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

Abstract

We have developed a spherical aberration corrected transmission electron microscopy (Cs-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 (TinO2n−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 (TinO2n−1) was visualized with a spatial resolution of 0.119 nm. 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.

HAADF‐STEM observation of Au nanoparticles on TiO2

“…The experimental estimation of the position of oxygen in TiO 2 is also important, and spherical aberration corrected TEM has the possibility to see the oxygen columns directly. [18] But it is still difficult for spherical aberration corrected TEM to observe the oxygen columns at heterointerfaces between nanoparticles and metal oxide substrates, because thin samples are required for the observations. In any case, the status of the oxygen atoms at interfaces affecting the status of Au layers is the key issue on the mechanism of the catalytic activity of the Au/oxide catalysts.…”

Thermodynamics of oxygen defective Magnéli phases in rutile: A first-principles study

“…[4][5][6] As the sample is reduced, defect structures with long range order form: The so-called Magnéli phases. 3,7 X-ray diffraction measurements reveal that these phases are extended planar defect structures, 2,7,8 the crystallographic shear planes ͑CS͒.…”

Understanding Phonon Interactions with Defects in Functional Oxide Materials

“…Evidence of these phases is seen in the form of crystallographically oriented features (streaking and weak diffraction peaks) in addition to the primary peaks in an SAED image [182,186,[194][195][196]. An early example of this is seen in Fig.…”

“…The most common characterization method for the identification of the presence of Magn'eli phases is by diffraction imaging [182,186,187,190,[194][195][196][197][198][199][200]. In polycrystalline samples, X-ray diffraction has been used to identify the formation of of new Magnélie phases in TiO 2 [190,[198][199][200].…”

“…The atomic scale layering of Magnéli phases makes TEM an ideal means of investigating the structure of these materials, as seen by the wealth of such studies revolving around TEM in the literature [182,186,187,[194][195][196][197]. With high resolution and scanning TEM imaging, the layered nature of the Magnéli phases can be directly visualized, examples of both HR-TEM and STEM images are [195] and (b) in a scanning TEM [197] included in Fig.…”