Preparation of a superhydrophobic and superoleophilic polyester textile by chemical vapor deposition of dichlorodimethylsilane for Water–Oil separation

Reconciling results of MOCVD of a CNT composite with equilibrium thermodynamics

The influence of chemical vapor deposition process parameters including carrier gas composition, deposition temperature, and content of reactants on the structure of graded SiC-C coating is discussed on the basis of thermodynamic calculation in this paper. The addition of enough hydrogen into carrier gas is necessary for the fabrication graded SiC-C coating. The increase of deposition temperature benefits the control of composition in graded coating but the concentration of free Si and free C becomes high at a too high deposition temperature. A high concentration of reactants is preferred while more defects are apt to exist in coatings if the concentration of reactants is too high. The optimum CVD process parameters for graded SiC-C coating are: gradually changing the molar ratio of SiCl4 and CH4 from 0 to 1 when the concentration of CH4 in hydrogen is 1-2 vol%, and the deposition temperature is 1200-1500 °C.

Super-Hydrophobic and Oloephobic Crystalline Coatings by Initiated Chemical Vapor Deposition

Abstract Preferred crystallographic orientation (texture) in thin films of technologically important materials frequently has a strong effect on the properties of these films and is important for stable surface properties. The deposition of organized molecular films of a poly‐perfluorodecylacrylate, poly‐(1H,1H,2H,2H‐perfluorodecyl acrylate) (p‐PFDA), by initiated chemical vapor deposition (iCVD) is described. The tendency of p‐PFDA to crystallize in a smectic B phase has been reported in films prepared from solution but not for those using a CVD technique. The degree of crystallinity and the preferred orientation of the perfluoro side chains, either parallel or perpendicular to the surface, are controlled by tuning the CVD process parameters (i.e., initiator to monomer flow rate ratio, filament temperature, and substrate temperature). Films with no observable X‐ray diffraction patterns are also achieved. The observed differences in crystal texture strongly impact the observed water contact angles (150° to 130°, advancing) and corresponding hysteresis behavior. Low hysteresis (<7°) is associated with high crystallinity, particularly when the orientation of the crystallites resulted in the perfluoro side groups being oriented parallel to the surface. The latter texture resulted in smoother film than the texture with the chains oriented perpendicular to the surface and this can be very advantageous for applications in which relatively smooth but still crystalline films are needed.

Silicon nanowire growth on glass substrates using hot wire chemical vapor deposition

The growth of tungsten oxynitride thin films by metalorganic chemical vapor deposition (MOCVD) was achieved using an all nitrogen coordinated tungsten imido-amidinato precursor in the presence of oxygen as the reactive gas. In particular the influence of CVD process parameters on the structure, morphology and composition of the films was studied by scanning electron microscopy (SEM), Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA) and X-ray diffraction XRD. It was possible to tune the content of the nitrogen of the films which could be an advantage in terms of functional properties of the tungsten oxide based materials.

Using a home-made aerosol nebulizer, we developed a new aerosol-assisted chemical vapor deposition (AACVD) process that made it possible to synthesize vertically-aligned carbon nanotube (VACNT) arrays with heights over a few millimeters routinely. An essential part of this technique was in-situ formation of metal catalyst nanoparticles via pyrolysis of ferrocene-ethanol aerosol right before CNT synthesis. Through the optimization of aerosol supply and CVD process parameters, we were able to synthesize clean VACNT arrays as long as 4.38 mm with very low metal contents in 20 min. Furthermore, it is worthy noting that such an outstanding height is achieved very quickly without supporting materials and water-assistance. By taking advantage of almost complete inhibition of CNT growth on low melting-temperature metals, we were able to fabricate patterned VACNT arrays by combining AACVD process with a conventional photolithograpic patterning of gold lines. Characterizations of as-grown nanotubes such as morphology, purity, and metal contents are presented.

Unconventional Ni–P alloy-catalyzed CVD of carbon coil-like micro- and nano-structures

We used Optical Emission Spectroscopy (OES) as a non-invasive optoelectronic tool of in-situ monitoring of plasma discharge. The low-temperature plasma, based on mixture of CH 4 and H 2 , was produced during Microwave Plasma Assisted Chemical Vapour Deposition (μPA CVD) synthesis process of thin diamond/DLC films. Molecular modelling showed that quality of the synthesized films is determined by total amount as well composition ratio of ions H + and CH + 3 , produced in an area of Electron Cyclotrone Resonance (ECR). Therefore, dissociation of H 2 molecules as well as excitation and ionization of hydrogen atoms were a subject of the presented OES studies. Developed monitoring systems uses spectrometers coupled with the reaction chamber by a dedicated optical probe and a fibre bundle. Intensity of Balmer and Paschen series were measured as a function of main CVD process parameters.

Gas-phase characterization in diamond hot-filament CVD by infrared tunable diode laser absorption spectroscopy

In this article, we report aspects of the growth of nanocrystalline diamond films using microwave-assisted plasma chemical vapor deposition and their relation to electron field emission. Nanodiamond films with grain size as small as 5–10nm by CH4∕H2∕N2 microwave plasma enhanced chemical vapor deposition (MPECVD) and 10–20nm by CH4∕H2 MPECVD have been achieved. An effective means to grow nanodiamond films is to increase the nucleation rate and decrease the growth rate by adjusting the CVD process parameters. With its relation to field emission, we infer that the combination of high dopant concentration resulting in lower electrical resistance of the diamond film and increased sp2 bonded nondiamond carbon content contributes effectively to the enhancement of field emission characteristics, while the reduction in grain size of the nanodiamond film has no similar effect.

The effect of growth rate control on the morphology of nanocrystalline diamond

The group-III nitrides GaN, InN, AlN and their alloys In x Ga 1-x N, Al x Ga 1-x N have recently acquired technological importance for LED and laser applications. However, InN has a low decomposition temperature and the growth of crystalline InN material at low temperatures is difficult. One of the approaches is to design single source precursors that decompose at low temperatures. Single source precursors of the type N 3 In[(CH 2 ) 3 NMe 2 ] 2 were developed and the growth of crystalline InN films with preferred orientation was achieved using this compound. However employing specific CVD process parameters we were able to grow InN whiskers consistently by CVD using a cold wall CVD reactor on sapphire substrates at 500°C. These whiskers were characterised by XRD, SEM, EDX and TEM measurements.

Investigations on InN whiskers grown by chemical vapour deposition

Abstract A MEMS-based gas turbine engine is being developed for use as a button-sized portable power generator or micro-aircraft propulsion source. Power densities expected for the micro- engine require high combustor exit temperatures (1300-1700K) and very high rotor peripheral speeds (300-600m/s). These harsh operating conditions induce high stress levels in the engine structure, and thus require refractory materials with high strength. Silicon carbide has been chosen as the most promising material for use in the near future due to its high strength and chemical inertness at elevated temperatures. However, techniques for microfabricating single- crystal silicon carbide to the level of high precision needed for the micro-engine are not currently available. To circumvent this limitation and to take advantage of the well-established precise silicon microfabrication technologies, silicon-silicon carbide (SiC) hybrid turbine structures are being developed using chemical vapor deposition of poly-SiC on silicon wafers and wafer bonding processes. Residual stress control of SiC coatings is of critical importance to all the silicon-silicon carbide hybrid structure fabrication steps since a high level of residual stresses causes wafer cracking during the planarization, as well as excessive wafer bow, which is detrimental to the subsequent planarization and bonding processes. The origins of the residual stresses in CVD SiC layers have been studied. SiC layers (as thick as 30µm) with low residual stresses (on the order of several tens of MPa) have been produced by controlling CVD process parameters such as temperature and gas ratio. Wafer-level SiC planarization has been accomplished by mechanical polishing using diamond grit and bonding processes are currently under development using interlayer materials such as silicon dioxide or poly-silicon. These process development efforts will be reviewed in the context of the overall micro-engine development program.

This paper presents results on molybdenum oxide films deposited by APCVD process from Mo(CO) 6 in a low-temperature range - 125-200°C. We first study the correlation between CVD-process growth parameters and the structure of MoO 3 films, from one side, and the relation between their structure and optical properties, from the other side. We present a study basically on the influence on the structure of the temperature - the deposition and the post-deposition annealing ones and the influence of the vapor pressure of Mo(CO) 6 . The structure of the films is studied by different methods including infrared spectroscopy. The purpose is to see what kind of additional information can supply the IR measurements on the structure of the films in dependence of the CVD-process parameters.

Superconducting BSCCO thin films were obtained with high deposition rate (about 35 nm/min) at temperatures of 720-810 o C by MOCVD-technique. Characteristics of evaporation process of precursors were determined. The influence of deposition temperature and oxygen partial pressure on superconducting phase formation and chemical composition of the films was studied

A detailed study has been made of the atmospheric pressure chemical vapour deposition (CVD) of aluminium oxide (Al2O3) coatings on powder metallurgy (PM) BT42 grade high speed steel (HSS) indexable cutting tool inserts. To facilitate this, a laboratory-scale CVD reactor was initially designed and purpose-built. The literature on the effect of process parameters on Al203 coatings chemically vapour deposited on cemented carbide substrates was comprehensively surveyed. With reference to deposition conditions quoted in this literature, a series of trial Al203 coating runs were then performed using uncoated and TiN, TiC and Ti(C1N) precoated PM HSS inserts. Concurrently, modifications to the laboratory-scale CVD reactor were made. Eventually, deposition conditions were established under which a preliminary a Al203 coating could be deposited on the PM HSS inserts and, in the case of the Ti(C1N) precoated inserts only, substantially retained during the obligatory post-coating HSS substrate heat treatment. The effect of the absence/presence and type of precoating on the CVD of AI203 coatings on the PM HSS inserts are discussed. Subsequent coating runs were carried out only on Ti(C1N) precoated inserts. The characteristics of the preliminary AlP, coating on the Ti(C1N) precoated PM HSS inserts were determined, both before and after the obligatory HSS substrate heat treatment, using an established characterisation procedure. This involved the following techniques: X-ray diffraction, Auger electron spectroscopy, optical microscopy, fractography, scanning electron microscopy, microhardness testing, profilometry and scratch-adhesion testing. Although many of the characteristics of the preliminary AI20, coating were found to be inferior to those presented in the literature, they were also established to be essentially unaffected by the post-coating HSS substrate heat treatment. To im prove upon the preliminary Al203 coating, the effect of two of the most important CVD process parameters quoted in the literature; C02JH 2 mole ratio and Alel3 concentration, on the characteristics of Al20, coatings chemically vapour deposited on the Ti(C1N) precoated PM HSS inserts was investigated. Both parameters were found to have a significant effect on Al203 coating characteristics. The reasons for this are discussed in detail.

For the characterization of high purity materials with respect to trace impurities in the ng/g range it is state of the art to use high sensitive methods such as GDMS and SIMS. The low sample consumption of these methods is a significant drawback in the characterization of sintered materials due to the heterogeneous distribution of the trace impurities. TMS procedures with AAS, ICP-AES and ICP-MS end determination overcome these problems by the enrichment of the impurities in a small volume of diluted acid. In many cases of research work and quality assurance distribution analysis is more meaningful than bulk analysis. A few examples are given to demonstrate the respective potential of SIMS. Diffusion processes of K and Si in doped Mo are investigated. Depth profiling on single grains shows the effect of surface cleaning of high purity Cr-powder by etching with HF-acid. Quality control of Mo foils is achieved by high resolution depth profiling for O and S. Influences on CVD process parameters can be derived from high resolution S depth profiling in the Al2O3 layer of coated hard metals. Furthermore, outlooks are given on the applications of high resolution SNMS, 3D-SIMS and high resolution ICP-MS.