Tantalum carbide films synthesized by hot-filament chemical vapor deposition technique

Chemical vapor deposition (CVD) with thermionic-emission of hot tantalum filaments with H2 diluted CH4 as precursor was used to deposit tantalum carbide composite films on silicon. Standard characterization techniques and analysis tools were employed to study the surface morphology and roughness, fracture cross-section, phase evolution and hardness of the deposited films. The results indicate that the morphology, surface roughness, structure, texture, thickness and hardness of the coatings are greatly influenced by the process parameters. The films are mainly composed of TaC along with C and Ta2C phases. TaC grains are very small at 60 Torr, while at 100 Torr, coarse grains are developed. With an increase in substrate temperature from 850 °C to 950 °C grain size becomes almost double and dense coating is formed, while by making methane concentration double coarse grains along with cluster formation are observed and porosity is increased. The higher the graphite content the lower the hardness. Composite structure of graphite and TaC grown by modified hot-filament CVD is likely to be a potential candidate for thermal barrier coatings.