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Photoluminescence (PL) from hydrogenated silicon carbide (SiC:H) films is studied at room temperature. The films were deposited by plasma-enhanced chemical vapor (PECVD) technique with and without substrate bias using methyltrichlorosilane as a main precursor. After the deposition the samples were annealed at various temperatures in vacuum. The films were characterized by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The samples deposited without substrate bias (series A) were amorphous, whereas the samples deposited with negative substrate bias -100V (series B) were nanocrystalline. The one-peak (470 nm) and double-peak (415 and 437 nm) PL structures of the as-deposited samples A and B were observed, respectively. Annealing strongly enhanced intensity of PL of the samples B and trandformed PL spectrum from double-peak into broad featureless band with intensity at about 470 nm. The blue PL in as-deposited films B is supposed to be assigned to the radiative recombination in the sites located at the nanocrystallite surface, whereas the photo excitation of carries mostly occurs in nanocrystallite cores. A further increase in annealing temperature causes hydrogen effusion, which leads to an increase of the concentration of non-raidative recombination centers associated with dangling-bonds and as a result, to the quenching of PL.

Polycrystalline, theoretically dense silicon carbide was deposited onto graphite substrates via the reductive pyrolysis of methyltrichlorosilane in a hot-walled chemical vapor deposition (CVD) chamber. The resulting product can be considered a bulk material with deposit thicknesses in the range of 4 to 8 millimeters. The material was characterized using powder x-ray diffraction and Laue back-reflection techniques. Under the deposition conditions investigated in this study, the crystallographic orientation varied as a function of distance from the substrate. The material exhibited a high degree of randomness in proximity to the substrate, and progressively showed a higher degree of preferred crystallographic orientation as the deposit progressed. This phenomenon is correlated with the microstructure of the material as well as such mechanical properties as hardness and fracture toughness.

In addition to its superior mechanical properties, the wide band gap (2.3 eV), high breakdown field, and high saturated electron velocity of cubic silicon carbide (3C-SiC) make it an attractive candidate for elevated-temperature, high-frequency, and high-power electronic devices. Optically transparent SiC deposits were grown via atmospheric pressure chemical vapor deposition (APCVD) on graphite substrates from methyltrichlorosilane (MTS) in hydrogen in a cold-walled, RF-induction furnace. Structural morphology was examined by scanning electron microscopy and correlated to substrate temperature, MTS/H{sub 2} ratio, and hydrogen flow. Photoluminescence revealed that high quality cubic material was grown. The PL spectra exhibited a zero phonon line (2.3787 eV) and attributable to an exiton bound to a neutral nitrogen donor, in addition to TA, LA, TO, and LO phonon replicas. Observed broadening and splitting of the PL spectral lines was associated with the morphological habit and internal strain of individual crystallites. In addition, the PL spectra for samples grown at higher MTS/H{sub 2} ratios and low H{sub 2} flows exhibited weak shoulders on the low energy side of the five-line spectra which might be associated with nonstoichiometric defects such as Si interstitials or C vacancies.

Using methyltrichlorosilane diluted with hydrogen and a modified temperature program during the initial stage of the deposition we have improved the deposition process and obtained high quality heteroepitaxial films on Si (100) without any carbon buffer layer. The maximum temperature of 1200°C which is used for the substrate cleaning and film deposition is significantly lower than that used in the conventional deposition system SiH4/C3H8 of about 1400°C for the buffer layer and 1350°C for deposition.

Sponge type deposits composed of nanometer sized Si whiskers were formed on Davisil (porous SiO2) gel substrates by chemical vapor deposition (CVD) using methyltrichlorosilane (MTS) as a precursor and H2 as carrier gas. The diameters of the fine whiskers are estimated to be 100 nm or smaller from SEM observations. XRD analyses revealed that the coatings formed at 800 and 900°C contained microcrystalline Si and the Auger analysis indicated the existence of free carbon. The surface area of the coated Davisil was approximately 189 ± 5 m2/g, as obtained from BET measurements. The coatings were also applied on several other substrates, such as AIN and low surface area (< 224 m2/g) silica gel, with the same coating conditions. On these substrates, highly porous Si has also been observed on AIN substrates, and nonporous, half sphere shaped coatings were observed on low surface area silica gel substrates.

Experimental measurements of the decomposition of methyltrichlorosilane (MTS), a common silicon carbide precursor, in a high-temperature flow reactor are presented. Methane, hydrogen chloride, and silicon tetrachloride are observed as products of the decomposition. Trapping experiments with acetylene and ethylene also detected SiCl3 as a decomposition product. Upper limits on the concentrations of any CH3Cl, HSiCl3, H2SiCl2, or H2C=SiCl2 which might form are provided. Quantitative measurements of product branching and MTS decomposition rates are presented. The results suggest a radical-chain mechanism for the decomposition in hydrogen but not in helium.

Methyltrichlorosilane (MTS) is a precursor commonly used in the production of silicon carbide for composites, protective coatings, and structural ceramics. Experiments suggest that MTS decomposes in the gas phase to produce a large number of species whose surface reactivity is expected to vary widely. In this work, we discuss the development of a gas-phase mechanism that describes the decomposition of MTS. Rate coefficients for the reactions were obtained from literature sources, theoretical methods, and comparisons with analogous reaction chemistry. Several unknown reaction rates were fit to experimental measurements of MTS decomposition. The results are used to predict the major reaction paths, identify reactions to which product concentrations are sensitive, and determine the rate-limiting step for MTS decomposition.

The fabrication, properties and optics applications of transparent and opaque Chemical Vapor Deposited (CVD) β-SiC are reviewed. CVD-SiC is fabricated by the pyrolysis of methyltrichlorosilane, in excess H2, in a low-pressure CVD reactor. The CVD process has been successfully scaled to produce monolithic SiC parts of diameter up to 1.5 m and thickness 2.5 cm. The characterization of CVD-SiC for important physical, optical, mechanical and thermal properties indicate that it is a superior material for optics applications. CVD-SiC properties are compared with those of the other candidate mirror and window materials. SiC process/property relationships are discussed, emphasizing the differences in process conditions, microstructure, and properties between transparent and opaque CVD-SiC.

Suitable feedgas compositions for monophase SiC deposition were determined starting from methyltrichlorosilane-hydrogen-argon mixtures at 1 bar total pressure and H2/MTS ratios between 50 and zero. At temperatures from 900 to 1400°C, only a ratio of 1 at Pmts = 18 mbar gave the desired result. The deposition rate of SiC was determined as a function of MTS and HCl partial pressures, of gas flow rate, and of temperature at a H2/MTS ratio of 1. Two different rate equations were found at [MTS]/[HC1] ≥ 5.8 (region I) and < 5.8 (region II), respectively: $${{{\text{j}}_{{\text{SiC}}}}\left( {\text{I}} \right){\text{ = k'}}\left[ {{\text{MTS}}} \right]{{\left[ {{\text{HCl}}} \right]}^{{\text{ - 1}}}}} \\ {{{\text{j}}_{{\text{SiC}}}}\left( {{\text{II}}} \right){\text{ = k''}}\left[ {{\text{MTS}}} \right]{{\left[ {{\text{HCl}}} \right]}^{{\text{ - 3}}}}{\text{,}}} \\

A theoretical model, which describes the coupled hydrodynamics, mass transport and chemical reaction, has been developed to simulate chemical vapor deposition (CVD) of silicon carbide (SiC) from gas mixture of methyltrichlorosilane (MTS), hydrogen and argon in a hot wall reactor. In the model analysis, the governing equations were developed in the cylindrical coordinate, and solved numerically by using a finite difference method. A kinetic rate expression of CVD-SiC deposition from the gas mixture was obtained from this study. The deposition rate has an Arrhenius-type dependence on the deposition temperature and is first order with respect to the MTS concentration. Estimated activation energy is 254 kJ/mol. Predicted deposition rate profiles by the model analysis incorporated with the obtained kinetic rate expression showed excellent agreement with experimental data over a variety of applied deposition conditions.

Experimental measurements of the decomposition of methyltrichlorosilane (MTS), a common silicon carbide precursor, in a high-temperature flow reactor are presented. The results indicate that methane and hydrogen chloride are major products of the decomposition. No chlorinated silane products were observed. Hydrogen carrier gas was found to increase the rate of MTS decomposition. The observations suggest a radical-chain mechanism for the decomposition. The implications for silicon carbide chemical vapor deposition are discussed.

We examine the dynamic behavior of a heterogeneous reaction model for the chemical vapor deposition of carbon, silicon, and silicon carbide from the precursors generated by the thermal decomposition of methyltrichlorosilane (MTS, CH3SiCl3 ). All reactions are treated as reversible in order to account for the strong inhibitory effect of the reaction by–products on the deposition process that was observed in our experiments and in other studies. The equilibrium constants of the adsorption steps of the reactions are treated as model parameters, and those of the other reactions are calculated from the thermodynamic constants of a set of overall deposition reactions. Results are presented on the influence of the various model parameters on the reaction rate, the stoichiometry of the deposit, and the variation of these quantities with the distance in a plug flow deposition reactor.

The traditional CVD phase diagrams are only valid for cold wall reactors because of the neglecting of the depletion effects in hot wall reactors. Due to the depletion effects along the reactor, the traditional CVD phase diagrams can not accurately predict the phases deposited on the substrate in a hot wall CVD system. In this paper, a new approach to calculate the local equilibrium CVD phase diagrams in a hot wall reactor is presented by combining the depletion effects with the equilibrium thermodynamic computer codes (SOLGASMIX–PV). In this study, the deposition of SiC using methyltrichlorosilane (MTS)–hydrogen (H2) was chosen to verify this new approach. The differences between the new CVD phase diagrams and the traditional phase diagrams were discussed. The calculated CVD phase diagrams were also compared with the experimental data. The single phase of SiC predicted by this approach is much better than the traditional phase diagrams. The experimental regions for depositing single phase SiC are larger than the calculated local phase diagrams because of the higher linear velocity of the gas flux under low pressure and the polarity of the Si carrying intermediate species.

β–SiC thin films were epitaxially grown on porous Si(100) substrates at 1150° C from methyltrichlorosilane (CH3SiCl3 or MTS) in a hot wall reactor by Vsing low pressure chemical vapor deposition (LPCVD). The growth rate was 120 Å/min. Epitaxial β–SiC(100) thin films were obtained after a deposition time of 12.5 min. The crystallinity of the β–SiC films was affected by the deposition time. For instance, rotational β–SiC(100) crystals and polycrystalline β–SiC with a highly preferred orientation of (100) planes were observed for a deposition time of 50 min. The results from XRD and TEM indicated that polycrystalline β–SiC films with a preferred orientation of β–SiC(111) appeared after further increasing the deposition times (time ≥ 75 min). The change in crystallinity is attributed to increasing roughness with increasing deposition time.

This work explores the reactivity of HCI and methyltrichlorosilane (MTS) with polycrystalline β-silicon carbide (SiC) surfaces using temperature-programmed desorption (TPD) and Auger electron spectroscopy. HCl is a corrosive gas that inhibits SiC deposition. The results show that HCl is adsorbed by SiC, forming a stable surface chloride that could inhibit SiC deposition. TPD shows that chlorine desorbs as HCI or SiCl4, confirming that HCl can etch SiC surfaces. Desorption is rate-limited by the breaking of Si-Cl bonds. MTS is also adsorbed by SiC; its desorption is similar to that of HCI.

Specific compositions of boron-carbon-silicon ceramics exhibit improved abrasive wear and good thermal shock resistance, but require bulk sintering at temperatures in excess of 2100K. The formation of such phases by chemical vapor deposition was investigated in the temperature range of 1073K–1573K. Methyltrichlorosilane (CH3SiCl3), boron trichloride, and methane were chosen as reactant gases, with hydrogen as a carrier gas and diluent. The coatings were deposited in a computer-controlled, hot-wall reactor at a pressure of 33 MPa (200 Torr).Below 1473K the coatings were amorphous. At higher temperatures non-equilibrium reactions controlled the deposition process. The most common coating consisted of a silicon carbide matrix and a silicon boride, SiB6, dispersed phase. Multiphase coatings of B+B4C+SiB6 and SiC+SiB6+SiB14 were also deposited by controlling the partial pressure of methane and boron trichloride. Non-equilibrium thermodynamic analysis qualitatively predicted the experimentally deposited multiphase coatings.

Light-scattering was used to monitor the chemical vapor deposition of silicon carbide from methyltrichlorosilane. The nucleation and growth of the SiC features caused changes in the surface topography that altered the angular scattering spectrum that was generated with a He-Ne laser. These scattering spectra were then analyzed to obtain information about the nucleation and growth processes that are occurring.

A kinetic model is presented for the deposition of silicon carbide through decomposition of methyltrichlorosilane (MTS). The developed model includes gas phase (homogeneous) reactions that lead to formation of deposition precursors and surface (heterogeneous) reactions that lead or can lead to deposition of silicon carbide, silicon, and carbon. The kinetic model is incorporated in a transport and reaction model for a tubular hot-wall reactor, and the overall reactor model is used to obtain some preliminary results on the effects of pressure and distance in the reactor on the rate of deposition and the composition of the deposit. The results show that the model can reproduce most of the experimental observations of the literature.

Silicon carbide was deposited from methyltrichlorosilane onto polished polycrystalline SiC substrates at reduced pressure, and the resultant surface morphology was characterized by analyzing the angular spectrum of scattered light which was generated with a He-Ne laser. Light-scattering analyses incorporating specific nucleation and growth models were developed. With these methods, it was possible to analyze the angular scattering spectra and directly measure the nucleation and growth rates. These results were verified by using image analysis to quantify the number and size distribution of surface features that were observed with scanning electron microscopy. The nucleation and growth rates that were obtained by fitting the models to the image-analysis results were in good agreement with the rates obtained from the light-scattering.

Surface morphologies created by the chemical vapor deposition (CVD) of silicon carbide were examined with light scattering. Silicon carbide was deposited from methyltrichlorosilane under various conditions to create different surfaces. A helium neon laser was used, and the scattered light was measured over a range of scattering angles. These measurements are compared with scanning electron microscopy (SEM) observations and profilometer measurements of the same surfaces. In theory the scattered light contains all of the information needed to provide a statistical description of a given surface; however, a complete vector theory for the scattering phenomena is too complex to provide any simple basis for experimental analysis. The application and limits of existing descriptions of scattering from a rough surface are discussed.

The microstructure and mechanical properties (adhesion, hardness) of beta-SiC coatings, prepared in a cold wall reactor, were studied by examining different substrates and deposition process conditions. Hard (3500 HK), fine grained beta-SiC coatings were deposited onto graphite at relatively high deposition terperatures (1473–1673 K) using SiC14,C3H8,H2 gas mixtures. The thermal decomposition of methyltrichlorosilane (MTS) in hydrogen and argon allowed the production of beta-SiC coatings onto a variety of substrate materials in the temperature range 1173–1373 K. The growth mechanisms of SiC deposited from MTS/H2/Ar system onto graphite and polycrystalline alfa-SiC substrates were studied. At low (40 kPa) and atmospheric pressure, the growth kinetics is limited by surface reactions. Also, a strong dependence of the microstructure and crystallographic orientation on the deposition parameters was observed. Hard metals (WC/Co) were succesfully coated with beta-SiC using the MTS/H2/Ar system. Problems of chemical compatibility between the substrate and the beta-SiC coating were minimized by deposition of an intermediate layer of TiN.