Tantalum carbide-graphite composite film synthesized by hot-filament chemical vapor deposition

A composite film of tantalum carbide (TaC)-graphite was synthesized on etched Si using thermal evaporation of Ta followed by C/H chemical vapor deposition (CVD). In the present study, Ta wire 0.5 mm in diameter was electrically heated without carburizing. Under high current conditions, filaments were thermally evaporated and interacted with chemically decomposed C, forming a composite film of TaC-graphite deposits on the substrates. The influence of chamber pressure, substrate temperature, and methane concentration on the film properties has been studied. By increasing chamber pressure from 25 to 100 torr in a gas mixture of H and methane (containing 3 % methane), the morphology of films changed with an increased growth rate and surface roughness. Increasing the methane concentration in the mixture resulted in broadening of X-ray diffraction (XRD) peaks, increase in film thickness, and coarsening of grains, along with formation of clusters. The growth rates of the films produced at a substrate temperature of 950 °C were lower than those deposited at 850 °C. Their grain sizes were bigger and exhibited a dense structure with higher surface roughness.