Growth twins in nanocrystalline SnO2 thin films by high-resolution transmission electron microscopy

Growth twins in nanocrystalline SnO2 thin films with grain size 5–50 nm have been investigated by high-resolution transmission electron microscopy. They show the {101}〈101〉 geometry, metal atom mirror symmetry, and slight distortion of oxygen atoms. Multiple twins and step twin boundaries with a density about 1015 m−2 were frequently observed in the films. It appears there are tin interstitials at step twin boundaries and, hence, electronic donors associated with the interstitials.