Direct observation of oxygen atoms in rutile titanium dioxide by spherical aberration corrected high-resolution transmission electron microscopy

We have developed a spherical aberration corrected transmission electron microscopy (C_s-corrected TEM) technique that allows us to obtain clearer images in real space than ever before. We applied this technique to titanium oxide, in which light elements such as oxygen are difficult to observe using TEM because of its small cross section and electronic damage. In the present study, we successfully observed oxygen atoms in rutile TiO₂. In addition, this direct observation of oxygen atoms enabled us to study the Magnéli structure (Ti_nO_2n-1), which is caused by oxygen vacancies. These vacancies caused an atomic relaxation of the titanium and oxygen atoms. The relaxed atoms formed a characteristic shear structure of rutile titanium dioxide phase. This shear structure of the Magnéli structure (Ti_nO_2n-1) was visualized with a spatial resolution of 0.119nm. At the same time, the selected area diffraction (SAD) pattern of the defect structure was obtained. Additional spots were shown inside the rutile [110] spot. We made structural models of the shear structure and simulated the diffraction pattern and images using a multi-slice simulation. Additional spots in the simulated diffraction patterns accurately reconstructed the experimental data. We also considered the possibility of the real-space analysis of local structures using spherical aberration corrected transmission electron microscopy.