Effect of process parameters on the structure of Si-Ti-N nanostructured coatings deposited by hypersonic plasma particle deposition

Si-Ti-N nanostructured coatings were synthesized by inertial impaction of nanoparticles using a process called hypersonic plasma particle deposition (HPPD). A study detailing the effect of plasma gases showed that in the case of an Ar + H2 plasma gas mixture, crystalline phases in the coatings consisted of TiN, TiSi2, and Ti5Si3. When the system was switched to a plasma gas mixture of Ar + N2, the only crystalline phase was TiN. Transmission electron microscopy confirmed the presence of TiN crystallites in an amorphous matrix. Warren-Averbach analysis indicated the average size of the TiN crystallites to be 14.9 nm. In separate experiments with the same conditions, aerodynamic lenses were used to deposit particles directly onto TEM grids. We observed agglomerated structures with an Ar + N2 plasma, while with an Ar + H2 plasma we found discrete TiSix and TiNx particles. In-situ particle diagnostics indicated only small changes in the particle size distributions when the plasma gases were changed.