Oxygen vacancies: The (in)visible friend of oxide electronics

Abstract

Oxygen vacancies play crucial roles in determining the physical properties of metal oxides, representing important building blocks in many scientific and technological fields due to their unique chemical, physical, and electronic properties. However, oxygen vacancies are often invisible because of their dilute concentrations. Therefore, characterizing and quantifying their presence is of utmost importance for understanding and realizing functional metal oxide devices. This, however, is oftentimes a non-trivial task. In this Perspective paper, we discuss the relevant regimes of concentrations and associated phenomena arising from oxygen vacancies. We then focus on experimental techniques available for observing oxygen vacancies at widely different levels of concentrations. Finally, we discuss current challenges and opportunities for utilizing oxygen vacancies in metal oxides.

Pushing the Study of Point Defects in Thin Film Ferrites to Low Temperatures Using In Situ Ellipsometry

“…A very promising family of methods for tracking point defects in oxides thin films are UV-visible optical characterization techniques. [4,25] As recently reviewed by Buckner et al, [26] point defects strongly modify the electronic band structure of many oxides, giving rise to unique changes of optical properties that can be tracked by optical methods. Although UV-visible techniques cannot directly probe the concentration of point defects, by measuring the evolution of the dielectric properties of the thin film by in situ Brower analysis, it is possible to indirectly achieve a quantification of the defect chemistry of the material, similar to the measurement of the electronic conductivity but without the limitation of a non-constant charge carrier mobility.…”

“…[ 1,2 ] In this family of materials, point defects, imperfections, and higher dimensional extended defects are known to severely impact the overall functional properties. [ 3,4 ] As a matter of example, oxygen vacancies were shown to enhance oxygen conductivity in oxide–ion electrolytes [ 5 ] or to boost oxygen incorporation and catalytic activity in mixed ionic electronic conductors (MIECs) [ 6,7 ] while weakening electronic and magnetic order in ferromagnetic oxides. [ 8 ] Besides, the presence of heterogeneous and homogenous interfaces in thin films was shown to drastically impact defect concentrations in such layers, which gives rise to deviations from bulk defect chemistry and, eventually, to new and unexpected properties.…”

Review on fabrication methods of SrTiO3-based two dimensional conductive interfaces

“…For examples, the origin of oxide-2DEG is still controversial, and the defects (such as oxygen defects, nonstoichiometries, cation intermixing, and nonhomogeneities) are inevitable in the heterointerfaces. [111,112] In addition, the mobilities can be influenced by the quality of sample, the composition of capping layer and the altering of sample structure. And it is not even clear how these properties are limited.…”

Stoichiometry and Termination Control of LaAlO3/SrTiO3 Bilayer Interfaces

“…Complex oxides are particularly appealing for advances in device technology due to a range of remarkable functional material properties, such as colossal magnetoresistance and high temperature superconductivity. [ 1–4 ] Currently, intense research effort is devoted to explore the emergent properties and potential applications of interfaces between dissimilar oxide materials. [ 5,6 ] At the interfaces, one can exploit not only incorporated materials, but also new emergent properties that are inherent to the specific interface.…”