Surface layers of ultrafine Si3N4 particles (30–100 nm. diameter) have been synthesized by laser-pyrolysis of a liquid precursor, dispersed as an aerosol. This aerosol was formed in a nitrogen environment (at near ambient pressure) using an ultrasonically activated nozzle. The organosilazane precursor, which was specially designed for CO2 laser pyrolysis, was of the type (CH3SiHNH)x, with x = 3 or 4. In the current experiments deposition was performed on Ni substrates using a (i) 7 cm/s. substrate translational velocity, and (ii) ˜2.8 × 102 w/cm2 power density.

Carbon fibre is an ideal material for reinforcing inorganic matrix composites, especially for high temperatures. Its main drawback is its susceptibility to oxidation and to reaction with metals.

Our challenge was to perfect a method of producing a carbon fibre in which each elementary filament is covered and protected by a very thin and adherent layer of a refractory carbide such as SiC, B4C, etc…

For this purpose, we use reactive chemical vapor deposition (R.C.V.D.) in which only the M element of the M C carbide is carried by the gas phase, carbon being supplied by the fibre itself. The growth rate is self regulated by the solid state diffusion.

This method has been developed in a continuous reactor with ex-PAN (6K) or ex-PITCH (2K) fibres.

The mechanical behaviour of the coated fibres is very near that of the initial ones, but their oxidation rate at 600°C is 100 times lower.

A novel low temperature process for the chemical vapour deposition of titanium nitride films has been developed. Titanium sub-halides generated “in situ” by chlorination of titanium pellets are subsequently reacted with ammonia at reduced pressure and temperatures of 450–600° C. The coatings have excellent adhesion and wear resistance. A description of the process and the properties of the coatings produced by it will be presented.

A review is presented of early and recent advances in the metal-organic chemical vapor deposition (MOCVD) of thin films from organotransition metal and related precursors. Routes to pure metals and alloys, metal carbides, metal borides, metal nitrides, metal silicides, and related materials will be summarized. Also included is a discussion of both the advantages and disadvantages of employing metal-organic precursors that contain transition elements.

A liquid methylsilazane compound, [CH3 SiHNH]n, was used, with H2, NH3, and a 60%/40% mixture of NH3/H2, to deposit silicon-based ceramic films in a CVD reactor at 873–1073 K. Characterization of the films by ellipsometry, Fourier transform infrared spectrometry (FTIR) and Auger electron spectrometry (AES) showed that the methylsilazane was pyrolyzed to form silicon carbonitride in H2, and silicon nitride in both NH3 and NH3 /H2, with the incorporation of appreciable amounts of oxygen. The deposition rate increases and the activation energy decreases in order from NH3-, NH3 /H2-, and H2-[CH3SiHNH]n gas mixtures. The temperature dependence of the structural density of the films increases in the same order.

Characterization of TiO2 films grown by the MOCVD technique was carried out using micro-Raman scattering. The effects of processing parameters on the film composition and morphology were investigated. The micro-Raman technique was shown to be a useful tool for characterizing oxide thin films grown by the MOCVD technique.

Titanium and vanadium oxide thin films have been prepared in a cold wall low pressure MOCVD system for the study of MOCVD processing of epitaxial oxide films. Films were deposited on Si(111) and sapphire (0001) and (1120) at temperatures from 400 to 800°C. Processing parameter-structureproperty relationship was examined in detail and the result is presented.

ZrO2 films were deposited on silicon substrates at temperatures from 350 to 550 °C by metallorganic chemical vapor deposition (MOCVD) using zirconium acetylacetonates. Depositions were carried out at both atmospheric and low pressures. The optical properties, structure, microstructure, and composition of these films were characterized by Ellipsometer, X-ray diffraction, scanning electron microscopy (SEM), and electron spectroscopy for chemical analysis (ESCA), respectively. The deposition was kinetically controlled at low temperatures and mass transfer controlled at high temperatures. Use of zirconium (IV) acetylacetonate resulted in cubic ZrO2 with some carbon contamination whereas, tetragonal pure ZrO2 were obtained with the precursor zirconium (IV) trifluroacetylacetonate. The tetragonal ZrO2 films are fine grained and showed preferential orientation. The measured values of dielectric constant, refractive index, and electrical resistivity of ZrO2 films are 18, 2.0, and 5E13 Ohm.cm, respectively.

A novel process for the low temperature synthesis of titanium nitride thin films by APCVD is described. TiN coatings containing less than one atom percent of carbon and oxygen were deposited at 200 °C on silicon, vitreous carbon, glass, stainless steel and plastic substrates using Ti(Nme2)4 and ammonia gas as precursors. The films were characterized by Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy.

Chemical vapor deposition from (MeCp)2Nb(allyl) at atmospheric pressure yields niobium carbide films at temperatures as low as 300°C. X-ray photoelectron spectroscopy (XPS) studies indicate that the bulk films contain a carbide phase and a nearly stoichiometric ratio of niobium to carbon. The morphology of the films has been examined by scanning electron microscopy (SEM).

Low-temperature chemical vapor deposition of M(allyl)3 (M = Rh, Ir; allyl = η3 -C3H5) in the presence of H• yields thin, crystalline metal films of greater than 97% metal composition. Depositions using H2 result in the formation of materials which are amorphous and contain a significant amount of residual carbon (14%). The composition of these materials does not differ significantly from that obtained from the vacuum thermal deposition of M(allyl)3.

SrTiO3 thin films were deposited by low pressure organometallic chemical vapor deposition on silicon substrates using the volatile metal-organic precursors titanium isopropoxide and Sr(dipivaloylmethanate)2. Oxygen and water vapor were used as reactant gases and argon was used as a carrier gas. Growth rates ranging from 0.6–2.1 μm/hr were obtained at 650–800°C. Polycrystalline films were obtained at growth temperatures of 650–750°C, and amorphous films above 750°C. SrTiO3 films deposited on silicon substrates exhibited resistivities greater than 109 Ω-cm and dielectric constants up to 100.

The impregnation of metallic oxides in ceramic bodies to convey information is as old as civilization itself. But unlike the potters of the past, whose purpose was mainly decorative, ours is to control the direction and the speed of traveling light. This may have practical uses with respect Optical waveguides, for integrated optic devices, and micro images for information storage. The ceramics we use are Porous Vycor Glass (PVG) and aerogels made from solgels, both composed mainly of SiO2.

It has recently been demonstrated that highly resolved images can be produced by photochemical deposition of metal oxides in porous Vycor glass. This process has potential applications to the development of integrated optics in glass since it enables one to deposit in the same material refractive index patterns of optically and electro-magnetically active adsorbates. In order to learn in more detail about the interaction of the metal oxides with the glass, we impregnated porous Vycor glass (PVC) with tin or iron oxides and analyzed the samples with electron microscopy, x-ray microprobe analysis, and small angle x-ray scattering (SAXS). The results indicate that even though both oxides produce images of comparable resolution (approx 1μ), the interaction with the glass surface and particulate distribution is different for the two oxides. In particular, the Sn oxide appears to chemically modify the glass surface and prevents its consolidation.