2 to generate more photocurrent

375

Evolution of different structural phases of TiO2 films with oxygen partial pressure and Fe doping and their electrical properties  

International Nuclear Information System (INIS)

Highlights: ? Fe doped and undoped TiO2 films are grown with varying oxygen partial pressure (OPP). ? Different structural and electrical phases of TiO2 films evolve with OPP. ? Phases obtained at different OPP are not same for films with different Fe doping. ? XPS confirms Fe is not in metal cluster form. ? Charge ordering is observed in magneli phase of Fe doped and undoped TiO2 films. -- Abstract: We have studied the influence of oxygen partial pressure (OPP; 250 mTorr–1 × 10?5 Torr) and Fe doping (2 and 4 at.%) on structural and electrical properties of TiO2 thin films on LaAlO3 substrates. X-ray photoelectron spectroscopy suggests that Fe is not in metal cluster form. It is found that the evolution of the three phases; anatase, rutile and brookite of TiO2 as well as the magneli phase (TinO2n?1) strongly depends on the OPP and Fe doping concentration. All the films grown at 250 mTorr show insulating behavior, whereas films grown at 1 × 10?2 and 1 × 10?4 Torr reveal high temperature metallic to low temperature semiconducting transition. Interestingly, films deposited at 1 × 10?5 Torr reveal charge ordering, which is contributed to the magneli phase of TiO2. The present study suggests that functionality of TiO2 thin film based devices can be tuned by properly selecting the

376

Antibacterial effect of silver modified TiO2/PECVD films  

Science.gov (United States)

This paper deals with photocatalytic activity of silver treated TiO2 films. The TiO2 films were deposited on glass substrates by plasma enhanced chemical vapor deposition (PECVD) in a vacuum reactor with radio frequency (RF) low temperature plasma discharge in the mixture of oxygen and titanium isopropoxide vapors (TTIP). The depositions were performed under different deposition conditions. Subsequently, the surface of TiO2 films was modified by deposition of silver nanoparticles. Photocatalytic activity of both silver modified and unmodified TiO2 films was determined by decomposition of the model organic matter (acid orange 7). Selected TiO2 samples were used for tests of antibacterial activity. These tests were performed on Gram-negative bacteria Escherichia coli. The results clearly proved that presence of silver clusters resulted in enhancement of the photocatalytic activity, which was up to four times higher than that for pure TiO2 films.

Hájková, P.; Patenka, P. Å.; Krumeich, J.; Exnar, P.; Kolouch, A.; Matoušek, J.; Ko?í, P.

2009-08-01

377

Photocatalytic activity of Cr-doped TiO2 nanoparticles deposited on porous multicrystalline silicon films.  

Science.gov (United States)

This work deals with the deposition of Cr-doped TiO2 thin films on porous silicon (PS) prepared from electrochemical anodization of multicrystalline (mc-Si) Si wafers. The effect of Cr doping on the properties of the TiO2-Cr/PS/Si samples has been investigated by means of X-ray diffraction (XRD), atomic force microcopy (AFM), photoluminescence, lifetime, and laser beam-induced current (LBIC) measurements. The photocatalytic activity is carried out on TiO2-Cr/PS/Si samples. It was found that the TiO2-Cr/PS/mc-Si type structure degrades an organic pollutant (amido black) under ultraviolet (UV) light. A noticeable degradation of the pollutant is obtained for a Cr doping of 2 at. %. This result is discussed in light of LBIC and photoluminescence measurements. PMID:25313302

Hajjaji, Anouar; Trabelsi, Khaled; Atyaoui, Atef; Gaidi, Mounir; Bousselmi, Latifa; Bessais, Brahim; El Khakani, My Ali

2014-01-01

378

Photocatalytic activity of Cr-doped TiO2 nanoparticles deposited on porous multicrystalline silicon films  

Science.gov (United States)

This work deals with the deposition of Cr-doped TiO2 thin films on porous silicon (PS) prepared from electrochemical anodization of multicrystalline (mc-Si) Si wafers. The effect of Cr doping on the properties of the TiO2-Cr/PS/Si samples has been investigated by means of X-ray diffraction (XRD), atomic force microcopy (AFM), photoluminescence, lifetime, and laser beam-induced current (LBIC) measurements. The photocatalytic activity is carried out on TiO2-Cr/PS/Si samples. It was found that the TiO2-Cr/PS/mc-Si type structure degrades an organic pollutant (amido black) under ultraviolet (UV) light. A noticeable degradation of the pollutant is obtained for a Cr doping of 2 at. %. This result is discussed in light of LBIC and photoluminescence measurements. PMID:25313302

2014-01-01

379

Novel Neo-Pentoxide Precursors for MOCVD Thin Films of TiO(2) and ZrO(2).[1  

Energy Technology Data Exchange (ETDEWEB)

Two novel Group IV precursors, titanium (IV) neo-pentoxide, [Ti({mu}-ONep)(ONep){sub 3}]{sub 2} (l), and zirconium (IV) neo-pentoxide, [Zr({mu}-ONep)(ONep){sub 3}]{sub 2} (2), were reported to possess relatively high volatility at low temperatures. These compounds were therefore investigated as MOCVD precursors using a lamp-heated cold-wall CVD reactor and direct sublimation without carrier gas. The ONep derivatives proved to be competitive precursors for the production of thin films of the appropriate MO{sub 2} (M = Ti or Zr) materials in comparison to other metallo-organic precursors. Compound 1 was found to sublime at 120 C with a deposition rate of {approximately}0.350 {mu}m/min onto a substrate at 330 C forming the anatase phase with < 1% residual C found in the final film. Compound 2 was found to sublime at 160 C and deposited as crystalline material at 300 C with < 1% residual C found in the final film. A comparison to standard alkoxide and {beta}-diketonates is presented where appropriate.

Boyle, Timothy J.; Francisco, Laila P.; Gallegos, Jesus J.; Rodriguez, Mark A.; Ward, Timothy L.

1999-07-14

380

Preparation and photoelectrocatalytic activity of Pt(TiO2)-TiO2 hybrid films  

International Nuclear Information System (INIS)

A novel platinised TiO2 film, Pt(TiO2)-TiO2, was prepared by a two-step procedure in which TiO2 as a 'binding layer' was first loaded on ITO (indium-tin oxide) conductive glass plates, and then the platinised TiO2 particles in the suspension was dip-coated on the TiO2 film. The resultant hybrid film was characterized by X-ray reflection diffraction, scanning electron microscope, diffuse reflectance spectra and photoelectrochemical measurement. The experimental results showed that the Pt(TiO2)-TiO2/ITO hybrid film not only was much more stable than the single Pt(TiO2)/ITO film but also possessed rather high photocatalytic and photoelectrocatalytic activities compared with the pure TiO2/ITO film. With respect to formic acid solution, the chemical-oxygen-demand removal efficiency of photoelectrocatalytic oxidation for Pt(TiO2)-TiO2/ITO film is apparently higher than that of photocatalytic and photoelectrocatalytic oxidation of TiO2/ITO film, respectively

 
 
 
 
381

Shifting to the red the absorption edge in TiO2 films: a photoacoustic study  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in english When Titanium dioxide in contact with a polluted water sample is irradiated with ultraviolet light, electron-hole pairs can be generated, which can react with oxygen and water producing free radicals that can degrade the pollutants, changing them into harmless compounds for the environment. The ultr [...] aviolet component of the solar radiation is around 7%. Therefore, it is convenient to modify the TiO2 films crystalline structure for obtaining photocatalytical processes with visible light. In this work we report on the growth of TiO2 thin films by the Sol-gel technique considering the incorporation of AgNO3 in the initial solution containing the precursor. The concentration of the AgNO3 saline solution was changed between 5 and 30% to control the grain size of the grown TiO2 nanocrystals, impregnating 6 layers over glass slide substrates and using a sintering temperature of 600 °C. The obtained films were characterized structurally by means of X-ray diffraction. The shift in the forbidden energy bandwidth value to the red part of the optical absorption spectrum was evidenced by Photoacoustic Spectroscopy. The photocatalytic activity was tested on a solution of methylene blue using also the Photoacoustic technique.

F., Gordillo-Delgado; K., Villa-Gómez; E, Marín.

2011-03-01

382

Shifting to the red the absorption edge in TiO2 films: a photoacoustic study  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in english When Titanium dioxide in contact with a polluted water sample is irradiated with ultraviolet light, electron-hole pairs can be generated, which can react with oxygen and water producing free radicals that can degrade the pollutants, changing them into harmless compounds for the environment. The ultr [...] aviolet component of the solar radiation is around 7%. Therefore, it is convenient to modify the TiO2 films crystalline structure for obtaining photocatalytical processes with visible light. In this work we report on the growth of TiO2 thin films by the Sol-gel technique considering the incorporation of AgNO3 in the initial solution containing the precursor. The concentration of the AgNO3 saline solution was changed between 5 and 30% to control the grain size of the grown TiO2 nanocrystals, impregnating 6 layers over glass slide substrates and using a sintering temperature of 600 °C. The obtained films were characterized structurally by means of X-ray diffraction. The shift in the forbidden energy bandwidth value to the red part of the optical absorption spectrum was evidenced by Photoacoustic Spectroscopy. The photocatalytic activity was tested on a solution of methylene blue using also the Photoacoustic technique.

F., Gordillo-Delgado; K., Villa-Gómez; E, Marín.

383

Fabrication of TiO2-based composite films by sequential ion implantation and subsequent annealing  

Science.gov (United States)

A special method for fabricating a series of TiO2-based composite catalyst film is presented. There are two steps in this method. Firstly, two kinds of elements are sequentially implanted into the substrate. Then, the implanted samples are annealed in oxygen atmosphere. This method involves a solid phase growth process, which can be successfully used to prepare noble metal nanoparticles modified TiO2 film (Au NP-TiO2), metallic (Fe, V) and non-metallic (N) doped TiO2, and narrow-width band gap heterojunctions (Fe2O3-TiO2). These TiO2-based composite catalyst films show good crystallinity and stability, easy catalyst immobilization and recycling in photocatalytic experiments. In addition, the detailed growth processes and mechanisms of these TiO2-based composite films were systematically studied.

Liu, Dan; Ren, Feng; Cai, Guang-Xu; Liu, Yi-Chao; Hong, Meng-Qing; Ying, Jian-Jian; Liu, Yong; Zhou, Juan; Wu, Wei; Xiao, Xiang-Heng; Jiang, Chang-Zhong

2014-04-01

384

Preparation and Characterization of Pure Rutile TiO2 Nanoparticles for Photo catalytic Study and Thin Films for Dye-Sensitized Solar Cells  

International Nuclear Information System (INIS)

Pure rutile-phase TiO2 (r-TiO2) was synthesized by a simple one pot experiment under hydrothermal condition using titanium (IV) n-butoxide as a Ti-precursor and HCl as a peptizer. The TiO2 products were characterized by XRD, TEM, ESCA, and BET surface area measurement. The r-TiO2 were rodlike in shape with average size of ? 61 x 32 nm at hydrothermal temperature of 220 degree C for 10 h. Hydrothermal treatment at longer reaction time increased the tendency of crystal growth and also decreased the BET surface area. The degradation of methylene blue was selected as a test reaction to confer the photocatalytic activity of as-obtained r-TiO2. The results showed a strong correlation between the structure evolution, particle size, and photocatalytic performance of r-TiO2. Furthermore, the r-TiO2-based solar cell was prepared for the photovoltaic characteristics study, and the best efficiency of ? 3.16% was obtained.

385

Appearance of room temperature ferromagnetism in Cu-doped TiO$_{2-\\delta}$ films  

CERN Document Server

In recent years there has been an intense search for room temperature ferromagnetism in doped dilute semiconductors, which have many potentially applications in spintronics and optoelectronics. We report here the unexpected observation of significant room temperature ferromagnetism in a semiconductor doped with nonmagnetic impurities, Cu-doped TiO$_2$ thin films grown by Pulsed Laser Deposition. The magnetic moment, calculated from the magnetization curves, resulted surprisingly large, about 1.5 $\\mu_B$ per Cu atom. A large magnetic moment was also obtained from ab initio calculations using the supercell method for TiO$_2$ with Cu impurities, but only if an oxygen vacancy in the nearest-neighbour shell of Cu was present. This result suggests that the role of oxygen vacancies is crucial for the appearance of ferromagnetism. The calculations also predict that Cu doping favours the formation of oxygen vacancies.

Duhalde, S; Chiliotte, C; Torres, C E R; Errico, L A; Cabrera, A F; Renteria, M; Sánchez, F; Weissmann, M

2005-01-01

386

Microporous TiO2-WO3/TiO2 films with visible-light photocatalytic activity synthesized by micro arc oxidation and DC magnetron sputtering  

Science.gov (United States)

This study reports the preparation of microporous TiO2-WO3/TiO2 films with a high surface area using a two-step approach. A porous WO3/TiO2 template was synthesized by oxidizing a titanium sheet using a micro arc oxidation (MAO) process. This sheet was subsequently overlaid with a visible light (Vis)-enabled TiO2 (N,C-TiO2) film, which was deposited by codoping nitrogen (N) and carbon (C) ions into a TiO2 lattice using direct current magnetron sputtering. The resulting microporous TiO2-WO3/TiO2 film with a 0.38-?m-thick N,C-TiO2 top-layer exhibited high photocatalytic activity in methylene blue (MB) degradation among samples under ultraviolet (UV) and Vis irradiation. This is attributable to the synergetic effect of two-step preparation method, which provides a highly porous microstructure and the well-crystallized N,C-TiO2 top-layer. This is because a higher surface area with high crystallinity favors the adsorption of more MB molecules and more photocatalytic active areas. Thus, the microporous TiO2-WO3/TiO2 film has promising applications in the photocatalytic degradation of dye solution under UV and Vis irradiation. These results imply that the microporous WO3/TiO2 can be used as a template of hybrid electrode because it enables rapid fabrication.

Wu, Kee-Rong; Hung, Chung-Hsuang; Yeh, Chung-Wei; Wu, Jiing-Kae

2012-12-01

387

The Effect of Film Thickness and TiO2 Content on Film Formation from PS/TiO2 Nano composites Prepared by Dip-Coating Method  

International Nuclear Information System (INIS)

Steady-state fluorescence (SSF) technique in conjunction with UV-visible (UVV) technique and atomic force microscope (AFM) was used for studying film formation from TiO2 covered nano sized polystyrene (PS) latex particles (320 nm). The effects of film thickness and TiO2 content on the film formation and structure properties of PS/TiO2 composites were studied. For this purpose, two different sets of PS films with thicknesses of 5 and 20?m were prepared from pyrene-(P-) labeled PS particles and covered with various layers of TiO2 using dip-coating method. These films were then annealed at elevated temperatures above glass transition temperature (Tg) of PS in the range of 100-280 degree C. Fluorescence emission intensity, Ip from P and transmitted light intensity, Itr were measured after each annealing step to monitor the stages of film formation. The results showed that film formation from PS latexes occurs on the top surface of PS/TiO2 composites and thus developed independent of TiO2 content for both film sets. But the surface morphology of the films was found to vary with both TiO2 content and film thickness. After removal of PS, thin films provide a quite ordered porous structure while thick films showed non porous structure.

388

Nanostructure of photocatalytic TiO 2 films sputtered at temperatures below 200 °C  

Science.gov (United States)

The article reports on correlations between the process parameters of reactive pulsed dc magnetron sputtering, physical properties and the photocatalytic activity (PCA) of TiO 2 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 + O 2 atmosphere in oxide mode of sputtering. The TiO 2 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 TiO 2 film with UV light was used for characterization of the film PCA. It was found that (i) the partial pressure of oxygen p and the total sputtering gas pressure pT are the key deposition parameters influencing the TiO 2 film phase composition that directly affects its PCA, (ii) the structure of sputtered TiO 2 films varies along the growth direction from the film/substrate interface to the film surface, (iii) ˜500 nm thick anatase TiO 2 films with high PCA were prepared and (iv) the structure of sputtered TiO 2 films is not affected by the substrate surface temperature Tsurf when Tsurf PCA of TiO 2 films and results in a decrease of maximum value of Tsurf necessary for the creation of nanocrystalline nc-TiO 2 film. It was demonstrated that crystalline TiO 2 films with high PCA can be sputtered at Tsurf ? 130 °C. Based on o