Adhesion of diamond coatings to cutting tool substrates is an important property that is needed to replace the polycrystalline diamond tools (PCD) in machine tool applications. The improvement in adhesion of diamond on WC(Co) tool substrates is brought about by formation of a composite layer. Composite layers made up of TiC or TiN and diamond were formed by laser physical vapor deposition of ceramic coatings and hot filament chemical vapor deposition of diamond films. A first layer of discontinuous diamond film on WC is embedded in the ceramic coatings followed by growth of a continuous diamond film that maintains continuity with the first diamond layer. The composite coatings were characterized by SEM and Raman spectroscopy. Adhesion and wear resistance of the diamond coatings were measured using a polishing wear test. The mechanisms of improvement in adhesion were analyzed by finite element modeling. Results show that TiC composite layers improve the adhesion of diamond coatings significantly. This improvement is considered to arise from the modification of the thermal stress at the interface between the diamond film and the WC(Co) tool substrate.

Transmission electron microscopy (TEM) has been used to examine defects in diamond films grown by the microwave plasma-enhanced chemical vapor deposition (CVD) method. Graphite was used as the sole carbon source during the CVD process with silicon substrates. Growth defects including twins, stacking faults, dislocations and second-phase precipitates were observed in the films. In plan-view TEM, defect clusters at the centers of diamond grains were observed, where the film is also the thickest. Cross-sectional TEM was carried out to show that the defect clusters fan out from a single nucleation site in each grain, at the diamond-silicon interface. Possible growth mechanisms of the defect clusters in diamond grains are considered.

Diamond have been deposited rapidly under low pressures (<0.1 Torr) via hot filament chemical vapor deposition (HFCVD) on either scratched or mirror-smooth single crystalline silicon and titanium with nucleation densities of 109–1011/cm2. The nucleation density increases with the pressure decreases. Hydrogen and methane were used as the gaseous source. Raman spectroscopy and scanning electron microscopy(SEM) were used to analyze the obtained films. This result breaks through the limit that diamond film can only be synthesized above 10 Torr, showing a promising prospect that, as is essential for heteroepitaxial growth of monocrystalline diamond films, diamond film can be easily nucleated on unscratched substrate via Hot Filament CVD.

Hydropyridine is introduced as a new ligand for use in constructing precursors for chemical vapor deposition. Detachment of hydropyridine occurs by a low-temperature reaction leaving hydrogen in place of the hydropyridine, and a very stable byproduct, pyridine vapor. Hydropyridine ligands can be attached to a variety of elements, including main group metals, such as aluminum and antimony, transition metals, such as titanium and tantalum, semiconductors such as silicon, and nonmetals such as phosphorus and arsenic.

Examples of chemical control in CVD of metallic and ceramic films are highlighted. Specific attention is paid to the complexity of precursor design. The effect of reactor environment on growth chemistry is investigated. Examples where reducing or oxidizing atmospheres provide a high level of control over deposit composition are outlined. The system examined centers on yttrium and yttria. These materials are, in general, desired less for their optical or electronic properties and more for their structural properties. Thus, the rigid purity demands of the microelectronics industry are somewhat relaxed. Nevertheless, critical attention must be paid to the issues of vapor pressure and decomposition profile. Where sufficient data is available to justify it, some explaination of the issues relevent to vapor pressure is presented.

We have investigated cyclopentadienyl (Cp) complexes of Ru and Os as precursors for low temperature CVD of pure ruthenium and osmium films. Films were grown on a variety of substrates in a warm-walled CVD reactor, equipped with a resistively heated wafer chuck, massflow controllers for carrier gas regulation, and a mechanically-backed oil-vapor diffusion pump. Typical depositions were done under ca. 1 Torr total pressure. Use of air or oxygen as a carrier gas and Cp2M (M = Ru or Os) as precursors gave high purity, conformal films of ruthenium and osmium at temperatures as low as 275°C and 350°C, respectively. Under these conditions, the only observable by-products were CO2 and H2O, indicating that surface-catalyzed, complete oxidation of the ligands was involved in the decomposition process. Growth rates, film purities, resistivities and conformality were measured.

Thin film AlN has been grown on Al2O3 and GaAs substrates by metalorganic molecular beam epitaxy (MOMBE) using amine bonded alane precursors, tertiarybutylamine, and nitrogen from a compact electron cyclotron resonance (ECR) plasma source operating at 2.45 GHz. Typical growth pressures were in the 0.5 − 1 × 10−4 Torr range. The growth rates, impurity backgrounds and surface morphologies were examined for both nitrogen sources and both the solid and liquid alanes. In general, growth efficiencies were good for both alane precursors, allowing for deposition of the low temperature, ∼ 400°C, AlN buffers needed for subsequent growth of GaN and InGaAlN alloys. Low growth temperatures could not be obtained using tertiarybutylamine, presumably due to poor decomposition efficiency of the source at low temperatures. The structural quality of material grown at high temperatures from the ECR plasma was measured by atomic force microscopy (AFM) and high resolution x-ray diffraction (HRXRD), indicating a surface roughness of ∼ 8 Å and an x-ray width half maximum (FWHM) of 430 arcsec.

ZnO and Al-doped ZnO films prepared using a low-pressure chemical vapor deposition (LP-CVD) method were studied. The films were prepared on fused quartz substrates using bis(2,4-pentanedionato)zinc and tris(2,4-pentanedionato)aluminum which are inexpensive and stable source materials. The highly c-axis oriented ZnO films were grown on the substrates above 500°C. The minimum electrical resistivity of ρ=6.5×10−5Ωm was obtained for the ZnO film, and of ρ = 3.5×10−5Ωm was obtained for the ZnO:Al film.

A rapid chemical vapor deposition method was studied for the preparation of tin dioxide films. The films were prepared under atmospheric-pressure on fused quartz and Si substrates at 200° to 600°C using bis(2,4-pentanedionato)tin as a source material. SnO2 films obtained at 300° to 600°C had polycrystalline rutile structures, while the film deposited at 200°C was amorphous judging from the XRD patterns. The deposition rate of SnO2 increased with increasing substrate temperature and vaporization temperature of the source material. The maximum deposition rate was 440 nm min−1. The transmittance of SnO2, deposited at Ts = 600°C, was more than 70% in the wavelength range 400–800 nm.

Composite coatings consisting of discrete phases of TiN and MoS2 were codeposited on graphite substrates from Ti((CH3)2N)4/NH3/MoF6/H2S gas mixtures in a cold-wall reactor at 1073 K and 1.3 kPa. Chemical composition and microstructure of the coatings were characterized by Auger electron spectroscopy, X-ray diffraction, and transmission electron microscopy. Kinetic friction coefficients of the coatings were determined by a computer-controlled friction microprobe and values less than 0.2 were obtained with a type-440C stainless-steel counterface under ambient condition.

The CVD of the coatings in the B-Si-C-H-C1-Ar system was accomplished using a statistically designed experiment. The experimental design used five factor half-fraction factorial with a central composite design that was both rotatable and orthogonal. Deposits were thick and dense and were composed of B13C2 and β-SiC with compositions ranging from 0 to 100%. Response surfaces were generated using multivariate regression for unit cell volumes of B13C2 and β-SiC, %B13C2/%SiC in the coating, and the Si to B ratio in the deposit. These equations could then be used to examine the significant variables in the reaction, as well as for tailoring and optimizing the deposition process.

Thin films of titanium nitride were chemical vapor deposited on (100)-oriented single-crystal silicon substrates from tetrakis (dimethylamino) titanium, Ti((CH3)2N)4, and ammonia gas mixtures in a cold-wall reactor at 623 K and 655 Pa. The films were characterized by Auger electron spectroscopy, X-ray diffraction, and transmission electron spectroscopy. The nano-scale hardness of the film, measured by nanoindentation, was 12.7±0.6 GPa. The average kinetic friction coefficient against unlubricated, type- 440C stainless steel was determined using a computer-controlled friction microprobe to be ∼0.43.

Functionally gradient coatings have the potential to eliminate sharp interfaces between the coating layer and substrate resulting in a great ability to tailor the thermo-mechanical properties of the coating systems to a variety of substrates. Primary examples of beneficial use of the functionally gradient materials are the crack free CVD C-SiC coatings that were recently produced by a number of researchers on C-C composites. Inherent limitations of the CVD technique make it practically difficult to obtain high deposition rates on very complex and large shapes combined with good coating uniformity. A new process termed Chemical Vapor Reaction (CVR) has been employed to produce virtually crack free SiC coatings on 2–D C–C composites. Properties of this new class of functionally gradient coatings will be presented and discussed.

In this work, a novel process is described for the fabrication of multi-metallic amorphous metal alloy coatings using a chemical vapor deposition (CVD) technique. Of special interest in this work are amorphous metal alloys containing Mo and/or Cr which have high crystallization temperatures and readily available low decomposition temperature metal-bearing precursors. The conditions for amorphous alloy formation via CVD are described as well as the chemical properties of these materials. High temperature, aqueous corrosion tests have shown these materials (especially those containing Cr) are among the most corrosion resistant metal alloys known.

The chemical vapor deposition (CVD) of Cu-Ag and Cu-Pd alloys using aerosol precursor delivery over a range of preheating temperatures, 70∼80 °C and substrate temperatures, 250∼300 °C is described. The precursors used include Cu(hfac)2, (hfac)Ag(Set2) and Pd(hfac)2 dissolved in toluene and 10% H2 in Ar as carrier gas. The films were characterized by SEM, EDS and X-ray diffraction (XRD). The X-ray diffraction results showed the Cu/Ag films were composed of α-and β-phases of Cu-Ag alloys, the Cu/Pd films were Cu-Pd alloy, solid solutions, under these conditions. Compositional variation studies in Cu-Pd and Pd-Ag alloy systems were also conducted by mixing Cu(hfac)2/Pd(hfac)2 and (hfac)Ag(SEt2)/Pd(hfac)2 in toluene solution in different ratios. The films were characterized by X-ray diffraction and the results showed the composition of films was affected by the solution stoichiometry.

The properties and structure characteristics of the ultrafine Si-N-C powders synthesized from laser induced hexamethyldisilazane and ammonia gas phase reactions were characterized by multiple techniques. Result shows that the Si-N-C particles are uniform in diameter with narrow size distributions and less agglomerated. The powders exhibited a short distance ordered structure which was distorted at high temperature annealing. HTEM observation shows that the particles are amorphous or have nano-composite structure with SiC particles dispersed in the amorphous Si-N-C matrix. The nucleation and growth of the composite particles occurred by the polymerization of the ligand formed from the decomposition of Si-CH3 and N-H bonds in hexamethyldisilazane accompanied by the release of small hydrocarbon gases.

α-Si3N4 whiskers were formed from laser-synthesized nanoscale amorphous Si-N-C powders at 1873K under 1 atm N2. The as-formed whiskers were characterized by TEM, STEM, XRD techniques and the process conditions for the whisker growth were studied. The whiskers exhibit various morphologies such as the long thick straight, the prismatic, the ribbon-like, and knuckled whiskers. The gas phase reaction among N2, SiO, and CO gases leads to Si3N4 whisker growth on the pre-crystallized α-Si3N4 grains by the Vapor-Solid (VS) mechanism along specific crystal planes such as {1101}., which ensures an in-situ formation. No addition of other catalyst and the atomic combination of the elements in the Si-N-C powders ensure a high purity of the whiskers.