Crystalline Ti-nanostructures prepared by oblique angle deposition at room temperature

Abstract

Nanostructured Ti thin films are fabricated by oblique angle deposition (OAD) in combination with electron beam evaporation in an ultrahigh vacuum chamber at room temperature on thermally and natively oxidized Si(100) substrates. The incidence angle θOAD of the incoming particle flux with respect to the substrate normal is varied between 70° ≤ θOAD ≤ 84°. This highly oblique deposition geometry leads to the formation of highly porous, thin, crystalline films consisting of separated Ti columns that are oriented toward the incoming particle flux. The influence of the incidence angle on the texture, morphology, and columnar tilt angles of these Ti thin films is investigated. It is found that the texture depends on the angle θOAD of the incoming particle flux. High-resolution transmission electron microscopy reveals that highly oblique deposited Ti columns tend to grow with single crystalline morphology. The orientation of the lattice planes in the Ti columns with respect to the substrate normal changes remarkably as the incidence angle is varied. Moreover, the orientation of the lattice planes differs from the growth direction of the columns. The samples are analyzed using x-ray diffraction measurements such as in-plane pole figure measurements and θ-2θ x-ray diffraction patterns, as well as by using transmission electron microscopy and scanning electron microscopy.