Quasi-periodic nanostructures grown by oblique angle deposition

We report that tungsten nanocolumns grown by oblique angle sputter deposition develop a quasi-periodic morphology which is not observed for continuous films deposited at normal incidence. The maximum position in power spectral density of the quasi-periodic nanostructures decreases exponentially as a function of thickness. We explain the formation of the quasi-periodic nature by a “shadowing length” concept which plays a similar role to conventional surface diffusion length. Also, we show that the change of the spatial frequency of the periodicity is a result of the elimination of shorter columns due to the shadowing effect during growth.