Controlled Nanostructuring of Thin Films by Oblique Angle Deposition

Using electron beam evaporation, thin films of various compositions (Al, Co, Ge, SiO₂) were obtained on inclined Si(001) substrates. It was found that at angles of incidence of the evaporated material on the substrate of more than 70° (sliding deposition), arrays of free-standing inclined nanocolumns with lateral dimensions from 10 to 100 nm and an aspect ratio (length/transverse dimension) of at least 10 were formed on the substrate. When substrate rotation was switched on during film growth, an array of nanospirals twisted in one direction was formed. Such films are chiral metamaterials and show pronounced optical activity. Simulation of film growth processes under oblique angle deposition conditions using the Monte Carlo method showed good qualitative agreement with the experimental data. It was found that the observed processes of nanostructuring during oblique angle deposition are based on universal mechanisms of competition between growing crystalline grains under conditions of neighbor shading. This makes it possible to obtain nanostructured films of various materials with the required functional characteristics under such conditions.