Vapor phase deposition of copper films with a Cu(I) β-diketiminate precursor

This work demonstrates the vapor phase deposition of copper films with a volatile Cu(I) β-diketiminate precursor. X-ray photoelectron spectroscopy (XPS) depth profiles of the deposited films show only background levels of carbon and oxygen. Film thickness depends on the length of precursor pulse, but the surface roughness does not, a result that suggests a uniform deposition. XPS data for the chemisorbed copper precursor show that the copper was in both the metallic and + 1 oxidation states. Chemisorption of the Cu(I) precursor deposited a Cu(I) species. However, disproportionation of some of the chemisorbed Cu(I) precursor generated Cu(0) and a volatile Cu(II) complex, which was removed from the surface. These results are characteristic of a pulsed chemical vapor deposition.     

Spray pyrolysis deposition of polycrystalline magnesia films and their use as buffer layers in Bi(Pb)-Sr-Ca-Cu-O/MgO/Al2O3 (or glass ceramics) structures

The deposition of MgO films on Al₂O₃ and glass ceramic substrates by spray pyrolysis of a water-ethanol magnesium nitrate precursor solution has been studied. Dense polycrystalline films have been obtained by repeated pyrolysis at 300–350 °C followed by annealing of the deposit in air at 970 °C. It has been established that the finest grains obtained under these experimental conditions correspond to the films deposited on glass ceramic substrates. It has been shown that the MgO films can be useful buffer layers preventing the interaction between the above substrates and the BiSr-Ca-Cu-O films deposited on them by spray pyrolysis of nitrates.     

Comparison of Structure and Conductivity of Multiwall Carbon Nanotubes Obtained over Ni and Ni/Fe Catalysts

Multiwall carbon nanotubes (MWNT) were produced by pyrolysis of acetonitrile (CH₃CN) on metallic particles of Ni and Ni/Fe at 850°C. The special program for statistical treatment of electron micrograph images was developed. Research of diameter distribution of MWNT grown over different catalysts was carried out. Two kinds of carbon nanotubes with different diameter and microstructure are formed on Ni catalyst. The MWNT with smaller diameter and cylindrical packing of layers were found to have the higher conductivity.     

Analysis of Zinc 65 Contamination After Vacuum Thermal Process

Radioactive contamination with a gamma energy emission consistent with ⁶⁵Zn was detected in a glovebox following a vacuum thermal process. The contaminated components were removed from the glovebox and subjected to examination. Selected analytical techniques were used to determine the nature of the precursor material, i.e., oxide or metallic, the relative transferability of the deposit and its nature. The deposit was determined to be borne from natural zinc and was further determined to be deposited as a metallic material from vapor.     

Characterization of titanium dioxide atomic layer growth from titanium ethoxide and water

Atomic layer growth of titanium dioxide from titanium ethoxide and water was studied. Real-time quartz crystal microbalance measurements revealed that adsorption of titanium ethoxide is a self-limited process at substrate temperatures 100–250°C. A relatively small amount of precursor ligands was released during titanium ethoxide adsorption while most of them was exchanged during the following water pulse. At temperatures 100–150°C, incomplete reaction between surface intermediates and water hindered the film growth. Nevertheless, the deposition rate reached 0.06 nm per cycle at optimized precursor doses. At substrate temperatures above 250°C, the thermal decomposition of titanium ethoxide markedly influenced the growth process. The growth rate increased with the reactor temperature and titanium ethoxide pulse time but it insignificantly depended on the titanium ethoxide pressure. Therefore reproducible deposition of thin films with uniform thickness was still possible at substrate temperatures up to 350°C. The films grown at 100–150°C were amorphous while those grown at 180°C and higher substrate temperature, contained polycrystalline anatase. The refractive index of polycrystalline films reached 2.5 at the wavelength 580 nm.     

Synthesis of platinum nanoparticles by aerosol assisted deposition method

An atmospheric pressure aerosol assisted deposition method has been developed to grow highly oriented nanoparticles and thin continuous films of platinum on a variety of substrates for applications such as catalysts including their use in proton exchange membrane fuel cells. Pt nanoparticles with sizes ranging from 4 nm to 78 nm were synthesized on Si, silicon dioxide coated Si substrates and carbon nanotubes. The size and density of the nanoparticles was found to depend strongly on the precursor carrier gas flow rate and deposition time. The particles showed preferential orientation of (111) that was independent of substrate used. The resulting nanoparticles were characterized by Scanning Electron Microscopy, X-ray Diffraction Spectroscopy and X-ray Photoelectron Spectroscopy in order to obtain information about their morphology, crystallinity and composition. The method developed can deposit uniform coatings of highly oriented, pure Pt nanoparticles without the need of any substrate pretreatment such as surface functionalization, deposition of seed layer for electrodeposition on insulating or semiconducting substrates, and without the use of expensive vacuum equipment.     

Stresses in sputtered RUOx thin films

RuO_x thin films have been deposited by reactive sputtering in an O₂/Ar atmosphere. The films were characterized for their stress and resistivity as a function of deposition temperature (room temperature, 300°C) and the O₂ content (25–100%) in the sputtering gas. Additionally, the stresses in these films were determined as a function of annealing temperature (up to 600°C) using an in-situ curvature measurement technique. The as-deposited films were found to be under a state of compressive stress for all deposition conditions. The compressive stresses sharply increased with increasing deposition temperature from a value of around 200 MPa at 200°C to 1400 MPa at 300°C. This dramatic increase has been attributed to differences in microstructure at these deposition temperatures. The microstructural differences also led to the widely differing stress-temperature behavior during annealing of these films. For films deposited at temperatures lower than 200°C, the annealing process resulted in a decrease in the compressive stress and resistivity of the films. However, films deposited at a temperature of 300°C did not show any changes in the compressive stress or resistivity after annealing. The results of this study can be used to deposit RuO_x thin films with low resistivity and minimal stresses.     

Precursor solvent influence on preparation and electrochemical properties of platinum nanoparticles electrodes

The crystalline sizes and loading efficiencies of metallic nanoparticles for fuel cell catalysts have been measured by changing solvent species containing precursors. By changing the solvent species containing carbon particles and metal salt, the microstructure and the according electrochemical property of catalysts could be controlled. Four kinds of solvent were investigated in this study. Pt catalysts that were deposited on carbon blacks supports by using an ethylene glycol solution showed the highest deposition efficiency, 85% and smallest crystalline size, 2.85 nm of particles. From the experimental result, it was concluded that the electrochemical performance of catalysts was dependent on the crystalline size and deposition efficiency of metal particles, by changing solvent species.     

Improved efficiency of the chemical bath deposition method during growth of ZnO thin films

Chemical bath deposition (CBD) is an inexpensive and low temperature method (25-90 °C) that allows to deposit large area semiconductor thin films. However, the extent of the desired heterogeneous reaction upon the substrate surface is limited first by the competing homogeneous reaction, which is responsible for colloidal particles formation in the bulk solution, and second, by the material deposition on the CBD reactor walls. Therefore, the CBD method exhibits low efficiency in terms of profiting the whole amount of starting materials. The present work describes a procedure to deposit ZnO thin films by CBD in an efficient way, since it offers the possibility to minimize both the undesirable homogeneous reaction in the bulk solution and the material deposition on the CBD reactor walls. In a first stage, zinc peroxide (ZnO₂) crystallizing with cubic structure is obtained. This compound shows a good average transparency (90%) and an optical bandgap of 4.2 eV. After an annealing process, the ZnO₂ suffers a transformation toward polycrystalline ZnO with hexagonal structure and 3.25 eV of optical bandgap. The surface morphology of the films, analyzed by atomic force microscope (AFM), reveals three-dimensional growth features as well as no colloidal particles upon the surface, therefore indicating the predominance of the heterogeneous reaction during the growth.     

Effect of vacuum heat treatment on microstructure and microhardness of cold-sprayed TiN particle-reinforced Al alloy-based composites

Cold spraying (CS) demonstrates great potentials in fabrication of metal matrix composites. The effect of post-spray heat treatment at 250 °C, 350 °C and 450 °C for 2 h on the microstructure and properties of CS Al5356/TiN composites was examined in this study. The results show that the heat treatment has little effect on the distribution of TiN particles in the matrix of all the composites. The pure Al5356 deposit presents large pores between the deposited particles after heat treatment, which is a common phenomenon for CS metallic coatings having an apparent increasing porosity during annealing. The adhesion between the deposit and substrate could be enhanced through atom diffusion, especially at elevated temperatures. However, the microhardness of all the deposits is significantly reduced after heat treatment because of the release of work-hardening effect within the as-sprayed metallic particles.     

Electrophoretic deposition infiltration of metallic fabrics with a boehmite sol for the preparation of ductile-phase-toughened ceramic composites

The infiltration of commercially available metallic fibre mats by a boehmite sol using the electrophoretic deposition (EPD) technique was investigated. The nanosized boehmite particles were positively charged in a colloidal suspension at pH 4 and migrated upon application of an electric field to the metallic fabric acting as the negative electrode. Three different type 316L stainless steel fabrics were considered and it was found that the quality of the infiltration depended on the fibre architecture. The EPD parameters, i.e., the applied voltage and deposition time, were optimized for obtaining a high solids loading in between the fibre tows and a firm adherent deposit. The infiltrated fibre mats, being of high quality, i.e., low macroporosity and absence of significant microcracking, serve as prepregs for the manufacture of alumina matrix composites reinforced with a two- or three-dimensional metallic phase. © 1998 Chapman & Hall     

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

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

CHEMICAL VAPOR DEPOSITION OF TiB2 FOR TiN-TiB2 LAMINAR COMPOSITES

TiB₂ is a material with very interesting properties with respect to erosion and corrosion resistance. Deposition on metallic substrates using TiCI₄, BBr₃ or BCI₃ and H₂ at temperatures around 900° C results in coronation of the substrate, which is most severe when using BBr₃. Therefore, a TiN diffusion barrier is applied. Here we discuss the deposition of TiB₂ using BCI₃ on molybdenum and TiN and compare the results with those of the thermodynamically more favorable reaction with BBr₃. Smooth TiB₂ layers are formed when using BCI₃, with faceting occurring above 900° C. The morphology seems to be independent of the BCI₃/TiCl₄ ratio in the gas phase for values between 0·5 and 4. With an excess of boron in the gas phase - BCI₃/TiCl₄ = 8, depletion occurs already at 800° C. An apparent activation energy of 210 KJ/mol has been determined for a stoichiometric gas phase with BCl₃/TiCI₄ = 2. When the supply of boron is limiting - BCl₃/TiCl₄ = 0·5, the activation energy is 120 KJ/mol.     

Optical properties of silver, gold and aluminum ultra-thin granular films evaporated on oxidized aluminum

The reflectivity of silver, gold and aluminum granular ultra-thin films deposited on an oxidized aluminum substrate has been measured in a spectral range from 300 to 700 nm. This measurement was done at 45° with p-polarized light, during the deposition of the different metals and also after a 300°C annealing at the end of the evaporation process. Some measurements were also performed in air at different incidence angles with p- and s-polarized light. Plasmon resonance effects of metal particles are seen directly in the reflectivity spectrum.     

In Situ Thermocouples in Macro-Components Fabricated Using SALD and SALDVI Techniques. II. Evaluation of Processing Parameters

In order to fabricate well-control led in situ SiC/C thermocouples embedded within macro-structural SiC components using an integrated selective area laser deposition (SALD) and the selective area laser deposition and vapor Infiltration (SALDVI) technique, the major processing parameters affecting the crystal structure, the deposition rate, surface morphology of deposits, and shapes and sizes of the cross section of deposited lines are evaluated. It is found that the growth rate of SiC deposits increases with temperature and tetramethy Isilane (TMS) gas pressure over the temperature and pressure range studied. The apparent activation energy for depositing SiC from TMS is 61 kJ/mole in the temperature range from 700 to 1200°C and independent of the TMS gas pressure ranging from 20 to 60 torr. The shape and size of the cross section of SiC lines depend strongly on the deposition temperature. XRD examination indicates that the deposition product using a C₂H₂ precursor at 900°C is crystalline graphite. The crytallinity of Si₃N₄ deposits is affected by the substrate material even though the deposition temperature and other process parameters are the same. These phenomena have been explained in terms of the growth controlling mechanisms of deposits, the temperature distribution induced by an incident laser beam, and the thermal conductivity of the substrate.     

Effect of substrate on the nucleation and growth of aluminum films deposited from methylpyrrolidine alane

Methylpyrrolidine alane complex was used to deposit aluminum films on various types of substrates in a low pressure chemical vapor deposition reactor. The films grow easily on metallic and transition metal oxide surfaces, but not on any other tested semiconductor and dielectric substrates below 200 °C, showing strong substrate dependency. The free energies of precursor adsorption, surface dissociation reaction and product desorption, as well as the film wettability to substrate are among the key factors which affect the energy barrier for nucleation or deposition selectivity. In general, a metal substrate can enhance nucleation because it catalyzes the surface reactions and bonds strongly with aluminum. The oxidation-reduction reaction may occur between the precursor and substrate on a metal oxide surface. The reduced metal sites can be the seed nuclei and are possibly responsible for Al growth on the surfaces of transition metal oxides.     

Effect of Erodent Particle Hardness on Velocity Exponent in Erosion of Steels and Cast Irons

This article reports the effect of hardness of erodent particles on velocity exponent of some weld deposited alloys. Three steels and two alloy cast irons were selected for the present investigation. The bulk hardness of the alloys was in the range of 300 to 800 HV, whereas erodnet particles were having hardness in the range of 400 to 1875 HV. Erosion tests were conducted with 125-150 µm cement clinker, 125-150 µm blast furnace sinter, 100-150 µm silica sand, and 125-150 µm alumina particles and at impingement angles of 30° and 90° and with impingement velocities in the range of 25 to 120 m sec^-1. The erosion rate showed power-law dependence on impingement velocity, E = kVⁿ, where kis a constant and nis the velocity exponent. The velocity exponents obtained in the present work were in the range of 1.91 to 2.52. The velocity exponent showed an increasing trend with increasing hardness of the alloys irrespective of the hardness of the erodent particles and the impingement angle. The velocity exponent increased with increasing hardness of erodent particles, irrespective of the impingement angle and hardness of the alloys. The velocity exponents obtained in the present work were rationalized with respect to erodent particle properties, material properties and erosion mechanisms.     

Nickel and copper deposition on fine alumina particles by using the chemical vapor deposition-circulation fluidized bed reactor technique

A Chemical Vapor Deposition-Circulation Fluidized Bed Reactor technique has been developed to deposit metallic Ni and Cu onto alumina particles of 45 m diameter. The furnaces consisted of upper and lower zones, and the deposition precursors were produced both in situ and by vaporization of chlorides. X-ray diffraction, metallographical examination, and compositional analysis were used to analyze the deposition layers. For both Ni and Cu deposition, the deposition rates increased with higher temperatures of the lower furnace. The rates increased with greater amounts of chloride addition as well, but they reached plateaus when the amounts of addition were more than 40%.     

金属玻璃基复合材料的微结构效应

基于自由体积理论和Ramberg-Osgood模型,并利用ABAQUS软件,建立颗粒随机分布代表性体积单元模型,模拟了Ti_(64.5)Zr_(14.5)V_(18.5)Cu_(2.5)颗粒增韧Ti基金属玻璃基复合材料在单轴拉伸状态下的微结构效应,讨论了颗粒的体积分数、团聚数目、长径比、定位取向和界面对金属玻璃韧性的影响。结果表明:提高颗粒体积分数能显著提高复合材料的塑性,但部分牺牲了复合材料的强度;增大颗粒长径比能够增强复合材料的塑性和屈服强度;使颗粒的取向与荷载方向成90°或0°,不仅增强了复合材料的塑性,而且与其他排布相比也增强了复合材料的强度;减少团聚数目至2个以下,能明显减少金属玻璃基复合材料的塑性和强度的损失,使团聚中颗粒与荷载成90°,却能改善复合材料的塑性和强度;在颗粒增韧金属玻璃基复合材料中加入零厚度界面,能观察到在主剪切带上颗粒和基体在界面处脱粘,得到与实验现象更加吻合的结果。通过上述的研究能够很好地理解复合材料的微结构效应,并有利于材料的设计。     

The thermophoretic capture of large volatile aerosol particles by growing or evaporating droplets in multicomponent gas mixtures

The motion of large two-component volatile aerosol particles in a three-component gas mixture containing droplets is considered, which is caused by optical radiation. An expression is derived for the rate of deposition of aerosol particles onto the droplet surface. Analysis is made of the conditions in which the aerosol particles either deposit on the droplet surface or scatter. Numerical estimates are given for antimony-bismuth aerosol particles.