Two-dimensional oxides

The novel physical and chemical properties and functionalities of two-dimensional (2-D) oxide materials are assessed. The synthesis of one unit-cell thick 2-D oxides poses particular challenges, since in contrast to other 2-D materials, which can be fabricated by exfoliation of layered bulk compounds, the majority of oxides do not occur in layered bulk structures. Most 2-D oxides are therefore prepared by thin-film deposition methods on substrates. However the fabrication of free-standing quasi-2-D oxide nanosheets, with less restrictive several monolayer thickness, has been successfully achieved by wet chemical procedures. New geometry concepts and electronic properties are observed in 2-D oxides, due to quantum confinement and interface proximity effects. Atomic geometries, electronic structure, ferroic properties and catalytic behaviour of 2-D oxides are discussed, together with promising prototypical proof-of-concept experiments for prospective applications. The edge states in oxide nanoribbons, 2-D objects of limited width, and their polarity aspects are discussed.