The Diffusion Behavior Of Particles In The Ta-Si-N Film Growth Process: First Principle Study

This research is a part of some projects, including the National Natural Science Foundation of China (NNSFC) under Grant 50845065, the Inner Mongolia Education and Research Foundation under Grant NJ06077 and the Inner Mongolia Natural Science Foundation under Grant 2010Zd02. The goal of these projects is to search for the nano-composite coatings whose strength, hardness and toughness are better than that of Ti-Si-N coatings. After some Ti-Si-N like nano-composite coatings to have been studied, it is recognized that the mechanical property of TaN crystallite are better than that of TiN one and the stability of interface of Si-N-Ta is better than that of Si-N-Ti interface. Therefore, the strength and toughness of Ta-Si-N nano-composite coatings may be better than that of Ti-Si-N nano-composite coatings. The formation of Ta-Si-N nano-composite structure depends heavily on the diffusion behavior of particles in the film growth process. Thus, our research focuses on the diffusion behavior of Ta, Si, N particles on the TaN (001) surface.The crystal lattice constant, single atomic energy and cohesive energy of Ta and Si particle, and the bond length, single atomic energy and cohesive energy of N2 molecule had been calculated with the first principle calculation in our research. Then, the total energy, adsorption energy and the corresponding potential energy surface, the diffusion paths and the activation energy of several diffusion ways had been calculates, including the single particle on the surface, the two particles on the surface and Ta single particle around the island. Finally, we detailed analysis the diffusion paths and the diffusion activation energy, and draw the following conclusions:(1) The diffusion behavior of Ta, Si, N particles on the TaN (001) surface and around the island is more difficult than that of Ti, Si, N particles.(2) The diffusion behavior of Si-N particles is easier than that of Ta-N particles. The diffusion behavior of Ta-N particles is more difficult than that of Ti-N particles. The diffusion behavior of Si-N particles on the TaN (001) is easier than that of Si-N particles on the TiN (001) surface. It is suggest that Si particle can promote the formation of Ta-Si-N nano-composite coatings, and the promotion of Si for the formation of Ta-Si-N nano-composite coatings is better than that of Ti-Si-N coatings.(3) The bond length and bond energy are also very important for the formation of nano-structures. Due to the energy of N-N bond is stronger than that of Ta-N, and the energy of N-N bond is weaker than that of Ta-Ta, which made the diffusion behaviors of Ta and N particles are difficult. The energy of Si-N and Si-Ta bond is weaker than that of N-N, Ta-N and Ta-Ta bond. It means that the diffusion behavior of Si and Si-N particles can promote the diffusion behavior of TaN particles, and it makes the diffusion behavior is easier during the forming process.