Modeling the influence of incident angle and deposition rate on a nanostructure grown by oblique angle deposition

In this study, numerical approaches were applied to theoretically investigate the influence of process parameters, such as the incident angle and the deposition rate, on the nanostructural formation of thin films by oblique angle deposition (OAD). A continuum model was first developed, and the atomic diffusion, shadowing effect and steering effect were incorporated in the formation mechanisms of the surface morphology and nanostructure of the deposited films. A characteristic morphology of columnar nanorods corresponding to an OAD was well reproduced through this kinetic model. With the increase of the incident angle, the shadowing effect played a significant role in the columnar structures and the ratio of the surface area to volume was raised, implying a high level of voids in the nanostructures. When the deposition rate decreased, the porosity was notably suppressed due to the atomic diffusion in the growth process. These simulation results coincide well with many experimental observations. With the manipulation of the numerical simulations, the underlying mechanisms of the morphological formation during OAD were revealed, which also provided plentiful information to stimulate the process designs for manufacturing advanced materials.