Abstract
Two dimensional (2D) materials consist of one to a few atomic layers, where the intra-layer atoms are chemically bonded and the atomic layers are weakly bonded. The high bonding anisotropicity in 2D materials make their growth on a substrate substantially different from the conventional thin film growth. Here, we proposed a general theoretical framework for the epitaxial growth of a 2D material on an arbitrary substrate. Our extensive density functional theory (DFT) calculations show that the propagating edge of a 2D material tends to align along a high symmetry direction of the substrate and, as a conclusion, the interplay between the symmetries of the 2D material and the substrate plays a critical role in the epitaxial growth of the 2D material. Based on our results, we have outlined that orientational uniformity of 2D material islands on a substrate can be realized only if the symmetry group of the substrate is a subgroup of that of the 2D material. Our predictions are in perfect agreement with most experimental observations on 2D materials’ growth on various substrates known up to now. We believe that this general guideline will lead to the large-scale synthesis of wafer-scale single crystals of various 2D materials in the near future.
Highlights
Two dimensional (2D) materials consist of one to a few atomic layers, where the intra-layer atoms are chemically bonded and the atomic layers are weakly bonded
We can classify the interactions between 2D materials and various substrates into two sceneries: (i) The edge of the 2D material is terminated by the substrate, such as graphene or hBN on an active metal substrate, where the strong interaction between the edge of the 2D material and the pristine substrate facet determines the alignment of the 2D material and its epitaxial growth behavior[29,30]; (ii) The edge of the 2D material is self-passivated or terminated by active atoms from the environment of its growth, such as H or OH groups[31,32,33,34], where the weak interaction between the bulk of the 2D material and the pristine substrate facet dominates the alignment of the 2D material
We would like to note that the fact that a high symmetric direction of a 2D material prefers to align along a high symmetric direction of a substrate, which is revealed by our extensive density functional theory (DFT) calculations in this study, is the foundation of our main conclusion
Summary
Two dimensional (2D) materials consist of one to a few atomic layers, where the intra-layer atoms are chemically bonded and the atomic layers are weakly bonded. The seamless coalescence of millions of well-aligned islands of a 2D material epitaxially grown on a substrate has been successfully used to synthesize wafer-scale single crystals of graphene[5,6,7], hexagonal boron nitride[8,9], and MoS210. This strategy is expected to be generalized to grow various 2D single crystals in the near future. Centimeter scale single-crystalline MoS2 was obtained by the coalescence of well-aligned MoS2 grains on a vicinal Au(111) surface[10]
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