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Ultrathin 2D-oxides: A perspective on fabrication, structure, defect, transport, electron, and phonon properties
Journal of Applied Physics ( IF 3.2 ) Pub Date : 2021-06-10 , DOI: 10.1063/5.0051093
Santosh Kumar Radha 1 , Kyle Crowley 1 , Brian A. Holler 1 , Xuan P. A. Gao 1 , Walter R. L. Lambrecht 1 , Halyna Volkova 2 , Marie-Hélène Berger 2 , Emily Pentzer 3 , Kevin G. Pachuta 4 , Alp Sehirlioglu 4
Affiliation  

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 V 2O 5 and MoO 3) and (2) layered materials with ionic bonding between positive alkali cation layers and negatively charged transition metal oxide layers (LiCoO 2). The chemical exfoliation process and its combination with mechanical exfoliation are presented for the latter. Structural phase stability of the resulting nanoflakes, 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. The electronic structure is discussed at the level of many-body-perturbation theory using the quasiparticle self-consistent G W method, the accuracy of which is critically evaluated including effects of electron–hole interactions on screening and electron–phonon coupling. The predicted occurrence of a two-dimensional electron gas on Li-covered surfaces of LiCoO 2 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.

中文翻译:

超薄二维氧化物:制造、结构、缺陷、传输、电子和声子特性的透视

在原子级薄 2D 材料领域,尽管存在大量易于剥离的层状氧化物结构,但对氧化物的探索相对较少。从应用的角度来看,人们对超薄膜氧化物纳米结构越来越感兴趣。在这篇 Perspective 论文中,讨论了在理解 2D 氧化物的基本特性方面的最新进展。考虑了两类二维氧化物:(1)范德华键合层状材料,其中过渡金属处于最高价态(由 V 2 5 和 MoO 3) 和 (2) 层状材料在正碱性阳离子层和带负电荷的过渡金属氧化物层 (LiCoO 2)。后者介绍了化学剥离过程及其与机械剥离的结合。讨论了所得纳米薄片的结构相稳定性、阳离子尺寸的作用以及氧化物中缺陷的重要性。二维对声子、电子能带结构和电子屏蔽的影响放在其他二维材料(例如过渡金属二硫属化物)上已知的背景下。使用准粒子自洽在多体微扰理论的水平上讨论电子结构 G 方法,其准确性受到严格评估,包括电子 - 空穴相互作用对筛选和电子 - 声子耦合的影响。预测在 LiCoO 的 Li 覆盖表面上出现二维电子气 2及其与能带结构和键合的拓扑方面的关系作为表面在超薄材料中的重要作用的一个例子。最后,介绍了电子传输的一些案例研究以及这些氧化物在纳米级场效应晶体管中的使用。
更新日期:2021-06-14
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