Atomistic simulation of surface evolution during PVD coating processes

To a great extent, the properties of thin film coatings are determined by their surface structure. PVD coating processes are simulated with an atomistic simulation to investigate the development of the surface structure at early stages of the film deposition. For this simulation, atoms are added to the surface of a single crystal fcc substrate with (100) and (111) surfaces and with a size of approximately 5000 atoms. These added atoms form a film on the substrate material. Periodic boundary conditions in two dimensions were used to reduce unwanted surface effects. During the simulation, the following parameters were varied: substrate temperature, substrate orientation, angular distribution and kinetic energy of the added atoms. The surface structure was evaluated after a deposition of approximately 10 atomic layers and cooling of the substrate. We found the number of neighbouring surface atoms to be a useful way to describe surface roughness and orientation. Obviously, the substrate temperature is the dominating parameter for the smoothening of the surface, but at temperatures below 0.6·Tm, the angular distribution and the kinetic energies of the film atoms have great influence as well. In addition, we investigated the resputtering and evaporation of film material during the deposition and its dependence on the process parameters.