Synthesis of Ti-Al-Si-N nanocomposite films using liquid injection PECVD from alkoxide precursors

A series of nitride films of the Ti-Al-Si system have been synthesized at about 750 °C using the liquid injection plasma-enhanced chemical vapor deposition technique from corresponding alkoxide precursors. The composition and structure of the films were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. Amorphous SiN_x and crystalline AlN and TiN films were formed in their individual cases, while the SiN_x-containing (Ti/Al)Si-N composite films showed a two-phase microstructure consisting of amorphous SiN_x matrix and embedded TiN, AlN, or TiAlN nanocrystals. The Si-rich nanocomposite films demonstrated superior high-temperature oxidation resistance. After two hours of air exposure at 900 °C, no elemental segregation was observed in the nitride films and their structures remained basically unaffected. The fundamental mechanism is discussed in terms of the chemically high inertness of amorphous SiN_x interfacial phase and thereby the high thermal stability of the composite nitride films with unique nanostructures.