Surface texture evolution of polycrystalline and nanostructured films: RHEED surface pole figure analysis

In this topical review, we outline the construction of a reflection high-energy electron diffraction (RHEED) surface pole figure from a polycrystalline film by recording multiple RHEED patterns as the substrate is rotated around the surface normal. Due to the short penetration depth of electrons, the constructed pole figure is a surface pole figure. It is in contrast to the conventional x-ray pole figure which gives the average texture information of the entire polycrystalline film. Examples of the surface pole figure construction processes of a fibre texture and a biaxial texture are illustrated using Ru vertical nanorods and Mg nanoblades, respectively. For a biaxially textured film, there often exists an in-plane morphological anisotropy. Then additional intensity normalization must be applied to compensate for the effects of anisotropic morphology on RHEED surface pole figure construction. Rich information on the texture evolution, such as the change in the tilt angle of the texture axis, has been obtained from the in situ study of oblique angle vapour deposition of Mg nanoblades using RHEED surface pole figures. Finally we make a comparison between the RHEED surface pole figure and the conventional x-ray pole figure techniques.