Electrophoretic coagulation behavior of ferroelectric barium titanate powders in mixed solutions of alcohol and acetylacetone

Although the deposition of BaTiO₃, known as a ferroelectric compound with spontaneous dipole moments, has never occurred in either propanol and acetylacetone, these mixtures were found to enhance the deposition of the powders on a cathode. The present study carried out the systematic investigation of the solution-mixing effect of propanol and acetylacetone on the electrophoretic deposition of BaTiO₃. The optimum mixing ratio for the deposition was 50–70 vol% of propanol, while a depressed migration of BaTiO₃ powders was observed in the mixed solutions. Therefore, it was considered that the enhanced deposition was attributed to the coagulation of the BaTiO₃ powders on the cathode. The deposition characteristics varied with the kind of alcohol used showed that a more highly enhanced deposition was achieved with alcohols having longer side-chains such as octanol. An intertwinement between the side-chains in the alcohols was considered to have an effect on the coagulation of the BaTiO₃ powders.     

Chemical vapour-deposited silicon nitride

Pyrolytic Si₃N₄ has been deposited on a graphite substrate, using a mixture of SiCl₄, NH₃ and H₂. The pyrolysis is performed with deposition temperatures of 1100 to 1500° C, total gas pressures of 5 to 300 Torr, and flow rates of H₂=700, NH₃=60 and SiCl₄ (liq.)=0.8 cm³ min^–1. Massive amorphous and crystalline pyrolytic forms of Si₃N₄ are prepared at a maximum thickness of 4.6 mm. The effects of deposition conditions on some properties of the deposited products and the dependence of formation of amorphous or crystalline deposits on deposition temperature and total pressure were investigated. The surface and cross-sectional structures show growth cones and oriented crystals which are strongly dependent on the deposition conditions. The thin deposits are translucent; the thick deposits vary in colour from white to black. The silicon content is close to the theoretical composition and independent of the deposition conditions, while the oxygen content increases with decreasing deposition temperature and total pressure. No segregation of silicon and nitrogen at cone boundaries was found.     

The effects of deposition variables on deposition rate in the chemical vapour deposition of silicon nitride

Amorphous Si₃N₄ was deposited by a chemical vapour deposition technique using an SiCl₄, NH₄₃ and H₂ gaseous mixture onto a silicon single crystal. The effects of deposition time, substrate temperature, gas flow rate, system pressure and partial pressure of reactant gases on the deposition rate were investigated. The metal-insulator-semiconductor (MIS) structure was fabricated by evaporating gold on Si₃N₄ to measure the charges stored in the interface between the insulator and silicon. The charges were determined for different deposition temperatures from capacitance-voltage plots. The experimental results indicate that the growth of Si₃N₄ is a thermally activated process in this experimental condition. It is calculated that the apparent activation energy is about 33 kcal mol^-1 below the deposition temperature of 1100 °C. The homogeneous reactions in the gas phase are promoted when the total pressure is increased. At pressures above 300 Torr, deposition rates are decreased because the reactant gases are depleted because of the homogeneous reaction. The charges stored in the MIS structure are found to be larger at lower deposition temperatures.     

Optimization of titanium dioxide film prepared by electrophoretic deposition for dye-sensitized solar cell application

Nanocrystalline TiO₂ films were deposited on a conducting glass substrate by the electrophoretic deposition technique. It was found that the thickness of TiO₂ film increased proportionally with an increase in deposition time and deposition voltage. However, as the deposition duration or deposition voltage increased, the film surface was more discontinuous, and microcracks became more evident. The characteristic of the dye-sensitized solar cell using TiO₂ film as a working electrode was analyzed. The results of the energy conversion efficiency and the photocurrent density exhibited a relationship dependent on the TiO₂ thickness. Curve fitting of energy conversion efficiency vs. TiO₂ thickness revealed the optimum solar cell efficiency ~ 2.8% at the film thickness of ~ 14 μm.     

Chemical deposition of PbS on NASICON from aqueous solutions

Phase-pure polycrystalline lead sulfide films have been grown on sodium-ion-conducting solid-electrolyte (NASICON, Na₃Zr₂Si₂PO₁₂) ceramic substrates by chemical deposition from solution. We have studied the microstructure of the films as a function of deposition time (5–180 min) at a fixed deposition temperature of 286 K and the effect of deposition temperature on their growth rate and microstructure. Empirical relations are obtained for the average crystallite size as a function of deposition time and temperature which can be used to select conditions for the growth of PbS films with tailored microstructure.     

Characterization of CVD tungsten deposited by silane reduction

The deposition of tungsten by silane reduction of WF₆ was investigated to determine the effect of the deposition chemistry on the layer properties. The influence of the deposition chemistry on the titanium adhesion layer was also investigated. To perform a direct comparison of the effect of the deposition parameters on the layer properties layers of equal thickness were deposited. In order to do this the deposition rates first had to be established experimentally. When the SiH₄WF₆ ratio was maintained constant at 1 and the deposition temperature increased the resistivity of the layers decreases, and the roughness increased significantly. When the temperature was maintained constant at 450 °C and the SiH₄WF₆ ratio was varied, it was found that the resistivity remained constant until the tungsten transformed to beta phase tungsten. At this transformation point the stress of the deposited layer and the roughness were seen to decrease significantly. It was found when the correct chemistry was applied at deposition temperatures up to 400 °C the initial reaction between the WF₆ and the Ti could be eliminated or reduced.     

Orientation of the BSCCO films prepared by low-pressure single-aerosol source metallorganic chemical vapour deposition

Thin films (0.7–0.8 μm) of Bi₂Sr₂CaCu₂O_x were deposited by low-pressure metallorganic chemical vapour deposition with a single aerosol source. The influence of the deposition parameters on the orientation of the films was studied. It was established that low deposition rate, high deposition temperature and the presence of the liquid phase resulted in films with predominant c-orientation.     

Evolutions of residual stress and microstructure in ZrO2 thin films deposited at different temperatures and rates

The residual stress in ZrO₂ thin films prepared by electron beam evaporation was measured by viewing the substrate deformation using an optical interferometer. The influences of deposition temperature and deposition rate on the residual stress have been studied. The results show that residual stress in ZrO₂ thin films varies from tensile to compressive depending on deposition temperature and deposition rate, respectively. The value of compressive stress increases with the increasing of deposition temperature and deposition rate. At the same time, X-ray diffraction measurement was carried out in order to examine the crystallization behavior of the ZrO₂ thin films as a function of deposition temperature and deposition rate. The relationship between the residual stress and the microstructure has also been discussed.     

Thermodynamics for the preparation of SiC-C nano-composites by chemical vapour deposition

SiC-C nano-composites covering every possible combination of carbon and SiC were prepared by chemical vapour deposition. The specific compositions of the deposits were controlled by changing the Si/C molar ratio in the source gases at deposition temperatures (T _dep) of 1673 to 1873 K and total gas pressures (P _tot) of 6.7 to 40 k Pa using the SiCl₄-C₃H₈-H₂ system. The prediction, based on the thermodynamic calculation on composition, morphology and deposition rate, was compared with experimental results. The optimal deposition conditions predicted by the calculations were nearly in agreement with the experimental results.     

The growth characteristics of chemical vapour-deposited β-SiC on a graphite substrate by the SiCl4/C3H8/H2 system

Silicon carbide has been grown at 1300–1800°C by chemical vapour deposition using the SiCl₄/C₃H₈/H₂ system on a graphite substrate. The effect of C₃H₈ flow rate and deposition temperature on the growth characteristics and structure of the deposit has been studied. The experimental results show that the degree of film density is changeable from a dense plate to a porous one with increasing C₃H₈ flow rate. The activation energy increases with increasing C₃H₈ flow rate. The grain size of the polycrystalline β-SiC becomes coarser when the C₃H₈ flow rate and the deposition temperature are increased. The preferred orientation of the deposited SiC layers changes from (111) to (220) on increasing deposition temperature from 1300°C to 1400°C. The deposition mechanism is also discussed.     

Characteristics of thin nitrided oxides prepared by an in-situ process

In this paper a new method of depositing silicon nitrided oxide by an in-situ process is introduced. Thin nitrided-oxide (NO) films were deposited on silicon by rapid thermal oxidation and rapid thermal chemical vapour deposition (RTCVD). Thin oxide films, 10.0 nm, were rapidly thermally grown in a dry oxygen ambient at 1000 °C and the silicon-nitride films were deposited on the oxide at 700–900 °C using an NH₃ and SiH₄ gaseous mixture. The effect of the NH₃/SiH₄ input ratio and the deposition temperature on the deposition rate and the electrical properties was studied. The experimental results show that the deposition rate increased with increasing deposition temperature and decreasing NH₃/SiH₄ input ratio. From the data for the Fourier-transform infrared spectroscopy (FTIR) and the C-V curves of the NO films, it was observed that the flat-band voltage is directly related to the N-H-bond peak intensity. The flat-band voltage shifts to the positive with increasing deposition temperature and to the negative with increasing NH₃/SiH₄ input ratio, and the breakdown field of NO films is higher than that of the RTP oxidation (RTO) films.     

Mechanical and thermal properties of physical vapour deposited alumina films Part I Thermal stability

Thermal stability of non-reactive physical vapour deposited alumina films of varying thickness on Al₂O₃-TiC and Si substrates, deposited at two different substrate biases, is examined. Substrate curvature measurements were used to determine the deposition stress and stress development during thermal cycling and annealing. Thermal cycling experiments revealed that the films deposited on Al₂O₃-TiC substrates become irreversibly more compressive on heating and annealing while films deposited on Si substrates become irreversibly more tensile. The deposition stress was found to be independent of film thickness, substrate material, and substrate bias during deposition. The thermal stability was independent of film thickness and substrate bias during deposition.     

The effect of substrate steel on the chemical vapour deposition of TiC onto tool steels

Titanium carbide (TiC) deposits on tools have been used to increase their wear resistance. Deposition experiments were performed on high alloy steels and on plain carbon steel by the chemical vapour deposition technique using a gaseous mixture of TiCl₄, CH₄ and H₂ in order to find a relationship between the steel composition and the characteristics of the deposited TiC. The experimental results show the considerable difference between the growth rates and the surface morphologies of deposits for various substrate steels. For the high alloy steels the TiC deposition reaction is a thermally activated process with an apparent activation energy of 40–45 kcal mol^-1. For the plain carbon steel, on which the TiC deposition rate is higher than that on the high alloy steel, although the TiC deposition reaction is also a thermally activated process at low deposition temperatures, the deposition rate depends on the gas phase mass transfer at high deposition temperatures. The microstructures of the deposited TiC films are composed of normal-sized grains and extremely fine grains.     

Deposition of Al2O3 and SiO2 Films via Pyrolysis of Aluminum Acetylacetonate and Hexamethyldisiloxane in the Presence of Nitrogen Compounds

Kinetic measurements were used to assess the effects of N₂O, NO, and diethylamine on the chemical vapor deposition of SiO₂ films on Si from hexamethyldisiloxane and the effect of diethylamine on the deposition of Al₂O₃ films on Si, GaAs, and InP from aluminum acetylacetonate. The composition of the films was determined by electron probe x-ray microanalysis and Auger electron spectroscopy. The deposition kinetics and properties of the films are correlated with the nature of the gaseous admixture and process parameters.     

Evaluation of stellite coatings by µ-PTA powder,laser, and PTA deposition processes

This article presents comparative evaluation of microplasma-transferred arc powder deposition (µ-PTAPD), laser deposition, and plasma-transferred arc deposition (PTAD) processes for sound quality and cost-effective deposition of Stellite 6 on AISI 4130 steel substrate. Dilution, deposition thickness, microstructure, secondary dendritic arm spacing (SDAS), microhardness, and abrasive wear resistance have been used for comparative evaluation. Analysis of morphology of Stellite deposition revealed that µ-PTAPD process and laser deposition processes could produce a coating of less than 1?mm thickness having good deposition quality, smaller dilution, and SDAS as compared with PTAD process. Analysis of X-ray diffraction patterns revealed that the Stellite coatings manufactured by all three processes had a lamellar structure consisting of Co phases, chromium-rich carbides (Cr₂₃C₆ and Cr₇C₃), and tungsten-containing compounds (W₂C). Analysis of microhardness and abrasive wear resistance found that the Stellite coatings manufactured by µ-PTAPD and laser deposition processes exhibited a lower coefficient of friction, wear volume, and higher microhardness as compared with the coating manufactured by PTAD process, this imparting them with higher abrasive wear resistance. This work proves that µ-PTAPD process has a capability to offer an economical and sustainable solution for good-quality thin coating of Stellite on metallic substrates.     

Effects of the experimental conditions of chemical vapour deposition on a TiC/TiN double-layer coating

Deposits of titanium nitride (TiN) were formed on TiC-coated 94wt.%WC-6wt.%Co substrates by chemical vapour deposition using a TiCl₄, H₂ and N₂ gas mixture. The effects of the deposition temperature, the total flow rate of the reactant gases and the partial pressure of TiCl₄ on the deposition rate, the preferred orientation and the surface morphology of the TiN deposit were investigated. The controlling mechanism of the TiN deposition reaction and its relationship with the deposition temperature and the total flow rate of the reactant gases were also investigated.The deposition rate and the TiN crystal growth along the (220) preferred orientation are increased with an increase in the deposition temperature and an increase in the partial pressure of TiCl₄ at a total flow rate of less than 700 cm³ min^-1. The particle size of the TiN deposit is reduced with an increase in the partial pressure of TiCl₄ and is increased with an increase in the deposition temperature at a total flow rate of less than 700 cm³ min^-1. When the total flow rate is greater than 700 cm³ min^-1, the deposition rate, the TiN crystal growth along the (220) preferred orientation and the particle size of the TiN deposit no longer vary.When the deposition temperature is lower than 1000 °C, the TiN deposition reaction is controlled by the surface reaction; at a temperature above 1000 °C, the reaction is controlled by mass transport. When the total flow rate is less than 700 cm³ min^-1, the deposition reaction is controlled by mass transport; with a total flow rate greater than 700 cm³ min^-1, the reaction is controlled by the surface reaction.     

Effects of different acetylene/nitrogen ratios on characteristics of carbon coatings on optical fibers prepared by thermal chemical vapor deposition

The effects of C₂H₂/(C₂H₂ + N₂) ratios on the characteristics of carbon coatings on optical fibers prepared by thermal chemical vapor deposition are investigated. The C₂H₂/(C₂H₂ + N₂) ratios are set to 60, 70, 80, 90, and 100%. Additionally, the deposition temperature, working pressure, and mass flow rate are 1003 K, 133 kPa, and 40 sccm, respectively. The deposition rate, microstructure, and electrical resistivity of carbon coatings are measured. The low-temperature surface morphology of carbon-coated optical fibers is elucidated. Experimental results indicate that the deposition rate increases with increasing the C₂H₂/(C₂H₂ + N₂) ratio, and the deposition process is located at a surface controlled regime. As the deposition rate increases, the electrical resistivity of carbon coatings increases, while the ordered degree, nano-crystallite size, and sp² carbon atoms of the carbon coatings decrease. Additionally, the low-temperature surface morphology of the carbon coatings shows that if the carbon coating thickness is not smaller than 289 nm, decreasing the deposition rate is good for producing hermetic optical fiber coatings.     

Synthesis of SrSnO3 thin films by pulsed laser deposition: Influence of substrate and deposition temperature

SrSnO₃ thin films were prepared by pulsed laser deposition on amorphous silica and single crystal substrates of R-sapphire, (100)LaAlO₃ and (100)SrTiO₃. High quality epitaxial (100) oriented films were obtained on LaAlO₃ and SrTiO₃ while a texture was revealed for films on sapphire deposited at the same deposition temperature of 700 °C. Amorphous films were obtained on silica but a post annealing at 800 °C induced crystallization with a random orientation. The screening of deposition temperature showed epitaxial features on SrTiO₃ from 650 °C while no crystallization was observed at 600 °C. The influence of substrate and deposition temperature was confirmed by Scanning Electron Microscopy and Atomic Force Microscopy observations.     

Effects of deposition temperature on the microstructure of MOCVD Y1Ba2Cu3O7−x thin films

The effects of deposition temperature on the microstucture and composition of Y₁Ba₂Cu₃O_7–x films deposited on MgO and SrTiO₃ substrates by the metal-organic chemical vapour deposition (MOCVD) method were investigated. As the deposition temperature decreased from 900 to 700 °C, the Cu content in the deposited film increased. SEM micrographs of the films showed that the growth direction of the film was changed from c axis to a axis perpendicular to the substrate surface, and then to random orientation, as the deposition temperature decreased. The superconducting transition temperature and the transition width of films deposited on SrTiO₃ substrates at temperatures higher than 810 °C were over 90 K and within 1 K, respectively.     

Comparison of high-pressure dc-sputtering and pulsed laser deposition of superconducting YBa2Cu3O x thin films

Superconducting YBa₂Cu₃O_x thin films were deposited on NdGaO₃ (110) substrates using two different techniques: dc sputtering at high oxygen pressure and pulsed laser deposition. The structure, electrical properties, and surface morphology of the obtained films were compared. The superior crystal quality of dc-sputtered films fabricated at the same temperature and at oxygen pressure of the same range as for laser-deposited films can be explained by a lower deposition rate providing time for recrystallization processes. The re-evaporation becomes significant for dc sputtering at high deposition temperatures and results in Badeficient films. The high mobility of atoms on the surface of the growing film during laser deposition helps in the formation of smoothc-oriented areas of the film.