Preparation of an orthodontic bracket coated with an nitrogen-doped TiO(2-x)N(y) thin film and examination of its antimicrobial performance.

PubMed

Cao, Baocheng; Wang, Yuhua; Li, Na; Liu, Bin; Zhang, Yingjie

2013-01-01

A bracket coated with a nitrogen-doped (N-doped) TiO(2-x)N(y) thin film was prepared using the RF magnetron sputtering method. The physicochemical properties of the thin film were measured using X-ray diffraction and energy-dispersive X-ray spectrometry, while the antimicrobial activity of the bracket against common oral pathogenic microbes was assessed on the basis of colony counts. The rate of antimicrobial activity of the bracket coated with nano-TiO(2-x)N(y) thin film against Streptococcus mutans, Lactobacillus acidophilus, Actinomyces viscous, and Candida albicans was 95.19%, 91.00%, 69.44%, and 98.86%, respectively. Scanning electron microscopy showed that fewer microbes adhered to the surface of this newly designed bracket than to the surface of the normal edgewise bracket. The brackets coated with the N-doped TiO(2-x)N(y) thin film showed high antimicrobial and bacterial adhesive properties against normal oral pathogenic bacterial through visible light, which is effective in prevention of enamel demineralization and gingivitis in orthodontic patients.

Synthesis and characterization of heteroleptic titanium MOCVD precursors for TiO2 thin films.

PubMed

Kim, Euk Hyun; Lim, Min Hyuk; Lah, Myoung Soo; Koo, Sang Man

2018-02-13

Heteroleptic titanium alkoxides with three different ligands, i.e., [Ti(O i Pr)(X)(Y)] (X = tridentate, Y = bidentate ligands), were synthesized to find efficient metal organic chemical vapor deposition (MOCVD) precursors for TiO 2 thin films. Acetylacetone (acacH) or 2,2,6,6-tetramethyl-3,5-heptanedione (thdH) was employed as a bidentate ligand, while N-methyldiethanolamine (MDEA) was employed as a tridentate ligand. It was expected that the oxygen and moisture susceptibility of titanium alkoxides, as well as their tendency to form oligomers, would be greatly reduced by placing multidentate and bulky ligands around the center Ti atom. The synthesized heteroleptic titanium alkoxides were characterized both physicochemically and crystallographically, and their thermal behaviors were also investigated. [Ti(O i Pr)(MDEA)(thd)] was found to be monomeric and stable against moisture; it also showed good volatility in the temperature window between volatilization and decomposition. This material was used as a single-source precursor during MOCVD to generate TiO 2 thin films on silicon wafers. The high thermal stability of [Ti(O i Pr)(MDEA)(thd)] enabled the fabrication of TiO 2 films over a wide temperature range, with steady growth rates between 500 and 800 °C.

Observation of shift in band gap with annealing in hydrothermally synthesized TiO2-thin films

NASA Astrophysics Data System (ADS)

Pawar, Vani; Jha, Pardeep K.; Singh, Prabhakar

2018-05-01

Anatase TiO2 thin films were synthesized by hydrothermal method. The films were fabricated on a glass substrate by spin coating unit and annealed at 500 °C for 2 hours in ambient atmosphere. The effect of annealing on microstructure and optical properties of TiO2 thin films namely, just deposited and annealed thin film were investigated. The XRD data confirms the tetragonal crystalline structure of the films with space group I41/amd. The surface morphology suggests that TiO2 particles are almost homogeneous in size and annealing of the film affect the grain growth of the particles. The band gap energy increases from 2.81 to 3.34 eV. On the basis of our observation, it can be concluded that the annealing of TiO2 thin films enhances the absorption range and it may find potential application in the field of solar cells.

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

NASA Astrophysics Data System (ADS)

Srivastava, Subodh; Sharma, S. S.; Sharma, Preetam; Sharma, Vinay; Rajura, Rajveer Singh; Singh, M.; Vijay, Y. K.

2014-04-01

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.

Gas sensing properties of very thin TiO2 films prepared by atomic layer deposition (ALD)

NASA Astrophysics Data System (ADS)

Boyadjiev, S.; Georgieva, V.; Vergov, L.; Baji, Zs; Gáber, F.; Szilágyi, I. M.

2014-11-01

Very thin titanium dioxide (TiO2) films of less than 10 nm were deposited by atomic layer deposition (ALD) in order to study their gas sensing properties. Applying the quartz crystal microbalance (QCM) method, prototype structures with the TiO2 ALD deposited thin films were tested for sensitivity to NO2. Although being very thin, the films were sensitive at room temperature and could register low concentrations as 50-100 ppm. The sorption is fully reversible and the films seem to be capable to detect for long term. These initial results for very thin ALD deposited TiO2 films give a promising approach for producing gas sensors working at room temperature on a fast, simple and cost-effective technology.

Electrochemical properties of thin films of V2O5 doped with TiO2

NASA Astrophysics Data System (ADS)

Moura, E. A.; Cholant, C. M.; Balboni, R. D. C.; Westphal, T. M.; Lemos, R. M. J.; Azevedo, C. F.; Gündel, A.; Flores, W. H.; Gomez, J. A.; Ely, F.; Pawlicka, A.; Avellaneda, C. O.

2018-08-01

The paper presents a systematic study of the electrochromic properties of thin films of V2O5:TiO2 for a possible utilization as counter-electrode in electrochromic devices. The V2O5:TiO2 thin films were prepared by the sol-gel process and deposited on a substrate of fluorine-tin oxide transparent electrode (FTO) using the dip coating technique and heat treatment at 350 °C for 30 min. The films were characterized by chronocoulometry, cyclic voltammetry (CV), UV-Vis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), profilometry, and X-ray diffraction (XRD). The best results were obtained for the film of V2O5 with 7.5 mol% of TiO2, which presented highest ion storage capacity of ∼106 mC cm-2 and redox reversibility of 1. The diffusion of the Li+ ions into the thin films was modeled by solving Fick equations with appropriate boundary conditions for a plane sheet geometry. Besides that, these films showed optical modulation of 35% at 633 nm after coloration and bleaching. The XRD patterns revealed that the films have an orthorhombic crystal structure; the AFM and the profilometry confirmed roughness and thickness of 16.76 and 617 nm, respectively.

Photocatalytic Antibacterial Performance of Glass Fibers Thin Film Coated with N-Doped SnO 2 /TiO 2

PubMed Central

Sikong, Lek; Niyomwas, Sutham; Rachpech, Vishnu

2014-01-01

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

Photocatalytic thin films containing TiO2:N nanopowders obtained by the layer-by-layer self-assembling method

NASA Astrophysics Data System (ADS)

Rojas-Blanco, L.; Urzúa, M. D.; Ramírez-Bon, R.; Espinoza Beltrán, F. J.

2012-01-01

In this work, TiO2-N powders were synthesized by high-energy ball milling, using commercial titanium dioxide (TiO2) in the anatase phase and urea to introduce nitrogen into TiO2 in order to enhance their photocatalytic properties in the visible spectral region. Several samples were prepared by milling a mixture of TiO2-urea during 2, 4, 8, 12 and 24 h and characterized by spectroscopic and analytical techniques. X-ray diffraction (XRD) results showed the coexistence of anatase and high-pressure srilankite TiO2 crystalline phases in the samples. Scanning electron microscopy (SEM) revealed that the grain size of the powder samples decreases to 200 nm at 24 h milling time. UV-Vis diffuse reflectance spectroscopic data showed a clear red-shift in the onset of light absorption from 387 to 469 nm as consequence of nitrogen doping in the samples. The photocatalytic activity of the TiO2-N samples was evaluated by methylene blue degradation under visible light irradiation. It was found that TiO2-N samples had higher photocatalytic activity than undoped TiO2 samples, which could be assigned to the effect of introducing N atoms and XPS results confirm it. Using polyethylenimine (PEI), transparent thin films of TiO2-N nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 15 min.

Experimental Study of Acid Treatment Toward Characterization of Structural, Optical, and Morphological Properties of TiO2-SnO2 Composite Thin Film

NASA Astrophysics Data System (ADS)

Fajar, M. N.; Hidayat, R.; Triwikantoro; Endarko

2018-04-01

The TiO2-SnO2 thin film with single and double-layer structure has successfully synthesized on FTO (Fluorine-doped Tin Oxide) substrate using the screen printing technique. The structural, optical, and morphological properties of the film were investigated by XRD, UV-Vis, and SEM, respectively. The results showed that the single and double-layer structure of TiO2-SnO2 thin film has mixed phase with a strong formation of casseritte phase. The acid treatment effect on TiO2-SnO2 thin film decreases the peak intensity of anatase phase formation and thin film’s absorbance values. The morphological study is also revealed that the single layer TiO2-SnO2 thin film had a more porous nature and decreased particle size distribution after acid treatment, while the double-layer TiO2-SnO2 thin film Eroded due to acid treatment.

Impact of bimetal electrodes on dielectric properties of TiO2 and Al-doped TiO2 films.

PubMed

Kim, Seong Keun; Han, Sora; Jeon, Woojin; Yoon, Jung Ho; Han, Jeong Hwan; Lee, Woongkyu; Hwang, Cheol Seong

2012-09-26

Rutile structured Al-doped TiO(2) (ATO) and TiO(2) films were grown on bimetal electrodes (thin Ru/thick TiN, Pt, and Ir) for high-performance capacitors. The work function of the top Ru layer decreased on TiN and increased on Pt and Ir when it was thinner than ~2 nm, suggesting that the lower metal within the electrodes influences the work function of the very thin Ru layer. The use of the lower electrode with a high work function for bottom electrode eventually improves the leakage current properties of the capacitor at a very thin Ru top layer (≤2 nm) because of the increased Schottky barrier height at the interface between the dielectric and the bottom electrode. The thin Ru layer was necessary to achieve the rutile structured ATO and TiO(2) dielectric films.

Study of nanoparticles TiO2 thin films on p-type silicon substrate using different alcoholic solvents

NASA Astrophysics Data System (ADS)

Muaz, A. K. M.; Hashim, U.; Arshad, M. K. Md.; Ruslinda, A. R.; Ayub, R. M.; Gopinath, Subash C. B.; Voon, C. H.; Liu, Wei-Wen; Foo, K. L.

2016-07-01

In this paper, sol-gel method spin coating technique is adopted to prepare nanoparticles titanium dioxide (TiO2) thin films. The prepared TiO2 sol was synthesized using titanium butoxide act as a precursor and subjected to deposited on the p-type silicon oxide (p-SiO2) and glass slide substrates under room temperature. The effect of different alcoholic solvents of methanol and ethanol on the structural, morphological, optical and electrical properties were systematically investigated. The coated TiO2 thin films were annealed in furnace at 773 K for 1 h. The structural properties of the TiO2 films were examined with X-ray Diffraction (XRD). From the XRD analysis, both solvents showing good crystallinity with anatase phase were the predominant structure. Atomic Force Microscopy (AFM) was employed to study the morphological of the thin films. The optical properties were investigated by Ultraviolet-visible (UV-Vis) spectroscopy were found that ethanol as a solvent give a higher optical transmittance if compare to the methanol solvent. The electrical properties of the nanoparticles TiO2 thin films were measured using two-point-probe technique.

Annealing effect on the structural, morphological and electrical properties of TiO2/ZnO bilayer thin films

NASA Astrophysics Data System (ADS)

Khan, M. I.; Imran, S.; Shahnawaz; Saleem, Muhammad; Ur Rehman, Saif

2018-03-01

The effect of annealing temperature on the structural, morphological and electrical properties of TiO2/ZnO (TZ) thin films has been observed. Bilayer thin films of TiO2/ZnO are deposited on FTO glass substrate by spray pyrolysis method. After deposition, these films are annealed at 573 K, 723 K and 873 K. XRD shows that TiO2 is present in anatase phase only and ZnO is present in hexagonal phase. No other phases of TiO2 and ZnO are present. Also, there is no evidence of other compounds like Zn-Ti etc. It also shows that the average grain size of TiO2/ZnO films is increased by increasing annealing temperature. AFM (Atomic force microscope) showed that the average roughness of TiO2/ZnO films is decreased at temperature 573-723 K and then increased at 873 K. The calculated average sheet resistivity of thin films annealed at 573 K, 723 K and 873 K is 152.28 × 102, 75.29 × 102 and 63.34 × 102 ohm-m respectively. This decrease in sheet resistivity might be due to the increment of electron concentration with increasing thickness and the temperature of thin films.

Antibacterial effect of visible light reactive TiO2/Ag nanocomposite thin film on the orthodontic appliances.

PubMed

Yun, Kwidug; Oh, Gyejeong; Vang, Mongsook; Yang, Hongso; Lim, Hyunpil; Koh, Jeongtae; Jeong, Woonjo; Yoon, Dongjoo; Lee, Kyungku; Lee, Kwangmin; Park, Sangwon

2011-08-01

This study evaluated the antibacterial effect of a visible light reactive TiO2/Ag nanocomposite thin film on dental orthodontic wire (STS 304 wire). The growth of S. mutans and A. actinomycetemcomitans was suppressed on the specimens coated with TiO2/Ag compared to the uncoated specimens. The antibacterial effect of the TiO2/Ag nanocomposite thin film was improved under visible light irradiation.

Structural, Morphological, Optical and Photocatalytic Properties of Y, N-Doped and Codoped TiO2 Thin Films

PubMed Central

Hamden, Zeineb; Conceição, David; Boufi, Sami; Vieira Ferreira, Luís Filipe; Bouattour, Soraa

2017-01-01

Pure TiO2, Y-N single-doped and codoped TiO2 powders and thin films deposited on glass beads were successfully prepared using dip-coating and sol-gel methods. The samples were analyzed using grazing angle X-ray diffraction (GXRD), Raman spectroscopy, time resolved luminescence, ground state diffuse reflectance absorption and scanning electron microscopy (SEM). According to the GXRD patterns and micro-Raman spectra, only the anatase form of TiO2 was made evident. Ground state diffuse reflectance absorption studies showed that doping with N or codoping with N and Y led to an increase of the band gap. Laser induced luminescence analysis revealed a decrease in the recombination rate of the photogenerated holes and electrons. The photocatalytic activity of supported catalysts, toward the degradation of toluidine, revealed a meaningful enhancement upon codoping samples at a level of 2% (atomic ratio). The photocatalytic activity of the material and its reactivity can be attributed to a reduced, but significant, direct photoexcitation of the semiconductor by the halogen lamp, together with a charge-transfer-complex mechanism, or with the formation of surface oxygen vacancies by the N dopant atoms. PMID:28772962

Effect of rapid thermal annealing on nanocrystalline TiO2 thin films synthesized by swift heavy ion irradiation

NASA Astrophysics Data System (ADS)

Thakurdesai, Madhavi; Kanjilal, D.; Bhattacharyya, Varsha

2012-08-01

Irradiation by swift heavy ions (SHI) is unique tool to synthesize nanocrystalline thin films. We have reported transformation of 100 nm thick amorphous films into nanocrystalline film due to irradiation by 100 MeV Ag ion beam. Oblate shaped nanoparticles having anatase phase of TiO2 were formed on the surface of the irradiated films. In the present investigation, these films are annealed at 350 °C for 2 min in oxygen atmosphere by Rapid Thermal Annealing (RTA) method. During RTA processing, the temperature rises abruptly and this thermal instability is expected to alter surface morphology, structural and optical properties of nanocrystalline TiO2 thin films. Thus in the present work, effect of RTA on SHI induced nanocrystalline thin films of TiO2 is studied. The effect of RTA processing on the shape and size of TiO2 nanoparticles is studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Glancing Angle X-ray Diffraction (GAXRD) studies are carried to investigate structural changes induced by RTA processing. Optical characterization is carried out by UV-vis spectroscopy and photoluminescence (PL) spectroscopy. The changes observed in structural and optical properties of nanocrystalline TiO2 thin films after RTA processing are attributed to the annihilation of SHI induced defects.

Rapid fabrication of mesoporous TiO2 thin films by pulsed fibre laser for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Hadi, Aseel; Alhabradi, Mansour; Chen, Qian; Liu, Hong; Guo, Wei; Curioni, Michele; Cernik, Robert; Liu, Zhu

2018-01-01

In this paper we demonstrate for the first time that a fibre laser with a wavelength of 1070 nm and a pulse width of milliseconds can be applied to generate mesoporous nanocrystalline (nc) TiO2 thin films on ITO coated glass in ambient atmosphere, by complete vaporisation of organic binder and inter-connection of TiO2 nanoparticles, without thermally damaging the ITO layer and the glass substrate. The fabrication of the mesoporous TiO2 thin films was achieved by stationary laser beam irradiation of 1 min. The dye sensitized solar cell (DSSC) with the laser-sintered TiO2 photoanode reached higher power conversion efficiency (PCE) of 3.20% for the TiO2 film thickness of 6 μm compared with 2.99% for the furnace-sintered. Electrochemical impedance spectroscopy studies revealed that the laser sintering under the optimised condition effectively decreased charge transfer resistance and increased electron lifetime of the TiO2 thin films. The use of the fibre laser with over 40% wall-plug efficiency offers an economically-feasible, industrial viable solution to the major challenge of rapid fabrication of large scale, mass production of mesoporous metal oxide thin film based solar energy systems, potentially for perovskite and monolithic tandem solar cells, in the future.

Polarization-Dependent Raman Spectroscopy of Epitaxial TiO 2 (B) Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jokisaari, Jacob R.; Bayerl, Dylan; Zhang, Kui

2015-12-08

The bronze polymorph of titanium dioxide, known as TiO 2(B), has promising photochemical and electronic properties for potential applications in Li-ion batteries, photocatalysis, chemical sensing, and solar cells. In contrast to previous studies performed with powder samples, which often suffer from impurities and lattice water, here we report Raman spectra from highly crystalline TiO 2(B) films epitaxially grown on Si substrates with a thin SrTiO 3 buffer layer. The reduced background from the Si substrate significantly benefits acquisition of polarization-dependent Raman spectra collected from the high-quality thin films, which are compared to nanopowder results reported in the literature. The experimentalmore » spectra were compared with density functional theory calculations to analyze the atomic displacements associated with each Raman-active vibrational mode. These results provide a standard reference for further investigation of the crystallinity, structure, composition, and properties of TiO 2(B) materials with Raman spectroscopy.« less

Highly antibacterial activity of N-doped TiO2 thin films coated on stainless steel brackets under visible light irradiation

NASA Astrophysics Data System (ADS)

Cao, Shuai; Liu, Bo; Fan, Lingying; Yue, Ziqi; Liu, Bin; Cao, Baocheng

2014-08-01

In this study, the radio frequency (RF) magnetron sputtering method was used to prepare a TiO2 thin film on the surface of stainless steel brackets. Eighteen groups of samples were made according to the experimental parameters. The crystal structure and surface morphology were characterized by X-ray diffraction, and scanning electron microscopy, respectively. The photocatalytic properties under visible light irradiation were evaluated by measuring the degradation ratio of methylene blue. The sputtering temperature was set at 300 °C, and the time was set as 180 min, the ratio of Ar to N was 30:1, and annealing temperature was set at 450 °C. The thin films made under these parameters had the highest visible light photocatalytic activity of all the combinations of parameters tested. Antibacterial activities of the selected thin films were also tested against Lactobacillus acidophilus and Candida albicans. The results demonstrated the thin film prepared under the parameters above showed the highest antibacterial activity.

Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

PubMed Central

Ali, Rizwan; Saleem, Muhammad Rizwan; Pääkkönen, Pertti; Honkanen, Seppo

2015-01-01

We investigate the optical and thermo-optical properties of amorphous TiO2–Al2O3 thin-film bilayers fabricated by atomic layer deposition (ALD). Seven samples of TiO2–Al2O3 bilayers are fabricated by growing Al2O3 films of different thicknesses on the surface of TiO2 films of constant thickness (100 nm). Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE®. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO2 films. The effects of TiO2 surface defects on the films’ thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al2O3 diffusion barrier layers. Increasing the ALD-Al2O3 thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO2. The thermo-optic coefficients of the 100 nm-thick ALD-TiO2 film and 30 nm-thick ALD-Al2O3 film in a bilayer are (0.048 ± 0.134) × 10−4 °C−1 and (0.680 ± 0.313) × 10−4 °C−1, respectively, at a temperature T = 62 °C.

Synthesis and electronic properties of Fe2TiO5 epitaxial thin films

NASA Astrophysics Data System (ADS)

Osada, Motoki; Nishio, Kazunori; Hwang, Harold Y.; Hikita, Yasuyuki

2018-05-01

We investigate the growth phase diagram of pseudobrookite Fe2TiO5 epitaxial thin films on LaAlO3 (001) substrates using pulsed laser deposition. Control of the oxygen partial pressure and temperature during deposition enabled selective stabilization of (100)- and (230)-oriented films. In this regime, we find an optical gap of 2.1 eV and room temperature resistivity in the range of 20-80 Ω cm, which are significantly lower than α-Fe2O3, making Fe2TiO5 potentially an ideal inexpensive visible-light harvesting semiconductor. These results provide a basis to incorporate Fe2TiO5 in oxide heterostructures for photocatalytic and photoelectrochemical applications.

The effect of heat treatment on superhydrophilicity of TiO2 nano thin films

NASA Astrophysics Data System (ADS)

Ashkarran, A. A.; Mohammadizadeh, M. R.

2007-11-01

TiO2 thin films were synthesized 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 166nm 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 10min under 2mW/cm2 UV irradiation. Water droplet on TiO2 thin film on Si(111), Si(100), and quartz substrates is spread to smaller angles rather than glass and polycrystalline Si substrates under UV irradiation.

The effect of TiO2 phase on the surface plasmon resonance of silver thin film

NASA Astrophysics Data System (ADS)

Hong, Ruijin; Jing, Ming; Tao, Chunxian; Zhang, Dawei

2016-10-01

A series of silver films with various thicknesses were deposited on TiO2 covered silica substrates by magnetron sputtering at room temperature. The effects of TiO2 phase on the structure, optical properties and surface plasmon resonance of silver thin films were investigated by x-ray diffraction, optical absorption and Raman scattering measurements, respectively. By adjusting the silver layer thickness, the resonance wavelength shows a redshift, which is due to a change in the electromagnetic field coupling strength from the localized surface plasmons excited between the silver thin film and TiO2 layer. Raman scattering measurement results showed that optical absorption plays an important role in surface plasmon enhancement, which is also related to different crystal phase.

A simple and low temperature process for super-hydrophilic rutile TiO 2 thin films growth

NASA Astrophysics Data System (ADS)

Mane, R. S.; Joo, Oh-Shim; Min, Sun-Ki; Lokhande, C. D.; Han, Sung-Hwan

2006-11-01

We investigate an environmentally friendly aqueous solution system for rutile TiO2 violet color nanocrystalline thin films growth on ITO substrate at room temperature. Film shows considerable absorption in visible region with excitonic maxima at 434 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV-vis, water surface contact angle and energy dispersive X-ray analysis (EDX) techniques in addition to actual photo-image that shows purely rutile phase of TiO2 with violet color, super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 3.15 ± 0.4 nm, characterize the films. Band gap energy of 4.61 eV for direct transition was obtained for the rutile TiO2 films. Film surface shows super-hydrophilic behavior, as exhibited water contact angle was 7°. Strong visible absorption (not due to chlorine) leaves future challenge to use these films in extremely thin absorber (ETA) solar cells.

The Effect of Film Thickness on the Gas Sensing Properties of Ultra-Thin TiO2 Films Deposited by Atomic Layer Deposition

PubMed Central

Wilson, Rachel L.; Blackman, Christopher S.; Carmalt, Claire J.; Stanoiu, Adelina; Di Maggio, Francesco

2018-01-01

Analyte sensitivity for gas sensors based on semiconducting metal oxides should be highly dependent on the film thickness, particularly when that thickness is on the order of the Debye length. This thickness dependence has previously been demonstrated for SnO2 and inferred for TiO2. In this paper, TiO2 thin films have been prepared by Atomic Layer Deposition (ALD) using titanium isopropoxide and water as precursors. The deposition process was performed on standard alumina gas sensor platforms and microscope slides (for analysis purposes), at a temperature of 200 °C. The TiO2 films were exposed to different concentrations of CO, CH4, NO2, NH3 and SO2 to evaluate their gas sensitivities. These experiments showed that the TiO2 film thickness played a dominant role within the conduction mechanism and the pattern of response for the electrical resistance towards CH4 and NH3 exposure indicated typical n-type semiconducting behavior. The effect of relative humidity on the gas sensitivity has also been demonstrated. PMID:29494504

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

NASA Astrophysics Data System (ADS)

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

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.

Synthesis and electronic properties of Fe 2TiO 5 epitaxial thin films

DOE PAGES

Osada, Motoki; Nishio, Kazunori; Hwang, Harold Y.; ...

2018-05-02

Here, we investigate the growth phase diagram of pseudobrookite Fe 2TiO 5 epitaxial thin films on LaAlO 3 (001) substrates using pulsed laser deposition. Control of the oxygen partial pressure and temperature during deposition enabled selective stabilization of (100)- and (230)-oriented films. In this regime, we find an optical gap of 2.1 eV and room temperature resistivity in the range of 20–80 Ω cm, which are significantly lower than α-Fe 2O 3, making Fe 2TiO 5 potentially an ideal inexpensive visible-light harvesting semiconductor. These results provide a basis to incorporate Fe 2TiO 5 in oxide heterostructures for photocatalytic and photoelectrochemicalmore » applications.« less

Enhanced photoelectrochemical and photocatalytic activity of WO3-surface modified TiO2 thin film

NASA Astrophysics Data System (ADS)

Qamar, Mohammad; Drmosh, Qasem; Ahmed, Muhammad I.; Qamaruddin, Muhammad; Yamani, Zain H.

2015-02-01

Development of nanostructured photocatalysts for harnessing solar energy in energy-efficient and environmentally benign way remains an important area of research. Pure and WO3-surface modified thin films of TiO2 were prepared by magnetron sputtering on indium tin oxide glass, and photoelectrochemical and photocatalytic activities of these films were studied. TiO2 particles were <50 nm, while deposited WO3 particles were <20 nm in size. An enhancement in the photocurrent was observed when the TiO2 surface was modified WO3 nanoparticles. Effect of potential, WO3 amount, and radiations of different wavelengths on the photoelectrochemical activity of TiO2 electrodes was investigated. Photocatalytic activity of TiO2 and WO3-modified TiO2 for the decolorization of methyl orange was tested.

Superhydrophilic TiO2 thin film by nanometer scale surface roughness and dangling bonds

NASA Astrophysics Data System (ADS)

Bharti, Bandna; Kumar, Santosh; Kumar, Rajesh

2016-02-01

A remarkable enhancement in the hydrophilic nature of titanium dioxide (TiO2) films is obtained by surface modification in DC-glow discharge plasma. Thin transparent TiO2 films were coated on glass substrate by sol-gel dip coating method, and exposed in DC-glow discharge plasma. The plasma exposed TiO2 film exhibited a significant change in its wetting property contact angle, which is a representative of wetting property, has reduced to considerable limits 3.02° and 1.85° from its initial value 54.40° and 48.82° for deionized water and ethylene glycol, respectively. It is elucidated that the hydrophilic property of plasma exposed TiO2 films dependent mainly upon nanometer scale surface roughness. Variation, from 4.6 nm to 19.8 nm, in the film surface roughness with exposure time was observed by atomic force microscopy (AFM). Analysis of variation in the values of contact angle and surface roughness with increasing plasma exposure time reveal that the surface roughness is the main factor which makes the modified TiO2 film superhydrophilic. However, a contribution of change in the surface states, to the hydrophilic property, is also observed for small values of the plasma exposure time. Based upon nanometer scale surface roughness and dangling bonds, a variation in the surface energy of TiO2 film from 49.38 to 88.92 mJ/m2 is also observed. X-ray photoelectron spectroscopy (XPS) results show change in the surface states of titanium and oxygen. The observed antifogging properties are the direct results of the development of the superhydrophilic wetting characteristics to TiO2 films.

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

NASA Astrophysics Data System (ADS)

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

2010-01-01

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.

Effect of laser irradiation on the structural, morphological and electrical properties of polycrystalline TiO2 thin films

NASA Astrophysics Data System (ADS)

Khan, M. I.; Ali, Asghar

TiO2 thin film is deposited on glass substrate by sol-gel dip coating technique. After deposition, films were irradiated by continuous wave (CW) diode laser at an angle of 45°. XRD shows both the anatase and brookite phases of TiO2. Nano particles of regular and control sizes are appeared in SEM micrographs. Therefore, shape and size of nano particles can be control by using Laser irradiation. The average sheet resistivity of TiO2 thin film irradiated by 0, 2, 4 and 6 min are 6.72 × 105, 5.32 × 105, 3.44 × 105 and 4.95 × 105 (ohm-m) respectively, according to four point probe.

Quantum-dot light-emitting diodes utilizing CdSe /ZnS nanocrystals embedded in TiO2 thin film

NASA Astrophysics Data System (ADS)

Kang, Seung-Hee; Kumar, Ch. Kiran; Lee, Zonghoon; Kim, Kyung-Hyun; Huh, Chul; Kim, Eui-Tae

2008-11-01

Quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated on Si wafers by embedding core-shell CdSe /ZnS nanocrystals in TiO2 thin films via plasma-enhanced metallorganic chemical vapor deposition. The n-TiO2/QDs /p-Si LED devices show typical p-n diode current-voltage and efficient electroluminescence characteristics, which are critically affected by the removal of QD surface ligands. The TiO2/QDs /Si system we presented can offer promising Si-based optoelectronic and electronic device applications utilizing numerous nanocrystals synthesized by colloidal solution chemistry.

Effect of SiO2 addition on photocatalytic activity, water contact angle and mechanical stability of visible light activated TiO2 thin films applied on stainless steel by a sol gel method

NASA Astrophysics Data System (ADS)

Momeni, Mansour; Saghafian, Hasan; Golestani-Fard, Farhad; Barati, Nastaran; Khanahmadi, Amirhossein

2017-01-01

Nanostructured N doped TiO2/20%SiO2 thin films were developed on steel surface via sol gel method using a painting airbrush. Thin films then were calcined at various temperatures in a range of 400-600 °C. The effect of SiO2 addition on phase composition and microstructural evolution of N doped TiO2 films were studied using XRD and FESEM. Optical properties, visible light photocatalytic activity, hydrophilic behavior, and mechanical behavior of the films were also investigated by DRS, methylene blue degradation, water contact angle measurements, and nanoscratch testing. Results indicated that the band gap energy of N doped TiO2/SiO2 was increased from 2.93 to 3.09 eV. Crack formation during calcination was also significantly promoted in the composite films. All composite films demonstrated weaker visible light photocatalytic activities and lower mechanical stability in comparison with N doped TiO2 films. Moreover, the N doped TiO2/SiO2 film calcined at 600 °C showed undesirable hydrophilic behavior with a water contact angle of 57° after 31 h of visible light irradiation. Outcomes of the present study reveal some different results to previous reports on TiO2/SiO2 films. In general, we believe the differences in substrate material as well as application in visible light are the main reasons for the above mentioned contradiction.

A new room temperature gas sensor based on pigment-sensitized TiO2 thin film for amines determination.

PubMed

Yanxiao, Li; Xiao-bo, Zou; Xiao-wei, Huang; Ji-yong, Shi; Jie-wen, Zhao; Holmes, Mel; Hao, Limin

2015-05-15

A new room temperature gas sensor was fabricated with pigment-sensitized TiO2 thin film as the sensing layer. Four natural pigments were extracted from spinach (Spinacia oleracea), red radish (Raphanus sativus L), winter jasmine (Jasminum nudiflorum), and black rice (Oryza sativa L. indica) by ethanol. Natural pigment-sensitized TiO2 sensor was prepared by immersing porous TiO2 films in an ethanol solution containing a natural pigment for 24h. The hybrid organic-inorganic formed films here were firstly exposed to atmospheres containing methylamine vapours with concentrations over the range 2-10 ppm at room temperature. The films sensitized by the pigments from black-rice showed an excellent gas-sensitivity to methylamine among the four natural pigments sensitized films due to the anthocyanins. The relative change resistance, S, of the films increased almost linearly with increasing concentrations of methylamine (r=0.931). At last, the black rice pigment sensitized TiO2 thin film was used to determine the biogenic amines generated by pork during storage. The developed films had good sensitivity to analogous gases such as putrscine, and cadaverine that will increase during storage. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural, Electrical and Optical Properties of TiO2 Thin Film Deposited on the Nano Porous Silicon Template

NASA Astrophysics Data System (ADS)

Bahar, Mahmood; Dermani, Ensieh Khalili

The porous silicon (PSi), which is produced by the electrochemical etching, has been used as a substrate for the growth of the titanium oxide (TiO2) thin films. By using the EBPVD method, TiO2 thin films have been deposited on the surface of the PSi substrate. TiO2/PSi layers were annealed at the temperature of 400∘C, 500∘C and 600∘C for different tests. The morphology and structures of layers were investigated by the scanning electron microscopy (SEM) and X-ray diffraction (XRD). The current-voltage characteristic curves of samples and the ideality factor of heterojunction were studied. The results showed that the electrical properties of the samples change with increase in the annealing temperature. The optical properties of the prepared samples were investigated by using UV-Vis and photoluminescence (PL) spectroscopy. Green light emission of the PSi combined with the blue light and violet-blue emission obtained from the TiO2/PSi PL spectra. The results showed that the optical band gap energy of the PSi has increased from 1.86eV to 2.93eV due to the deposition of TiO2 thin film.

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

NASA Technical Reports Server (NTRS)

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

1977-01-01

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.

Electrochromic TiO2 Thin Film Prepared by Dip-Coating Technique

NASA Astrophysics Data System (ADS)

Suriani, S.; Kamisah, M. M.

2002-12-01

Titanium dioxide (TiO2) thin films were prepared by using sol-gel dip coating technique. The coating solutions were prepared by reacting titanium isopropoxide as precursors and ethanol as solvent. The films were formed on transparent ITO-coated glass by a dip coating technique and final dried at various temperatures up to 600 °C for 30 minutes. The films were characterized with the UV-Vis-NIR Spectrometer, Scanning Electron Microscopy (SEM) and X-ray diffractometer (XRD). XRD results show that the films dried at 600 °C form anatase structure. From the spectroscopic studies, the sample shows electrochromic property.

Optical, Electrical, and Crystal Properties of TiO2 Thin Films Grown by Atomic Layer Deposition on Silicon and Glass Substrates

NASA Astrophysics Data System (ADS)

Kupa, I.; Unal, Y.; Cetin, S. S.; Durna, L.; Topalli, K.; Okyay, A. K.; Ates, H.

2018-05-01

TiO2 thin films have been deposited on glass and Si(100) by atomic layer deposition (ALD) technique using tetrakis(diethylamido)titanium(IV) and water vapor as reactants. Thorough investigation of the properties of the TiO2/glass and TiO2/Si thin films was carried out, varying the deposition temperature in the range from 100°C to 250°C while keeping the number of reaction cycles fixed at 1000. Physical and material property analyses were performed to investigate optical and electrical properties, composition, structure, and morphology. TiO2 films grown by ALD may represent promising materials for future applications in optoelectronic devices.

Synergistic effects of graphene quantum dot sensitization and nitrogen doping of ordered mesoporous TiO2 thin films for water splitting photocatalysis(Conference Presentation)

NASA Astrophysics Data System (ADS)

Islam, Syed Z.; Wanninayake, Namal; Reed, Allen D.; Kim, Doo-Young; Rankin, Stephen E.

2016-10-01

The optical and electronic properties of TiO2 thin films provide tremendous opportunities in several applications including photocatalysis, photovoltaics and photoconductors for energy production. Despite many attractive features of TiO2, critical challenges include the innate inability of TiO2 to absorb visible light and the fast recombination of photoexcited charge carriers. In this study, we prepared ordered mesoporous TiO2 films co-modified by graphene quantum dot sensitization and nitrogen doping (GQD-N-TiO2) for hydrogen production from photoelectrochemical water splitting under visible light irradiation. First, cubic ordered mesoporous TiO2 films were prepared by a surfactant templated sol-gel method. Then, TiO2 films were treated with N2/Ar plasma for the incorporation of substitutional N atoms into the lattice of TiO2. GQDs were prepared by chemically oxidizing carbon nano-onions. The immobilization of GQDs was accomplished by reacting carboxyl groups of GQDs with amine groups of N-TiO2 developed by the prior immobilization of (3-aminopropyl)triethoxysilane (APTES). Successful immobilization of GQDs onto N-TiO2 was probed by UV-Vis, FT-IR, and scanning electron microscopy. Further, zeta potential and contact angle measurements showed enhanced surface charge and hydrophilicity, confirming the successful immobilization of GQDs. The GQD-N-TiO2, N-TiO2 and GQD-TiO2 films showed 400 times, 130 times and 8 times photocurrent enhancement, respectively, compared to TiO2 films for water splitting with a halogen bulb light source. This outstanding enhancement is attributed to the high surface area of mesoporous films and synergistic effects of nitrogen doping and GQD sensitization resulting in enhanced visible light absorption, efficient charge separation and transport.

In situ photoelectrochemical/photocatalytic study of a dye discoloration in a microreactor system using TiO2 thin films.

PubMed

Montero-Ocampo, C; Gago, A; Abadias, G; Gombert, B; Alonso-Vante, N

2012-11-01

In this work, we report in situ studies of UV photoelectrocatalytic discoloration of a dye (indigo carmine) by a TiO(2) thin film in a microreactor to demonstrate the driving force of the applied electrode potential and the dye flow rate toward dye discoloration kinetics. TiO(2) 65-nm-thick thin films were deposited by PVD magnetron sputtering technique on a conducting glass substrate of fluorinated tin oxide. A microreactor to measure the discoloration rate, the electrode potential, and the photocurrent in situ, was developed. The dye solutions, before and after measurements in the microreactor, were analyzed by Raman spectroscopy. The annealed TiO(2) thin films had anatase structure with preferential orientation (101). The discoloration rate of the dye increased with the applied potential to TiO(2) electrode. Further, acceleration of the photocatalytic reaction was achieved by utilizing dye flow recirculation to the microreactor. In both cases the photoelectrochemical/photocatalytic discoloration kinetics of the dye follows the Langmuir-Hinshelwood model, with first-order kinetics. The feasibility of dye discoloration on TiO(2) thin film electrodes, prepared by magnetron sputtering using a flow microreactor system, has been clearly demonstrated. The discoloration rate is enhanced by applying a positive potential (E (AP)) and/or increasing the flow rate. The fastest discoloration and shortest irradiation time (50 min) produced 80% discoloration with an external anodic potential of 0.931 V and a flow rate of 12.2 mL min(-1).

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

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 ΔEV(100) > ΔEV(111) > ΔEV(110) and a conduction band-offset relation of ΔEC(110) > ΔEC(111) > ΔEC(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-κ dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors.

A weak-light-responsive TiO2/g-C3N4 composite film: photocatalytic activity under low-intensity light irradiation.

PubMed

Wang, Peifang; Guo, Xiang; Rao, Lei; Wang, Chao; Guo, Yong; Zhang, Lixin

2018-05-10

A TiO 2 /g-C 3 N 4 composite photocatalytic film was prepared by in situ synthesis method and its photocatalytic capability under weak-visible-light condition was studied. The co-precursor with different ratio of melamine and TiO 2 sol-gel precursor were treated using ultrasonic mixing, physical deposition, and co-sintering method to form the smooth, white-yellow, and compact TiO 2 /g-C 3 N 4 composite films. The prepared TiO 2 /g-C 3 N 4 materials were characterized by SEM, TEM, EDS, XRD, BET, VBXPS, and UV-vis diffuse reflectance spectra. The results of composite showed that TiO 2 and g-C 3 N 4 have close interfacial connections which are favorable to charge transfer between these two semiconductors with suitable band structure, g-C 3 N 4 retard the anatase-to-rutile phase transition of TiO 2 significantly, the specific surface area were increased with g-C 3 N 4 ratio raised. Under weak-light irradiation, composite films photocatalytic experiments exhibited RhB removal efficiency approaching 90% after three recycles. Powders suspension degradation experiments revealed the removal efficiency of TiO 2 /g-C 3 N 4 (90.8%) was higher than pure TiO 2 (52.1%) and slightly lower than pure g-C 3 N 4 (96.6%). By control experiment, the enhanced photocatalysis is ascribed to the combination of TiO 2 and g-C 3 N 4 , which not only produced thin films with greater stability but also formed heterojunctions that can be favorable to charge transfer between these two semiconductors with suitable band structure. This study presents the potential application of photocatalytic film in the wastewater treatment under weak-light situation.

Enhanced Charge Extraction of Li-Doped TiO2 for Efficient Thermal-Evaporated Sb2S3 Thin Film Solar Cells

PubMed Central

Lan, Chunfeng; Luo, Jingting; Lan, Huabin; Fan, Bo; Peng, Huanxin; Zhao, Jun; Sun, Huibin; Zheng, Zhuanghao; Liang, Guangxing; Fan, Ping

2018-01-01

We provided a new method to improve the efficiency of Sb2S3 thin film solar cells. The TiO2 electron transport layers were doped by lithium to improve their charge extraction properties for the thermal-evaporated Sb2S3 solar cells. The Mott-Schottky curves suggested a change of energy band and faster charge transport in the Li-doped TiO2 films. Compared with the undoped TiO2, Li-doped mesoporous TiO2 dramatically improved the photo-voltaic performance of the thermal-evaporated Sb2S3 thin film solar cells, with the average power conversion efficiency (PCE) increasing from 1.79% to 4.03%, as well as the improved open-voltage (Voc), short-circuit current (Jsc) and fill factors. The best device based on Li-doped TiO2 achieved a power conversion efficiency up to 4.42% as well as a Voc of 0.645 V, which are the highest values among the reported thermal-evaporated Sb2S3 solar cells. This study showed that Li-doping on TiO2 can effectively enhance the charge extraction properties of electron transport layers, offering a new strategy to improve the efficiency of Sb2S3-based solar cells. PMID:29495612

Tunability of p- and n-channel TiOx thin film transistors.

PubMed

Peng, Wu-Chang; Chen, Yao-Ching; He, Ju-Liang; Ou, Sin-Liang; Horng, Ray-Hua; Wuu, Dong-Sing

2018-06-18

To acquire device-quality TiO x films usually needs high-temperature growth or additional post-thermal treatment. However, both processes make it very difficult to form the p-type TiO x even under oxygen-poor growth condition. With the aid of high energy generated by high power impulse magnetron sputtering (HIPIMS), a highly stable p-type TiO x film with good quality can be achieved. In this research, by varying the oxygen flow rate, p-type γ-TiO and n-type TiO 2 films were both prepared by HIPIMS. Furthermore, p- and n-type thin film transistors employing γ-TiO and TiO 2 as channel layers possess the field-effect carrier mobilities of 0.2 and 0.7 cm 2 /Vs, while their on/off current ratios are 1.7 × 10 4 and 2.5 × 10 5 , respectively. The first presented p-type γ-TiO TFT is a major breakthrough for fabricating the TiO x -based p-n combinational devices. Additionally, our work also confirms HIPIMS offers the possibility of growing both p- and n-type conductive oxides, significantly expanding the practical usage of this technique.

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

PubMed

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

2013-04-01

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. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis and Characterization of TiO2/SiO2 Thin Film via Sol-Gel Method

NASA Astrophysics Data System (ADS)

Halin, D. S. C.; Abdullah, M. M. A. B.; Mahmed, N.; Malek, S. N. A. Abdul; Vizureanu, P.; Azhari, A. W.

2017-06-01

TiO2/SiO2 thin films were prepared by sol-gel spin coating method. Structural, surface morphology and optical properties were investigated for different annealing temperatures at 300°C, 400°C and 500°C. X-ray diffraction pattern show that brookite TiO2 crystalline phase with SiO2 phase presence at 300°C. At higher temperatures of 400-500°C, the only phase presence was brookite. The surface morphology of film was characterized by scanning electron microscopy (SEM). The films annealed at 300°C shows an agglomeration of small flaky with crack free. When the temperature of annealing increase to 400-500°C, the films with large flaky and large cracks film were formed which was due to surface tension between the film and the air during the drying process. The UV-Vis spectroscopy shows that the film exhibits a low transmittance around 30% which was due to the substrate is inhomogeneously covered by the films. In order to improve the coverage of the film on the substrate, it has to repeatable the spin coating to ensure the substrate is fully covered by the films.

Strain Effects in Epitaxial VO2 Thin Films on Columnar Buffer-Layer TiO2/Al2O3 Virtual Substrates.

PubMed

Breckenfeld, Eric; Kim, Heungsoo; Burgess, Katherine; Charipar, Nicholas; Cheng, Shu-Fan; Stroud, Rhonda; Piqué, Alberto

2017-01-18

Epitaxial VO 2 /TiO 2 thin film heterostructures were grown on (100) (m-cut) Al 2 O 3 substrates via pulsed laser deposition. We have demonstrated the ability to reduce the semiconductor-metal transition (SMT) temperature of VO 2 to ∼44 °C while retaining a 4 order of magnitude SMT using the TiO 2 buffer layer. A combination of electrical transport and X-ray diffraction reciprocal space mapping studies help examine the specific strain states of VO 2 /TiO 2 /Al 2 O 3 heterostructures as a function of TiO 2 film growth temperatures. Atomic force microscopy and transmission electron microscopy analyses show that the columnar microstructure present in TiO 2 buffer films is responsible for the partially strained VO 2 film behavior and subsequently favorable transport characteristics with a lower SMT temperature. Such findings are of crucial importance for both the technological implementation of the VO 2 system, where reduction of its SMT temperature is widely sought, as well as the broader complex oxide community, where greater understanding of the evolution of microstructure, strain, and functional properties is a high priority.

Effect of sintering on transparent TiO2 18NR-T type thin films as the working electrode for transparent solar cells

NASA Astrophysics Data System (ADS)

Supriyanto, A.; Nandani; Wahyuningsih, S.; Ramelan, A. H.

2018-03-01

The working electrode based on semiconductor transparent TiO2 type 18NR-T for transparent solar cells have been grown by screen printing method. This study aim is to determine the effect of sintering on TiO2 thin films transparent as the working electrode of transparent solar cells. TiO2 films will be sintered at temperature 450°C, 500°C, 550°C and 600°C. TiO2 films optical properties were characterized using UV-Vis spectrophotometer, electrical properties were characterized using 4 point probemethods and the crystallization was characterized by X-Ray Diffraction (XRD). The lowest transmittance due to the treatment of annealing temperature variations is 550°C because the 550°C TiO2 layer is more absorbing. The peaks resulted from the annealing temperature treatment show that the high temperature the more anatase peaks. Characterization using four-point probe showed that the highest conductivity of TiO2 18NR-T thin film was 2.42 x 102 Ω-1m-1 at annealing temperature 550°C.

Synthesis, characterization and application of Co doped TiO2 multilayer thin films

NASA Astrophysics Data System (ADS)

Khan, M. I.

2018-06-01

To use the visible portion of solar light, 2% cobalt doped TiO2 (Co: TiO2) multilayer thin films having 1, 2, 3 and 4 stacked layers have been deposited on FTO substrates using spray pyrolysis technique. XRD results show that 1 and 2 layers of films have anatase phase. Brookite phase has been appeared at the 3 and 4 layered films. The average grain size of 1, 2, 3 and 4 layers of films are 14.4, 23.5, 29.7 and 33.6 nm respectively. UV-Vis results show that 4th layer film has high absorption in the visible region. The calculated Eg of 1, 2, 3 and 4 layers is 3.54, 3.42, 3.30 and 3.03 eV respectively. The calculated average sheet resistivity of 1, 2, 3 and 4 layers of films is 7.68 × 104, 4.54 × 104, 8.85 × 103 and 7.95 × 102 (ohm-m) respectively, according to four point probe technique. Solar simulator results show that highest solar conversion efficiency (5.6%) has been obtained by using 3 stacked layers photoanode. This new structure in the form of stack layers provides a way to improve the efficiency of optoelectronic devices.

Thin-Film Photoluminescent Properties and the Atomistic Model of Mg2TiO4 as a Non-rare Earth Matrix Material for Red-Emitting Phosphor

NASA Astrophysics Data System (ADS)

Huang, Chieh-Szu; Chang, Ming-Chuan; Huang, Cheng-Liang; Lin, Shih-kang

2016-12-01

Thin-film electroluminescent devices are promising solid-state lighting devices. Red light-emitting phosphor is the key component to be integrated with the well-established blue light-emitting diode chips for stimulating natural sunlight. However, environmentally hazardous rare-earth (RE) dopants, e.g. Eu2+ and Ce2+, are commonly used for red-emitting phosphors. Mg2TiO4 inverse spinel has been reported as a promising matrix material for "RE-free" red light luminescent material. In this paper, Mg2TiO4 inverse spinel is investigated using both experimental and theoretical approaches. The Mg2TiO4 thin films were deposited on Si (100) substrates using either spin-coating with the sol-gel process, or radio frequency sputtering, and annealed at various temperatures ranging from 600°C to 900°C. The crystallinity, microstructures, and photoluminescent properties of the Mg2TiO4 thin films were characterized. In addition, the atomistic model of the Mg2TiO4 inverse spinel was constructed, and the electronic band structure of Mg2TiO4 was calculated based on density functional theory. Essential physical and optoelectronic properties of the Mg2TiO4 luminance material as well as its optimal thin-film processing conditions were comprehensively reported.

Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Islam, Syed Z.; Reed, Allen; Nagpure, Suraj

In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO 2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H 2 plasma treatment makes TiO 2 films black, with broad-spectrum enhancementmore » of visible light absorption, and XPS analysis shows peak for Ti 3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO 2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO 2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO 2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO 2 is accompanied by significant hydrogen uptake and not just Ti 3+ generation or surface disordering.« less

Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

DOE PAGES

Islam, Syed Z.; Reed, Allen; Nagpure, Suraj; ...

2017-10-26

In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO 2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H 2 plasma treatment makes TiO 2 films black, with broad-spectrum enhancementmore » of visible light absorption, and XPS analysis shows peak for Ti 3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO 2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO 2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO 2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO 2 is accompanied by significant hydrogen uptake and not just Ti 3+ generation or surface disordering.« less

Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Islam, Syed Z.; Reed, Allen; Nagpure, Suraj

2018-05-01

In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H2 plasma treatment makes TiO2 films black, with broad-spectrum enhancement of visible lightmore » absorption, and XPS analysis shows peak for Ti3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO2 is accompanied by significant hydrogen uptake and not just Ti3+ generation or surface disordering.« less

Evolution of structural and optical properties of rutile TiO2 thin films synthesized at room temperature by chemical bath deposition method

NASA Astrophysics Data System (ADS)

Mayabadi, A. H.; Waman, V. S.; Kamble, M. M.; Ghosh, S. S.; Gabhale, B. B.; Rondiya, S. R.; Rokade, A. V.; Khadtare, S. S.; Sathe, V. G.; Pathan, H. M.; Gosavi, S. W.; Jadkar, S. R.

2014-02-01

Nanocrystalline thin films of TiO2 were prepared on glass substrates from an aqueous solution of TiCl3 and NH4OH at room temperature using the simple and cost-effective chemical bath deposition (CBD) method. The influence of deposition time on structural, morphological and optical properties was systematically investigated. TiO2 transition from a mixed anatase-rutile phase to a pure rutile phase was revealed by low-angle XRD and Raman spectroscopy. Rutile phase formation was confirmed by FTIR spectroscopy. Scanning electron micrographs revealed that the multigrain structure of as-deposited TiO2 thin films was completely converted into semi-spherical nanoparticles. Optical studies showed that rutile thin films had a high absorption coefficient and a direct bandgap. The optical bandgap decreased slightly (3.29-3.07 eV) with increasing deposition time. The ease of deposition of rutile thin films at low temperature is useful for the fabrication of extremely thin absorber (ETA) solar cells, dye-sensitized solar cells, and gas sensors.

TiO2/SiO2 porous composite thin films: Role of TiO2 areal loading and modification with gold nanospheres on the photocatalytic activity

NASA Astrophysics Data System (ADS)

Levchuk, Irina; Sillanpää, Mika; Guillard, Chantal; Gregori, Damia; Chateau, Denis; Parola, Stephane

2016-10-01

The aim of the work was to study photocatalytic activity of composite TiO2/Au/SiO2 thin films. Coatings were prepared using sol-gel technique. Physicochemical parameters of coatings were characterized using UV-vis spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), ellipsometry, tactile measurements, goniometry and diffuse reflectance measurements. The photocatalytic activity of the films was tested in batch mode using aqueous solution of formic acid. Changes of formic acid concentration were determined by means of high pressure liquid chromatography (HPLC). Increase of initial degradation rate of formic acid was detected for TiO2/Au/SiO2 films with gold nanoparticle's load 0.5 wt.% and 1.25 wt.%. However, deeper insights using more detailed characterization of these coatings demonstrated that the improvement of the photocatalytic activity is more probably attributed to an increase in the areal loading of TiO2.

Influence of surfactant and annealing temperature on optical properties of sol-gel derived nano-crystalline TiO2 thin films.

PubMed

Vishwas, M; Sharma, Sudhir Kumar; Rao, K Narasimha; Mohan, S; Gowda, K V Arjuna; Chakradhar, R P S

2010-03-01

Titanium dioxide thin films have been synthesized by sol-gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 degrees C. The influence of surfactant and annealing temperature on optical properties of TiO(2) thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO(2) films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO(2) films was estimated by Tauc's method at different annealing temperature. Copyright 2010 Elsevier B.V. All rights reserved.

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

PubMed Central

Tsao, Yu-Chia; Tsai, Woo-Hu; Shih, Wen-Ching; Wu, Mu-Shiang

2013-01-01

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. PMID:23881144

An in-situ real-time optical fiber sensor based on surface plasmon resonance for monitoring the growth of TiO2 thin films.

PubMed

Tsao, Yu-Chia; Tsai, Woo-Hu; Shih, Wen-Ching; Wu, Mu-Shiang

2013-07-23

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.

Oxygen vacancy induced phase formation and room temperature ferromagnetism in undoped and Co-doped TiO2 thin films

NASA Astrophysics Data System (ADS)

Mohanty, P.; Mishra, N. C.; Choudhary, R. J.; Banerjee, A.; Shripathi, T.; Lalla, N. P.; Annapoorni, S.; Rath, Chandana

2012-08-01

TiO2 and Co-doped TiO2 (CTO) thin films deposited at various oxygen partial pressures by pulsed laser deposition exhibit room temperature ferromagnetism (RTFM) independent of their phase. Films deposited at 0.1 mTorr oxygen partial pressure show a complete rutile phase confirmed from glancing angle x-ray diffraction and Raman spectroscopy. At the highest oxygen partial pressure, i.e. 300 mTorr, although the TiO2 film shows a complete anatase phase, a small peak corresponding to the rutile phase along with the anatase phase is identified in the case of CTO film. An increase in O to Ti/(Ti+Co) ratio with increase in oxygen partial pressure is observed from Rutherford backscattering spectroscopy. It is revealed from x-ray photoelectron spectroscopy (XPS) that oxygen vacancies are found to be higher in the CTO film than TiO2, while the valency of cobalt remains in the +2 state. Therefore, the CTO film deposited at 300 mTorr does not show a complete anatase phase unlike the TiO2 film deposited at the same partial pressure. We conclude that RTFM in both films is not due to impurities/contaminants, as confirmed from XPS depth profiling and cross-sectional transmission electron microscopy (TEM), but due to oxygen vacancies. The magnitude of moment, however, depends not only on the phase of TiO2 but also on the crystallinity of the films.

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

NASA Astrophysics Data System (ADS)

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

2013-12-01

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.

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

PubMed

Ghrairi, Najla; Bouaicha, Mongi

2012-07-01

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 μA, where the surface of the formed cell is 3.14 cm2.

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

PubMed Central

2012-01-01

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 μA, where the surface of the formed cell is 3.14 cm2. PMID:22747886

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

PubMed

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

2008-05-01

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.

Preparation of anatase TiO2 thin film by low temperature annealing as an electron transport layer in inverted polymer solar cells

NASA Astrophysics Data System (ADS)

Noh, Hongche; Oh, Seong-Geun; Im, Seung Soon

2015-04-01

To prepare the anatase TiO2 thin films on ITO glass, amorphous TiO2 colloidal solution was synthesized through the simple sol-gel method by using titanium (IV) isopropoxide as a precursor. This amorphous TiO2 colloidal solution was spread on ITO glass by spin-coating, then treated at 450 °C to obtain anatase TiO2 film (for device A). For other TiO2 films, amorphous TiO2 colloidal solution was treated through solvothermal process at 180 °C to obtain anatase TiO2 colloidal solution. This anatase TiO2 colloidal solution was spread on ITO glass by spin coating, and then annealed at 200 °C (for device B) and 130 °C (for device C), respectively. The average particle size of amorphous TiO2 colloidal solution was about 1.0 nm and that of anatase TiO2 colloidal solution was 10 nm. The thickness of TiO2 films was about 15 nm for all cases. When inverted polymer solar cells were fabricated by using these TiO2 films as an electron transport layer, the device C showed the highest PCE (2.6%) due to the lack of defect, uniformness and high light absorbance of TiO2 films. The result of this study can be applied for the preparation of inverted polymer solar cell using TiO2 films as a buffer layer at low temperature on plastic substrate by roll-to roll process.

Effect of precursor concentration and film thickness deposited by layer on nanostructured TiO2 thin films

NASA Astrophysics Data System (ADS)

Affendi, I. H. H.; Sarah, M. S. P.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

2018-05-01

Sol-gel spin coating method is used in the production of nanostructured TiO2 thin film. The surface topology and morphology was observed using the Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The electrical properties were investigated by using two probe current-voltage (I-V) measurements to study the electrical resistivity behavior, hence the conductivity of the thin film. The solution concentration will be varied from 14.0 to 0.01wt% with 0.02wt% interval where the last concentration of 0.02 to 0.01wt% have 0.01wt% interval to find which concentrations have the highest conductivity then the optimized concentration's sample were chosen for the thickness parameter based on layer by layer deposition from 1 to 6 layer. Based on the result, the lowest concentration of TiO2, the surface becomes more uniform and the conductivity will increase. As the result, sample of 0.01wt% concentration have conductivity value of 1.77E-10 S/m and will be advanced in thickness parameter. Whereas in thickness parameter, the 3layer deposition were chosen as its conductivity is the highest at 3.9098E9 S/m.

Influence of annealing on X-ray radiation sensing properties of TiO2 thin film

NASA Astrophysics Data System (ADS)

Sarma, M. P.; Kalita, J. M.; Wary, G.

2018-03-01

A recent study shows that the titanium dioxide (TiO2) thin film synthesised by a chemical bath deposition technique is a very useful material for the X-ray radiation sensor. In this work, we reported the influence of annealing on the X-ray radiation detection sensitivity of the TiO2 film. The films were annealed at 333 K, 363 K, 393 K, 473 K, and 573 K for 1 hour. Structural analyses showed that the microstrain and dislocation density decreased whereas the average crystallite size increased with annealing. The band gap of the films also decreased from 3.26 eV to 3.10 eV after annealing. The I-V characteristics record under the dark condition and under the X-ray irradiation showed that the conductivity increased with annealing. The influence of annealing on the detection sensitivity was negligible if the bias voltage applied across the films was low (within 0.2 V‒1.0 V). At higher bias voltage (>1.0 V), the contribution of electrons excited by X-ray became less significant which affected the detection sensitivity.

Self-Assembled Multilayer Structure and Enhanced Thermochromic Performance of Spinodally Decomposed TiO2-VO2 Thin Film.

PubMed

Sun, Guangyao; Zhou, Huaijuan; Cao, Xun; Li, Rong; Tazawa, Masato; Okada, Masahisa; Jin, Ping

2016-03-23

Composite films of VO2-TiO2 were deposited on sapphire (11-20) substrate by cosputtering method. Self-assembled well-ordered multilayer structure with alternating Ti- and V-rich epitaxial thin layer was obtained by thermal annealing via a spinodal decomposition mechanism. The structured thermochromic films demonstrate superior optical modulation upon phase transition, with significantly reduced transition temperature. The results provide a facile and novel approach to fabricate smart structures with excellent performance.

Absorbing TiO x thin film enabling laser welding of polyurethane membranes and polyamide fibers.

PubMed

Amberg, Martin; Haag, Alexander; Storchenegger, Raphael; Rupper, Patrick; Lehmeier, Frederike; Rossi, René M; Hegemann, Dirk

2015-10-01

We report on the optical properties of thin titanium suboxide (TiO x ) films for applications in laser transmission welding of polymers. Non-absorbing fibers were coated with TiO x coatings by reactive magnetron sputtering. Plasma process parameters influencing the chemical composition and morphology of the deposited thin films were investigated in order to optimize their absorption properties. Optical absorption spectroscopy showed that the oxygen content of the TiO x coatings is the main parameter influencing the optical absorbance. Overtreatment (high power plasma input) of the fiber surface leads to high surface roughness and loss of mechanical stability of the fiber. The study shows that thin substoichiometric TiO x films enable the welding of very thin polyurethane membranes and polyamide fibers with improved adhesion properties.

Optical properties of dip coated titanium-di-oxide (TiO2) thin films annealed at different temperatures

NASA Astrophysics Data System (ADS)

Biswas, Sayari; Kar, Asit Kumar

2018-02-01

Titanium dioxide (TiO2) thin films were synthesized by hydrothermal assisted sol-gel dip coating method on quartz substrate. The sol was prepared by hydrothermal method at 90 °C. Dip coating method was used to deposit the thin films. Later films were annealed at four different temperatures -600 °C, 800 °C, 1000 °C and 1200 °C. XRD study showed samples annealed at 600 °C are almost amorphous. At 800 °C, film turns into anatase phase and with further increment of annealing temperature they turn into rutile phase. Transmission spectra of thin films show sharp rise in the violet-ultraviolet transition region and a maximum transmittance of ˜60% was observed in the visible region for the sample annealed at the lowest temperature. Band gap of the prepared films varies from 2.9 eV to 3.5 eV.

Optical and electrical responses of magnetron-sputtered amorphous Nb-doped TiO2 thin films annealed at low temperature

NASA Astrophysics Data System (ADS)

Quynh, Luu Manh; Tien, Nguyen Thi; Thanh, Pham Van; Hieu, Nguyen Minh; Doanh, Sai Cong; Thuat, Nguyen Tran; Tuyen, Nguyen Viet; Luong, Nguyen Hoang; Hoang, Ngoc Lam Huong

2018-03-01

Nb-doped TiO2 (TNO) thin films were prepared by annealing at 300 °C for 30 min after a magnetron-sputter process. A laser-irradiated post-annealing Raman scattering analysis indirectly showed the possible formation of small size anatase TNO clusters within the thin film matrix Although the TNO thin films were not crystallized, oxygen vacancies were created by adding H2 into the sputter gas during the deposition process. This improved the conductivity and carrier concentration of the thin films. As the ratio of H2 in sputter gas is f(H2) = [H2/Ar+H2] = 10%, the carrier concentration of the amorphous TNO thin film reached 1022 (cm-3) with the resistivity being about 10-2 (Ω.cm). Even though a new methodology to decrease the fabrication temperature is not presented; this study demonstrates an efficient approach to shorten the annealing process, which ends prior to the crystallization of the thin films. Besides, in situ H2 addition into the sputter atmosphere is proven to be a good solution to enhance the electrical conductivity of semiconductor thin films like TNOs, despite the fact that they are not well crystallized.

S180 cell growth on low ion energy plasma treated TiO 2 thin films

NASA Astrophysics Data System (ADS)

Dhayal, Marshal; Cho, Su-In; Moon, Jun Young; Cho, Su-Jin; Zykova, Anna

2008-03-01

X-ray photoelectron spectroscopy (XPS) was used to characterise the effects of low energy (<2 eV) argon ion plasma surface modification of TiO 2 thin films deposited by radio frequency (RF) magnetron sputter system. The low energy argon ion plasma surface modification of TiO 2 in a two-stage hybrid system had increased the proportion of surface states of TiO 2 as Ti 3+. The proportion of carbon atoms as alcohol/ether (C sbnd OX) was decreased with increase the RF power and carbon atoms as carbonyl (C dbnd O) functionality had increased for low RF power treatment. The proportion of C( dbnd O)OX functionality at the surface was decreased at low power and further increase in power has showed an increase in its relive proportion at the surface. The growth of S180 cells was observed and it seems that cells are uniformly spreads on tissue culture polystyrene surface and untreated TiO 2 surfaces whereas small-localised cell free area can be seen on plasma treated TiO 2 surfaces which may be due to decrease in C( dbnd O)OX, increase in C dbnd O and active sites at the surface. A relatively large variation in the surface functionalities with no change in the surface roughness was achieved by different RF plasma treatments of TiO 2 surface whereas no significant change in S180 cell growth with different plasma treatments. This may be because cell growth on TiO 2 was mainly influenced by nano-surface characteristics of oxide films rather than surface chemistry.

A micro oxygen sensor based on a nano sol-gel TiO2 thin film.

PubMed

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

2014-09-03

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 μm × 350 μm 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.

Study the target effect on the structural, surface and optical properties of TiO2 thin film fabricated by RF sputtering method

NASA Astrophysics Data System (ADS)

Vyas, Sumit; Tiwary, Rohit; Shubham, Kumar; Chakrabarti, P.

2015-04-01

The effect of target (Ti metal target and TiO2 target) on Titanium Dioxide (TiO2) thin films grown on ITO coated glass substrate by RF magnetron sputtering has been investigated. A comparative study of both the films was done in respect of crystalline structure, surface morphology and optical properties by using X-ray diffractometer (XRD), Atomic Force Microscopy (AFM) studies and ellipsometric measurements. The XRD results confirmed the crystalline structure and indicated that the deposited films have the intensities of anatase phase. The surface morphology and roughness values indicated that the film using Ti metal target has a smoother surface and densely packed with grains as compared to films obtained using TiO2 target. A high transmission in the visible region, and direct band gap of 3.67 eV and 3.75 eV for films derived by using Ti metal and TiO2 target respectively and indirect bandgap of 3.39 eV for the films derived from both the targets (Ti metal and TiO2 target) were observed by the ellipsometric measurements.

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

NASA Astrophysics Data System (ADS)

Eraković, S.; Janković, A.; Ristoscu, C.; Duta, L.; Serban, N.; Visan, A.; Mihailescu, I. N.; Stan, G. E.; Socol, M.; Iordache, O.; Dumitrescu, I.; Luculescu, C. R.; Janaćković, Dj.; Miškovic-Stanković, V.

2014-02-01

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.

Matching characteristics of different buffer layers with VO2 thin films

NASA Astrophysics Data System (ADS)

Yang, Kai; Zhang, Dongping; Liu, Yi; Guan, Tianrui; Qin, Xiaonan; Zhong, Aihua; Cai, Xingmin; Fan, Ping; Lv, Weizhong

2016-10-01

VO2 thin films were fabricated by reactive DC magnetron sputtering on different buffer layers of MgF2, Al2O3 and TiO2, respectively. The crystallinity and orientation relationship, thickness of VO2 thin films, atoms vibrational modes, optical and electrical property, surface morphology of films were characterized by X-ray diffraction, Raman scattering microscopy, step profiler, spectrophotometer, four-probe technique, and scanning electron microscopy, respectively. XRD results investigated that the films have preferential crystalline planes VO2 (011). The crystallinity of VO2 films grown on TiO2 buffer layers are superior to VO2 directly deposited on soda-lime glass. The Raman bands of the VO2 films correspond to an Ag symmetry mode of VO2 (M). The sample prepared on 100nm TiO2 buffer layer appears nanorods structure, and exhibits remarkable solar energy modulation ability as high as 5.82% in full spectrum and 23% in near infrared spectrum. Cross-sectional SEM image of the thin films samples indicate that MgF2 buffer layer has clear interface with VO2 layer. But there are serious interdiffusion phenomenons between Al2O3, TiO2 buffer layer with VO2 layer.

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

NASA Astrophysics Data System (ADS)

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

2014-03-01

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 Csbnd Osbnd Ti 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.

Fabrication of assembled ZnO/TiO2 heterojunction thin film transistors using solution processing technique

NASA Astrophysics Data System (ADS)

Liau, Leo Chau-Kuang; Lin, Yun-Guo

2015-01-01

Ceramic-based metal-oxide-semiconductor (MOS) field-effect thin film transistors (TFTs), which were assembled by ZnO and TiO2 heterojunction films coated using solution processing technique, were fabricated and characterized. The fabrication of the device began with the preparation of ZnO and TiO2 films by spin coating. The ZnO and TiO2 films that were stacked together and annealed at 450 °C were characterized as a p-n junction diode. Two types of the devices, p-channel and n-channel TFTs, were produced using different assemblies of ZnO and TiO2 films. Results show that the p-channel TFTs (p-TFTs) and n-channel TFTs (n-TFTs) using the assemblies of ZnO and TiO2 films were demonstrated by source-drain current vs. drain voltage (IDS-VDS) measurements. Several electronic properties of the p- and n- TFTs, such as threshold voltage (Vth), on-off ratio, channel mobility, and subthreshold swing (SS), were determined by current-voltage (I-V) data analysis. The ZnO/TiO2-based TFTs can be produced using solution processing technique and an assembly approach.

Seebeck coefficient of synthesized Titanium Dioxide thin film on FTO glass substrate

NASA Astrophysics Data System (ADS)

Usop, R.; Hamed, N. K. A.; Megat Hasnan, M. M. I.; Ikeda, H.; Sabri, M. F. M.; Ahmad, M. K.; Said, S. M.; Salleh, F.

2018-04-01

In order to fabricate a thermoelectric device on glass substrate for harvesting waste heat energy through house appliances, the Seebeck coefficient of translucent TiO2 thin film was investigated. The TiO2 thin film was synthesized by using hydrothermal method with F-SnO2 coated glass as substrate. From scanning electron microscopy analysis, the synthesized TiO2 thin film was found to be in nanometer-scale rod structure with a thickness of 4 µm. The Seebeck coefficient was measured in the temperature range of 300 – 400 K. The Seebeck coefficient is found to be in negative value which shows that synthesized film is an n-type semiconductor material, and is lower than the value of bulk-size material. This reduction in Seebeck coefficient of TiO2 thin film is likely due to the low dimensional effect and the difference of carrier concentration.

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

PubMed Central

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

2014-01-01

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 μm × 350 μm 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

Structural and mechanical properties of CVD deposited titanium aluminium nitride (TiAlN) thin films

NASA Astrophysics Data System (ADS)

Das, Soham; Guha, Spandan; Ghadai, Ranjan; Kumar, Dhruva; Swain, Bibhu P.

2017-06-01

Titanium aluminium nitride (TiAlN) thin films were deposited by chemical vapour deposition using TiO2 powder, Al powder and N2 gas. The morphology and mechanical properties of the films were characterized by scanning electron microscopy and nanoindentation technique, respectively. The structural properties were characterized by Raman spectroscopy and X-ray diffraction. The XRD result shows TiAlN films are of NaCl-type metal nitride structure. Micro-Raman peaks of the TiAlN thin film were observed within 450 and 642 cm-1 for acoustic and optic range, respectively. A maximum hardness and Young modulus up to 22 and 272.15 GPa, respectively, were observed in the TiAlN film deposited at 1200 °C.

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

NASA Astrophysics Data System (ADS)

Dam Le, Duy; Dung Dang, Thi My; Thang Chau, Vinh; Chien Dang, Mau

2010-03-01

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.

Fabrication of a pure TiO2 thin film using a self-polymeric titania nano-sol and its properties.

PubMed

Park, Won-Kyu; Song, Jeong-Hwan; Kim, Soo-Ryong; Kim, Tae-Hyun; Iwasaki, Mitusnobo

2012-02-01

A pure TiO2 thin film without adding any organic binder was fabricated by using a self-polymeric titania nano-sol (14 mass%), which was prepared by the acid peptization method. The particle size distribution in the 14 mass% TiO2 sol, in which almost of particles had a size below 10.2 nm and the crystal phase confirmed by X-ray diffraction analysis was anatase. The diluted nano-sol had a capability to form a thin film at a low temperature (100-400 degrees C) on the slide glass by dipping method. The average thickness of a coating film was measured to be about 0.25-0.30 microm. A coated film had a high refractive index over 1.88 at least irrespective of the heat-treatment even at room temperature drying and showed a super-hydrophilicity (< 5 degrees) after 20 minutes under Ultra Violet light irradiation, and it sustained in the darkness during a long period over 7 days depending on the heat-treatment conditions. Atomic Force Microscopic observation shows that the morphology of a heat-treated film had a relationship with the long-term hydrophilicity in the darkness.

Synthesis and characterization of a mixed phase of anatase TiO2 and TiO2(B) by low pressure chemical vapour deposition (LPCVD) for high photocatalytic activity

NASA Astrophysics Data System (ADS)

Chimupala, Y.; Hyett, G.; Simpson, R.; Brydson, R.

2014-06-01

This project is concerned with enhancing photocatalytic activity by preparing a mixed phase of nano-sized TiO2. TiO2 thin films were synthesized by using Low Pressure Chemical Vapour Deposition (LPCVD). Titanium isopropoxide and N2 gas were used as the precursor and carrier gas respectively. The effects of reaction temperature, carrier gas flow rate and deposited area were studied. TiO2 thin films with nano-sized TiO2 particles were obtained under suitable conditions and SEM, TEM, powder XRD and Raman spectroscopy were employed to characterize the phase and physical appearance of synthesized materials. Preliminary results show that a dual phase (TiO2(B) and anatase) thin film nanopowder was successfully prepared by LPCVD with needle- and polygonal plate-shape crystallites respectively. This thin film deposit produced a preferred orientation of TiO2(B) needles in the [001] direction of average crystallite size 50-80 nm in length and 5-10 nm in width, whilst the crystallite size of anatase polygonal-plates was around 200 nm. The optimal LPCVD condition for preparing this mixed phase of TiO2 was 600°C with a 1 mL/s N2 flow rate.

Effect of substrate type on the electrical and structural properties of TiO2 thin films deposited by reactive DC sputtering

NASA Astrophysics Data System (ADS)

Cheng, Xuemei; Gotoh, Kazuhiro; Nakagawa, Yoshihiko; Usami, Noritaka

2018-06-01

Electrical and structural properties of TiO2 thin films deposited at room temperature by reactive DC sputtering have been investigated on three different substrates: high resistivity (>1000 Ω cm) float zone Si(1 1 1), float zone Si(1 0 0) and alkali free glass. As-deposited TiO2 films on glass substrate showed extremely high resistivity of (∼5.5 × 103 Ω cm). In contrast, lower resistivities of ∼2 Ω cm and ∼5 Ω cm were obtained for films on Si(1 1 1) and Si(1 0 0), respectively. The as-deposited films were found to be oxygen-rich amorphous TiO2 for all the substrates as evidenced by X-ray photoemission spectroscopy and X-ray diffraction. Subsequent annealing led to appearance of anatase TiO2 on Si but not on glass. The surface of as-deposited TiO2 on Si was found to be rougher than that on glass. These results suggest that the big difference of electrical resistivity of TiO2 would be related with existence of more anatase nuclei forming on crystalline substrates, which is consistent with the theory of charged clusters that smaller clusters tend to adopt the substrate structure.

Gd, I-doped TiO2 thin films coated on solid waste material: synthesis, characterization, and photocatalytic activity under UV or visible light irradiation

NASA Astrophysics Data System (ADS)

Deng, Siwei; Yu, Jiang; Yang, Chun; Chang, Jiahua; Wang, Yizheng; Wang, Ping; Xie, Shiqian

2017-10-01

In this work, titanium dioxide thin films doped with different concentrations of gadolinium (Gd) and iodine (I) were synthesized using the sol-gel method and successfully coated on solid waste material (made in our lab) by dipping, resulting in the titanium dioxide thin-film-coated material (TiO2M). Then, the doped titanium dioxide thin films were characterized by X-ray diffraction (XRD), SEM, and UV-Vis spectroscopy; the optimum coating cycle was evaluated by removal rates of COD and ammonia nitrogen in raw wastewater and secondary effluent. Moreover, the photocatalytic activity was determined by degradation efficiency of methyl orange. The results showed that TiO2M had desirable reusability and the photocatalytic activity was attractive under ultraviolet light irradiation. Furthermore, it is found that the amount of dopant in TiO2 was a key parameter in increasing the photoactivity. 1% Gd-doped TiO2M exhibited the best photocatalytic activity for the degradation of methyl orange with the removal rate reaching 85.55%. The result was in good agreement with the observed smaller crystallite size and profitable crystal structure (anatase phase). Besides, the TiO2M (0.8% Gd-doped TiO2M, 1% Gd-doped TiO2M, 10% I-doped TiO2M, and 5% I-1% Gd-doped TiO2M) with desirable photocatalytic activity at ultraviolet light irradiation was selected for the visible light photocatalytic experiments with taking methyl orange as the target pollutants. The results showed that all of them exhibited the similar photocatalytic activity after 7 h of sunlight irradiation (around 90% removal effect). In general, this research developed a very effective and environmentally friendly photocatalyst for pollutant degradation.

Dye sensitized solar cell applications of CdTiO3-TiO2 composite thin films deposited from single molecular complex

NASA Astrophysics Data System (ADS)

Ehsan, Muhammad Ali; Khaledi, Hamid; Pandikumar, Alagarsamy; Huang, Nay Ming; Arifin, Zainudin; Mazhar, Muhammad

2015-10-01

A heterobimetallic complex [Cd2Ti4(μ-O)6(TFA)8(THF)6]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO3-TiO2 composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity, phase identification and chemical composition of microspherical architectured CdTiO3-TiO2 composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application.

Chemically synthesized TiO2 and PANI/TiO2 thin films for ethanol sensing applications

NASA Astrophysics Data System (ADS)

Gawri, Isha; Ridhi, R.; Singh, K. P.; Tripathi, S. K.

2018-02-01

Ethanol sensing properties of chemically synthesized titanium dioxide (TiO2) and polyaniline/titanium dioxide nanocomposites (PANI/TiO2) had been performed at room temperature. In-situ oxidative polymerization process had been employed with aniline as a monomer in presence of anatase titanium dioxide nanoparticles. The prepared samples were structurally and morphologically characterized by x-ray diffraction, fourier transform infrared spectra, high resolution-transmission electron microscopy and field emission-scanning electron microscopy. The crystallinity of PANI/TiO2 nanocomposite was revealed by XRD and FTIR spectra confirmed the presence of chemical bonding between the polymer chains and metal oxide nanoparticles. HR-TEM micrographs depicted that TiO2 particles were embedded in polymer matrix, which provides an advantage over pure TiO2 nanoparticles in efficient adsorption of vapours. These images also revealed that the TiO2 nanoparticles were irregular in shape with size around 17 nm. FE-SEM studies revealed that in the porous structure of PANI/TiO2 film, the intercalation of TiO2 in PANI chains provides an advantage over pure TiO2 film for uniform interaction with ethanol vapors. The sensitivity values of prepared samples were examined towards ethanol vapours at room temperature. The PANI/TiO2 nanocomposite exhibited better sensing response and faster response-recovery examined at different ethanol concentrations ranging from 5 ppm to 20 ppm in comparison to pure TiO2 nanoparticles. The increase in vapour sensing of PANI/TiO2 sensing film as compared to pure TiO2 film had been explained in detail with the help of gas sensing mechanism of TiO2 and PANI/TiO2. This provides strong evidence that gas sensing properties of TiO2 had been considerably improved and enhanced with the addition of polymer matrix.

Photocatalytic Anatase TiO2 Thin Films on Polymer Optical Fiber Using Atmospheric-Pressure Plasma.

PubMed

Baba, Kamal; Bulou, Simon; Choquet, Patrick; Boscher, Nicolas D

2017-04-19

Due to the undeniable industrial advantages of low-temperature atmospheric-pressure plasma processes, such as low cost, low temperature, easy implementation, and in-line process capabilities, they have become the most promising next-generation candidate system for replacing thermal chemical vapor deposition or wet chemical processes for the deposition of functional coatings. In the work detailed in this article, photocatalytic anatase TiO 2 thin films were deposited at a low temperature on polymer optical fibers using an atmospheric-pressure plasma process. This method overcomes the challenge of forming crystalline transition metal oxide coatings on polymer substrates by using a dry and up-scalable method. The careful selection of the plasma source and the titanium precursor, i.e., titanium ethoxide with a short alkoxy group, allowed the deposition of well-adherent, dense, and crystalline TiO 2 coatings at low substrate temperature. Raman and XRD investigations showed that the addition of oxygen to the precursor's carrier gas resulted in a further increase of the film's crystallinity. Furthermore, the films deposited in the presence of oxygen exhibited a better photocatalytic activity toward methylene blue degradation assumedly due to their higher amount of photoactive {101} facets.

The structure and photocatalytic activity of TiO2 thin films deposited by dc magnetron sputtering

NASA Astrophysics Data System (ADS)

Yang, W. J.; Hsu, C. Y.; Liu, Y. W.; Hsu, R. Q.; Lu, T. W.; Hu, C. C.

2012-12-01

This paper seeks to determine the optimal settings for the deposition parameters, for TiO2 thin film, prepared on non-alkali glass substrates, by direct current (dc) sputtering, using a ceramic TiO2 target in an argon gas environment. An orthogonal array, the signal-to-noise ratio and analysis of variance are used to analyze the effect of the deposition parameters. Using the Taguchi method for design of a robust experiment, the interactions between factors are also investigated. The main deposition parameters, such as dc power (W), sputtering pressure (Pa), substrate temperature (°C) and deposition time (min), were optimized, with reference to the structure and photocatalytic characteristics of TiO2. The results of this study show that substrate temperature and deposition time have the most significant effect on photocatalytic performance. For the optimal combination of deposition parameters, the (1 1 0) and (2 0 0) peaks of the rutile structure and the (2 0 0) peak of the anatase structure were observed, at 2θ ˜ 27.4°, 39.2° and 48°, respectively. The experimental results illustrate that the Taguchi method allowed a suitable solution to the problem, with the minimum number of trials, compared to a full factorial design. The adhesion of the coatings was also measured and evaluated, via a scratch test. Superior wear behavior was observed, for the TiO2 film, because of the increased strength of the interface of micro-blasted tools.

Photoinduced underwater superoleophobicity of TiO2 thin films.

PubMed

Sawai, Yusuke; Nishimoto, Shunsuke; Kameshima, Yoshikazu; Fujii, Eiji; Miyake, Michihiro

2013-06-11

The photoinduced wettabilities of water, n-hexadecane, dodecane, and n-heptane on a flat TiO2 surface prepared by a sol-gel method-based coating were investigated. An amphiphilic surface produced by UV irradiation exhibited underwater superoleophobicity with an extremely high static oil contact angle (CA) of over 160°. The TiO2 surface almost completely repelled the oil droplet in water. A robust TiO2 surface with no fragile nanomicrostructure was fabricated on a Ti mesh with a pore size of approximately 150 μm. The fabricated mesh was found to be applicable as an oil/water separation filter.

Preparation and characterization of WO3 nanoparticles, WO3/TiO2 core/shell nanocomposites and PEDOT:PSS/WO3 composite thin films for photocatalytic and electrochromic applications

NASA Astrophysics Data System (ADS)

Boyadjiev, Stefan I.; Santos, Gustavo dos Lopes; Szżcs, Júlia; Szilágyi, Imre M.

2016-03-01

In this study, monoclinic WO3 nanoparticles were obtained by thermal decomposition of (NH4)xWO3 in air at 600 °C. On them by atomic layer deposition (ALD) TiO2 films were deposited, and thus core/shell WO3/TiO2 nanocomposites were prepared. We prepared composites of WO3 nanoparticles with conductive polymer as PEDOT:PSS, and deposited thin films of them on glass and ITO substrates by spin coating. The formation, morphology, composition and structure of the as-prepared pure and composite nanoparticles, as well thin films, were studied by TEM, SEM-EDX and XRD. The photocatalytic activity of both the WO3 and core/shell WO3/TiO2 nanoparticles was studied by decomposing methyl orange in aqueous solution under UV light irradiation. Cyclic voltammetry measurements were performed on the composite PEDOT:PSS/WO3 thin films, and the coloring and bleaching states were studied.

Ambiguous Role of Growth-Induced Defects on the Semiconductor-to-Metal Characteristics in Epitaxial VO2/TiO2 Thin Films.

PubMed

Mihailescu, Cristian N; Symeou, Elli; Svoukis, Efthymios; Negrea, Raluca F; Ghica, Corneliu; Teodorescu, Valentin; Tanase, Liviu C; Negrila, Catalin; Giapintzakis, John

2018-04-25

Controlling the semiconductor-to-metal transition temperature in epitaxial VO 2 thin films remains an unresolved question both at the fundamental as well as the application level. Within the scope of this work, the effects of growth temperature on the structure, chemical composition, interface coherency and electrical characteristics of rutile VO 2 epitaxial thin films grown on TiO 2 substrates are investigated. It is hereby deduced that the transition temperature is lower than the bulk value of 340 K. However, it is found to approach this value as a function of increased growth temperature even though it is accompanied by a contraction along the V 4+ -V 4+ bond direction, the crystallographic c-axis lattice parameter. Additionally, it is demonstrated that films grown at low substrate temperatures exhibit a relaxed state and a strongly reduced transition temperature. It is suggested that, besides thermal and epitaxial strain, growth-induced defects may strongly affect the electronic phase transition. The results of this work reveal the difficulty in extracting the intrinsic material response to strain, when the exact contribution of all strain sources cannot be effectively determined. The findings also bear implications on the limitations in obtaining the recently predicted novel semi-Dirac point phase in VO 2 /TiO 2 multilayer structures.

Some studies on TiO2 films deposited by sol-gel technique

NASA Astrophysics Data System (ADS)

Narasimha Rao, K.; Vishwas, M.; Kumar Sharma, Sudhir; Arjuna Gowda, K. V.

2008-08-01

TiO2 films are extensively used in various applications including optical multi-layers, sensors, photo catalysis, environmental purification, and solar cells etc. These are prepared by both vacuum and non-vacuum methods. In this paper, we present the results on TiO2 thin films prepared by a sol-gel spin coating process in non-aqueous solvent. Titanium isopropoxide is used as TiO2 precursor. The films were annealed at different temperatures up to 3000 C for 5 hours in air. The influence of the various deposition parameters like spinning speed, spinning time and annealing temperature on the thickness of the TiO2 films has been studied. The variation of film thickness with time in ambient atmosphere was also studied. The optical, structural and morphological characteristics were investigated by optical transmittance-reflectance measurements, X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The refractive index and extinction coefficient of the films were determined by envelope technique and spectroscopic ellipsometry. TiO2 films exhibited high transparency (92%) in the visible region with a refractive index of 2.04 at 650 nm. The extinction coefficient was found to be negligibly small. The X-ray diffraction analysis showed that the TiO2 film deposited on glass substrate changes from amorphous to crystalline (anatase) phase with annealing temperature above 2500 C. SEM results show that the deposited films are uniform and crack free.

Electrospinning processed nanofibrous TiO2 membranes for photovoltaic applications

NASA Astrophysics Data System (ADS)

Onozuka, Katsuhiro; Ding, Bin; Tsuge, Yosuke; Naka, Takayuki; Yamazaki, Michiyo; Sugi, Shinichiro; Ohno, Shingo; Yoshikawa, Masato; Shiratori, Seimei

2006-02-01

We have recently fabricated dye-sensitized solar cells (DSSCs) comprising nanofibrous TiO2 membranes as electrode materials. A thin TiO2 film was pre-deposited on fluorine doped tin oxide (FTO) coated conducting glass substrate by immersion in TiF4 aqueous solution to reduce the electron back-transfer from FTO to the electrolyte. The composite polyvinyl acetate (PVac)/titania nanofibrous membranes can be deposited on the pre-deposited thin TiO2 film coated FTO by electrospinning of a mixture of PVac and titanium isopropoxide in N,N-dimethylformamide (DMF). The nanofibrous TiO2 membranes were obtained by calcining the electrospun composite nanofibres of PVac/titania as the precursor. Spectral sensitization of the nanofibrous TiO2 membranes was carried out with a ruthenium (II) complex, cis-dithiocyanate-N,N'-bis(2,2'-bipyridyl-4,4'-dicarboxylic acid) ruthenium (II) dihydrate. The results indicated that the photocurrent and conversion efficiency of electrodes can be increased with the addition of the pre-deposited TiO2 film and the adhesion treatment using DMF. Additionally, the dye loading, photocurrent, and efficiency of the electrodes were gradually increased by increasing the average thickness of the nanofibrous TiO2 membranes. The efficiency of the fibrous TiO2 photoelectrode with the average membrane thickness of 3.9 µm has a maximum value of 4.14%.

Combination of short-length TiO2 nanorod arrays and compact PbS quantum-dot thin films for efficient solid-state quantum-dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Zhang, Zhengguo; Shi, Chengwu; Chen, Junjun; Xiao, Guannan; Li, Long

2017-07-01

Considering the balance of the hole diffusion length and the loading quantity of quantum-dots, the rutile TiO2 nanorod array with the length of 600 nm, the diameter of 20 nm, and the areal density of 500 μm-2 is successfully prepared by the hydrothermal method using the aqueous grown solution of 38 mM titanium isopropoxide and 6 M hydrochloric acid at 170 °C for 105 min. The compact PbS quantum-dot thin film on the TiO2 nanorod array is firstly obtained by the spin-coating-assisted successive ionic layer absorption and reaction with using 1,2-ethanedithiol (EDT). The result reveals that the strong interaction between lead and EDT is very important to control the crystallite size of PbS quantum-dots and obtain the compact PbS quantum-dot thin film on the TiO2 nanorod array. The all solid-state sensitized solar cell with the combination of the short-length, high-density TiO2 nanorod array and the compact PbS quantum-dot thin film achieves the photoelectric conversion efficiency of 4.10%, along with an open-circuit voltage of 0.52 V, a short-circuit photocurrent density of 13.56 mA cm-2 and a fill factor of 0.58.

Heterogeneous photocatalytic degradation of toluene in static environment employing thin films of nitrogen-doped nano-titanium dioxide

NASA Astrophysics Data System (ADS)

Kannangara, Yasun Y.; Wijesena, Ruchira; Rajapakse, R. M. G.; de Silva, K. M. Nalin

2018-04-01

Photocatalytic semiconductor thin films have the ability to degrade volatile organic compounds (VOCs) causing numerous health problems. The group of VOCs called "BTEX" is abundant in houses and indoor of automobiles. Anatase phase of TiO2 has a band gap of 3.2 eV and UV radiation is required for photogeneration of electrons and holes in TiO2 particles. This band gap can be decreased significantly when TiO2 is doped with nitrogen (N-TiO2). Dopants like Pd, Cd, and Ag are hazardous to human health but N-doped TiO2 can be used in indoor pollutant remediation. In this research, N-doped TiO2 nano-powder was prepared and characterized using various analytical techniques. N-TiO2 was made in sol-gel method and triethylamine (N(CH2CH3)3) was used as the N-precursor. Modified quartz cell was used to measure the photocatalytic degradation of toluene. N-doped TiO2 nano-powder was illuminated with visible light (xenon lamp 200 W, λ = 330-800 nm, intensity = 1 Sun) to cause the degradation of VOCs present in static air. Photocatalyst was coated on a thin glass plate, using the doctor-blade method, was inserted into a quartz cell containing 2.00 µL of toluene and 35 min was allowed for evaporation/condensation equilibrium and then illuminated for 2 h. Remarkably, the highest value of efficiency 85% was observed in the 1 μm thick N-TiO2 thin film. The kinetics of photocatalytic degradation of toluene by N-TiO2 and P25-TiO2 has been compared. Surface topology was studied by varying the thickness of the N-TiO2 thin films. The surface nanostructures were analysed and studied with atomic force microscopy with various thin film thicknesses.

Optical properties of rhodamine 6G-doped TiO2 sol-gel films

NASA Astrophysics Data System (ADS)

Tomás, S. A.; Stolik, S.; Palomino, R.; Lozada, R.; Persson, C.; Ahuja, R.; Pepe, I.; Ferreira da Silva, A.

2005-06-01

The optical properties of titania (TiO2) thin films prepared by the sol-gel process and doped with rhodamine 6G were studied by Photoacoustic Spectroscopy. Rhodamine 6G-doping was achieved by adding 0.01%, 0.02%, 0.05% y 0.1% mol rhodamine to a solution that contained titanium isopropoxide as precursor. Two absorption regions were distinguished in the absorption spectrum of a typical rhodamine 6G-doped TiO2 film. A shift of these bands occured as a function of rhodamine 6G-doping concentration. In addition, the optical absorption and band gap energy for rutile-phase TiO2 films were calculated employing the full-potential linearized augmented plane wave method. A comparison of these calculations with experimental data of TiO2 films prepared by sol-gel at room temperature was performed.

Formation of thin film like assembly of exfoliated C3N4 nanoflakes by solvent non-evaporative method using centrifuge

NASA Astrophysics Data System (ADS)

Tejasvi, Ravi; Basu, Suddhasatwa

2017-12-01

A simple method for depositing a thin film of nanomaterial on a substrate using centrifugation technique has been developed, whereby solvent evaporation is prevented and solvent reuse is possible. The centrifuge technique of deposition yields uniform, smooth thin film irrespective of substrate surface texture. The deposited TiO2/eC3N4 film studied, through field emission scanning electron microscope, atomic force microscope, and optical surface profilometer, shows variation in surface roughness on the basis of centrifugation speeds. Initially film coverage improves and surface roughness decreases with the increase in rpm of the centrifuge and the surface roughness slightly increases with further increase in rpm. The photoelectrochemical studies of TiO2/eC3N4 films suggest that the centrifuge technique forms better heterojunctions compared to that by spin coating technique leading to enhanced photoelectrochemical water splitting.

Optimization of Al2O3/TiO2 nanolaminate thin films prepared with different oxide ratios, for use in organic light-emitting diode encapsulation, via plasma-enhanced atomic layer deposition.

PubMed

Kim, Lae Ho; Jeong, Yong Jin; An, Tae Kyu; Park, Seonuk; Jang, Jin Hyuk; Nam, Sooji; Jang, Jaeyoung; Kim, Se Hyun; Park, Chan Eon

2016-01-14

Encapsulation is essential for protecting the air-sensitive components of organic light-emitting diodes (OLEDs), such as the active layers and cathode electrodes. Thin film encapsulation approaches based on an oxide layer are suitable for flexible electronics, including OLEDs, because they provide mechanical flexibility, the layers are thin, and they are easy to prepare. This study examined the effects of the oxide ratio on the water permeation barrier properties of Al2O3/TiO2 nanolaminate films prepared by plasma-enhanced atomic layer deposition. We found that the Al2O3/TiO2 nanolaminate film exhibited optimal properties for a 1 : 1 atomic ratio of Al2O3/TiO2 with the lowest water vapor transmission rate of 9.16 × 10(-5) g m(-2) day(-1) at 60 °C and 90% RH. OLED devices that incorporated Al2O3/TiO2 nanolaminate films prepared with a 1 : 1 atomic ratio showed the longest shelf-life, in excess of 2000 hours under 60 °C and 90% RH conditions, without forming dark spots or displaying edge shrinkage.

Fabrication of SnO2-TiO2 core-shell nanopillar-array films for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Cheng, Hsyi-En; Lin, Chun-Yuan; Hsu, Ching-Ming

2017-02-01

Immobilized or deposited thin film TiO2 photocatalysts are suffering from a low photocatalytic activity due to either a low photon absorption efficiency or a high carrier recombination rate. Here we demonstrate that the photocatalytic activity of TiO2 can be effectively improved by the SnO2-TiO2 core-shell nanopillar-array structure which combines the benefits of SnO2/TiO2 heterojunction and high reaction surface area. The SnO2-TiO2 core-shell nanopillar-array films were fabricated using atomic layer deposition and dry etching techniques via barrier-free porous anodic alumina templates. The photocatalytic activity of the prepared films was evaluated by methylene blue (MB) bleaching under 352 nm UV light irradiation. The results show that the photocatalytic activity of TiO2 film was 45% improved by introducing a SnO2 film between TiO2 and ITO glass substrate and was 300% improved by using the SnO2-TiO2 core-shell nanopillar-array structure. The 45% improvement by the SnO2 interlayer is attributed to the SnO2/TiO2 heterojunction which separates the photogenerated electron-hole pairs in TiO2 for MB degradation, and the high photocatalytic activity of the SnO2-TiO2 core-shell nanopillar-array films is attributed to the three dimensional SnO2/TiO2 heterojunction which owns both the carrier separation ability and the high photocatalytic reaction surface area.

Suppressing the Photocatalytic Activity of TiO2 Nanoparticles by Extremely Thin Al2O3 Films Grown by Gas-Phase Deposition at Ambient Conditions

PubMed Central

Guo, Jing; Valdesueiro, David; Yuan, Shaojun; Liang, Bin; van Ommen, J. Ruud

2018-01-01

This work investigated the suppression of photocatalytic activity of titanium dioxide (TiO2) pigment powders by extremely thin aluminum oxide (Al2O3) films deposited via an atomic-layer-deposition-type process using trimethylaluminum (TMA) and H2O as precursors. The deposition was performed on multiple grams of TiO2 powder at room temperature and atmospheric pressure in a fluidized bed reactor, resulting in the growth of uniform and conformal Al2O3 films with thickness control at sub-nanometer level. The as-deposited Al2O3 films exhibited excellent photocatalytic suppression ability. Accordingly, an Al2O3 layer with a thickness of 1 nm could efficiently suppress the photocatalytic activities of rutile, anatase, and P25 TiO2 nanoparticles without affecting their bulk optical properties. In addition, the influence of high-temperature annealing on the properties of the Al2O3 layers was investigated, revealing the possibility of achieving porous Al2O3 layers. Our approach demonstrated a fast, efficient, and simple route to coating Al2O3 films on TiO2 pigment powders at the multigram scale, and showed great potential for large-scale production development. PMID:29364840

Structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics for a-IGZO thin-film transistors

PubMed Central

2013-01-01

In this letter, we investigated the structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics on the amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) devices. Compared with the Er2O3 dielectric, the a-IGZO TFT device incorporating an Er2TiO5 gate dielectric exhibited a low threshold voltage of 0.39 V, a high field-effect mobility of 8.8 cm2/Vs, a small subthreshold swing of 143 mV/decade, and a high Ion/Ioff current ratio of 4.23 × 107, presumably because of the reduction in the oxygen vacancies and the formation of the smooth surface roughness as a result of the incorporation of Ti into the Er2TiO5 film. Furthermore, the reliability of voltage stress can be improved using an Er2TiO5 gate dielectric. PMID:23294730

Structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics for a-IGZO thin-film transistors.

PubMed

Chen, Fa-Hsyang; Her, Jim-Long; Shao, Yu-Hsuan; Matsuda, Yasuhiro H; Pan, Tung-Ming

2013-01-08

In this letter, we investigated the structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics on the amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) devices. Compared with the Er2O3 dielectric, the a-IGZO TFT device incorporating an Er2TiO5 gate dielectric exhibited a low threshold voltage of 0.39 V, a high field-effect mobility of 8.8 cm2/Vs, a small subthreshold swing of 143 mV/decade, and a high Ion/Ioff current ratio of 4.23 × 107, presumably because of the reduction in the oxygen vacancies and the formation of the smooth surface roughness as a result of the incorporation of Ti into the Er2TiO5 film. Furthermore, the reliability of voltage stress can be improved using an Er2TiO5 gate dielectric.

Characterization of N,C-codoped TiO 2 films prepared by reactive DC magnetron sputtering

NASA Astrophysics Data System (ADS)

Wu, Kee-Rong; Hung, Chung-Hsuang

2009-12-01

Titanium dioxide (TiO 2) films are deposited by codoping nitrogen and carbon on indium tin oxide-coated substrates as visible light (Vis)-enabled catalysts. The X-ray diffraction peak intensity of the preferential orientation in (2 1 1) plane declines when the topmost 1.0 μm layer of the film is ground off. The decrease in the crystallite size and the crystallinity of anatase TiO 2 film is also evidenced by a shift towards the high wave number and broadening of the Raman spectra. Low doping concentrations of N (1.3%) and C (1.8%) are estimated by X-ray photoelectron spectroscopy (XPS) which displays an N 1 s peak at 396.8 eV and a C 1 s peak at 282.1 eV, respectively. This is attributed to the substitution of the oxygen sites with nitrogen and carbon, which is believed to be responsible for the Vis photocatalytic activity into a wavelength of >500 nm. The cross-sectional transmission electron microscopy images show larger pores at the grain boundaries and in larger columnar crystals than in the undoped TiO 2 film. All of these results indicate that porosity, crystallinity and shift in the preferential orientation are more pronounced close to the surface than close to the bottom of the sample. Wettability upon measurement of the water contact angle, methylene blue degradation and radical formation tests under both ultraviolet and Vis irradiation demonstrate that the topmost surface renders not only a larger reactive surface area but also a better carrier transport route than the rest of the film, improving its photocatalytic activity. These results show that surface porosity of the film is dominant than the tailoring of the photocatalytic activities of N,C-codoped TiO 2 catalysts.

Studies on transient characteristics of unipolar resistive switching processes in TiO2 thin film grown by atomic layer deposition

NASA Astrophysics Data System (ADS)

Sahu, Vikas Kumar; Das, Amit K.; Ajimsha, R. S.; Misra, P.

2018-05-01

The transient characteristics of resistive switching processes have been investigated in TiO2 thin films grown by atomic layer deposition (ALD) to study the temporal evolution of the switching processes and measure the switching times. The reset and set switching times of unipolar Au/TiO2/Pt devices were found to be ~250 µs and 180 ns, respectively in the voltage windows of 0.5–0.9 V for reset and 1.9–4.8 V for set switching processes, obtained from quasi-static measurements. The reset switching time decreased exponentially with increasing amplitude of applied reset voltage pulse, while the set switching time remained insensitive to the amplitude of the set voltage pulse. A fast reset process with a switching time of ~400 ns was achieved by applying a reset voltage of ~1.8 V, higher than that of the quasi-static reset voltage window but below the set voltage window. The sluggish reset process in TiO2 thin film and the dependence of the reset switching time on the amplitude of the applied voltage pulse was understood on the basis of a self-accelerated thermal dissolution model of conducting filaments (CFs), where a higher temperature of the CFs owing to enhanced Joule heating at a higher applied voltage imposes faster diffusion of oxygen vacancies, resulting in a shorter reset switching time. Our results clearly indicate that fast resistive switching with switching times in hundreds of nanoseconds can be achieved in ALD-grown TiO2 thin films. This may find applications in fast non-volatile unipolar resistive switching memories.

Sol-gel preparation of silica and titania thin films

NASA Astrophysics Data System (ADS)

Thoř, Tomáš; Václavík, Jan

2016-11-01

Thin films of silicon dioxide (SiO2) and titanium dioxide (TiO2) for application in precision optics prepared via the solgel route are being investigated in this paper. The sol-gel process presents a low cost approach, which is capable of tailoring thin films of various materials in optical grade quality. Both SiO2 and TiO2 are materials well known for their application in the field of anti-reflective and also highly reflective optical coatings. For precision optics purposes, thickness control and high quality of such coatings are of utmost importance. In this work, thin films were deposited on microscope glass slides substrates using the dip-coating technique from a solution based on alkoxide precursors of tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TIP) for SiO2 and TiO2, respectively. As-deposited films were studied using spectroscopic ellipsometry to determine their thickness and refractive index. Using a semi-empirical equation, a relationship between the coating speed and the heat-treated film thickness was described for both SiO2 and TiO2 thin films. This allows us to control the final heat-treated thin film thickness by simply adjusting the coating speed. Furthermore, films' surface was studied using the white-light interferometry. As-prepared films exhibited low surface roughness with the area roughness parameter Sq being on average of 0.799 nm and 0.33 nm for SiO2 and TiO2, respectively.

Transport properties of ultra-thin VO2 films on (001) TiO2 grown by reactive molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Paik, Hanjong; Moyer, Jarrett A.; Spila, Timothy; Tashman, Joshua W.; Mundy, Julia A.; Freeman, Eugene; Shukla, Nikhil; Lapano, Jason M.; Engel-Herbert, Roman; Zander, Willi; Schubert, Jürgen; Muller, David A.; Datta, Suman; Schiffer, Peter; Schlom, Darrell G.

2015-10-01

We report the growth of (001)-oriented VO2 films as thin as 1.5 nm with abrupt and reproducible metal-insulator transitions (MIT) without a capping layer. Limitations to the growth of thinner films with sharp MITs are discussed, including the Volmer-Weber type growth mode due to the high energy of the (001) VO2 surface. Another key limitation is interdiffusion with the (001) TiO2 substrate, which we quantify using low angle annular dark field scanning transmission electron microscopy in conjunction with electron energy loss spectroscopy. We find that controlling island coalescence on the (001) surface and minimization of cation interdiffusion by using a low growth temperature followed by a brief anneal at higher temperature are crucial for realizing ultrathin VO2 films with abrupt MIT behavior.

Preparation, stabilization and characterization of TiO(2) on thin polyethylene films (LDPE). Photocatalytic applications.

PubMed

Zhiyong, Yu; Mielczarski, E; Mielczarski, J; Laub, D; Buffat, Ph; Klehm, U; Albers, P; Lee, K; Kulik, A; Kiwi-Minsker, L; Renken, A; Kiwi, J

2007-02-01

An innovative way to fix preformed nanocrystalline TiO(2) on low-density polyethylene film (LDPE-TiO(2)) is presented. The LDPE-TiO(2) film was able to mediate the complete photodiscoloration of Orange II using about seven times less catalyst than a TiO(2) suspension and proceeded with a photonic efficiency of approximately 0.02. The catalyst shows photostability over long operational periods during the photodiscoloration of the azo dye Orange II. The LDPE-TiO(2) catalyst leads to full dye discoloration under simulated solar light but only to a 30% TOC reduction since long-lived intermediates generated in solution seem to preclude full mineralization of the dye. Physical insight is provided into the mechanism of stabilization of the LDPE-TiO(2) composite during the photocatalytic process by X-ray photoelectron spectroscopy (XPS). The adherence of TiO(2) on LDPE is investigated by electron microscopy (EM) and atomic force microscopy (AFM). The thickness of the TiO(2) film is seen to vary between 1.25 and 1.69 microm for an unused LDPE-TiO(2) film and between 1.31 and 1.50 microm for a sample irradiated 10h during Orange II discoloration pointing out to a higher compactness of the TiO(2) film after the photocatalysis.

Influence of Operating Parameters on Surface Properties of RF Glow Discharge Oxygen Plasma Treated TiO2/PET Film for Biomedical Application

EPA Science Inventory

Thin transparent titania (TiO2) films were coated on the surface of flexible poly (ethylene terephthalate) (PET) surface using standard sol gel techniques. The TiO2/PET thin film surfaces were further modified by exposing the films to a RF glow discharge oxygen plasma. The exposu...

TiO2-BASED Composite Films for the Photodegradation of Oxytetracycline

NASA Astrophysics Data System (ADS)

Li, Hui; Guan, Ling-Xiao; Feng, Ji-Jun; Li, Fang; Yao, Ming-Ming

2015-02-01

The spread of the antibiotic oxytetracycline (OTC) has been thought as a threat to the safety of drinking water. In this paper, the photocatalytic activity of the nanocrystalline Fe/Ca co-doped TiO2-SiO2 composite film for the degradation of OTC was studied. The films were characterized by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), N2 adsorption/desorption isotherms, photoluminescence (PL) spectra, and UV-Vis diffraction reflectance absorption spectra (DRS). The FE-SEM results indicated that the Fe/Ca co-doped TiO2-SiO2 film was composed of smaller nanoparticles compared to pure TiO2 or TiO2-SiO2 film. The BET surface area results showed that the specific surface area of the pure TiO2, TiO2-SiO2 and Ca2+/Fe3+ co-doped TiO2-SiO2 is 118.3 m2g-1, 294.3 m2g-1 and 393.7 m2g-1, respectively. The DRS and PL spectra revealed that the Fe/Ca co-doped TiO2-SiO2 film had strong visible light adsorption and diminished electrons/holes recombination. Experimental results showed that the Fe/Ca co-doped TiO2-SiO2 film is effective in the degradation of OTC under both UV and visible light irradiation.

Single-Nanoparticle Photoelectrochemistry at a Nanoparticulate TiO2 -Filmed Ultramicroelectrode.

PubMed

Peng, Yue-Yi; Ma, Hui; Ma, Wei; Long, Yi-Tao; Tian, He

2018-03-26

An ultrasensitive photoelectrochemical method for achieving real-time detection of single nanoparticle collision events is presented. Using a micrometer-thick nanoparticulate TiO 2 -filmed Au ultra-microelectrode (TiO 2 @Au UME), a sub-millisecond photocurrent transient was observed for an individual N719-tagged TiO 2 (N719@TiO 2 ) nanoparticle and is due to the instantaneous collision process. Owing to a trap-limited electron diffusion process as the rate-limiting step, a random three-dimensional diffusion model was developed to simulate electron transport dynamics in TiO 2 film. The combination of theoretical simulation and high-resolution photocurrent measurement allow electron-transfer information of a single N719@TiO 2 nanoparticle to be quantified at single-molecule accuracy and the electron diffusivity and the electron-collection efficiency of TiO 2 @Au UME to be estimated. This method provides a test for studies of photoinduced electron transfer at the single-nanoparticle level. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elaboration and Characterization of TiO2 and Study of the Influence of The Number of Thin Films on the Methylene Blue Adsorption Rate

NASA Astrophysics Data System (ADS)

Madoui, Karima; Medjahed, Aicha; Hamici, Melia; Djamila, Abdi; Boudissa, Mokhtar

2018-05-01

Thin films of titanium oxide (TiO2) deposited on glass substrates were fabricated by using the sol-gel route. The realization of these thin layers was made using the dip-coating technique with a solution of titanium isopropoxyde as a precursor. The samples prepared with different numbers of deposited layers were annealed at 400 ° C for 2 hours. The main purposes of this work were investigations of both the effect of the number of thin TiO2 layers on the crystal structure of the anatase form first and, their ability to adsorb the solution of methylene blue in order to make colored filters from a photocatalytic process. The deposited titanium-oxide layers were characterized by using various techniques: namely, X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM) and UV-Visible spectrometry. The result obtained by using the XRD technique showed the appearance of an anatase phase, as was confirmed by using Raman spectroscopy. The AFM surface analysis allowed the surface topography to be characterized and the surface roughness to be measured, which increased with increasing number of layers. The UV-Visible spectra showed that the TiO2 films had a good transmittance varying from 65% to 95% according to the number of layers. The gap energy varied as a function of the number of deposited layers. The as deposited TiO2 layers were tested as a photocatalyst towards the adsorption of methylene blue dye. The results obtained during this study showed that the adsorption capacity varied according to the number of deposited thin layers and the exposing duration to ultraviolet (UV) light. The maximum absorption rate of the dye was obtained for the two-layer sample. Seventy-two hours of irradiation allowed the adsorption intensity of the dye to be maximized for two-layer films.

Towards developing an efficient sensitive element for trinitrotoluene detection: TiO2 thin films functionalized with molecularly imprinted copolymer films

NASA Astrophysics Data System (ADS)

Lazau, Carmen; Iordache, Tanta-Verona; Florea, Ana-Mihaela; Orha, Corina; Bandas, Cornelia; Radu, Anita-Laura; Sarbu, Andrei; Rotariu, Traian

2016-10-01

In this study, TiO2 films were successfully grown in-situ onto a FTO substrate by a hydrothermal method, using TiCl4 as Ti precursor, and further on functionalized with a 2,4,6-trinitrotoluene-molecularly imprinted polymer (TNT-MIP) film as a preliminary step in developing a trinitrotoluene (TNT) reusable sensor to overcome the international security issues. For investigating the TiO2 film thickness, crystalline structure and morphology, the films were autoclaved at 200 °C at different times. The X-ray diffraction showed that TiO2 films possessed a rutile structure, with no cracks visible by atomic force microscopy (AFM), and the films morphology observed by scanning electron microscopy (SEM) was highly dependent upon the hydrothermal treatment time. Yet, the TiO2 films with a more porous surface were more suitable for TNT-MIP film deposit. Rheology of precursor polymer film solutions, based on poly (acrylonitrile-co-acrylic acid), poly (acrylonitrile-co-methacrylic acid) or poly (acrylonitrile- co-itaconic acid), and the structure and adherence of TNT-MIP films were investigated in order to establish the correct recipe of the MIP. The removal yield of TNT from the imprinted films, the thickness, the porosity and the compatibility with the inorganic TiO2 film were adequate for the poly (acrylonitrile-co-acrylic acid) system with an acrylonitrile: acrylic acid practical ratio of 86.1:13.9 (wt./wt.). Farmore, AFM morphology corroborated with SEM results highlighted the effect of TNT imprinting in the copolymer matrix as the surface of the imprinted layer was quite different from that of the non-imprinted layer.

In situ construction of g-C3N4/TiO2 heterojunction films with enhanced photocatalytic activity over magnetic-driven rotating frame

NASA Astrophysics Data System (ADS)

Pan, Chao; Jia, Jia; Hu, Xiaoyun; Fan, Jun; Liu, Enzhou

2018-02-01

Corn-shaped TiO2 nanofilms were fabricated by a glycerol-assisted hydrothermal method, and then g-C3N4 was deposited on the surface of TiO2 films using melamine as precursor under air atmosphere by an in site microwave-heating technique. The investigations indicate that microwave-heating process is a facile strategy to obtain g-C3N4 by thermal polymerization of melamine, which can achieve in situ constructing of g-C3N4/TiO2 heterojunction films with high stability. The as-prepared TiO2 films with crack and holes have visible light scattering capability, and the scattering light overlaps with the intrinsic absorption of g-C3N4, leading to an absorption plateau in the range of 400-550 nm. Besides, a magnetic-driven rotating frame was developed to enhance the mass transfer processes during the photocatalytic water splitting. The result shows that g-C3N4/TiO2 films exhibit excellent activities under simulated-sunlight irradiation, in addition to the enhanced mass transfer, the overlapped visible light absorption, stable contact and effective charge transfer between g-C3N4 and TiO2 can facilitate the hydrogen production and light utilization efficiency as well. The hydrogen production rate can reach 13.8 mmol h-1 m-2 over g-C3N4/TiO2 films prepared using 0.5 g of melamine and 16.0 cm2 of TiO2.

Structure and optical properties of TiO2 thin films deposited by ALD method

NASA Astrophysics Data System (ADS)

Szindler, Marek; Szindler, Magdalena M.; Boryło, Paulina; Jung, Tymoteusz

2017-12-01

This paper presents the results of study on titanium dioxide thin films prepared by atomic layer deposition method on a silicon substrate. The changes of surface morphology have been observed in topographic images performed with the atomic force microscope (AFM) and scanning electron microscope (SEM). Obtained roughness parameters have been calculated with XEI Park Systems software. Qualitative studies of chemical composition were also performed using the energy dispersive spectrometer (EDS). The structure of titanium dioxide was investigated by X-ray crystallography. A variety of crystalline TiO2 was also confirmed by using the Raman spectrometer. The optical reflection spectra have been measured with UV-Vis spectrophotometry.

Tuning the Phase and Microstructural Properties of TiO2 Films Through Pulsed Laser Deposition and Exploring Their Role as Buffer Layers for Conductive Films

NASA Astrophysics Data System (ADS)

Agarwal, S.; Haseman, M. S.; Leedy, K. D.; Winarski, D. J.; Saadatkia, P.; Doyle, E.; Zhang, L.; Dang, T.; Vasilyev, V. S.; Selim, F. A.

2018-04-01

Titanium oxide (TiO2) is a semiconducting oxide of increasing interest due to its chemical and thermal stability and broad applicability. In this study, thin films of TiO2 were deposited by pulsed laser deposition on sapphire and silicon substrates under various growth conditions, and characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), optical absorption spectroscopy and Hall-effect measurements. XRD patterns revealed that a sapphire substrate is more suitable for the formation of the rutile phase in TiO2, while a silicon substrate yields a pure anatase phase, even at high-temperature growth. AFM images showed that the rutile TiO2 films grown at 805°C on a sapphire substrate have a smoother surface than anatase films grown at 620°C. Optical absorption spectra confirmed the band gap energy of 3.08 eV for the rutile phase and 3.29 eV for the anatase phase. All the deposited films exhibited the usual high resistivity of TiO2; however, when employed as a buffer layer, anatase TiO2 deposited on sapphire significantly improves the conductivity of indium gallium zinc oxide thin films. The study illustrates how to control the formation of TiO2 phases and reveals another interesting application for TiO2 as a buffer layer for transparent conducting oxides.

Sol-gel preparation of self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective coating for solar glass

NASA Astrophysics Data System (ADS)

Lin, Wensheng; Zheng, Jiaxian; Yan, Lianghong; Zhang, Xinxiang

2018-03-01

Self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective (AR) coating is prepared by sol-gel process. SiO2 sol is prepared by using tetraethyl orthosilicate (TEOS) as precursor and ammonia as catalyst, while TiO2 sol was prepared by using tetrabutyl orthotitanate (TBOT) as precursor and hydrochloric acid as catalyst. The effect of TiO2 content on refractive index, abrasion-resistance and photo-catalytic activity of SiO2-TiO2 hybrid thin films or powders is systematically investigated. It is found that the refractive index of SiO2-TiO2 hybrid thin films increases gradually from 1.18 to 1.53 as the weight ratio of TiO2 to SiO2 increased from 0 to 1.0. The SiO2-TiO2 hybrid thin film and powder possesses good abrasion-resistance and photo-catalytic activity, respectively, as the weight ratio of TiO2 to SiO2 is 0.4. The degradation degree of Rhodamine B by SiO2-TiO2 hybrid powder is 88.3%. Finally, SiO2-TiO2/SiO2-TiO2 double-layer AR coating with high transmittance, abrasion-resistance and self-cleaning property is realized.

Effect of substrate surface treatment on electrochemically assisted photocatalytic activity of N-S co-doped TiO2 films

NASA Astrophysics Data System (ADS)

Parada-Gamboa, N. J.; Pedraza-Avella, J. A.; Meléndez, A. M.

2017-01-01

To investigate whether different metal surface treatments, performed on meshes of stainless steel 304 and titanium, affect the photocatalytic activity (PCA) of supported modified anodic TiO2 films, metallic substrates were coated with titanium isopropoxide sol-gel precursor modified with thiourea. Substrates were pretreated by some of the following techniques: a) sandblasting, b) pickling, c) hydroxylation and d) passivation. The as-prepared electrode materials were characterized by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and voltammetry in the dark and under light UVA irradiation. PCA of modified N-S-TiO2 electrodes was evaluated by electrochemically assisted photocatalytic degradation of methyl orange. The results of XPS revealed that N and S were incorporated into the lattice of TiO2. FESEM showed that surface roughness and thickness of films varies depending on surface treatment. Voltammetric and XPS characterization of N-S co-doped TiO2 films supported on stainless steel revealed that their surface contains alpha-Fe2O3/FeOOH. Accordingly, iron contamination of the films coming from stainless steel was detrimental to the degradation of methyl orange. Prior to sol-gel coating process, sandblasting followed by nitric acid passivation for stainless steel or hydrofluoric acid pickling process in the case of titanium improved the PCA of N-S co-doped TiO2 films.

Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.

PubMed

Yoshida, Tomoko; Niimi, Satoshi; Yamamoto, Muneaki; Nomoto, Toyokazu; Yagi, Shinya

2015-06-01

The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts. Copyright © 2015 Elsevier Inc. All rights reserved.

Preparation and Optimization of Fluorescent Thin Films of Rosamine-SiO2/TiO2 Composites for NO2 Sensing

PubMed Central

Guillén, María G.; Gámez, Francisco; Suárez, Belén; Queirós, Carla; Silva, Ana M. G.; Barranco, Ángel; Sánchez-Valencia, Juan Ramón; Pedrosa, José María; Lopes-Costa, Tânia

2017-01-01

The incorporation of a prototypical rosamine fluorescent dye from organic solutions into transparent and microstructured columnar TiO2 and SiO2 (MO2) thin films, prepared by evaporation at glancing angles (GAPVD), was evaluated. The aggregation of the adsorbed molecules, the infiltration efficiency and the adsorption kinetics were studied by means of UV-Vis absorption and fluorescence spectroscopies. Specifically, the infiltration equilibrium as well as the kinetic of adsorption of the emitting dye has been described by a Langmuir type adsorption isotherm and a pseudosecond order kinetic model, respectively. The anchoring mechanism of the rosamine to the MO2 matrix has been revealed by specular reflectance Fourier transform infrared spectroscopy and infiltration from aqueous solutions at different pH values. Finally, the sensing performance towards NO2 gas of optimized films has been assessed by following the changes of its fluorescence intensity revealing that the so-selected device exhibited improved sensing response compared to similar hybrid films reported in the literature. PMID:28772484

Effects of atomic oxygen on titanium dioxide thin film

NASA Astrophysics Data System (ADS)

Shimosako, Naoki; Hara, Yukihiro; Shimazaki, Kazunori; Miyazaki, Eiji; Sakama, Hiroshi

2018-05-01

In low earth orbit (LEO), atomic oxygen (AO) has shown to cause degradation of organic materials used in spacecrafts. Similar to other metal oxides such as SiO2, Al2O3 and ITO, TiO2 has potential to protect organic materials. In this study, the anatese-type TiO2 thin films were fabricated by a sol-gel method and irradiated with AO. The properties of TiO2 were compared using mass change, scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmittance spectra and photocatalytic activity before and after AO irradiation. The results indicate that TiO2 film was hardly eroded and resistant against AO degradation. AO was shown to affects only the surface of a TiO2 film and not the bulk. Upon AO irradiation, the TiO2 films were slightly oxidized. However, these changes were very small. Photocatalytic activity of TiO2 was still maintained in spite of slight decrease upon AO irradiation, which demonstrated that TiO2 thin films are promising for elimination of contaminations outgassed from a spacecraft's materials.

TiO2 films photocatalytic activity improvements by swift heavy ions irradiation

NASA Astrophysics Data System (ADS)

Rafik, Hazem; Mahmoud, Izerrouken; Mohamed, Trari; Abdenacer, Benyagoub

2014-08-01

TiO2 thin films synthesized by sol-gel on glass substrates are irradiated by 90 MeV Xe ions at various fluences and room temperature under normal incidence. The structural, electrical, optical and surface topography properties before and after Xe ions irradiation are investigated. X-ray diffraction (XRD) reveals that the crystallinity is gradually destroyed, and the films become amorphous above 5×1012 ions/cm2. The band gap is not affected by Xe ions irradiation as evidenced from the optical measurements. By contrast, the conductivity increases with raising Xe fluence. The energy band diagram established from the electrochemical characterization shows the feasibility of TiO2 films for the photo-electrochemical chromate reduction. Xe ion irradiation results in enhanced photocatalytic activity in aquatic medium, evaluated by the reduction of Cr(VI) into trivalent state. TiO2 films irradiated at 1013 Xe/cm2 exhibit the highest photoactivity; 69% of chromate (10 ppm) is reduced at pH 3 after 4 h of exposure to sunlight (1120 mW cm-2) with a quantum yield of 0.06%.

Preparation and characterization of nanostructured Pt/TiO2 thin films treated using electron beam.

PubMed

Shin, Joong-Hyeok; Woo, Hee-Gweon; Kim, Bo-Hye; Lee, Byung Cheol; Jun, Jin

2010-05-01

Pt nanoparticle-doped titanium dioxide (Pt/TiO2) thin films were prepared on a silicon wafer substrate by sol-gel spin coating process. The prepared thin films were treated with electron beam (EB at 1.1 MeV, 100, 200, 300 kGy) at air atmosphere. The effect of EB-irradiation on the composition of the treated thin films, optical properties and morphology of thin films were investigated by various analytical techniques such as X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The crystal structure of the TiO2 layer was found to be an anatase phase and the size of TiO2 particles was determined to be about 13 nm. Pt nanoparticles with diameter of 5 nm were observed on surface of the films. A new layer (presumed to be Pt-Ti complex and/or PtO2 compound) was created in the Pt/TiO2 thin film treated with EB (300 kGy). The transmittance of thin film decreased with EB treatment whereas the refractive index increased.

Growth of ultra-thin TiO 2 films by spray pyrolysis on different substrates

NASA Astrophysics Data System (ADS)

Oja Acik, I.; Junolainen, A.; Mikli, V.; Danilson, M.; Krunks, M.

2009-12-01

In the present study TiO 2 films were deposited by spray pyrolysis method onto ITO covered glass and Si (1 0 0) substrates. The spray solution containing titanium(IV) isopropoxide, acetylacetone and ethanol was sprayed at a substrate temperature of 450 °C employing 1-125 spray pulses (1 s spray and 30 s pause). According to AFM, continuous coverage of ITO and Si substrates with TiO 2 layer is formed by 5-10 and below 5 spray pulses, respectively. XPS studies revealed that TiO 2 film growth on Si substrate using up to 4 spray pulses follows 2D or layer-by-layer-growth. Above 4 spray pulses, 3D or island growth becomes dominant irrespective of the substrate. Only 50 spray pulses result in TiO 2 layer with the thickness more than XPS measurement escape depth as any signal from the substrate could not be detected. TiO 2 grain size remains 30 nm on ITO and increases from 10-20 nm to 50-100 nm on Si substrate with the number of spray pulses from 1 to 125.

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

NASA Astrophysics Data System (ADS)

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

2014-04-01

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]).

Degradation product analysis from the photocatalytic oxidation/reduction of 2,4-dichlorophenol in the presence of mesoporous silica encapsulated TiO2 particles and TiO2 dispersions (presentation)

EPA Science Inventory

Thin films of Degussa P-25 TiO2 encapsulated in an SBA-15 mesoporous silica matrix were prepared. The TiO2/SBA-15 thin film structure was verified using transmission electron microscopy (TEM) and small angle X-ray diffraction (XRD). During irradiation with 350 nm light, the TiO...

Optical, electrical and dielectric properties of TiO2-SiO2 films prepared by a cost effective sol-gel process.

PubMed

Vishwas, M; Rao, K Narasimha; Gowda, K V Arjuna; Chakradhar, R P S

2011-12-01

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 (100) 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. Copyright © 2011 Elsevier B.V. All rights reserved.

Preparation of TiO2/Ag/TiO2 (TAT) multilayer films with optical and electrical properties enhanced by using Cr-added Ag film

NASA Astrophysics Data System (ADS)

Loka, Chadrasekhar; Lee, Kee-Sun

2017-09-01

The dielectric-metal-dielectric tri-layer films have attracted much attention by virtue of their low-cost and high quality device performance as a transparent conductive electrode. Here, we report the deposition of Cr doped Ag films sandwiched between thin TiO2 layers and investigation on the surface microstructure, optical and electrical properties depending on the thickness of the Ag(Cr). The activation energy (1.18 eV) for grain growth of Ag was calculated from the Arrhenius plot using the law Dn -D0n = kt , which was comparable to the bulk diffusion of Ag. This result indicated the grain growth of Ag was effectively retarded by the Cr addition, which was presumed to related with blocking the surface and grain boundary diffusion due to Cr segregation. Based on thermal stability of Cr added Ag film, we deposited TiO2/Ag(Cr)/TiO2 (TAT) multilayer thin films and with a 10 nm thick Ag(Cr), the TAT films showed high optical transmittance in the visible region (94.2%), low electrical resistivity (8.66 × 10-5 Ω cm), and hence the high figure of merit 57.15 × 10-3 Ω-1 was achieved. The high transmittance of the TAT film was believed to be attributed to the low optical loss due to a reduction in the Ag layer thickness, the surface plasmon effect, and the electron scattering reduced by the Ag layer with a low electrical resistivity.

Spray pyrolysed Ru:TiO2 thin film electrodes prepared for electrochemical supercapacitor

NASA Astrophysics Data System (ADS)

Fugare, B. Y.; Thakur, A. V.; Kore, R. M.; Lokhande, B. J.

2018-04-01

Ru doped TiO2 thin films are prepared by using 0.06 M aqueous solution of potassium titanium oxalate (pto), and 0.005 M aqueous solution of ruthenium tri chloride (RuCl3) precursors. The deposition was carried on stainless steel (SS) by using well known ultrasonic spray pyrolysis technique (USPT) at 723° K by maintaining the spray rate 12 cc/min and compressed air flow rate 10 Lmin-1. Prepared Ru:TiO2 thin films were characterized by structurally, morphologically and electrochemically. Deposited RuO2 shows amorphous structure and TiO2 shows tetragonal crystal structure with rutile as prominent phase at very low decomposition temperature. SEM micrographs of RuO2 exhibits porous, interconnected, spherical grains type morphology and TiO2 shows porous, nanorods and nanoplates like morphology and also Ru doped TiO2 shows porous, spherical, granular and nanorods type morphology. The electrochemical cyclic voltammetery shows mixed capacitive behavior. The achieved highest value of specific capacitance 2692 F/g was Ru doped TiO2 electrode in 0.5 M H2SO4.

Radio Frequency Magnetron Sputtering Deposition of TiO2 Thin Films and Their Perovskite Solar Cell Applications

PubMed Central

Chen, Cong; Cheng, Yu; Dai, Qilin; Song, Hongwei

2015-01-01

In this work, we report a physical deposition based, compact (cp) layer synthesis for planar heterojunction perovskite solar cells. Typical solution-based synthesis of cp layer for perovskite solar cells involves low-quality of thin films, high-temperature annealing, non-flexible devices, limitation of large-scale production and that the effects of the cp layer on carrier transport have not been fully understood. In this research, using radio frequency magnetron sputtering (RFMS), TiO2 cp layers were fabricated and the thickness could be controlled by deposition time; CH3NH3PbI3 films were prepared by evaporation & immersion (E & I) method, in which PbI2 films made by thermal evaporation technique were immersed in CH3NH3I solution. The devices exhibit power conversion efficiency (PCE) of 12.1% and the photovoltaic performance can maintain 77% of its initial PCE after 1440 h. The method developed in this study has the capability of fabricating large active area devices (40 × 40 mm2) showing a promising PCE of 4.8%. Low temperature and flexible devices were realized and a PCE of 8.9% was obtained on the PET/ITO substrates. These approaches could be used in thin film based solar cells which require high-quality films leading to reduced fabrication cost and improved device performance. PMID:26631493

Influence of TiO2(110) surface roughness on growth and stability of thin organic films.

PubMed

Szajna, K; Kratzer, M; Wrana, D; Mennucci, C; Jany, B R; Buatier de Mongeot, F; Teichert, C; Krok, F

2016-10-14

We have investigated the growth and stability of molecular ultra-thin films, consisting of rod-like semiconducting para-hexaphenyl (6P) molecules vapor deposited on ion beam modified TiO 2 (110) surfaces. The ion bombarded TiO 2 (110) surfaces served as growth templates exhibiting nm-scale anisotropic ripple patterns with controllable parameters, like ripple depth and length. In turn, by varying the ripple depth one can tailor the average local slope angle and the local step density/terrace width of the stepped surface. Here, we distinguish three types of substrates: shallow, medium, and deep rippled surfaces. On these substrates, 6P sub-monolayer deposition was carried out in ultra-high vacuum by organic molecular beam evaporation (OMBE) at room temperature leading to the formation of islands consisting of upright standing 6P molecules, which could be imaged by scanning electron microscopy and atomic force microscopy (AFM). It has been found that the local slope and terrace width of the TiO 2 template strongly influences the stability of OMBE deposited 6P islands formed on the differently rippled substrates. This effect is demonstrated by means of tapping mode AFM, where an oscillating tip was used as a probe for testing the stability of the organic structures. We conclude that by increasing the local slope of the TiO 2 (110) surface the bonding strength between the nearest neighbor standing molecules is weakened due to the presence of vertical displacement in the molecular layer in correspondence to the TiO 2 atomic step height.

Observation of Significant enhancement in the efficiency of a DSSC by InN nanoparticles over TiO 2-nanoparticle films

NASA Astrophysics Data System (ADS)

Wang, Tsai-Te; Raghunath, P.; Lu, Yun-Fang; Liu, Yu-Chang; Chiou, Chwei-Huawn; Lin, M. C.

2011-06-01

We have studied the effect of InN deposited over TiO2 nanoparticle (NP) films on the performance of dye-sensitized solar cells (DSSCs) using N3 dye with I/I3- electrolyte. A 10-20% increase in efficiency was observed for InN deposited, N3 sensitized 5-8.5 μm thick TiO2 films as compared to similar non-treated films. The deposition of InN was carried out in the temperature range of 573-723 K organometallic chemical vapor deposition (OMCVD). Spectral shifts and DFT calculations with a model anchoring group (R‧COOH) both suggest binding of the N3 dye directly to both InN and the InN/TiO2 sites.

Sprayed nanostructured TiO2 films for efficient photocatalytic degradation of textile azo dye.

PubMed

Stambolova, Irina; Shipochka, Capital Em Cyrillicaria; Blaskov, Vladimir; Loukanov, Alexandrе; Vassilev, Sasho

2012-12-05

Spray pyrolysis procedure for preparation of nanostructured TiO(2) films with higher photocatalytic effectiveness and longer exploitation life is presented in this study. Thin films of active nanocrystalline TiO(2) were obtained from titanium isopropoxide, stabilized with acetyl acetone and characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The activity of sprayed nanostructured TiO(2) is tested for photocatalytic degradation of Reactive Black 5 dye with concentrations up to 80 ppm. Interesting result of the work is the reduction of toxicity after photocatalytic treatment of RB5 with TiO(2), which was confirmed by the lower percentage of mortality of Artemia salina. It was proved that the film thickness, conditions of post deposition treatment and the type of the substrate affected significantly the photocatalytic reaction. Taking into account that the parameters are interdependent, it is necessary to optimize the preparation conditions in order to synthesize photocatalytic active films. Copyright © 2012 Elsevier B.V. All rights reserved.

Mechanism of room temperature oxygen sensor based on nanocrystalline TiO2 film

NASA Astrophysics Data System (ADS)

Bakri, A. S.; Sahdan, M. Z.; Nafarizal, N.; Abdullah, S. A.; Said, N. D. M.; Raship, N. A.; Sari, Y.

2018-04-01

A titanium dioxide (TiO2) thin film is proposed as the active layer for the detection of oxygen gas. The sensor is fabricated on silicon wafer using sol-gel dip coating technique with a constant withdrawal speed. The field emission scanning electron microscope image reveals that the film has a uniform structure while the x-ray diffraction analysis indicates that the film is anatase phase with tetragonal lattice structure. The film exhibit the highest intensity peak at (101) plane. The surface roughness measurement shows that the film has low surface roughness with small grain size. The electrical studies revealed that the resistivity is about 4.02 x 10-3 Ω.cm and the thickness of TiO2 film is 127.44 nm. The gas sensor measurement showed that the sensor response of the film is about 4.21% at room temperature.

Nanostructured Gd3+-TiO2 surfaces for self-cleaning application

NASA Astrophysics Data System (ADS)

Saif, M.; El-Molla, S. A.; Aboul-Fotouh, S. M. K.; Ibrahim, M. M.; Ismail, L. F. M.; Dahn, Douglas C.

2014-06-01

Preparation of self-cleaning surfaces based on lanthanide modified titanium dioxide nanoparticles has rarely been reported. In the present work, gadolinium doped titanium dioxide thin films (x mol Gd3+-TiO2 where x = 0.000, 0.005, 0.008, 0.010, 0.020 and 0.030 mol) were synthesized by sol-gel method and deposited using doctor-blade method. These films were characterized by studying their structural, optical and electrical properties. Doping with gadolinium decreases the band gap energy and increase conductivity of thin films. The photo self-cleaning activity in term of quantitative determination of the active oxidative species (rad OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results show that, the highly active thin film is the 0.020 Gd3+-TiO2. The structural, morphology, optical, electrical and photoactivity properties of Gd3+-TiO2 thin films make it promising surfaces for self-cleaning application. Mineralization of commercial textile dye (Remazol Red RB-133, RR) and durability using 0.020Gd3+-TiO2 film surface was studied.

MEMS-Based Gas Sensor Using PdO-Decorated TiO2 Thin Film for Highly Sensitive and Selective H2 Detection with Low Power Consumption

NASA Astrophysics Data System (ADS)

Kwak, Seungmin; Shim, Young-Seok; Yoo, Yong Kyoung; Lee, Jin-Hyung; Kim, Inho; Kim, Jinseok; Lee, Kyu Hyoung; Lee, Jeong Hoon

2018-03-01

We report a micromachined H2 sensor that is composed of a Pt micro-heater, low-stress insulating layer (SiO2/SiNx/SiO2), Pt-interdigitated electrodes, and gas sensing materials. Three types of Pt micro-heater are designed as function of electrode width, and their thermal properties are systematically analyzed by finite element modeling FEM with infrared camera. The power consumptions when the surface temperature reached 150, 200, 250, and 300 °C are calculated to approximately 33, 48, 67 and 85 mW, respectively. The response of the PdO nanoparticles-decorated TiO2 thin films to H2 is much higher than those of other gases such as CH4 and CO at 200 °C (48 mW). Further, the response time is reduced to approximately 3 s. The enhancement of gas sensing properties is related to well-designed micro-heater and catalytic effects of PdO nanoparticles such as electronic and chemical sensitization. These results suggest that the PdO nanoparticles-decorated TiO2 thin film, namely MEMS-based H2 sensors are very promising for use in IoT application to improve the quality of human's life.

MEMS-Based Gas Sensor Using PdO-Decorated TiO2 Thin Film for Highly Sensitive and Selective H2 Detection with Low Power Consumption

NASA Astrophysics Data System (ADS)

Kwak, Seungmin; Shim, Young-Seok; Yoo, Yong Kyoung; Lee, Jin-Hyung; Kim, Inho; Kim, Jinseok; Lee, Kyu Hyoung; Lee, Jeong Hoon

2018-05-01

We report a micromachined H2 sensor that is composed of a Pt micro-heater, low-stress insulating layer (SiO2/SiNx/SiO2), Pt-interdigitated electrodes, and gas sensing materials. Three types of Pt micro-heater are designed as function of electrode width, and their thermal properties are systematically analyzed by finite element modeling FEM with infrared camera. The power consumptions when the surface temperature reached 150, 200, 250, and 300 °C are calculated to approximately 33, 48, 67 and 85 mW, respectively. The response of the PdO nanoparticles-decorated TiO2 thin films to H2 is much higher than those of other gases such as CH4 and CO at 200 °C (48 mW). Further, the response time is reduced to approximately 3 s. The enhancement of gas sensing properties is related to well-designed micro-heater and catalytic effects of PdO nanoparticles such as electronic and chemical sensitization. These results suggest that the PdO nanoparticles-decorated TiO2 thin film, namely MEMS-based H2 sensors are very promising for use in IoT application to improve the quality of human's life.

500 keV Ar2+ ion irradiation induced anatase to brookite phase transformation and ferromagnetism at room temperature in TiO2 thin films

NASA Astrophysics Data System (ADS)

Bharati, B.; Mishra, N. C.; Kanjilal, D.; Rath, Chandana

2018-01-01

In our earlier report, where we have demonstrated ferromagnetic behavior at room temperature (RT) in TiO2 thin films deposited through electron beam evaporation technique followed by annealing either in Ar or O2 atmosphere [Mohanty et al., Journal of Magnetism and Magnetic Materials 355 (2014) 240-245], here we have studied the evolution of structure and magnetic properties after irradiating the TiO2 thin films with 500 keV Ar2+ ions. The pristine film while exhibits anatase phase, the films become amorphous after irradiating at fluence in the range 1 × 1014 to 1 × 1016 ions/cm2. Increasing the fluence up to 5 × 1016 ions/cm2, amorphous to crystalline phase transformation occurs and the structure becomes brookite. Although anatase to rutile phase transformation is usually reported in literatures, anatase to brookite phase transformation is an unusual feature which we have reported here for the first time. Such anatase to brookite phase transformation is accompanied with grain growth without showing any change in film thickness evidenced from Rutherford's Back Scattering (RBS) measurement. From scanning probe micrographs (SPM), roughness is found to be more in amorphous films than in the crystalline ones. Anatase to brookite phase transformation could be realized by considering the importance of intermediate amorphous phase. Because due to amorphous phase, heat deposited by energetic ions are localized as dissipation of heat is less and as a result, the localized region crystallizes in brookite phase followed by grain growth as observed in highest fluence. Further, we have demonstrated ferromagnetic behavior at RT in irradiated films similar to pristine one, irrespective of their phase and crystallinity. Origin for room temperature ferromagnetism (RTFM) is attributed to the presence of oxygen vacancies which is confirmed by carrying out XPS measurement.

Effect of growth time on the structure, morphology and optical properties of hydrothermally synthesized TiO2 nanorod thin films

NASA Astrophysics Data System (ADS)

Mohapatra, A. K.; Nayak, J.

2018-05-01

Titanium dioxide (TiO2) nanorod thin films were deposited on fluorine doped tin oxide coated glass substrates by a single step rapid hydrothermal process. The concentration of the precursor, the temperature of the reaction mixture were optimized in order to enhance the rate of deposition. Unlike the previously reported hydrothermal treatment for 24 - 48 h, the deposition of well aligned titanium dioxide nanorods was achieved in a short time such as 3 - 8 h. The crystal structure of the films were investigated by X-rays diffraction. The morphology of the nanorod films were studied with scanning electron microscopy. The optical properties were studied by photoluminescence spectroscopy.

Epitaxial Fe16N2 thin film on nonmagnetic seed layer

NASA Astrophysics Data System (ADS)

Hang, Xudong; Zhang, Xiaowei; Ma, Bin; Lauter, Valeria; Wang, Jian-Ping

2018-05-01

Metastable α″ -Fe16N2 has attracted much interest as a candidate for rare-earth-free hard magnetic materials. We demonstrate that Fe16N2 thin films were grown epitaxially on Cr seed layers with MgO (001) substrates by facing-target sputtering. Good crystallinity with the epitaxial relation MgO (001 )[110 ] ∥ Cr (001 )[100 ] ∥ Fe16N2 (001 )[100 ] was obtained. The chemical order parameter, which quantifies the degree of N ordering in the Fe16N2 (the N-disordered phase is α' -Fe8N martensite), reaches 0.75 for Cr-seeded samples. Cr has a perfect lattice constant match with Fe16N2, and no noticeable strain can be assigned to Fe16N2. The intrinsic saturation magnetization of this non-strained Fe16N2 thin film at room temperature is determined to be 2.31 T by polarized neutron reflectometry and confirmed with vibrating sample magnetometry. Our work provides a platform to directly study the magnetic properties of high purity Fe16N2 films with a high order parameter.

Semi-transparent ordered TiO2 nanostructures prepared by anodization of titanium thin films deposited onto the FTO substrate

NASA Astrophysics Data System (ADS)

Szkoda, Mariusz; Lisowska-Oleksiak, Anna; Grochowska, Katarzyna; Skowroński, Łukasz; Karczewski, Jakub; Siuzdak, Katarzyna

2016-09-01

In a significant amount of cases, the highly ordered TiO2 nanotube arrays grow through anodic oxidation of a titanium metal plate immersed in electrolyte containing fluoride ions. However, for some practical applications, e.g. solar cells or electrochromic windows, the semi-transparent TiO2 formed directly on the transparent, conductive substrate is very much desired. This work shows that high-quality Ti coating could be formed at room temperature using an industrial magnetron sputtering system within 50 min. Under optimized conditions, the anodization process was performed on 2 μm titanium films deposited onto the FTO (fluorine-tin-oxide) support. Depending on the electrolyte type, highly ordered tubular or porous titania layers were obtained. The fabricated samples, after their thermal annealing, were investigated using scanning electron microscopy, Raman spectroscopy and UV-vis spectroscopy in order to investigate their morphology, crystallinity and absorbance ability. The photocurrent response curves indicate that materials are resistant to the photocorrosion process and their activity is strongly connected to optical properties. The most transparent TiO2 films were fabricated when Ti was anodized in water electrolyte, whereas the highest photocurrent densities (12 μA cm-2) were registered for titania received after Ti anodization in ethylene glycol solution. The obtained results are of significant importance in the production of thin, semi-transparent titania nanostructures on a commercial scale.

n-Type Conductivity of Cu2O Thin Film Prepared in Basic Aqueous Solution Under Hydrothermal Conditions

NASA Astrophysics Data System (ADS)

Ursu, Daniel; Miclau, Nicolae; Miclau, Marinela

2018-03-01

We report for the first time in situ hydrothermal synthesis of n-type Cu2O thin film using strong alkaline solution. The use of copper foil as substrate and precursor material, low synthesis temperature and short reaction time represent the arguments of a new, simple, inexpensive and high field synthesis method for the preparation of n-type Cu2O thin film. The donor concentration of n-type Cu2O thin film obtained at 2 h of reaction time has increased two orders of magnitude than previous reported values. We have demonstrated n-type conduction in Cu2O thin film prepared in strong alkaline solution, in the contradiction with the previous works. Based on experimental results, the synthesis mechanism and the origin of n-type photo-responsive behavior of Cu2O thin film were discussed. We have proposed that the unexpected n-type character could be explained by H doping of Cu2O thin film in during of the hydrothermal synthesis that caused the p-to-n conductivity-type conversion. Also, this work raises new questions about the origin of n-type conduction in Cu2O thin film, the influence of the synthesis method on the nature of the intrinsic defects and the electrical conduction behavior.

Aging behavior of near atmospheric N2 ambient sputtered/patterned Au IR absorber thin films

NASA Astrophysics Data System (ADS)

Gaur, Surender P.; Kothari, Prateek; Rangra, Kamaljit; Kumar, Dinesh

2018-03-01

Near atmospheric N2 ambient sputtered Au thin films exhibit significant spectral absorptivity over medium to long wave infrared radiations. Thin films were found adequately robust for micropatterning using conventional photolithography and metal lift off processes. Since long term spectral absorptivity is major practical concern for Au blacks, this paper reports on aging behavior of near atmospheric Ar and Ar + N2 (1:1) ambient sputtered infrared absorber Au thin films. Comparative analysis on electrical, morphological and spectral absorption behavior of twenty-five weeks room temperature/vacuum aged Au infrared absorber thin films is performed. The Ar and Ar + N2 ambient sputtered Au thing films have shown anticipated consistency in their physical, electrical and spectral properties regardless the long term aging in this work.

The effect of CO2 gas adsorption on the electrical properties of Fe doped TiO2 films

NASA Astrophysics Data System (ADS)

Mardare, Diana; Adomnitei, Catalin; Florea, Daniel; Luca, Dumitru; Yildiz, Abdullah

2017-11-01

CO2 has to be monitored for indoor air quality, being also an important greenhouse gas. The electrical and sensing gas properties of the undoped and Fe doped TiO2 thin films, obtained by RF sputtering, have been investigated in different CO2 atmospheres. It was observed that the response to CO2 increases by Fe doping for the lowest doped film, and then decreases, as the dopant concentration increases. An explanation was given based on multiphonon-assisted hopping model. By studying the films electrical conductivity in front of a certain CO2 atmosphere, we have qualitatively evidenced the semiconducting n-type nature of the films under study, except for the highest Fe doped film which has a p-type behavior. An important finding is that Fe doping determines the decrease of the optimum operating temperature, approaching the room temperature.

Characterization of TiO2 films obtained by a wet chemical process

NASA Astrophysics Data System (ADS)

Sedik, Asma; Ferraria, Ana M.; Carapeto, Ana P.; Bellal, Bouzid; Trari, Mohamed; Outemzabet, Ratiba

2017-12-01

TiO2 has an easily tunable bandgap and a great absorption dye ability being widely used in many fields and in a number of fascinating applications. In this study, a wet chemical route, particularly a sol gel method using spin-coating is adopted to deposit TiO2 thin films onto soda lime glass and silicon substrates. TiO2 films were prepared by using an alcoholic solution of analytical reagent grade TiCl4 as titanium precursor at various experimental conditions. The accent was put on the conditions of preparation (spin time, spin speed, precursor concentration, number of coating layers etc), doping and on the post-deposit treatment namely the drying and the crystallization. The results showed a strong dependence on the drying temperature and on the temperature and duration of the crystallization. We found that the solution preparation and its color are important for getting a reproducible final product. The Raman spectra recorded at room temperature, showed the characteristic peaks of anatase which appear at 143 and around 396 cm-1. These peaks confirm the presence of TiO2. The X-ray diffraction (XRD) was used to identify the crystalline characteristic of TiO2 while the chemical states and relative amounts of the main elements existing in the samples were investigated by X-ray Photoelectron Spectroscopy (XPS). The morphology of the samples was visualized by AFM. We show by this work the feasibility to obtain different nanostructured TiO2 by changing the concentration of the solution. Photocatalytic activity of TiO2 films was evaluated. Rhodamine B is a recalcitrant dye and TiO2 was successfully tested for its oxidation. An abatement of 60% was obtained under sunlight for an initial concentration of 10 mg/l.

Characteristics and anticorrosion performance of Fe-doped TiO2 films by liquid phase deposition method

NASA Astrophysics Data System (ADS)

Liu, Yu; Xu, Chao; Feng, ZuDe

2014-09-01

Fe-doped TiO2 thin films were fabricated by liquid phase deposition (LPD) method, using Fe(III) nitrate as both Fe element source and fluoride scavenger instead of commonly-used boric acid (H3BO3). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis spectrum were employed to examine the effects of Fe element on morphology, structure and optical characteristics of TiO2 films. The as-prepared films were served as photoanode applied to photogenerated cathodic protection of SUS304 stainless steel (304SS). It was observed that the photoelectrochemical properties of the as-prepared films were enhanced with the addition of Fe element compared to the undoped TiO2 film. The highest photoactivity was achieved for Ti13Fe (Fe/Ti = 3 molar ratio) film prepared in precursor bath containing 0.02 M TiF4 + 0.06 M Fe(NO3)3 under white-light illumination. The effective anticorrosion behaviors can be attributed to the Fe element incorporation which decreases the probability of photogenerated charge-carrier recombination and extends the light response range of Fe-doped TiO2 films appeared to visible-light region.

Wastewater treatment by sonophotocatalysis using PEG modified TiO2 film in a circular Photocatalytic-Ultrasonic system.

PubMed

Hu, Xiaohong; Zhu, Qi; Gu, Zhibin; Zhang, Nan; Liu, Na; Stanislaus, Mishma S; Li, Dawei; Yang, Yingnan

2017-05-01

TiO 2 photocatalyst film recently has been utilized as the potential candidate for the wastewater treatment, due to its high stability and low toxicity. In order to further increase the photocatalytic ability and stability, different molecular weight of polyethylene glycol (PEG) were used to modify TiO 2 structure to synthesize porous thin film used in the developed Photocatalytic-Ultrasonic system in this work. The results showed that PEG2000 modified TiO 2 calcinated under 450°C for 2h exhibited the highest photocatalytic activity, attributed to the smallest crystallite size and optimal particle size. Over 95.0% of rhodamine B (Rh B) was photocatalytically degraded by optimized PEG 2000 -TiO 2 film after 60min of UV irradiation, while only about 50.8% of Rh B was decolored over pure TiO 2 film. Furthermore, optimized PEG 2000 -TiO 2 film was used in a circular Photocatalytic-Ultrasonic system, and the obtained synergy (0.6519) of sonophotocatalysis indicated its extremely high efficiency for Rh B degradation. In this Photocatalytic-Ultrasonic system, larger amount of PEG 2000 -TiO 2 coated glass beads, stronger ultrasonic power and longer experimental time could result to higher degradation efficiency of Rh B. In addition, repetitive experiments showed that about 97.2% of Rh B were still degraded in the fifth experiment by sonophotocatalysis using PEG 2000 -TiO 2 film. Therefore, PEG 2000 -TiO 2 film used in Photocatalytic-Ultrasonic system has promising potential for wastewater treatment, due to its excellent photocatalytic activity and high stability. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation of p-type GaN-doped SnO2 thin films by e-beam evaporation and their applications in p-n junction

NASA Astrophysics Data System (ADS)

Lv, Shuliang; Zhou, Yawei; Xu, Wenwu; Mao, Wenfeng; Wang, Lingtao; Liu, Yong; He, Chunqing

2018-01-01

Various transparent GaN-doped SnO2 thin films were deposited on glass substrates by e-beam evaporation using GaN:SnO2 targets of different GaN weight ratios. It is interesting to find that carrier polarity of the thin films was converted from n-type to p-type with increasing GaN ratio higher than 15 wt.%. The n-p transition in GaN-doped SnO2 thin films was explained for the formation of GaSn and NO with increasing GaN doping level in the films, which was identified by Hall measurement and XPS analysis. A transparent thin film p-n junction was successfully fabricated by depositing p-type GaN:SnO2 thin film on SnO2 thin film, and a low leakage current (6.2 × 10-5 A at -4 V) and a low turn-on voltage of 1.69 V were obtained for the p-n junction.

Fabrication of doped TiO2 nanotube array films with enhanced photo-catalytic activity

NASA Astrophysics Data System (ADS)

Peighambardoust, Naeimeh-Sadat; Khameneh-asl, Shahin; Khademi, Adib

2018-01-01

In the present work, we investigate the N and Fe-doped TiO2 nanotube array film prepared by treating TiO2 nanotube array film with ammonia solution and anodizing in Fe(NO3)3 solution respectively. This method avoided the use of hazardous ammonia gas, or laborious ion implantation process. N and Fe-doped TiO2 nanotube arrays (TiO2 NTs) were prepared by electrochemical anodization process in 0.5 wt % HF aqueous solution. The anodization was performed at the conditions of 20 V and 20 min, Followed by a wet immersion in NH3.H2O (1M) for N-doping for 2 hr and annealing post-treatment at 450 °C. The morphology and structure of the nanotube films were characterized by field emission scanning electron microscope (FESEM) and EDX. UV-vis. illumination test were done to observe photo-enhanced catalysis. The effect of different annealing temperature on the structure and photo-absorption property of the TiO2-TNTs was investigated. The results showed that N-TNTs nanotubes exhibited higher photocatalytic activity compared whit the Fe-doped and pure TNTs, because doping N promoted the separation of the photogenerated electrons and holes.

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

NASA Astrophysics Data System (ADS)

Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

2016-02-01

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions.

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

PubMed Central

Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

2016-01-01

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions. PMID:26911529

Thin film nano-photocatalyts with low band gap energy for gas phase degradation of p-xylene: TiO2 doped Cr, UiO66-NH2 and LaBO3 (B  =  Fe, Mn, and Co)

NASA Astrophysics Data System (ADS)

Loc Luu, Cam; Thuy Van Nguyen, Thi; Nguyen, Tri; Nguyen, Phung Anh; Hoang, Tien Cuong; Ha, Cam Anh

2018-03-01

By dip-coating technique the thin films of nano-photocatalysts TiO2, Cr-doped TiO2, LaBO3 perovskites (B  =  Fe, Mn, and Co) prepared by sol-gel method, and UiO66-NH2 prepared by a solvothermal were obtained and employed for gas phase degradation of p-xylene. Physicochemical characteristics of the catalysts were examined by the methods of BET, SEM, TEM, XRD, FT-IR, TGA, Raman and UV-vis spectroscopies. The thickness of film was determined by a Veeco-American Dektek 6M instrument. The activity of catalysts was evaluated in deep photooxidation of p-xylene in a microflow reactor at room temperature with the radiation sources of a UV (λ  =  365 nm) and LED lamps (λ  =  400-510 nm). The obtained results showed that TiO2 and TiO2 doped Cr thin films was featured by an anatase phase with nanoparticles of 10-100 nm. Doping TiO2 with 0.1%mol Cr2O3 led to reduce band gap energy from 3.01 down to 1.99 eV and extend the spectrum of photon absorption to the visible region (λ  =  622 nm). LaBO3 perovkite thin films were also featured by a crystal phase with average particle nanosize of 8-40 nm, a BET surface area of 17.6-32.7 m2 g-1 and band gap energy of 1.87-2.20 eV. UiO66-NH2 was obtained in the ball shape of 100-200 nm, a BET surface area of 576 m2 g-1 and a band gap energy of 2.83 eV. The low band gap energy nano-photocatalysts based on Cr-doped TiO2 and LaBO3 perovskites exhibited highly stable and active for photo-degradation of p-xylene in the gas phase under radiation of UV-vis light. Perovskite LaFeO3 and Cr-TiO2 thin films were the best photocatalysts with a decomposition yield being reached up to 1.70 g p-xylene/g cat.

Effect of SiN x diffusion barrier thickness on the structural properties and photocatalytic activity of TiO2 films obtained by sol-gel dip coating and reactive magnetron sputtering.

PubMed

Ghazzal, Mohamed Nawfal; Aubry, Eric; Chaoui, Nouari; Robert, Didier

2015-01-01

We investigate the effect of the thickness of the silicon nitride (SiN x ) diffusion barrier on the structural and photocatalytic efficiency of TiO2 films obtained with different processes. We show that the structural and photocatalytic efficiency of TiO2 films produced using soft chemistry (sol-gel) and physical methods (reactive sputtering) are affected differentially by the intercalating SiN x diffusion barrier. Increasing the thickness of the SiN x diffusion barrier induced a gradual decrease of the crystallite size of TiO2 films obtained by the sol-gel process. However, TiO2 obtained using the reactive sputtering method showed no dependence on the thickness of the SiN x barrier diffusion. The SiN x barrier diffusion showed a beneficial effect on the photocatalytic efficiency of TiO2 films regardless of the synthesis method used. The proposed mechanism leading to the improvement in the photocatalytic efficiency of the TiO2 films obtained by each process was discussed.

Synthesis and energy applications of mesoporous titania thin films

NASA Astrophysics Data System (ADS)

Islam, Syed Z.

The optical and electronic properties of TiO2 thin films provide tremendous opportunities in several applications including photocatalysis, photovoltaics and photoconductors for energy production. Despite many attractive features of TiO2, critical challenges include the innate inability of TiO2 to absorb visible light and the fast recombination of photoexcited charge carriers. In this study, mesoporous TiO2 thin films are modified by doping using hydrogen and nitrogen, and sensitization using graphene quantum dot sensitization. For all of these modifiers, well-ordered mesoporous titania films were synthesized by surfactant templated sol-gel process. Two methods: hydrazine and plasma treatments have been developed for nitrogen and hydrogen doping in the mesoporous titania films for band gap reduction, visible light absorption and enhancement of photocatalytic activity. The hydrazine treatment in mesoporous titania thin films suggests that hydrazine induced doping is a promising approach to enable synergistic incorporation of N and Ti3+ into the lattice of surfactant-templated TiO2 films and enhanced visible light photoactivity, but that the benefits are limited by gradual mesostructure deterioration. The plasma treated nitrogen doped mesoporous titania showed about 240 times higher photoactivity compared to undoped film in hydrogen production from photoelectrochemical water splitting under visible light illumination. Plasma treated hydrogen doped mesoporous titania thin films has also been developed for enhancement of visible light absorption. Hydrogen treatment has been shown to turn titania (normally bright white) black, indicating vastly improved visible light absorption. The cause of the color change and its effectiveness for photocatalysis remain open questions. For the first time, we showed that a significant amount of hydrogen is incorporated in hydrogen plasma treated mesoporous titania films by neutron reflectometry measurements. In addition to the

Electrophoretic deposited TiO 2 pigment-based back reflectors for thin film solar cells

DOE PAGES

Bills, Braden; Morris, Nathan; Dubey, Mukul; ...

2015-01-16

Highly reflective coatings with strong light scattering effect have many applications in optical components and optoelectronic devices. This paper reports titanium dioxide (TiO 2) pigment-based reflectors that have 2.5 times higher broadband diffuse reflection than commercially produced aluminum or silver based reflectors and result in efficiency enhancements of a single-junction amorphous Si solar cell. Electrophoretic deposition is used to produce pigment-based back reflectors with high pigment density, controllable film thickness and site-specific deposition. Electrical conductivity of the pigment-based back reflectors is improved by creating electrical vias throughout the pigment-based back reflector by making holes using an electrical discharge / dielectricmore » breakdown approach followed by a second electrophoretic deposition of conductive nanoparticles into the holes. While previous studies have demonstrated the use of pigment-based back reflectors, for example white paint, on glass superstrate configured thin film Si solar cells, this work presents a scheme for producing pigment-based reflectors on complex shape and flexible substrates. Finally, mechanical durability and scalability are demonstrated on a continuous electrophoretic deposition roll-to-roll system which has flexible metal substrate capability of 4 inch wide and 300 feet long.« less

Antibacterial activity of DLC films containing TiO2 nanoparticles.

PubMed

Marciano, F R; Lima-Oliveira, D A; Da-Silva, N S; Diniz, A V; Corat, E J; Trava-Airoldi, V J

2009-12-01

Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to their potential applications as surface coatings on biomedical devices. Titanium dioxide (TiO2) in the anatase crystalline form is a strong bactericidal agent when exposed to near-UV light. In this work we investigate the bactericidal activity of DLC films containing TiO2 nanoparticles. The films were grown on 316L stainless-steel substrates from a dispersion of TiO2 in hexane using plasma-enhanced chemical vapor deposition. The composition, bonding structure, surface energy, stress, and surface roughness of these films were also evaluated. The antibacterial tests were performed against Escherichia coli (E. coli) and the results were compared to the bacterial adhesion force to the studied surfaces. The presence of TiO2 in DLC bulk was confirmed by Raman spectroscopy. As TiO2 content increased, I(D)/I(G) ratio, hydrogen content, and roughness also increased; the films became more hydrophilic, with higher surface free energy and the interfacial energy of bacteria adhesion decreased. Experimental results show that TiO2 increased DLC bactericidal activity. Pure DLC films were thermodynamically unfavorable to bacterial adhesion. However, the chemical interaction between the E. coli and the studied films increased for the films with higher TiO2 concentration. As TiO2 bactericidal activity starts its action by oxidative damage to the bacteria wall, a decrease in the interfacial energy of bacteria adhesion causes an increase in the chemical interaction between E. coli and the films, which is an additional factor for the increasing bactericidal activity. From these results, DLC with TiO2 nanoparticles can be useful for producing coatings with antibacterial properties.

Impact of Film Thickness of Ultrathin Dip-Coated Compact TiO2 Layers on the Performance of Mesoscopic Perovskite Solar Cells.

PubMed

Masood, Muhammad Talha; Weinberger, Christian; Sarfraz, Jawad; Rosqvist, Emil; Sandén, Simon; Sandberg, Oskar J; Vivo, Paola; Hashmi, Ghufran; Lund, Peter D; Österbacka, Ronald; Smått, Jan-Henrik

2017-05-31

Uniform and pinhole-free electron-selective TiO 2 layers are of utmost importance for efficient perovskite solar cells. Here we used a scalable and low-cost dip-coating method to prepare uniform and ultrathin (5-50 nm) compact TiO 2 films on fluorine-doped tin oxide (FTO) glass substrates. The thickness of the film was tuned by changing the TiCl 4 precursor concentration. The formed TiO 2 follows the texture of the underlying FTO substrates, but at higher TiCl 4 concentrations, the surface roughness is substantially decreased. This change occurs at a film thickness close to 20-30 nm. A similar TiCl 4 concentration is needed to produce crystalline TiO 2 films. Furthermore, below this film thickness, the underlying FTO might be exposed resulting in pinholes in the compact TiO 2 layer. When integrated into mesoscopic perovskite solar cells there appears to be a similar critical compact TiO 2 layer thickness above which the devices perform more optimally. The power conversion efficiency was improved by more than 50% (from 5.5% to ∼8.6%) when inserting a compact TiO 2 layer. Devices without or with very thin compact TiO 2 layers display J-V curves with an "s-shaped" feature in the negative voltage range, which could be attributed to immobilized negative ions at the electron-extracting interface. A strong correlation between the magnitude of the s-shaped feature and the exposed FTO seen in the X-ray photoelectron spectroscopy measurements indicates that the s-shape is related to pinholes in the compact TiO 2 layer when it is too thin.

Characteristics of TiO2/ZnO bilayer film towards pH sensitivity prepared by different spin coating deposition process

NASA Astrophysics Data System (ADS)

Rahman, Rohanieza Abdul; Zulkefle, Muhammad Al Hadi; Abdullah, Wan Fazlida Hanim; Rusop, M.; Herman, Sukreen Hana

2016-07-01

In this study, titanium dioxide (TiO2) and zinc oxide (ZnO) bilayer film for pH sensing application will be presented. TiO2/ZnO bilayer film with different speed of spin-coating process was deposited on Indium Tin Oxide (ITO), prepared by sol-gel method. This fabricated bilayer film was used as sensing membrane for Extended Gate Field-Effect Transistor (EGFET) for pH sensing application. Experimental results indicated that the sensor is able to detect the sensitivity towards pH buffer solution. In order to obtained the result, sensitivity measurement was done by using the EGFET setup equipment with constant-current (100 µA) and constant-voltage (0.3 V) biasing interfacing circuit. TiO2/ZnO bilayer film which the working electrode, act as the pH-sensitive membrane was connected to a commercial metal-oxide semiconductor FET (MOSFET). This MOSFET then was connected to the interfacing circuit. The sensitivity of the TiO2 thin film towards pH buffer solution was measured by dipping the sensing membrane in pH4, pH7 and pH10 buffer solution. These thin films were characterized by using Field Emission Scanning Electron Microscope (FESEM) to obtain the surface morphology of the composite bilayer films. In addition, I-V measurement was done in order to determine the electrical properties of the bilayer films. According to the result obtained in this experiment, bilayer film that spin at 4000 rpm, gave highest sensitivity which is 52.1 mV/pH. Relating the I-V characteristic of the thin films and sensitivity, the sensing membrane with higher conductivity gave better sensitivity.

Effects of annealing on the optical, structural, and chemical properties of TiO2 and MgF2 thin films prepared by plasma ion-assisted deposition.

PubMed

Woo, Seouk-Hoon; Hwangbo, Chang Kwon

2006-03-01

Effects of thermal annealing at 400 degrees C on the optical, structural, and chemical properties of TiO2 single-layer, MgF2 single-layer, and TiO2/MgF2 narrow-bandpass filters deposited by conventional electron-beam evaporation (CE) and plasma ion-assisted deposition (PIAD) were investigated. In the case of TiO2 films, the results show that the annealing of both CE and PIAD TiO2 films increases the refractive index slightly and the extinction coefficient and surface roughness greatly. Annealing decreases the thickness of CE TiO2 films drastically, whereas it does not vary that of PIAD TiO2 films. For PIAD MgF2 films, annealing increases the refractive index and decreases the extinction coefficient drastically. An x-ray photoelectron spectroscopy analysis suggests that an increase in the refractive index and a decrease in the extinction coefficient for PIAD MgF2 films after annealing may be related to the enhanced concentration of MgO in the annealed PIAD MgF2 films and the changes in the chemical bonding states of Mg 2p, F 1s, and O is. It is found that (TiO2/MgF2) multilayer filters, consisting of PIAD TiO2 and CE MgF2 films, are as deposited without microcracks and are also thermally stable after annealing.

Influence of microstructure and chemical composition of sputter deposited TiO2 thin films on in vitro bioactivity.

PubMed

Lilja, Mirjam; Genvad, Axel; Astrand, Maria; Strømme, Maria; Enqvist, Håkan

2011-12-01

Functionalisation of biomedical implants via surface modifications for tailored tissue response is a growing field of research. Crystalline TiO(2) has been proven to be a bone bioactive, non-resorbable material. In contact with body fluids a hydroxyapaptite (HA) layer forms on its surface facilitating the bone contact. Thus, the path of improving biomedical implants via deposition of crystalline TiO(2) on the surface is interesting to follow. In this study we have evaluated the influence of microstructure and chemical composition of sputter deposited titanium oxide thin films on the in vitro bioactivity. We find that both substrate bias, topography and the flow ratio of the gases used during sputtering affect the HA layer formed on the films after immersion in simulated body fluid at 37°C. A random distribution of anatase and rutile crystals, formed at negative substrate bias and low Ar to O(2) gas flow ratios, are shown to favor the growth of flat HA crystal structures whereas higher flow ratios and positive substrate bias induced growth of more spherical HA structures. These findings should provide valuable information when optimizing the bioactivity of titanium oxide coatings as well as for tailoring process parameters for sputtered-based production of bioactive titanium oxide implant surfaces.

Effects of acid catalyst type on structural, morphological, and optoelectrical properties of spin-coated TiO2 thin film

NASA Astrophysics Data System (ADS)

Golobostanfard, Mohammad Reza; Abdizadeh, Hossein

2013-03-01

The effects of different acid catalysts of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, acetic acid, and citric acid on structural, morphological, and optoelectrical properties of nanocrystalline spin-coated TiO2 thin films synthesized via alkoxide sol-gel route were investigated. It was found that only the sols with HNO3 and HCl are suitable for film preparation. The X-ray diffractometry and Raman analysis showed that crystalline phases could be controlled by the type of acid catalyst. Although the H2SO4 sol shows good stability, it causes extremely different morphology to form due to its different sol nature and high contact angle. Fourier transformed infrared spectra confirmed the presence of acid anion species in all samples even after calcination. Furthermore, it was inferred from UV-visable absorption spectra that although the band gap and thickness of the films are independent of acid catalyst type, the refractive index and porosity of the films are strongly affected by the type of acids.

Electrical response of electron selective atomic layer deposited TiO2‑x heterocontacts on crystalline silicon substrates

NASA Astrophysics Data System (ADS)

Ahiboz, Doğuşcan; Nasser, Hisham; Aygün, Ezgi; Bek, Alpan; Turan, Raşit

2018-04-01

Integration of oxygen deficient sub-stoichiometric titanium dioxide (TiO2‑x) thin films as the electron transporting-hole blocking layer in solar cell designs are expected to reduce fabrication costs by eliminating high temperature processes while maintaining high conversion efficiencies. In this paper, we conducted a study to reveal the electrical properties of TiO2‑x thin films grown on crystalline silicon (c-Si) substrates by atomic layer deposition (ALD) technique. Effect of ALD substrate temperature, post deposition annealing, and doping type of the c-Si substrate on the interface states and TiO2‑x bulk properties were extracted by performing admittance (C-V, G-V) and current-voltage (J-V) measurements. Moreover, the asymmetry in C-V and J-V measurements between the p-n type and n-n TiO2‑x-c-Si heterojunction types were examined and the electron transport selectivity of TiO2‑x was revealed.

Resistive switching characteristics of thermally oxidized TiN thin films

NASA Astrophysics Data System (ADS)

Biju, K. P.

2018-04-01

Resistive switching characteristics of thermally oxidized TiN thin films and mechanisms were investigated.XPS results indicates Ti-O content decreases with sputter etching and Ti 2p peak shift towards lower binding energy due to formation of Ti-O-N and Ti-N. Pt/TiO2/TiON/TiN stack exhibits both clockwise switching (CWS) and counter clockwise switching(CCWS) characteristic depending on polarity of the applied voltage. However the transition from CCWS to CWS is irreversible. Two stable switching modes with opposite switching polarity and different electrical characteristics are found to coexist in the same memory cell. Clockwise switching shows filamentary characteristics that lead to faster switching with excellent retention at high temperature. Counter-clockwise switching exhibits homogeneous conduction with slower switching and moderate retention. The field-induced switching in both CCWS and CWS might be due to inhomogeneous defect distribution due to thermal oxidation.

Preparation of TiO2/boron-doped diamond/Ta multilayer films and use as electrode materials for supercapacitors

NASA Astrophysics Data System (ADS)

Shi, Chao; Li, Hongji; Li, Cuiping; Li, Mingji; Qu, Changqing; Yang, Baohe

2015-12-01

We report nanostructured TiO2/boron-doped diamond (BDD)/Ta multilayer films and their electrochemical performances as supercapacitor electrodes. The BDD films were grown on Ta substrates using electron-assisted hot filament chemical vapor deposition. Ti metal layers were deposited on the BDD surfaces by radio frequency magnetron sputtering, and nanostructured TiO2/BDD/Ta thin films were prepared by electrochemical etching and thermal annealing. The successful formation of TiO2 and Ta layered nanostructures was demonstrated using scanning electron and transmission electron microscopies. The electrochemical responses of these electrodes were evaluated by examining their use as electrical double-layer capacitors, using cyclic voltammetry, and galvanostatic charge/discharge and impedance measurements. When the TiO2/BDD/Ta film was used as the working electrode with 0.1 M Na2SO4 as the electrolyte, the capacitor had a specific capacitance of 5.23 mF cm-2 at a scan rate of 5 mV s-1 for a B/C ratio of 0.1% w/w. Furthermore, the TiO2/BDD/Ta film had improved electrochemical stability, with a retention of 89.3% after 500 cycles. This electrochemical behavior is attributed to the quality of the BDD, the surface roughness and electrocatalytic activities of the TiO2 layer and Ta nanoporous structures, and the synergies between them. These results show that TiO2/BDD/Ta films are promising as capacitor electrodes for special applications.

Atomic layer deposition of TiO2 on surface modified nanoporous low-k films.

PubMed

Levrau, Elisabeth; Devloo-Casier, Kilian; Dendooven, Jolien; Ludwig, Karl F; Verdonck, Patrick; Meersschaut, Johan; Baklanov, Mikhail R; Detavernier, Christophe

2013-10-01

This paper explores the effects of different plasma treatments on low dielectric constant (low-k) materials and the consequences for the growth behavior of atomic layer deposition (ALD) on these modified substrates. An O2 and a He/H2 plasma treatment were performed on SiCOH low-k films to modify their chemical surface groups. Transmission FTIR and water contact angle (WCA) analysis showed that the O2 plasma changed the hydrophobic surface completely into a hydrophilic surface, while the He/H2 plasma changed it only partially. In a next step, in situ X-ray fluorescence (XRF), ellipsometric porosimetry (EP), and Rutherford backscattering spectroscopy (RBS) were used to characterize ALD growth of TiO2 on these substrates. The initial growth of TiO2 was found to be inhibited in the original low-k film containing only Si-CH3 surface groups, while immediate growth was observed in the hydrophilic O2 plasma treated film. The latter film was uniformly filled with TiO2 after 8 ALD cycles, while pore filling was delayed to 17 ALD cycles in the hydrophobic film. For the He/H2 plasma treated film, containing both Si-OH and Si-CH3 groups, the in situ XRF data showed that TiO2 could no longer be deposited in the He/H2 plasma treated film after 8 ALD cycles, while EP measurements revealed a remaining porosity. This can be explained by the faster deposition of TiO2 in the hydrophilic top part of the film than in the hydrophobic bulk which leaves the bulk porous, as confirmed by RBS depth profiling. The outcome of this research is not only of interest for the development of advanced interconnects in ULSI technology, but also demonstrates that ALD combined with RBS analysis is a handy approach to analyze the modifications induced by a plasma treatment on a nanoporous thin film.

Growth and structure of Bi 0.5(Na 0.7K 0.2Li 0.1) 0.5TiO 3 thin films prepared by pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Lu, Lei; Xiao, Dingquan; Lin, Dunmin; Zhang, Yongbin; Zhu, Jianguo

2009-02-01

Bi 0.5(Na 0.7K 0.2Li 0.1) 0.5TiO 3 (BNKLT) thin films were prepared on Pt/Ti/SiO 2/Si substrates by pulsed laser deposition (PLD) technique. The films prepared were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The effects of the processing parameters, such as oxygen pressure, substrate temperature and laser power, on the crystal structure, surface morphology, roughness and deposition rates of the thin films were investigated. It was found that the substrate temperature of 600 °C and oxygen pressure of 30 Pa are the optimized technical parameters for the growth of textured film, and all the thin films prepared have granular structure, homogeneous grain size and smooth surfaces.

Plasmonic metamaterial-based chemical converted graphene/TiO2/Ag thin films by a simple spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Kumar, Promod; Swart, H. C.

2018-04-01

Graphene based hybrid nanostructures have received special attention in both the scientific and technological development due to their unique physicochemical behavior, which make them attractive in various applications such as, batteries, supercapacitors, fuel cells, solar cells, photovoltaic devices and bio-sensors. In the present study, the role of plasmonic metamaterials in light trapping photovoltaics for inorganic semiconducting materials by a simple and low cost spray pyrolysis technique has been studied. The plasmonic metamaterials thin film has been fabricated by depositing chemically converted graphene (CCG) onto TiO2-Ag nanoparticles which has a low resistivity and a low electron-hole recombination probability. The localized surface plasmon resonance at the metal-dielectric interface for the Ag nanoparticles has been observed at 403 nm after depositing chemical converted graphene (CCG) on the TiO2-Ag thin film. The results suggest that the stacking order of the CCG/TiO2/Ag plasmonic metamaterials samples did not change the band gap of TiO2 while it changed the conductivity of the film. Thus the diffusion of the noble metals in the glass and TiO2 matrices based thin films can trap the light of a particular wavelength by mean of plasmonic resonance and may be useful for superior photovoltaic and optoelectronic applications.

Ti{sub 2}AlN thin films synthesized by annealing of (Ti+Al)/AlN multilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cabioch, Thierry, E-mail: Thierry.cabioch@univ-poitiers.fr; Alkazaz, Malaz; Beaufort, Marie-France

2016-08-15

Highlights: • Epitaxial thin films of the MAX phase Ti{sub 2}AlN are obtained by thermal annealing. • A new metastable (Ti,Al,N) solid solution with the structure of α-T is evidenced. • The formation of the MAX phase occurs at low temperature (600 °C). - Abstract: Single-phase Ti{sub 2}AlN thin films were obtained by annealing in vacuum of (Ti + Al)/AlN multilayers deposited at room temperature by magnetron sputtering onto single-crystalline (0001) 4H-SiC and (0001) Al{sub 2}O{sub 3} substrates. In-situ X-ray diffraction experiments combined with ex-situ cross-sectional transmission electron microscopy observations reveal that interdiffusion processes occur in the multilayer at amore » temperature of ∼400 °C leading to the formation of a (Ti, Al, N) solid solution, having the hexagonal structure of α-Ti, whereas the formation of Ti{sub 2}AlN occurs at 550–600 °C. Highly oriented (0002) Ti{sub 2}AlN thin films can be obtained after an annealing at 750 °C.« less

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

PubMed

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

2010-03-15

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.

Sol-gel TiO2 films as NO2 gas sensors

NASA Astrophysics Data System (ADS)

Georgieva, V.; Gadjanova, V.; Grechnikov, A.; Donkov, N.; Sendova-Vassileva, M.; Stefanov, P.; Kirilov, R.

2014-05-01

TiO2 films were prepared by a sol-gel technique with commercial TiO2 powder as a source material (P25 Degussa AG). After a special treatment, printing paste was prepared. The TiO2 layers were formed by means of drop-coating on Si-control wafers and on the Au-electrodes of quartz resonators. The surface morphology of the films was examined by scanning electron microscopy (SEM). Their structure was studied by Raman spectroscopy and the surface composition was determined by X-ray photoelectron spectroscopy (XPS). The layers had a grain-like surface morphology and consisted mainly of anatase TiO2 phase. The sensitivity of the TiO2 films to NO2 was assessed by the quartz crystal microbalance (QCM) technique. To this end, the films were deposited on both sides of a 16-MHz QCM. The sensing characteristic of the TiO2-QCM structure was investigated by measuring the resonant frequency shift (ΔF) of the QCM due to the mass loading caused by NO2 adsorption. The Sauerbrey equation was applied to establish the correlation between the QCM frequency changes measured after exposure to different NO2 concentrations and the mass-loading of the QCM. The experiments were carried out in a dynamic mode on a special laboratory setup with complete control of the process parameters. The TiO2 films were tested in the NO2 concentration interval from 10 ppm to 5000 ppm. It was found that a TiO2 loading of the QCM by 5.76 kHz corresponded to a system sensitive to NO2 concentrations above 250 ppm. On the basis of the frequency-time characteristics (FTCs) measured, AF at different NO2 concentrations was defined, the adsorption/desorption cycles were studied and the response and recovery times were estimated. The results obtained show that the process is reversible in the NO2 interval investigated. The results further suggested that TiO2 films prepared by a sol-gel method on a QCM can be used as a sensor element for NO2 detection.

Synthesis of polycarbonate-r-polyethylene glycol copolymer for templated synthesis of mesoporous TiO2 films.

PubMed

Patel, Rajkumar; Kim, Jinkyu; Lee, Chang Soo; Kim, Jong Hak

2014-12-01

We synthesized a novel polycarbonate Z-r-polyethylene glycol (PCZ-r-PEG) copolymer by solution polycondensation. Successful synthesis of PCZ-r-PEG copolymer was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), and transmission electron microscopy (TEM). PCZ-r-PEG copolymer was used as a structure-directing agent for fabrication of mesoporous thin film containing a titanium dioxide (TiO2) layer. To control the porosity of the resultant inorganic layer, the ratio of titanium(IV) isopropoxide (TTIP) to PCZ-r-PEG copolymer was varied. The structure and porosity of the resulting mesoporous films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Mesoporous TiO2 films fabricated on an F-doped tin oxide (FTO) surface were used as photoanodes for quasi-solid-state dye-sensitized solar cells (qssDSSCs). The highest efficiency achieved was 3.3% at 100 mW/cm2 for a film thickness of 750 nm, which is high considering the thickness of TiO2 film, indicating the importance of the structure-directing agent.

Deposition of functional nanoparticle thin films by resonant infrared laser ablation.

NASA Astrophysics Data System (ADS)

Haglund, Richard; Johnson, Stephen; Park, Hee K.; Appavoo, Kannatessen

2008-03-01

We have deposited thin films containing functional nanoparticles, using tunable infrared light from a picosecond free-electron laser (FEL). Thin films of the green light-emitting molecule Alq3 were first deposited by resonant infrared laser ablation at 6.68 μm, targeting the C=C ring mode of the Alq3. TiO2 nanoparticles 50-100 nm diameter were then suspended in a water matrix, frozen, and transferred by resonant infrared laser ablation at 2.94 μm through a shadow mask onto the Alq3 film. Photoluminescence was substantially enhanced in the regions of the film covered by the TiO2 nanoparticles. In a second experiment, gold nanoparticles with diameters in the range of 50-100 nm were suspended in the conducting polymer and anti-static coating material PEDOT:PSS, which was diluted by mixing with N-methyl pyrrolidinone (NMP). The gold nanoparticle concentration was 8-10% by weight. The mixture was frozen and then ablated by tuning the FEL to 3.47 μm, the C-H stretch mode of NMP. Optical spectroscopy of the thin film deposited by resonant infrared laser ablation exhibited the surface-plasmon resonance characteristic of the Au nanoparticles. These experiments illustrate the versatility of matrix-assisted resonant infrared laser ablation as a technique for depositing thin films containing functionalized nanoparticles.

Hydrogenated TiO2 Thin Film for Accelerating Electron Transport in Highly Efficient Planar Perovskite Solar Cells.

PubMed

Yao, Xin; Liang, Junhui; Li, Yuelong; Luo, Jingshan; Shi, Biao; Wei, Changchun; Zhang, Dekun; Li, Baozhang; Ding, Yi; Zhao, Ying; Zhang, Xiaodan

2017-10-01

Intensive studies on low-temperature deposited electron transport materials have been performed to improve the efficiency of n-i-p type planar perovskite solar cells to extend their application on plastic and multijunction device architectures. Here, a TiO 2 film with enhanced conductivity and tailored band edge is prepared by magnetron sputtering at room temperature by hydrogen doping (HTO), which accelerates the electron extraction from perovskite photoabsorber and reduces charge transfer resistance, resulting in an improved short circuit current density and fill factor. The HTO film with upward shifted Fermi level guarantees a smaller loss on V OC and facilitates the growth of high-quality absorber with much larger grains and more uniform size, leading to devices with negligible hysteresis. In comparison with the pristine TiO 2 prepared without hydrogen doping, the HTO-based device exhibits a substantial performance enhancement leading to an efficiency of 19.30% and more stabilized photovoltaic performance maintaining 93% of its initial value after 300 min continuous illumination in the glove box. These properties permit the room-temperature magnetron sputtered HTO film as a promising electron transport material for flexible and tandem perovskite solar cell in the future.

Control of crystallographic texture and surface morphology of Pt/Tio2 templates for enhanced PZT thin film texture.

PubMed

Fox, Austin J; Drawl, Bill; Fox, Glen R; Gibbons, Brady J; Trolier-McKinstry, Susan

2015-01-01

Optimized processing conditions for Pt/TiO2/SiO2/Si templating electrodes were investigated. These electrodes are used to obtain [111] textured thin film lead zirconate titanate (Pb[ZrxTi1-x ]O3 0 ≤ x ≤ 1) (PZT). Titanium deposited by dc magnetron sputtering yields [0001] texture on a thermally oxidized Si wafer. It was found that by optimizing deposition time, pressure, power, and the chamber pre-conditioning, the Ti texture could be maximized while maintaining low surface roughness. When oxidized, titanium yields [100]-oriented rutile. This seed layer has as low as a 4.6% lattice mismatch with [111] Pt; thus, it is possible to achieve strongly oriented [111] Pt. The quality of the orientation and surface roughness of the TiO2 and the Ti directly affect the achievable Pt texture and surface morphology. A transition between optimal crystallographic texture and the smoothest templating surface occurs at approximately 30 nm of original Ti thickness (45 nm TiO2). This corresponds to 0.5 nm (2 nm for TiO2) rms roughness as determined by atomic force microscopy and a full-width at half-maximum (FWHM) of the rocking curve 0002 (200) peak of 5.5/spl degrees/ (3.1/spl degrees/ for TiO2). A Pb[Zr0.52Ti 0.48]O3 layer was deposited and shown to template from the textured Pt electrode, with a maximum [111] Lotgering factor of 87% and a minimum 111 FWHM of 2.4/spl degrees/ at approximately 30 nm of original Ti.

Resonant infrared matrix-assisted pulsed laser evaporation of TiO2 nanoparticle films

NASA Astrophysics Data System (ADS)

Mayo, Daniel C.; Paul, Omari; Airuoyo, Idemudia J.; Pan, Zhengda; Schriver, Kenneth E.; Avanesyan, Sergey M.; Park, Hee K.; Mu, Richard R.; Haglund, Richard F.

2013-03-01

The successful development of flexible, high performance thin films that are competitive with silicon-based technology will likely require fabricating films of hybrid materials that incorporate nanomaterials, glasses, ceramics, polymers, and thin films. Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is an ideal method for depositing organic materials and nanoparticles with minimal photochemical or photothermal damage to the deposited material. Furthermore, there are many nonhazardous solvents containing chemical functional groups with infrared absorption bands that are accessible using IR lasers. We report here results of recent work in which RIR-MAPLE has been employed successfully to deposit thin films of TiO2 nanoparticles on Si substrates. Using an Er:YAG laser ( λ=2.94 μm), we investigated a variety of MAPLE matrices containing -OH moieties, including water and all four isomers of butyl alcohol. The alcohol isomers are shown to provide effective and relatively nontoxic solvents for use in the RIR-MAPLE process. In addition, we examine the effects of varying concentration and laser fluence on film roughness and surface coverage.

Optical properties of titanium di-oxide thin films prepared by dip coating method

NASA Astrophysics Data System (ADS)

Biswas, Sayari; Rahman, Kazi Hasibur; Kar, Asit Kumar

2018-05-01

Titanium dioxide (TiO2) thin films were prepared by sol-gel dip coating method on ITO coated glass substrate. The sol was synthesized by hydrothermal method at 90°C. The sol was then used to make TiO2 films by dip coating. After dip coating the rest of the sol was dried at 100°C to make TiO2 powder. Thin films were made by varying the number of dipping cycles and were annealed at 500°C. XRD study was carried out for powder samples that confirms the formation of anatase phase. Transmission spectra of thin films show sharp rise in the violet-ultraviolet transition region and a maximum transmittance of ˜60%. Band gap of the prepared films varies from 3.15 eV to 3.22 eV.

Antimicrobial effect of TiO2 doped with Ag and Cu on Escherichia coli and Pseudomonas putida

NASA Astrophysics Data System (ADS)

Angelov, O.; Stoyanova, D.; Ivanova, I.

2016-10-01

Antimicrobial effect of TiO2 doped with Ag and Cu on Gram-negative bacteria Escherichia coli and Pseudomonas putida is studied. The thin films are deposited on glass substrates without heating during the deposition by r.f. magnetron co-sputtering of TiO2 target and pieces of Ag and Cu. The studied films, thickness about 65 nm, were as deposited and annealed (5200C, 4h, N2+5%H2, 4Pa). The as deposited thin films TiO2:Ag:Cu have band gap energy of 3.56 eV little higher than the band gap of crystalline anatase TiO2 which can be explained with the quantum effect of the granular structure of r.f. magnetron sputtered films. The annealed samples have band gap of 2.52 eV due to formation of donor levels from Ag and Cu atoms near the bottom of the conduction band. The toxic effect was determined through the classical Koch's method and the optical density measurements at λ=610 nm. The as deposited TiO2:Ag:Cu thin films demonstrate stronger inhibition effect - bactericidal for P. putida and bacteriostatic for E. coli (up to the 6th hour) in comparison with the annealed samples. The both methods of study show the same trends of the bacterial growth independently of their different sensitivity which confirms the observed effect.

Calcination Conditions on the Properties of Porous TiO2 Film

NASA Astrophysics Data System (ADS)

Zhang, Wenjie; Pei, Xiaobei; Bai, Jiawei; He, Hongbo

2014-03-01

Porous TiO2 films were deposited on SiO2 precoated glass-slides by sol-gel method using PEG1000 as template. The strongest XRD diffraction peak at 2θ = 25.3° is attributed to [101] plane of anatase TiO2 in the film. The increases of calcination temperature and time lead to stronger diffraction peak intensity. High transmittance and blue shift of light absorption edge are the properties of the film prepared at high calcination temperature. The average pore size of the films increases with the increasing calcination temperature as the result of TiO2 crystalline particles growing up and aggregation, accompanied with higher specific surface area. Photocatalytic activity of porous TiO2 films increases with the increasing calcination temperature. The light absorption edge of the films slightly moves to longer wavelength region along with the increasing calcination time. The mesoporous film calcinated at 500 °C for 2 h has the highest transmittance, the maximum surface area, and the maximum total pore volume. Consequently, the optimum degradation activity is achieved on the porous TiO2 film calcinated at 500 °C for 2 h.

Improved metal-insulator-transition characteristics of ultrathin VO2 epitaxial films by optimized surface preparation of rutile TiO2 substrates

NASA Astrophysics Data System (ADS)

Martens, Koen; Aetukuri, Nagaphani; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.

2014-02-01

Key to the growth of epitaxial, atomically thin films is the preparation of the substrates on which they are deposited. Here, we report the growth of atomically smooth, ultrathin films of VO2 (001), only ˜2 nm thick, which exhibit pronounced metal-insulator transitions, with a change in resistivity of ˜500 times, at a temperature that is close to that of films five times thicker. These films were prepared by pulsed laser deposition on single crystalline TiO2(001) substrates that were treated by dipping in acetone, HCl and HF in successive order, followed by an anneal at 700-750 °C in flowing oxygen. This pretreatment removes surface contaminants, TiO2 defects, and provides a terraced, atomically smooth surface.

Self assembled sulfur induced interconnected nanostructure TiO2 electrode for visible light photoresponse and photocatalytic application

NASA Astrophysics Data System (ADS)

Anitha, B.; Ravidhas, C.; Venkatesh, R.; Raj, A. Moses Ezhil; Ravichandran, K.; Subramanian, B.; Sanjeeviraja, C.

2017-07-01

Pristine TiO2 and sulfur doped TiO2 (S-TiO2) thin films were coated over the glass substrates by varying the concentration of sulfur source (thiourea - 2, 4, 6, 8 and 10 at%) using a cost-effective Jet nebulizer spray technique. The deposited thin films were in anatase phase with the tetragonal structure analyzed from the XRD pattern. The chemical state of the elements was determined from XPS analysis. Pristine TiO2 and S-TiO2 thin films depict the presence of spherical particles embedded over 3-D interconnected wire-like structure from SEM analysis. Optical studies revealed reduction in band gap of S-TiO2 films on increasing the sulfur concentration (3.2-2.8 eV). The sulfur incorporation in TiO2 lattice confirmed by the fall in intensity of near band edge emission as observed from room temperature PL spectra. The charge carrier dynamics of the prepared thin films were studied by means of steady state and transient photoconduction measurements. The photocatalytic performance of pristine TiO2 and S-TiO2 thin films for the degradation of malachite green dye was investigated under visible light.

Surface Structure and Photocatalytic Activity of Nano-TiO2 Thin Film

EPA Science Inventory

Controlled titanium dioxide (TiO2) thin films were deposited on stainless steel surfaces using flame aerosol synthetic technique, which is a one-step coating process, that doesn’t require further calcination. Solid state characterization of the coatings was conducted by different...

Control of conduction type in ferromagnetic (Zn,Sn,Mn)As2 thin films by changing Mn content and effect of annealing on thin films with n-type conduction

NASA Astrophysics Data System (ADS)

Minamizawa, Yuto; Kitazawa, Tomohiro; Hidaka, Shiro; Toyota, Hideyuki; Nakamura, Shin-ichi; Uchitomi, Naotaka

2018-04-01

The conduction type in (Zn,Sn,Mn)As2 thin films grown by molecular beam epitaxy (MBE) on InP substrates was found to be controllable from p-type to n-type as a function of Mn content. n-type (Zn,Sn,Mn)As2 thin films were obtained by Mn doping of more than approximately 11 cat.%. It is likely that Mn interstitials (MnI) incorporated by excess Mn doping are located at tetrahedral hollow spaces surrounded by Zn and Sn cation atoms and four As atoms, which are expected to act as donors in (Zn,Sn,Mn)As2, resulting in n-type conduction. The effect of annealing on the structural, electrical and magnetic properties of n-type (Zn,Sn,Mn)As2 thin films was investigated as functions of annealing temperature and time. It was revealed that even if the annealing temperature is considerably higher than the growth temperature of 320 °C, the magnetic properties of the thin films remain stable. This suggests that a MnI complex surrounded by Zn and Sn atoms is thermally stable during high-temperature annealing. The n-type (Zn,Sn,Mn)As2 thin films may be suitable for application as n-type spin-polarized injectors.

Facile fabrication of transparent TiO2-C@TiO2-C free-standing film for visible-light photocatalytic application

NASA Astrophysics Data System (ADS)

Hu, Luyang; Zhang, Yumin; Zhang, Shanmei; Li, Benxia

2017-02-01

A transparent TiO2-C@TiO2-C free-standing film has been synthesized by two-step hydrothermal method and subsequent thermal annealing. The chemical composition and morphological features of the TiO2-C@TiO2-C film are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and N2 adsorption-desorption measurement. The results indicate that the flower-like micro/nanostructure TiO2-C particle layers are intimately inhered to porous TiO2-C fibers. The fibers in film are interconnected each other to form a three-dimensional reticulate microstructure, and exhibit intense visible light absorption and high adsorptivity of dye molecules. The interaction between TiO2 and its surface carbon layer in TiO2-C particle promotes the generation of Ti-O-C bonds, which leads to effective charge transfer. Under visible-light irradiation, TiO2-C@TiO2-C film presents enhanced photocatalytic activity for degradation of methylene blue. This work may provide a new viewpoint for designing transparent photocatalytic film for promising applications in heterogeneous photocatalysis.

Thin Film Synthesis of New Complex Titanates.

NASA Astrophysics Data System (ADS)

Salvador, Paul

2008-03-01

Thin film deposition methods allow for one to synthesize rationally specific compositions in targeted crystal structures. Because most of the thermodynamic and kinetic variables that control the range of materials that can be synthesized are unknown for specific compounds/processes, epitaxial stabilization and design of artificially layered crystals are driven through empirical investigations. Using examples taken primarily from the family of complex titanates, which exhibit a range of interesting physicochemical behaviors, the thermodynamic and kinetic factors that control materials design using thin film deposition are discussed. The phase competition between the pyrochlore and the (110) layered perovskite structure in the RE2Ti2O7 family (RE = rare-earth, Bi) will be explored, using pulsed laser deposition as a synthesis method. For RE = Gd, Sm, Nd, and La, the phase stability over a wide range of conditions is dictated entirely by substrate choice, indicating that the free energies of the phases are similar enough such that by controlling nucleation one controls the phase formation. In a related fashion, the growth of AETi2O5 films (AE = Ba or Sr) will be discussed with respect to the formation of single-phase films or films that phase separate into AETiO3 and TiO2. The entire Ba1-xSrxTi2O5 series was grown and will be discussed with respect to growth technique (using MBE and PLD) and/or substrate choice. In this case, rock-salt substrates, which are not expected to interact strongly with any phase in the system, allow for the formation of single-phase films. Finally, several examples will be discussed with respect to the (SrO)m(TiO2)n system, which includes the perovskite SrTiO3 and the Ruddlesden-Popper phase Sr2TiO4, grown using layer-by-layer molecular beam epitaxy. The solid phase epitaxial formation of the perovskite SrTiO3 from superlattices of rock-salt SrO and anatase TiO2 is discussed from both a kinetic and thermodynamic perspective by exploring the

Comparative Study of Two Different TiO2 Film Sensors on Response to H2 under UV Light and Room Temperature

PubMed Central

Peng, Xiaoying; Wang, Zhongming; Huang, Pan; Chen, Xun; Fu, Xianzhi; Dai, Wenxin

2016-01-01

An anatase TiO2 film sensor was prepared by a facile in-situ method on the interdigitated Au electrode deposited on the alumina substrate. The structure, morphology and the optical properties of the in-situ TiO2 film sensor were characterized by X-ray diffraction, Scanning Electron Microscopy, and UV-vis diffuse reflectance spectra. The photo-assisted gas sensitivities of the prepared film towards H2 gas were evaluated at room temperature in N2 and synthetic air atmospheres. As compared to TiO2 film sensor prepared by drop-coating method, this in-situ TiO2 film sensor exhibited a more compact structure composed of uniform TiO2 microspheres as well as a better gas sensitivity towards H2 under UV irradiation, especially in synthetic air. The photo-electrochemical measurements suggest that these improvements may be associated with the efficient charge transfer in the TiO2 interface induced by the TiO2 microsphere structure. This study might offer a feasible approach to develop photo-assisted gas sensors at ambient temperature. PMID:27509502

Electron-Selective TiO 2 Contact for Cu(In,Ga)Se 2 Solar Cells

DOE PAGES

Hsu, Weitse; Sutter-Fella, Carolin M.; Hettick, Mark; ...

2015-11-03

The non-toxic and wide bandgap material TiO 2 is explored as an n-type buffer layer on p-type Cu(In,Ga)Se 2 (CIGS) absorber layer for thin film solar cells. The amorphous TiO 2 thin film deposited by atomic layer deposition process at low temperatures shows conformal coverage on the CIGS absorber layer. Solar cells from non-vacuum deposited CIGS absorbers with TiO 2 buffer layer result in a high short-circuit current density of 38.9 mA/cm 2 as compared to 36.9 mA/cm 2 measured in the reference cell with CdS buffer layer, without compromising open-circuit voltage. The significant photocurrent gain, mainly in the UVmore » part of the spectrum, can be attributed to the low parasitic absorption loss in the ultrathin TiO 2 layer (~10 nm) with a larger bandgap of 3.4 eV compared to 2.4 eV of the traditionally used CdS. Overall the solar cell conversion efficiency was improved from 9.5% to 9.9% by substituting the CdS by TiO 2 on an active cell area of 10.5 mm2. In conclusion, optimized TiO 2/CIGS solar cells show excellent long-term stability. The results imply that TiO 2 is a promising buffer layer material for CIGS solar cells, avoiding the toxic CdS buffer layer with added performance advantage.« less

Photocatalytic activity of Cr-doped TiO2 nanoparticles deposited on porous multicrystalline silicon films

PubMed Central

2014-01-01

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

Photocatalytic activity of Cr-doped TiO2 nanoparticles deposited on porous multicrystalline silicon films.

PubMed

Hajjaji, Anouar; Trabelsi, Khaled; Atyaoui, Atef; Gaidi, Mounir; Bousselmi, Latifa; Bessais, Brahim; El Khakani, My Ali

2014-01-01

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.

Epitaxial growth and dielectric properties of Pb0.4Sr0.6TiO3 thin films on (00l)-oriented metallic Li0.3Ni0.7O2 coated MgO substrates

NASA Astrophysics Data System (ADS)

Li, X. T.; Du, P. Y.; Mak, C. L.; Wong, K. H.

2007-06-01

Highly (00l)-oriented Li0.3Ni0.7O2 thin films have been fabricated on (001) MgO substrates by pulsed laser deposition. The Pb0.4Sr0.6TiO3 (PST40) thin film deposited subsequently also shows a significant (00l)-oriented texture. Both the PST40 and Li0.3Ni0.7O2 have good epitaxial behavior. The epitaxial growth of the PST40 thin film is more perfect with the Li0.3Ni0.7O2 buffer layer due to the less distortion in the film. The dielectric tunability of the PST40 thin film with Li0.3Ni0.7O2 buffer layer therefore reaches 70%, which is 75% higher than that without Li0.3Ni0.7O2 buffer layer, and the dielectric loss of the PST40 thin film is 0.06.

Preparation of atomically flat rutile TiO 2(001) surfaces for oxide film growth

DOE PAGES

Wang, Yang; Lee, Shinbuhm; Vilmercati, P.; ...

2016-01-01

The availability of low-index rutile TiO 2 single crystal substrates with atomically flat surfaces is essential for enabling epitaxialgrowth of rutile transition metal oxide films. The high surface energy of the rutile (001) surface often leads to surface faceting, which precludes the sputter and annealing treatment commonly used for the preparation of clean and atomically flat TiO 2(110) substrate surfaces. In this work, we reveal that stable and atomically flat rutile TiO 2(001) surfaces can be prepared with an atomically ordered reconstructedsurface already during a furnace annealing treatment in air. We tentatively ascribe this result to the decrease in surfacemore » energy associated with the surface reconstruction, which removes the driving force for faceting. Despite the narrow temperature window where this morphology can initially be formed, we demonstrate that it persists in homoepitaxialgrowth of TiO 2(001) thin films. The stabilization of surface reconstructions that prevent faceting of high-surface-energy crystal faces may offer a promising avenue towards the realization of a wider range of high quality epitaxial transition metal oxide heterostructures.« less

Ion Beam Assisted Deposition of Thin Epitaxial GaN Films.

PubMed

Rauschenbach, Bernd; Lotnyk, Andriy; Neumann, Lena; Poppitz, David; Gerlach, Jürgen W

2017-06-23

The assistance of thin film deposition with low-energy ion bombardment influences their final properties significantly. Especially, the application of so-called hyperthermal ions (energy <100 eV) is capable to modify the characteristics of the growing film without generating a large number of irradiation induced defects. The nitrogen ion beam assisted molecular beam epitaxy (ion energy <25 eV) is used to deposit GaN thin films on (0001)-oriented 6H-SiC substrates at 700 °C. The films are studied in situ by reflection high energy electron diffraction, ex situ by X-ray diffraction, scanning tunnelling microscopy, and high-resolution transmission electron microscopy. It is demonstrated that the film growth mode can be controlled by varying the ion to atom ratio, where 2D films are characterized by a smooth topography, a high crystalline quality, low biaxial stress, and low defect density. Typical structural defects in the GaN thin films were identified as basal plane stacking faults, low-angle grain boundaries forming between w-GaN and z-GaN and twin boundaries. The misfit strain between the GaN thin films and substrates is relieved by the generation of edge dislocations in the first and second monolayers of GaN thin films and of misfit interfacial dislocations. It can be demonstrated that the low-energy nitrogen ion assisted molecular beam epitaxy is a technique to produce thin GaN films of high crystalline quality.

Exploring a new phenomenon in the bactericidal response of TiO2 thin films by Fe doping: Exerting the antimicrobial activity even after stoppage of illumination

NASA Astrophysics Data System (ADS)

Naghibi, Sanaz; Vahed, Shohreh; Torabi, Omid; Jamshidi, Amin; Golabgir, Mohammad Hossein

2015-02-01

Antibacterial properties of Fe-doped TiO2 thin films prepared on glass by the sol-gel hot-dipping technique were studied. The films were characterized by X-ray diffraction, field emission scanning electron microscopy, scanning probe microscopy and X-ray photoelectron spectroscopy. The photocatalytic activities were evaluated by measuring the decomposition rate of methylene blue under ultra violet and visible light. The antibacterial properties of the coatings were investigated against Escherichia coli, Staphylococcus aureus, Saccharomyces cerevisia and Aspergillus niger. The principle of incubation methods was also discussed. The results indicated that Fe doping of thin films eventuated in high antibacterial properties under visible light and this performance remained even after stoppage of illumination. This article tries to provide some explanation for this fact.

TiO2 film properties as a function of processing temperature, volume 3

NASA Technical Reports Server (NTRS)

Fitzgibbons, E. T.; Sladek, K. J.; Hartwig, W. H.

1972-01-01

Thin film TiO2 was produced at 150 C by chemical vapor deposition using hydrolysis of tetraisopropyl titanate. Films were amorphous as grown, but annealing in air caused crystallization, with anatase formed beginning at 350 C and rutile at 700 C. Density and index of refraction increased substantially with increasing anneal temperature, while etch susceptibility in HF and H2SO4 decreased. Comparison with literature data showed two groups of processes. One group yields films having properties that gradually approach those of rutile with increasing process temperature. The other group gives rutile directly at moderate temperatures. Deposition of amorphous film followed by etching and annealing is suggested as a means for pattern definition.

The effects of strain relaxation on the dielectric properties of epitaxial ferroelectric Pb(Zr0.2Ti0.8)TiO3 thin films

NASA Astrophysics Data System (ADS)

Khan, Asif Islam; Yu, Pu; Trassin, Morgan; Lee, Michelle J.; You, Long; Salahuddin, Sayeef

2014-07-01

We study the effects of strain relaxation on the dielectric properties of epitaxial 40 nm Pb(Zr0.2Ti0.8)TiO3 (PZT) films. A significant increase in the defect and dislocation density due to strain relaxation is observed in PZT films with tetragonality c/a < 1.07 grown on SrTiO3 (001) substrates, which results in significant frequency dispersion of the dielectric constant and strong Rayleigh type behavior in those samples. This combined structural-electrical study provides a framework for investigating strain relaxation in thin films and can provide useful insights into the mechanisms of fatigue in ferroelectric materials.

Mesoporous TiO2 implants for loading high dosage of antibacterial agent

NASA Astrophysics Data System (ADS)

Park, Se Woong; Lee, Donghyun; Choi, Yong Suk; Jeon, Hoon Bong; Lee, Chang-Hoon; Moon, Ji-Hoi; Kwon, Il Keun

2014-06-01

We have fabricated mesoporous thin films composed of TiO2 nanoparticles on anodized titanium implant surfaces for loading drugs at high doses. Surface anodization followed by treatment with TiO2 paste leads to the formation of mechanically stable mesoporous thin films with controllable thickness. A series of antibacterial agents (silver nanoparticles, cephalothin, minocycline, and amoxicillin) were loaded into the mesoporous thin films and their antibacterial activities were evaluated against five bacterial species including three oral pathogens. Additionally, two agents (silver nanoparticles and minocycline) were loaded together on the thin film and tested for antibacterial effectiveness. The combination of silver nanoparticles and minocycline was found to display a wide range of effectiveness against all tested bacteria.

Properties of Superconducting Mo, Mo2n and Trilayer Mo2n-Mo-Mo2n Thin Films

NASA Technical Reports Server (NTRS)

Barrentine, E. M.; Stevenson, T. R.; Brown, A. D.; Lowitz, A. E.; Noroozian, O.; U-Yen, K.; Eshan, N.; Hsieh, W. T.; Moseley, S. H.; Wollack, E. J.

2014-01-01

We present measurements of the properties of thin film superconducting Mo, Mo2N and Mo2N/Mo/Mo2N trilayers of interest for microwave kinetic inductance detector (MKID) applications. Using microwave resonator devices, we investigate the transition temperature, energy gaps, kinetic inductance, and internal quality factors of these materials. We present an Usadel-based interpretation of the trilayer transition temperature as a function of trilayer thicknesses, and a 2-gap interpretation to understand the change in kinetic inductance and internal resonance quality factor (Q) as a function of temperature.

Nb and Ta Co-Doped TiO2 Transparent Conductive Thin Films by Magnetron Sputtering: Fabrication, Structure, and Characteristics

NASA Astrophysics Data System (ADS)

Liu, Yang; Peng, Qian; Qiao, Yadong; Yang, Guang

2018-06-01

Nb and Ta co-doped anatase titanium dioxide (NTTO) nanocrystalline thin films were deposited on quartz and Si (100) substrates by RF magnetron sputtering. The influence of RF power on the growth, structure, morphology, and properties of the samples are discussed in detail. X-ray diffraction measurements show that the films are polycrystalline with anatase tetragonal structure, which is further confirmed by Raman spectroscopy analysis. Meanwhile, Raman spectroscopy results indicate that the peak width of E g(1) mode, which is directly correlated to the carrier density, changes obviously with RF power. It is found that the substitution of Nb5+ and Ta5+ at Ti site is significantly improved with the increase of RF power from 150 W to 210 W. For the sample deposited at 210 W, the optical transmittance is above 82% in the visible range and the electrical resistivity is as low as 1.3 × 10-3 Ω cm with carrier density of 1.1 × 1021 cm-3 and Hall mobility of 4.5 cm2 V-1 s-1. The optical and electrical properties of NTTO thin films can be compared to those of Nb or Ta doped anatase TiO2. However, co-doping with Nb and Ta gives a possible platform to complement the limitations of each individual dopant.

Understanding of gas phase deposition of reactive magnetron sputtered TiO2 thin films and its correlation with bactericidal efficiency

NASA Astrophysics Data System (ADS)

Panda, A. B.; Mahapatra, S. K.; Barhai, P. K.; Das, A. K.; Banerjee, I.

2012-10-01

Nanostructured TiO2 thin films were deposited using RF reactive magnetron sputtering at different O2 flow rates (20, 30, 50 and 60 sccm) and constant RF power of 200 W. In situ investigation of the nucleation and growth of the films was made by Optical Emission Spectroscopy (OES). The nano amorphous nature as revealed from X-ray diffraction (XRD) of the as deposited films and abundance of the Ti3+ surface oxidation states and surface hydroxyl group (OH-) in the films deposited at 50 sccm as determined from X-ray photo electron spectroscopy (XPS) was explained on the basis of emission spectra studies. The increase in band gap and decrease in particle size with O2 flow rate was observed from transmission spectra of UV-vis spectroscopy. Photoinduced hydrophilicity has been studied using Optical Contact Angle (OCA) measurement. The post irradiated films showed improved hydrophilicity. The bactericidal efficiency of these films was investigated taking Escherichia coli as model bacteria. The films deposited at 50 sccm shows better bactericidal activity as revealed from the optical density (OD) measurement. The qualitative analysis of the bactericidal efficiency was depicted from Scanning Electron Microscope images. A correlation between bactericidal efficiency and the deposited film has been established and explained on the basis of nucleation growth, band gap and hydrophilicity of the films.

Platinum role in hydrophilicity enhancement of Cr-doped TiO2 thin films

NASA Astrophysics Data System (ADS)

Mardare, D.; Mita, C.; Cornei, N.; Tascu, S.; Luca, D.; Dobromir, M.; Adomnitei, C.

2016-10-01

In this paper, we have investigated the hydrophilic properties of the titania films doped with increasing chromium percentages (from 2.1 at.% till 4.0 at.%). Cr-doping induces an increase in the rutile weight %, a more compact structure, and a significant red shift of the TiO2 absorption edge, the last property being very important in the self cleaning applications. For the chosen Cr concentrations, the films did not show promising hydrophilic properties. To improve them, we have applied a novel surface modification method, reported in literature mainly for powders, namely, surface metallisation. We have observed that, by depositing Pt islands on the film with the highest Cr content, its hydrophilic properties improve for a certain metal coverage area. The explanation was based on FT-IR and X-ray photoelectron spectroscopy analysis, performed on the UV irradiated and non-irradiated films, which gives information on the relationship between hydrophilicity and the amount of the adsorbed hydroxyl groups.

Photocatalytic production of hydrogen from fixed titanium dioxide thin film

NASA Astrophysics Data System (ADS)

Okoye, Njideka Helen

This thesis is focused on further developing of an efficient method for the photocatalytic hydrogen production. The research aimed to use thin films deposited with TiO2 and doped with Pt in order to substitute slurry solutions that are currently being used. A new depositing experimental approach to manufacture the thin films was proposed and tested for both physical properties and chemical reactivity. Therefore, the experiment was designed into two parts: The first part was on the manufacturing and the physical characterization of titanium dioxide deposited on glass surfaces and the second part was focused on the ability of the thin film to produce hydrogen. For the second part, a photochemical reactor vessel was used to properly place the glass slides to UV-irradiation. This was yielded by a mercury lamp located at the centre of the reactor. The thesis is organized into five different chapters including introduction, literature review, characterization of TiO2 coated surface, experimental design and hydrogen production, finally conclusive observations and future work. Hydrogen production by photodecomposition of water into H2 and O2 has a very low efficiency due to rapid reverse reaction and, as mentioned above, it usually requires a slurry type of solution. This needs additional processing steps such as filtration and recycling of particles. Therefore, it is important to develop an efficient process for hydrogen production. TiO2 coated surfaces could be an excellent technological alternative. In this study, a sol-gel method was used to produce a transparent TiO 2 thin film which was deposited on a glass substrate by using a new coating technique introduced in this work for H2 production. The TiO2 deposited film on a glass substrate by using the spraying method of coating was characterized for physical analysis (surface characteristics, size of nanoparticles and distribution, etc.) by using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission

Oxygen-vacancy-mediated dielectric property in perovskite Eu0.5Ba0.5TiO3-δ epitaxial thin films

NASA Astrophysics Data System (ADS)

Li, Weiwei; Gu, Junxing; He, Qian; Zhang, Kelvin H. L.; Wang, Chunchang; Jin, Kuijuan; Wang, Yongqiang; Acosta, Matias; Wang, Haiyan; Borisevich, Albina Y.; MacManus-Driscoll, Judith L.; Yang, Hao

2018-04-01

Dielectric relaxation in ABO3 perovskite oxides can result from many different charge carrier-related phenomena. Despite a strong understanding of dielectric relaxations, a detailed investigation of the relationship between the content of oxygen vacancies (VO) and dielectric relaxation has not been performed in perovskite oxide films. In this work, we report a systematic investigation of the influence of the VO concentration on the dielectric relaxation of Eu0.5Ba0.5TiO3-δ epitaxial thin films. Nuclear resonance backscattering spectrometry was used to directly measure the oxygen concentration in Eu0.5Ba0.5TiO3-δ films. We found that dipolar defects created by VO interact with the off-centered Ti ions, which results in the dielectric relaxation in Eu0.5Ba0.5TiO3-δ films. Activation energy gradually increases with the increasing content of VO. The present work significantly extends our understanding of relaxation properties in oxide films.

Electronic and Optical Properties of Atomic Layer-Deposited ZnO and TiO2

NASA Astrophysics Data System (ADS)

Ates, H.; Bolat, S.; Oruc, F.; Okyay, A. K.

2018-05-01

Metal oxides are attractive for thin film optoelectronic applications. Due to their wide energy bandgaps, ZnO and TiO2 are being investigated by many researchers. Here, we have studied the electrical and optical properties of ZnO and TiO2 as a function of deposition and post-annealing conditions. Atomic layer deposition (ALD) is a novel thin film deposition technique where the growth conditions can be controlled down to atomic precision. ALD-grown ZnO films are shown to exhibit tunable optical absorption properties in the visible and infrared region. Furthermore, the growth temperature and post-annealing conditions of ZnO and TiO2 affect the electrical properties which are investigated using ALD-grown metal oxide as the electron transport channel on thin film field-effect devices.

Photocatalytic properties of P25-doped TiO2 composite film synthesized via sol-gel method on cement substrate.

PubMed

Guo, Xiang; Rao, Lei; Wang, Peifang; Wang, Chao; Ao, Yanhui; Jiang, Tao; Wang, Wanzhong

2018-04-01

TiO 2 films have received increasing attention for the removal of organic pollutants via photocatalysis. To develop a simple and effective method for improving the photodegradation efficiency of pollutants in surface water, we herein examined the preparation of a P25-TiO 2 composite film on a cement substrate via a sol-gel method. In this case, Rhodamine B (RhB) was employed as the target organic pollutant. The self-generated TiO 2 film and the P25-TiO 2 composite film were characterized by X-ray diffraction (XRD), N 2 adsorption/desorption measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). The photodegradation efficiencies of the two films were studied by RhB removal in water under UV (ultraviolet) irradiation. Over 4day exposure, the P25-TiO 2 composite film exhibited higher photocatalytic performance than the self-generated TiO 2 film. The photodegradation rate indicated that the efficiency of the P25-TiO 2 composite film was enhanced by the addition of the rutile phase Degussa P25 powder. As such, cooperation between the anatase TiO 2 and rutile P25 nanoparticles was beneficial for separation of the photo-induced electrons and holes. In addition, the influence of P25 doping on the P25-TiO 2 composite films was evaluated. We found that up to a certain saturation point, increased doping enhanced the photodegradation ability of the composite film. Thus, we herein demonstrated that the doping of P25 powders is a simple but effective strategy to prepare a P25-TiO 2 composite film on a cement substrate, and the resulting film exhibits excellent removal efficiency in the degradation of organic pollutants. Copyright © 2017. Published by Elsevier B.V.

Ferromagnetism in spin-coated cobalt-doped TiO2 thin films and the role of crystalline phases

NASA Astrophysics Data System (ADS)

Salazar Cuaila, J. L.; Alayo, W.; Avellaneda, César O.

2017-11-01

Two sets of Cobalt-doped (1-10% at) TiO2 thin films, for different molar concentrations of the Ti precursor (0.3 and 0.5 mol/L), have been deposited onto Si substrates by combining the Sol Gel process and the Spin Coating technique. The structure of the samples was studied by X-ray reflectivity (XRR) and X-ray diffraction (XRD) and their magnetic properties were analyzed by magnetization measurements as a function of the applied magnetic field. The XRR results provided the thickness and interfacial roughness of the films, while XRD patterns revealed the crystalline phases and lattice parameters. Room temperature ferromagnetic behaviour was observed for some of the atomic Co concentrations by the magnetization measurements. This behaviour has been correlated to the crystalline phases, which were found to be modified by both the molar ratio of Ti precursor and the concentration of the Co dopant. A suppression of ferromagnetism is observed for some atomic Co fractions and it was attributed to the presence of secondary crystalline phases.

Enhanced interfacial contact between PbS and TiO2 layers in quantum dot solar cells using 2D-arrayed TiO2 hemisphere nanostructures

NASA Astrophysics Data System (ADS)

Lee, Wonseok; Ryu, Ilhwan; Lee, Haein; Yim, Sanggyu

2018-02-01

Two-dimensionally (2D) arrayed hemispherical nanostructures of TiO2 thin films were successfully fabricated using a simple procedure of spin-coating or dip-coating TiO2 nanoparticles onto 2D close-packed polystyrene (PS) nanospheres, followed by PS extraction. The nanostructured TiO2 film was then used as an n-type layer in a lead sulfide (PbS) colloidal quantum dot solar cell. The TiO2 nanostructure could provide significantly increased contacts with subsequently deposited PbS quantum dot layer. In addition, the periodically arrayed nanostructure could enhance optical absorption of the cell by redirecting the path of the incident light and increasing the path length passing though the active layer. As a result, the power conversion efficiency (PCE) reached 5.13%, which is approximately a 1.7-fold increase over that of the control cell without nanostructuring, 3.02%. This PCE enhancement can mainly be attributed to the increase of the short-circuit current density from 19.6 mA/cm2 to 30.6 mA/cm2, whereas the open-circuit voltage and fill factor values did not vary significantly.

Observation of interacting polaronic gas behavior in Ta-doped TiO2 thin films via terahertz time-domain spectroscopy

NASA Astrophysics Data System (ADS)

Chia, Elbert; Cheng, Liang; Lourembam, James; Wu, S. G.; Motapothula, Mallikarjuna R.; Sarkar, Tarapada; Venkatesan, Venky

Using terahertz time-domain spectroscopy (THz-TDS), we obtained the complex optical conductivity [ σ (ω) ] of Ta-doped TiO2 thin films - a transparent conducting oxide (TCO), in the frequency range 0.3-2.7 THz, temperature range 10-300 K and various Ta dopings. Our results reveal the existence of an interacting polaronic gas in these TCOs, and suggest that their large conductivity is caused by the combined effects of large carrier density and small electron-phonon coupling constant due to Ta doping. NUSNNI-NanoCore, NRF-CRP (NRF2008NRF-CRP002-024), NUS cross-faculty Grant and FRC (ARF Grant No. R-144-000-278-112), MOE Tier 1 (RG123/14), SinBeRISE CREATE.

A two-layer structured PbI2 thin film for efficient planar perovskite solar cells.

PubMed

Ying, Chao; Shi, Chengwu; Wu, Ni; Zhang, Jincheng; Wang, Mao

2015-07-28

In this paper, a two-layer structured PbI2 thin film was constructed by the spin-coating procedure using a 0.80 M PbI2 solution in DMF and subsequent close-spaced vacuum thermal evaporation using PbI2 powder as a source. The bottom PbI2 thin film was compact with a sheet-like appearance, parallel to the FTO substrate, and can be easily converted to a compact perovskite thin film to suppress the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band. The top PbI2 thin film was porous with nano-sheet arrays, perpendicular to the FTO substrate, and can be easily converted to a porous perovskite thin film to improve the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured PbI2 thin film exhibited a photoelectric conversion efficiency of 11.64%, along with an open-circuit voltage of 0.90 V, a short-circuit photocurrent density of 19.29 mA cm(-2) and a fill factor of 0.67.

Synthesis and characterization of ZnO:TiO2 nano composites thin films deposited on glass substrate by sol-gel spray coating technique

NASA Astrophysics Data System (ADS)

Sutanto, Heri; Nurhasanah, Iis; Hidayanto, Eko; Wibowo, Singgih; Hadiyanto

2015-12-01

In this work, (ZnO)x:(TiO2)1-x nano composites thin films, with x = 1, 0.75, 0.5, 0.25, and 0, have been prepared by sol-gel spray coating technique onto glass substrate. Pure TiO2 and ZnO thin films were synthesized from titanium isopropoxide-based and zinc acetate-based precursor solutions, respectively, whereas the composite films were obtained from the mixture of these solutions at the specific % vol ratios. The properties and performance of nano composite ZnO, TiO2 and ZnO:TiO2 thin films at different composition have been investigated. Ultraviolet - Visible (UV-Vis) Spectrophotometer and Scanning Electron Microscopy (SEM) were employed in order to get morphology and transmittance of thin films. Testing the ability of photocatalytic activity of obtained films was conducted on photodegradation of methylene blue (MB) dye and organic pollutants of wastewater under a 30 watt UV light irradiation, then testing BOD, COD and TPC were conducted. Using the Tauc model, the band-gap energy decreased from 3.12 eV to 3.02 eV for the sample with x = 1 and 0, respectively. This decrease occured along with the replacement of percentage of ZnO by TiO2 on the films. This decrease also reduced the minimum energy that required for electron excitation. Obtained thin films had nanoscale roughness level with range 3.64 to 17.30 nm. The film with x= 0 has the biggest removal percentage on BOD, COD and TPC mesurements with percentage 54.82%, 62.73% and 99.88%, respectively.

Epitaxial integration of CoFe2O4 thin films on Si (001) surfaces using TiN buffer layers

NASA Astrophysics Data System (ADS)

Prieto, Pilar; Marco, José F.; Prieto, José E.; Ruiz-Gomez, Sandra; Perez, Lucas; del Real, Rafael P.; Vázquez, Manuel; de la Figuera, Juan

2018-04-01

Epitaxial cobalt ferrite thin films with strong in-plane magnetic anisotropy have been grown on Si (001) substrates using a TiN buffer layer. The epitaxial films have been grown by ion beam sputtering using either metallic, CoFe2, or ceramic, CoFe2O4, targets. X-ray diffraction (XRD) and Rutherford spectrometry (RBS) in random and channeling configuration have been used to determine the epitaxial relationship CoFe2O4 [100]/TiN [100]/Si [100]. Mössbauer spectroscopy, in combination with XRD and RBS, has been used to determine the composition and structure of the cobalt ferrite thin films. The TiN buffer layer induces a compressive strain in the cobalt ferrite thin films giving rise to an in-plane magnetic anisotropy. The degree of in-plane anisotropy depends on the lattice mismatch between CoFe2O4 and TiN, which is larger for CoFe2O4 thin films grown on the reactive sputtering process with ceramic targets.

Colossal photo-conductive gain in low temperature processed TiO2 films and their application in quantum dot solar cells

NASA Astrophysics Data System (ADS)

Mandal, Debranjan; Goswami, Prasenjit N.; Rath, Arup K.

2017-03-01

Colloidal quantum dot (QD) solar cells have seen remarkable progress in recent past to reach the certified efficiency of 10.6%. Anatase titanium oxide (TiO2) is a widely studied n-type widow layer for the collection of photogenerated electrons in QD solar cells. Requirement of high temperature (˜500 °C) processing steps proved to be disadvantageous for its applications in flexible solar cells and roll to roll processing, and it also has adverse commercial implications. Here, we report that solar light exposure to low temperature processed (80 °C-150 °C) TiO2 and niobium doped TiO2 films leads to unprecedented enhancement in their electron densities and electron mobilities, which enables them to be used as efficient n-type layers in quantum dot solar cells. Such photoinduced high conducting states in these films show gradual decay over hours after the light bias is taken off and can be retrieved under solar illumination. On the contrary, TiO2 films processed at 500 °C show marginal photo induced enhancements in their characteristics. In bilayer configuration with PbS QDs, photovoltaic devices based on low temperature processed TiO2 films show improved performance over high temperature processed TiO2 films. The stability of photovoltaic devices also improved in low temperature processed TiO2 films under ambient working conditions.

Three dimensional-stacked complementary thin-film transistors using n-type Al:ZnO and p-type NiO thin-film transistors.

PubMed

Lee, Ching-Ting; Chen, Chia-Chi; Lee, Hsin-Ying

2018-03-05

The three dimensional inverters were fabricated using novel complementary structure of stacked bottom n-type aluminum-doped zinc oxide (Al:ZnO) thin-film transistor and top p-type nickel oxide (NiO) thin-film transistor. When the inverter operated at the direct voltage (V DD ) of 10 V and the input voltage from 0 V to 10 V, the obtained high performances included the output swing of 9.9 V, the high noise margin of 2.7 V, and the low noise margin of 2.2 V. Furthermore, the high performances of unskenwed inverter were demonstrated by using the novel complementary structure of the stacked n-type Al:ZnO thin-film transistor and p-type nickel oxide (NiO) thin-film transistor.

Orientation effect on microwave dielectric properties of Si-integrated Ba0.6Sr0.4TiO3 thin films for frequency agile devices

NASA Astrophysics Data System (ADS)

Kim, Hyun-Suk; Hyun, Tae-Seon; Kim, Ho-Gi; Kim, Il-Doo; Yun, Tae-Soon; Lee, Jong-Chul

2006-07-01

The effect of texture with (100) and (110) preferred orientations on dielectric properties of Ba0.6Sr0.4TiO3 (BST) thin films grown on SrO (9nm) and CeO2 (70nm ) buffered Si substrates, respectively, was investigated. The coplanar waveguide (CPW) phase shifter using (100) oriented BST films on SrO buffered Si exhibited a much-enhanced figure of merit of 24.7°/dB, as compared to that (10.2°/dB) of a CPW phase shifter using (110) oriented BST films on CeO2 buffered Si at 12GHz. This work demonstrates that the microwave properties of the Si-integrated BST thin films are highly correlated with crystal orientation.

Efficient photocatalytic degradation of tetrabromodiphenyl ethers and simultaneous hydrogen production by TiO2-Cu2O composite films in N2 atmosphere: Influencing factors, kinetics and mechanism.

PubMed

Hu, Zhe; Wang, Xi; Dong, Haitai; Li, Shangyi; Li, Xukai; Li, Laisheng

2017-10-15

TiO 2 -Cu 2 O photocatalyst composite film with a heterostructure was synthesized on a copper substrate for 2,2',4,4'-tetrabromodiphenyl ether (BDE47) reduction. First, Cu 2 O film was synthesized by the electrochemical deposition method, and then TiO 2 was coated on the surface of the Cu 2 O film. The morphology, surface chemical composition and optical characteristics of TiO 2 -Cu 2 O film were characterized. The degradation efficiency of BDE47 and hydrogen production by TiO 2 -Cu 2 O films was higher than those by pure TiO 2 or Cu 2 O films. The highest BDE47 degradation efficiency of 90% and hydrogen production of 12.7mmolL liq -1 after 150min were achieved by 67%TiO 2 -Cu 2 O films. The influencing factors were investigated in terms of film component, solvent condition, and initial pH. A kinetics study demonstrated that BDE47 degradation followed a pseudo-first-order model. Photocatalytic apparent reaction rate constant of BDE47 by TiO 2 -Cu 2 O films was 0.0070min -1 , which was 3.3 times of that by directly photolysis process. During photocatalytic debrmination process, the photogenerated holes were reserved in the valance band of Cu 2 O to oxidize methanol. Meanwhile, the partial photogenerated electrons transferred to the conduction band of TiO 2 and directly eliminated the ortho-Br of BDE47 and yielded BDE28 and BDE15. The other partial photogenerated electrons reduced protons (H + ) to form atomic hydrogen (H°), which could substitute the para-Br of BDE47 and generated BDE17 and produce hydrogen. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of different TiO2 blocking films on the photovoltaic performance of perovskite solar cells

NASA Astrophysics Data System (ADS)

Zhang, Chenxi; Luo, Yudan; Chen, Xiaohong; Ou-Yang, Wei; Chen, Yiwei; Sun, Zhuo; Huang, Sumei

2016-12-01

Organolead trihalide perovskite materials have been successfully used as light absorbers in efficient photovoltaic (PV) cells. Cell structures based on mesoscopic metal oxides and planar heterojunctions have already demonstrated very impressive and brisk advances, holding great potential to grow into a mature PV technology. High power conversion efficiency (PCE) values have been obtained from the mesoscopic configuration in which a few hundred nano-meter thick mesoporous scaffold (e.g. TiO2 or Al2O3) infiltrated by perovskite absorber was sandwiched between the electron and hole transport layers. A uniform and compact hole-blocking layer is necessary for high efficient perovskite-based thin film solar cells. In this study, we investigated the characteristics of TiO2 compact layer using various methods and its effects on the PV performance of perovskite solar cells. TiO2 compact layer was prepared by a sol-gel method based on titanium isopropoxide and HCl, spin-coating of titanium diisopropoxide bis (acetylacetonate), screen-printing of Dyesol's bocking layer titania paste, and a chemical bath deposition (CBD) technique via hydrolysis of TiCl4, respectively. The morphological and micro-structural properties of the formed compact TiO2 layers were characterized by scanning electronic microscopy and X-ray diffraction. The analyses of devices performance characteristics showed that surface morphologies of TiO2 compact films played a critical role in affecting the efficiencies. The nanocrystalline TiO2 film deposited via the CBD route acts as the most efficient hole-blocking layer and achieves the best performance in perovskite solar cells. The CBD-based TiO2 compact and dense layer offers a small series resistance and a large recombination resistance inside the device, and makes it possible to achieve a high power conversion efficiency of 12.80%.

Enhanced electrochromic properties of TiO2 nanoporous film prepared based on an assistance of polyethylene glycol

NASA Astrophysics Data System (ADS)

Xu, Shunjian; Luo, Xiaorui; Xiao, Zonghu; Luo, Yongping; Zhong, Wei; Ou, Hui; Li, Yinshuai

2017-01-01

Polyethylene glycol (PEG) was employed as pore-forming agent to prepare TiO2 nanoporous film based on spin-coating a TiO2 nanoparticle mixed paste on fluorine doped tin oxide (FTO) glass. The electrochromic and optical properties of the obtained TiO2 film were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and UV-Vis spectrophotometer. The results show that the PEG in the mixed paste endows the TiO2 film with well-developed porous structure and improves the uniformity of the TiO2 film, which are helpful for the rapid intercalation and extraction of lithium ions within the TiO2 film and the strengthening of the diffuse reflection of visible light in the TiO2 film. As a result, the TiO2 film derived from the mixed paste with PEG displays higher electrochemical activity and more excellent electrochromic performances compared with the TiO2 film derived from the mixed paste without PEG. The switching times of coloration/bleaching are respectively 10.16/5.65 and 12.77/6.13 s for the TiO2 films with PEG and without PEG. The maximum value of the optical contrast of the TiO2 film with PEG is 21.2% while that of the optical contrast of the TiO2 film without PEG is 14.9%. Furthermore, the TiO2 film with PEG has better stability of the colored state than the TiO2 film without PEG.

Thermal Vapor Deposition and Characterization of Polymer-Ceramic Nanoparticle Thin Films and Capacitors

NASA Astrophysics Data System (ADS)

Iwagoshi, Joel A.

Research on alternative energies has become an area of increased interest due to economic and environmental concerns. Green energy sources, such as ocean, wind, and solar power, are subject to predictable and unpredictable generation intermittencies which cause instability in the electrical grid. This problem could be solved through the use of short term energy storage devices. Capacitors made from composite polymer:nanoparticle thin films have been shown to be an economically viable option. Through thermal vapor deposition, we fabricated dielectric thin films composed of the polymer polyvinylidine fluoride (PVDF) and the ceramic nanoparticle titanium dioxide (TiO2). Fully understanding the deposition process required an investigation of electrode and dielectric film deposition. Film composition can be controlled by the mass ratio of PVDF:TiO2 prior to deposition. An analysis of the relationship between the ratio of PVDF:TiO2 before and after deposition will improve our understanding of this novel deposition method. X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy were used to analyze film atomic concentrations. The results indicate a broad distribution of deposited TiO2 concentrations with the highest deposited amount at an initial mass concentration of 17% TiO2. The nanoparticle dispersion throughout the film is analyzed through atomic force microscopy and energy dispersive x-ray spectroscopy. Images from these two techniques confirm uniform TiO2 dispersion with cluster size less than 300 nm. These results, combined with spectroscopic analysis, verify control over the deposition process. Capacitors were fabricated using gold parallel plates with PVDF:TiO 2 dielectrics. These capacitors were analyzed using the atomic force microscope and a capacohmeter. Atomic force microscope images confirm that our gold films are acceptably smooth. Preliminary capacohmeter measurements indicate capacitance values of 6 nF and break down voltages of 2.4 V

Pulsed photonic fabrication of nanostructured metal oxide thin films

NASA Astrophysics Data System (ADS)

Bourgeois, Briley B.; Luo, Sijun; Riggs, Brian C.; Adireddy, Shiva; Chrisey, Douglas B.

2017-09-01

Nanostructured metal oxide thin films with a large specific surface area are preferable for practical device applications in energy conversion and storage. Herein, we report instantaneous (milliseconds) photonic synthesis of three-dimensional (3-D) nanostructured metal oxide thin films through the pulsed photoinitiated pyrolysis of organometallic precursor films made by chemical solution deposition. High wall-plug efficiency-pulsed photonic irradiation (xenon flash lamp, pulse width of 1.93 ms, fluence of 7.7 J/cm2 and frequency of 1.2 Hz) is used for scalable photonic processing. The photothermal effect of subsequent pulses rapidly improves the crystalline quality of nanocrystalline metal oxide thin films in minutes. The following paper highlights pulsed photonic fabrication of 3-D nanostructured TiO2, Co3O4, and Fe2O3 thin films, exemplifying a promising new method for the low-cost and high-throughput manufacturing of nanostructured metal oxide thin films for energy applications.

Porous CrN thin films by selectively etching CrCuN for symmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wei, Binbin; Mei, Gui; Liang, Hanfeng; Qi, Zhengbing; Zhang, Dongfang; Shen, Hao; Wang, Zhoucheng

2018-05-01

Transition metal nitrides are regarded as a new class of excellent electrode materials for high-performance supercapacitors due to their superior chemical stability and excellent electrical conductivity. We synthesize successfully the porous CrN thin films for binder-free supercapacitor electrodes by reactive magnetron co-sputtering and selective chemical etching. The porous CrN thin film electrodes exhibit high-capacitance performance (31.3 mF cm-2 at 1.0 mA cm-2) and reasonable cycling stability (94% retention after 20000 cycles). Moreover, the specific capacitance is more than two-fold higher than that of the CrN thin film electrodes in previous work. In addition, a symmetric supercapacitor device with a maximum energy density of 14.4 mWh cm-3 and a maximum power density of 6.6 W cm-3 is achieved. These findings demonstrate that the porous CrN thin films will have potential applications in supercapacitors.

Worm-like mesoporous TiO2 thin films templated using comb copolymer for dye-sensitized solar cells with polymer electrolyte

NASA Astrophysics Data System (ADS)

Lee, Jae Hun; Park, Cheol Hun; Jung, Jung Pyo; Kim, Jong Hak

2015-12-01

A comb copolymer consisting of hydrophobic poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate) (PBEM) and hydrophilic poly(oxyethylene methacrylate) (POEM) is synthesized via one-pot free radical polymerization. The PBEM-POEM comb copolymer is used as an agent to direct the structure toward one consisting of worm-like mesoporous TiO2 (WM-TiO2) films. The selective, preferential interaction between the titania precursor and the hydrophilic POEM chains is responsible for the formation of a well-organized worm-like mesostructure. The morphology of the WM-TiO2 films is characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In particular, the effects of film thickness on the optical and electrochemical properties are systematically investigated. The introduction of the WM-TiO2 layer between the nanocrystalline TiO2 (NC-TiO2) layer and fluorine-doped tin oxide (FTO) glass results in increased transmittance of visible light due to an antireflective property, decreased interfacial resistance and suppressed charge recombination at the interfaces of NC-TiO2/FTO glass. As a result, the photovoltaic conversion efficiency of the dye-sensitized solar cell (DSSC) with a polymer electrolyte is improved from 5.3% to 6.6% at an optimum film thickness (310 nm). The obtained efficiency represents a higher efficiency for the N719-based DSSC with a solvent-free, polymer electrolyte.

In situ Fenton reagent generated from TiO2/Cu2O composite film: a new way to utilize TiO2 under visible light irradiation.

PubMed

Zhang, Yong-Gang; Ma, Li-Li; Li, Jia-Lin; Yu, Ying

2007-09-01

TiO2/Cu2O composite is prepared by a simple electrochemical method and coated on glass matrix through a spraying method. The obtained composite is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of TiO2/Cu2O composite films with different ratio of TiO2 and Cu2O on photodegradation of the dye methylene blue under visible light is investigated in detail. It is found that the photocatalytic activity of TiO2/Cu2O composite film with the presence of FeSO4 and EDTA is much higher than that for the similar system with only TiO2 and Cu2O film respectively. Without the presence of FeSO4 and EDTA, there is no degradation for methylene blue. The exploration of the optimized parameters for the degradation of methylene blue by using TiO2/Cu2O composite film as catalyst under visible light was also carried out. The most significant factor is the amount of Ti02 in the composite, and the second significant factor is the concentration of FeSO4. During the degradation of methylene blue under visible light, TiO2/Cu2O composite film generates H202, and Fenton regent is formed with Fe2+ and EDTA, which is detected in this study. The mechanism for the great improvement of photocatalytic activity of TiO2/Cu2O composite film under visible light is proposed by the valence band theory. Electrons excitated from TiO2/Cu2O composite under visible light are transferred from the conduction band of Cu2O to that of Ti02. The formed intermediate state of Ti 3+ ion is observed by X-ray photoelectron spectroscopy (XPS) on the TiO/Cu2O composite film. Additionally, the accumulated electrons in the conduction band of TiO2 are transferred to oxygen on the TiO2 surface for the formation of O2- or O2(2-), which combines with H+ to form H2O2. The evolved H202 with FeSO4 and EDTA forms Fenton reagentto degrade methylene blue. Compared to the traditional Fenton reagent, this new kind of in situ Fenton reagent generated from TiO2/Cu2O composite film does not need to

Synthesis of Ag-TiO2 composite nano thin film for antimicrobial application

NASA Astrophysics Data System (ADS)

Yu, Binyu; Leung, Kar Man; Guo, Qiuquan; Lau, Woon Ming; Yang, Jun

2011-03-01

TiO2 photocatalysts have been found to kill cancer cells, bacteria and viruses under mild UV illumination, which offers numerous potential applications. On the other hand, Ag has long been proved as a good antibacterial material as well. The advantage of Ag-TiO2 nanocomposite is to expand the nanomaterial's antibacterial function to a broader range of working conditions. In this study neat TiO2 and Ag-TiO2 composite nanofilms were successfully prepared on silicon wafer via the sol-gel method by the spin-coating technique. The as-prepared composite Ag-TiO2 and TiO2 films with different silver content were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) to determine the topologies, microstructures and chemical compositions, respectively. It was found that the silver nanoparticles were uniformly distributed and strongly attached to the mesoporous TiO2 matrix. The morphology of the composite film could be controlled by simply tuning the molar ratio of the silver nitrate aqueous solution. XPS results confirmed that the Ag was in the Ag0 state. The antimicrobial effect of the synthesized nanofilms was carried out against gram-negative bacteria (Escherichia coli ATCC 29425) by using an 8 W UV lamp with a constant relative intensity of 0.6 mW cm - 2 and in the dark respectively. The synthesized Ag-TiO2 thin films showed enhanced bactericidal activities compared to the neat TiO2 nanofilm both in the dark and under UV illumination.

Berkovich Nanoindentation on AlN Thin Films

PubMed Central

2010-01-01

Berkovich nanoindentation-induced mechanical deformation mechanisms of AlN thin films have been investigated by using atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM) techniques. AlN thin films are deposited on the metal-organic chemical-vapor deposition (MOCVD) derived Si-doped (2 × 1017 cm−3) GaN template by using the helicon sputtering system. The XTEM samples were prepared by means of focused ion beam (FIB) milling to accurately position the cross-section of the nanoindented area. The hardness and Young’s modulus of AlN thin films were measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) option. The obtained values of the hardness and Young’s modulus are 22 and 332 GPa, respectively. The XTEM images taken in the vicinity regions just underneath the indenter tip revealed that the multiple “pop-ins” observed in the load–displacement curve during loading are due primarily to the activities of dislocation nucleation and propagation. The absence of discontinuities in the unloading segments of load–displacement curve suggests that no pressure-induced phase transition was involved. Results obtained in this study may also have technological implications for estimating possible mechanical damages induced by the fabrication processes of making the AlN-based devices. PMID:20672096

Berkovich Nanoindentation on AlN Thin Films.

PubMed

Jian, Sheng-Rui; Chen, Guo-Ju; Lin, Ting-Chun

2010-03-31

Berkovich nanoindentation-induced mechanical deformation mechanisms of AlN thin films have been investigated by using atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM) techniques. AlN thin films are deposited on the metal-organic chemical-vapor deposition (MOCVD) derived Si-doped (2 × 1017 cm-3) GaN template by using the helicon sputtering system. The XTEM samples were prepared by means of focused ion beam (FIB) milling to accurately position the cross-section of the nanoindented area. The hardness and Young's modulus of AlN thin films were measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) option. The obtained values of the hardness and Young's modulus are 22 and 332 GPa, respectively. The XTEM images taken in the vicinity regions just underneath the indenter tip revealed that the multiple "pop-ins" observed in the load-displacement curve during loading are due primarily to the activities of dislocation nucleation and propagation. The absence of discontinuities in the unloading segments of load-displacement curve suggests that no pressure-induced phase transition was involved. Results obtained in this study may also have technological implications for estimating possible mechanical damages induced by the fabrication processes of making the AlN-based devices.

Effect of TiCl4 treatment on the refractive index of nanoporous TiO2 films

NASA Astrophysics Data System (ADS)

Lee, Jeeyoung; Lee, Myeongkyu

2015-12-01

We investigate the effect of TiCl4 treatment on the refractive index of a nanoporous TiO2 film. A nanoparticulate TiO2 film prepared on a glass substrate was immersed in a TiCl4 aqueous solution. The subsequent reaction of TiCl4 with H2O produces TiO2 and thus modifies the density and the refractive index of the film. With increasing TiCl4 concentration, the refractive index initially increased and then declined after being maximized (n = 2.02 at 633 nm) at 0.08 M concentration. A refractive index change as large as 0.45 could be obtained with the TiCl4 treatment, making it possible to achieve diffraction efficiency exceeding 80% in a diffraction grating-embedded TiO2 film. For high TiCl4 concentrations of 0.32 M and 0.64 M, the refractive index remained nearly unchanged. This was attributed to the limited permeability of high-viscosity TiCl4 solutions into the nanoporous films. The measured pore size distributions were in good agreement with the results of a diffraction analysis and refractive index measurement.