MICROCOMPOSITE AND NANOCOMPOSITE STRUCTURES FROM CHEMICAL-VAPOR-DEPOSITION IN THE SILICON TITANIUM CARBON SYSTEM

Microcomposite and nanocomposite structures composed of SiC-TiC and C have been prepared by chemical vapor deposition at atmospheric pressur e (APCVD) from an initial gaseous mixture with the composition C4H10-S iH2Cl2-TiCl4-H-2. Transmission electron microscopy reveals that deposi ts with a nanocomposite structure consist of a network of 10-nm-thick needles surrounded by small areas of amorphous carbon. The relative am ounts of TiC and SiC as well as the microstructure depend on the SiH2C l2 and TiCl4 content in the initial gas-phase mixture. The variations of composition of the deposits are in good accordance with the thermod ynamic calculations. Amorphous carbon is always present in the deposit s. This amount can be lowered to 1 at. % at low deposition temperature s but, at such a concentration, still has a great influence on microha rdness. The variation of the preferred orientation of crystals is also discussed with respect to the composition of the samples and the depo sition temperature.