General synthesis of 2D rare-earth oxide single crystals with tailorable facets

Abstract

Two-dimensional (2D) rare-earth oxides (REO) are a large family of materials with various intriguing applications and the precise facet control is essential for investigating new properties in the 2D limit. However, a bottleneck remains for obtaining their 2D single crystals with specific facets because of the intrinsic non-layered structure and disparate thermodynamic stability of different facets. Herein, for the first time, we achieved the synthesis of a wide variety of high-quality 2D REO single crystals with tailorable facets via designing a hard-soft-acid-base (HSAB) couple for controlling the 2D nucleation of the predetermined facets and adjusting the growth mode and direction of crystals. Also, the facet-related magnetic properties of 2D REO single crystals were revealed. Our approach provides a foundation for further exploring other facet-dependent properties and various applications of 2D REO and an inspiration for the precise growth of other non-layered 2D materials as well.

Infinite possibilities of ultrathin III-V semiconductors: Starting from synthesis

“…It is necessary to study the differences between them ( Cai et al., 2021 ). An appropriate crystal facet controller has been selected to effectively control the exposed crystal facet of the 2D materials, which is useful and enlightening in preparing the III-V semiconductors with different facets ( Li et al., 2021 ). (6) Preparation of twist-angle ultrathin III-V semiconductors: the growing research of twisted bilayer graphene in recent years reveals many unique electronic properties, which brings inspiration for the study of other 2D materials with twist angles.…”

Recent advances in the fabrication of 2D metal oxides

“…In addition, Li et al. successfully synthesized 2D rare-earth oxides (REO) single crystal by using the above strategy ( Li et al., 2021b ). Besides, it is still a great challenge to obtain 2D single crystals with specific crystal facets for REO due to their intrinsic non-layered structure and disparate thermodynamic stability of different facets.…”

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Figure 7 Bottom-up synthesis: liquid metal-assisted CVD strategy and ALD synthesis of 2D MOXs (A) The schematic for the growth of ultrathin antimony oxide on the resolidified Ag substrate and related optical microscope image ( Yang et al., 2020a ) Copyright 2020, Springer Nature. (B) Schematic illustration of the facet-controllable synthesis strategy assisted by the FCA (blue atoms, RE atoms; white atoms, O atoms; red atoms, X ions) ( Li et al., 2021b ) Copyright 2021, Oxford University Press. (C) The schematic to prepare the 2D α-MoO 3 nanofilms via the ALD method ( Wei et al., 2018 ) Copyright 2018, Elsevier.

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“… (B) Schematic illustration of the facet-controllable synthesis strategy assisted by the FCA (blue atoms, RE atoms; white atoms, O atoms; red atoms, X ions) ( Li et al., 2021b ) Copyright 2021, Oxford University Press. …”

Facet engineering of ultrathin two-dimensional materials

“…Ultrathin two-dimensional (2D) materials are a promising class of nanomaterials with a typical atomic thickness of less than 5 nm and a lateral size greater than 100 nm, or up to several micrometers or even wafer-scale, which are considered one of the best candidates for extending Moore's law. 1,2 Since the successful exfoliation of graphene in 2004, 3 ultrathin 2D materials such as graphene, 4–6 hexagonal boron nitride (h-BN), 7,8 transition metal dichalcogenides (TMDs), 9–12 III–V group semiconductors, 13–15 black phosphorus, 16 MXenes, 17–20 as well as some materials like layered double hydroxides (LDH), 21,22 metal oxides, 23–25 transition metal phosphides (TMPs) 26,27 and elemental materials 28–31 have attracted tremendous interest. Ultrathin 2D materials are generally divided into layered materials and non-layered materials.…”