Unveiling Oxygen Vacancy Superstructures in Reduced Anatase Thin Films

Abstract

Oxygen vacancies are known to play a crucial role in tuning the physical properties and technological applications of titanium dioxide TiO2. Over the last decades, defects in substoichiometric TiO2 have been commonly associated with the formation of Ti n O2n–x Magnéli phases, which are extended planar defects originating from crystallographic shear planes. By combining advanced transmission electron microscopy techniques, electron energy-loss spectroscopy and atomistic simulations, we reach new understanding of the oxygen vacancy induced structural modulations in anatase, ruling out the earlier shear-plane model. Structural modulations are instead shown to be due to the formation of oxygen vacancy superstructures that extend periodically inside the films, preserving the crystalline order of anatase. Elucidating the structure of oxygen defects in anatase is a crucial step for improving the functionalities of such material system and to engineer devices with targeted properties.

Manipulating the Conversion Kinetics of Polysulfides by Engineering Oxygen p‐Band of Halloysite for Improved Li‐S Batteries

“…[ 10 ] Specifically, Ti L 2 and L 3 peaks for TiO 2 ‐Hal positively shift compared with those for TiO 2 (≈1.89 eV for L 2 and ≈1.18 eV for L 3 ), which verifies the electron transfer from TiO 2 NPs to the interfacial oxygen sites in TiO 2 ‐Hal. [ 11 ] The electronic structure of TiO 2 ‐Hal was further determined by titanium K ‐edge extended X‐ray absorption fine structure (EXAFS) spectroscopy. The pre‐peak (marked as A ) in normalized Ti K ‐edge X‐ray absorption near‐edge structure (XANES) spectra is assigned to the dipolar electronic transitions from Ti 1 s to e g levels (Figure 2h), and the decreasing intensity probably originates from the changes of the Ti valence state caused by the electronic interaction between TiO 2 and Hal.…”

Oxygen‐Driven Metal–Insulator Transition in SrNbO3 Thin Films Probed by Infrared Spectroscopy

“…This preparation procedure had been proved to minimize structural and chemical modifications of cross-sectional TEM samples and had successfully been applied to other oxide thin-film systems. [40][41][42] Infrared reflectance measurements at room temperature were performed at the SISSI-Material Science branchline at Elettra synchrotron in Trieste by means of FTIR spectroscopy with an infrared microscope Bruker Hyperion 2000 coupled with a Michelson interferometer Bruker Vertex 70v. [43] By changing the internal source, the beam-splitter, and the detector in the experimental set-up, the authors were able to cover the infrared spectral range of 70-8000 cm −1 , that is ≈ 0.009-1 eV.…”

“…This preparation procedure had been proved to minimize structural and chemical modifications of cross‐sectional TEM samples and had successfully been applied to other oxide thin‐film systems. [ 40–42 ]…”

Automatic indexing of two-dimensional patterns in reciprocal space

“…of IOM-CNR at the synchrotron Elettra in Trieste [58]. For details on this sample the reader is referred to preceding work [59,60]. Cross-sectional TEM samples were then prepared with a conventional polishing technique followed by dimpling and ion milling [60].…”