Two dimensional and layered transition metal oxides

Single- or multi-layer transition metal oxides (TMOs) have a relatively longer history than other atomically thin materials. TMOs comprise many earth-abundant minerals and have been used for millenia as construction materials, pigments, lubricants, for heat management and many other applications. In TMOs, the transition metal s electrons are strongly pulled by oxygen, and consequently the structural, physical and chemical properties are mostly determined by the strongly correlated d electrons. TMOs are also highly tunable owing to the diversity of their chemical composition, crystal structure and relative ease in inducing oxygen defects. Two dimensional (2D) TMOs often show different physical and chemical properties in comparison to their bulk counterparts. These differences give rise to a variety of remarkable electronic properties such as high temperature superconductivity and multiferroicity and also unique optical, mechanical and thermal phenomena. Additionally, reducing the thickness of TMOs can alter their catalytic and chemical characteristics. Despite their unique properties, single- and few-layer TMOs have received relatively little attention compared to other recent families of atomically thin materials such as layered transition metal dichalcogenides. The overarching aim of this review is to bring the unique aspects of TMOs to the attention of the research community to establish a strong future for research on 2D and layered TMOs. In this review, a comprehensive overview regarding 2D and layered TMOs will be presented. The fundamentals and applications of planar TMOs are discussed. The manuscript will also present future prospects and pathways to new developments that are offered by such TMOs.