Ultrathin 2D-oxides: A perspective on fabrication, structure, defect, transport, electron, and phonon properties

Santosh Kumar Radha (1) , Kyle Crowley (1) , Brian Holler (1) , Xuan Gao (1) , Walter Lambrecht (1) , Halyna Volkova (2) , Marie-Hélène Berger (2) , Emily Pentzer (3) , Kevin Pachuta (1) , Alp Sehirlioglu (1)

1 Case Western Reserve University [Cleveland]
2 CDM - Centre des Matériaux
3 Texas A&M University [College Station]

In the field of atomically thin 2D materials, oxides are relatively unexplored in spite of the large number of layered oxide structures amenable to exfoliation. There is an increasing interest in ultrathin film oxide nanostructures from applied points of view. In this perspective paper, recent progress in understanding the fundamental properties of 2D oxides is discussed. Two families of 2D oxides are considered: (1) van der Waals bonded layered materials in which the transition metal is in its highest valence state (represented by V2O5 and MoO3) and (2) layered materials with ionic bonding between positive alkali cation layers and negatively charged transition metal oxide layers (LiCoO2). The chemical exfoliation process and its combinaton with mechanical exfoliation are presented for the latter. Structural phase stability of the resulting nano akes, the role of cation size and the importance of defects in oxides are discussed. Effects of two-dimensionality on phonons, electronic band structures and electronic screening are placed in the context of what is known on other 2D materials, such as transition metal dichalcogenides. Electronic structure is discussed at the level of many-body-perturbation theory using the quasiparticle self-consistent GW method, the accuracy of which is critically evaluated including effects of electron-hole interactions on screening and electronphonon coupling. The predicted occurence of a two-dimensional electron gas on Li covered surfaces of LiCoO2 and its relation to topological aspects of the band structure and bonding is presented as an example of the essential role of the surface in ultrathin materials. Finally, some case studies of the electronic transport and the use of these oxides in nanoscale field effect transistors are presented.

Mots clés: 2D conductors; oxides

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Santosh Kumar Radha, Kyle Crowley, Brian Holler, Xuan Gao, Walter Lambrecht, et al.. Ultrathin 2D-oxides: A perspective on fabrication, structure, defect, transport, electron, and phonon properties. Journal of Applied Physics, 2021, 129 (22), pp.220903. ⟨10.1063/5.0051093⟩. ⟨hal-03616648⟩