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Plasma-Assisted Chemical Vapor Deposition of TiO2 Thin Films for Highly Hydrophilic Performance  [PDF]
Satoshi Yamauchi, Yoh Imai
Crystal Structure Theory and Applications (CSTA) , 2013, DOI: 10.4236/csta.2013.21001
Abstract: Titanium-oxide layer was grown on glass substrate by plasma-assisted chemical vapor deposition (PCVD) using oxygen gas plasma excited by radio-frequency power at 13.56 MHz in the pressure as low as 3mtorr at relatively low temperature below 400oC, and studied on the crystallographic properties with the hydrophilic behavior comparing to the layer deposited by low-pressure chemical vapor deposition (LPCVD). Raman spectra indicated anatase-phase TiO2 layer without amorphous-phase could be formed above 340oC by simultaneous supply of plasma-cracked and non-cracked titanium-tetra-iso-propoxide (TTIP) used as preliminary precursor. Surface Scanning Electron Microscope images indicated the PCVD-layer consists of distinct nanometer-size plate-like columnar grains, in contrast to rugged micrometer-size grains in the LPCVD-layer. Extremely small water contact angle about 5o in dark and the quick conversion to super-hydrophilicity by UV-irradiation with a light-power density as low as 50 W/cm2 were observed on the PCVD- layer grown at 380oC, while the large initial contact angle was above 40o and the response for the UV-irradiation was gradual on the LPCVD-layer.
Influence of the carrier gas in the growth kinetics of TiO2 films deposited by aerosol assisted chemical vapor deposition with titanium-diisopropoxide as precursor
Conde-Gallardo, A.;Guerrero, M.;Soto, A. B;Fragoso, R.;Castillo, N.;
Revista mexicana de física , 2006,
Abstract: titanium dioxide thin films were deposited on crystalline silicon (100) substrates by delivering a liquid aerosol of titanium-diisopropoxide and by using oxygen and nitrogen as carrier gases. the crystalline and morphological features indicate that the films are deposited by a metal organic chemical vapor deposition process. this is strongly supported by the behavior of the growth rate rg as a function of the deposition temperature, which indicates that the film formation is limited by both, the diffusion in gas phase of the precursor species to the surface substrate and reaction of those species at that surface. even though the rg line shape does not depend on the kind of carrier gas used to transport the aerosol, its absolute value and the activation energy ea that characterizes the surface reaction do. a fitting procedure to an equation that takes into account both limiting mechanisms (gas phase diffusion and surface reaction) yields: ea 26.4 kj/mol o ea = 21.4 kj/mol when oxygen or nitrogen is employed as carrier gas, respectively.
Influence of the carrier gas in the growth kinetics of TiO2 films deposited by aerosol assisted chemical vapor deposition with titanium-diisopropoxide as precursor  [cached]
A. Conde-Gallardo,M. Guerrero,A. B Soto,R. Fragoso
Revista mexicana de física , 2006,
Abstract: Películas de dióxido de titanio fueron depositadas mediante la liberación de un aerosol líquido de diisopropoxido de titanio sobre substratos de silicio orientados (100), y empleando oxígeno y nitrógeno como gases de arrastre. Las propiedades cristalinas y morfológicas indican que el proceso de depósito se lleva a cabo mediante los vapores químicos de los precursores. Esto es fuertemente apoyado por el comportamiento de la taza de crecimiento rg como función de la temperatura de depósito, cuya forma de línea indica que el crecimiento esta gobernado por la difusión de los precursores en fase vapor hacia el substrato y la consecuente reacción de estos en la superficie. Aunque la forma de línea de rg no depende del tipo de gas utilizado en el arrastre del aerosol, el valor absoluto de rg y la energía de activación EA que caracteriza a la reacción superficial si. Un ajuste a una ecuación que toma en cuenta a ambos mecanismos (difusión de vapores y reacción de superficie) da como resultado: EA =26.4 kJ/mol o EA=21.4 kJ/mol cuando se utiliza oxígeno o nitrógeno como gas de arrastre, respectivamente
Fabrication and Characterization of Hydrophilic Thin Films on Unheated Substrates Prepared by Pulsed DC Reactive Magnetron Sputtering  [PDF]
M. Horprathum,P. Chindaudom,P. Limnonthakul,P. Eiamchai,N. Nuntawong,V. Patthanasettakul,A. Pokaipisit,P. Limsuwan
Journal of Nanomaterials , 2010, DOI: 10.1155/2010/841659
Abstract: thin films were deposited on unheated silicon wafers (100) and glass slides by a pulsed DC reactive magnetron sputtering in an ultrahigh vacuum (UHV) system. The effects of both an operating pressure and deposition time on film structure, surface morphology, and optical property were studied. The film structure and microstructure were characterized by grazing-incidence X-ray diffraction (GIXRD) technique and transmission electron microscopy (TEM). The surface morphology was investigated by field emission scanning electron microscopy (FE-SEM). The optical property of the thin films was determined by spectroscopic ellipsometry (SE). The water contact angle measurement was also used to determine hydrophilicity of the films after exposed to UV light. The results suggested that the thin film at less than 40?nm was amorphous. As the thickness was increased, the mixture of anatase and rutile phases of began to form. By reducing the operating pressure during the film deposition, the rutile phase component can also be enhanced. Both the increased film thickness and decrease operating pressure were the critical factors to improve the hydrophilicity of the thin films. 1. Introduction Titanium dioxide (TiO2) is a well-known photocatalyst with good chemical stability, high refractive index, and good mechanical hardness. Photocatalytic reactions proceed under UV-irradiation, with photon energy greater than the band gap energy of TiO2 anatase phase (3.20?eV). The electron hole pairs generated by absorption of a photon play also a fundamental role at the photo-induced superhydrophilicity. The electrons reduce Ti4+ cation to Ti3+ and the holes oxidize oxygen anions near the surface. Thereby oxygen vacancies are created. These vacancies can be occupied by water molecules creating adsorbed OH groups [1–3]. Thus, the surface energy is minimized and the surface becomes hydrophilicity. For these unique properties, TiO2 can be used for preparation of self-cleaning, antifogging, and antibacterial coating. Such TiO2 thin films can be prepared by many methods which include sol-gel [4, 5], metal-organic chemical vapor deposition (MOCVD) [6], molecular beam epitaxy (MBE) [7], ion-beam assisted deposition [8, 9], and sputtering technique [10–14]. Reactive magnetron sputtering has become a preferred technique because of its applications in large area coating on glass, such as architectural glass and exterior rear view mirrors of the cars. Several literatures suggest modifications of structure; the structure, optical, and photo-induced hydrophilic properties can be modified by
Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Layer at Room-Temperature  [PDF]
Satoshi Yamauchi, Hiromi Suzuki, Risa Akutsu
Journal of Crystallization Process and Technology (JCPT) , 2014, DOI: 10.4236/jcpt.2014.41003
Abstract:

Plasma-assisted chemical vapor deposition (PCVD) at pressure as low as 3 mtorr using titanium-tetra-isopropoxide (TTIP) and oxygen mixed gas plasma generated by 13.56 MHz radio frequency power (RF-power) below 70 W were applied to deposit titanium-oxide layer at temperature under 40°C. Plasma optical emission spectroscopy and FTIR indicated that density of OH group in the amorphous layer was related to the density of OH or H2O in the plasma and the species was formed on electrode to induce the RF-power. Hydrophilicity on the layer was dependent on the density of chemisorbed OH, but was degraded by the excess OH. The PCVD-TiOx coating was demonstrated on polyethylene terephthalate and showed good hydrophilic property with the contact angle of water about 5°.

Synthesis and Photocatalytic Properties of CNT/Fe―Ni/TiO2 by Fluidized Bed―chemical Vapor Deposition Method  [PDF]
MA Lei, CHEN Ai-Ping, LU Jin-Dong, HE Hong-Bo, LI Chun-Zhong
无机材料学报 , 2012, DOI: 10.3724/sp.j.1077.2012.00033
Abstract: Fe―Ni/TiO2 was used as catalyst to synthesize carbon nanotube(CNT)/Fe―Ni/TiO2 composite photocatalyst by fluidized bed chemical vapor deposition (FBCVD) method. Carbon nanotube grew in situ on TiO2 surface. The CNT/Fe―Ni/TiO2 composite photocatalyst were characterized by X―ray diffraction (XRD), UV―Vis absorption spectroscope and field emission scanning electron microscope (FESEM). The photocatalytic activities of prepared samples were investigated by the photodegradation of methylene blue (MB). The results showed that Ni was characterized as catalytic center for CNT growth in FBCVD process. In CNT/Fe―Ni/TiO2 composite photocatalyst, Fe (III) cation was characterized as an electron capture center and efficiently promoted the separation of photogenerated holes and electrons. The electron transfer from TiO2 was facilitated by Ni particles and CNTs, which could reduce the electron ― hole recombination. The synergistic effects of Fe―Ni and CNT significantly enhanced the photocatalytic activity of the catalysts. The degradation ratio of MB of CNT/Fe―Ni/TiO2 doped with 0.25mol% Fe and 4.75mol% Ni was increased about 70% than that of pure TiO2.
Direct Fabrication of Carbon Nanotubes STM Tips by Liquid Catalyst-Assisted Microwave Plasma-Enhanced Chemical Vapor Deposition  [PDF]
Fa-Kuei Tung,Masamichi Yoshimura,Kazuyuki Ueda
Journal of Nanomaterials , 2009, DOI: 10.1155/2009/612549
Abstract: Direct and facile method to make carbon nanotube (CNT) tips for scanning tunneling microscopy (STM) is presented. Cobalt (Co) particles, as catalysts, are electrochemically deposited on the apex of tungsten (W) STM tip for CNT growth. It is found that the quantity of Co particles is well controlled by applied DC voltage, concentration of catalyst solution, and deposition time. Using optimum growth condition, CNTs are successfully synthesized on the tip apex by catalyst-assisted microwave-enhanced chemical vapor deposition (CA-MPECVD). A HOPG surface is clearly observed at an atomic scale using the present CNT-STM tip.
Optical and gas sensing studies of transparent ZnO thin film deposited from a new precursor by ultrasonic aerosol assisted chemical vapor deposition  [cached]
Muzammil Hussain,Syed Tajammul Hussain
European Journal of Chemistry , 2010, DOI: 10.5155/eurjchem.1.2.96-101.49
Abstract: Transparent semi-conducting ZnO thin films with low resistivity and high transmittance in the visible optical region were deposited by the decomposition of bis(2,4-pentanedionate)-bis(aminoethanol) zinc(II) under an atmosphere of oxygen on ceramic, metal and quartz substrates by ultrasonic aerosol assisted chemical vapor deposition. The precursor was synthesized from bis(2,4-pentanedionate) zinc(II) and aminoethanol by sonication in acetonitrile and was characterized by melting point, infrared spectroscopy, CHNS-O elemental, atomic absorption, and single crystal X-ray diffraction analysis. TGA-FTIR was used to identify the cause of the weight losses and evolved gases formed during the breakup of the molecules. Electrical and optical measurements showed that the ZnO film has a band gap of 3.02 eV and typical semiconductor properties with a resistivity that depends on the thickness of the film. Powder XRD, SEM and EDX show that films are uniform, smooth and crystalline in nature, giving particle sizes in the range of 30-60 nm and exhibit a (002) orientation with the c-axis perpendicular to the substrate surface.
Gallium Arsenide Nanowires Formed by Au-assisted Metal-organic Chemical Vapor Deposition: Effect of Growth Temperature  [cached]
Rosnita Muhammad,Zulkafli Othaman,Yussof Wahab,Samsudi Sakrani
Modern Applied Science , 2009, DOI: 10.5539/mas.v3n7p73
Abstract: We have investigated the growth of gallium arsenide (GaAs) nanowires as a function of temperatures in metal organic chemical vapor deposition (MOCVD) to establish the mechanisms that govern wire growth and to optimize growth conditions. The growth follows the vapor-liquid-solid method by applying nanoparticle gold colloid as a catalyst to forms a eutectic liquid alloy with the substrate. The semi insulating undoped (111)B GaAs was first dipped in the poly-L-lysine solution before 30nm gold colloid dropped on the substrate surface. Growth process in the MOCVD system were done at temperatures between 380 and 600oC with growth time set is 30 min. All the grown samples were analyzed using a field emmission scanning electron microscope (FE-SEM) and scanning electron microscopy (SEM). With increasing temperature the nanowire height increases but leads to significant tapering of the nanowire due to competing growth at the (111) substrate surface. At low temperatures nanowires grown are cylindrical-shaped with diameter wires between 50 and 100 nm.
Monte Carlo simulation of optical emission spectra in electron assisted chemical vapor deposition of diamond
电子助进化学气相沉积金刚石中发射光谱的蒙特卡罗模拟

Wang Zhi-Jun,Dong Li-Fang,Shang Yong,
王志军
,董丽芳,尚 勇

物理学报 , 2005,
Abstract: The optical emission spectra of atomic hydrogen, atomic carbon and radical CH in electron assisted chemical vapor deposition (EACVD) were studied by using the Monte Carlo simulation when CH4/H2 gas mixture was used as the input gases. Effects of the experimental parameters on emission spectra and synthesis of di amond films were investigated. The results obtained suggested that the CH radica ls should be considered as a precursor species for diamond deposition but atomic carbon C is not. The diamond growth rate may be enhanced by the substrate bias due to the changes of atomic hydrogen concentration and the increase of mean ele ctron temperature. A method of determining the mean temperature of electron was gained by using atomic hydrogen emission line, and the optimum experimental cond ition for diamond deposition was also obtained. These results are of great impor tance for depositing high_quality diamond films by controlling the conditions of technology efficiently.
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