Computational Determination of Metallic Thin Film Stress Dependencies on Solute Segregation during Epitaxial Growth

The physical behavior of metallic thin films can vary drastically from bulk metal structures of the same composition. This is believed to result from electrochemical surface forces preferentially moving adatoms towards grain boundaries during epitaxial film growth. Experimental confirmation of this hypotheses is difficult due to the dynamic nature of the growth process, which has shifted research efforts towards computational modelling of such growth processes and comparing the computational results with the experimentally determined behavior of grown films. The purpose of this project was to develop and use computational techniques to predict the time dependent intermolecular stresses present during the growth processes of different metallic thin films. The LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) molecular dynamics simulator was used to model the changes in stress that result from changing alloy composition and solute segregation about grain boundaries. These predictions will be used to both guide the direction of experimental work as well as determine the underlying relations between solute concentration/segregation and thin film intermolecular stress. The knowledge of how altering thin film stress affects the physical properties of the material would allow for the development of materials with tunable physical properties by altering the stress state of the material during its synthesis. Such films could see implementation in technologies including: metallic coatings, thin film solar cells, small scale electronics, and MEMS (micro-electro-mechanical systems) devices.