Microstructural evolution during ion beam assisted Deposition

Abstract

AbstractThe advantages of energetic deposition are low temperature processing, oriented or single crystal films, high phase purity, high density and good adhesion to substrates. The time and spatial scales over which the atoms arrange themselves on a surface are not easy accessed experimentally. Therefore, these advantages are customarily verified by ex-situ examination of films after deposition is complete, which gives little information on atomic scale processes that lead to the listed advantages. The addition of energy to the deposition flux effects surface processes that are otherwise only controllable by changing the substrate temperature. Thus, understanding the mechanisms by which energetic atoms alter surface processes in analogy with thermal effects is of paramount interest for optimization of the deposition parameters. This review summarizes the state of knowledge on the effects of energetic ions on film formation. For high quality, defect free films, the energy must be controlled in the energy region of 5 eV to 30 eV. Below about 5 eV, the energy is ineffective for changing the physical processes, and above about 30 eV, defects are added to the film by displacement damage that cannot anneal out due to low temperature of the deposition. Models for the composition and chemistry of films energetically deposited are progressing well, while models for prediction of the phases that form are almost nonexistent. Molecular dynamics provide the best information, but only a handful of cases have been simulated.