Double-Spiral Hexagonal Boron Nitride and Shear Strained Coalescence Boundary

Abstract

Among the different growth mechanisms for two-dimensional (2D) hexagonal boron nitride (h-BN) synthesized using chemical vapor deposition, spiraling growth of h-BN has not been reported. Here we report the formation of intertwined double-spiral few-layer h-BN that are driven by screw-dislocations located at the anti-phase boundaries of monolayer domains. The microstructure and stacking configurations were studied using a combination of dark-field and atomic-resolution transmission electron microscopy. Distinct from other 2D materials with single-spiral structures, the double-spiral structure enables the intertwined h-BN layers to preserve the most stable AA′ stacking configuration. We also found that the occurrence of shear strains at the boundaries of merged spiral islands is dependent on the propagation directions of encountering screw dislocations, and presented the strained features by density functional theory calculations and atomic image simulations. This study unveils the doublespiral growth of 2D h-BN multilayers and the creation of shear strain band at the coalescence boundary of two h-BN spiral clusters.

Chemical Etching of Screw Dislocated Transition Metal Dichalcogenides

“…In addition to the conventional monolayer or layer-by-layer structures, 2D materials often contain screw dislocations. ,− A screw dislocation is a line defect that shears part of the crystal lattice. In layered materials, it typically shears along the out-of-plane direction, connects layers into one continuous helicoid, and results in a spiral morphology. , Screw dislocation growth has been observed in CVD grown 2D materials, such as graphene, h-BN, MoS 2 , , WS 2 , ,− WSe 2 , , SnS 2 , SnSe 2 , SnS, and GeS, , as well as Bi 2 Se 3 and Sb 2 Te 3 grown via solution synthesis and molecular beam epitaxy. − Screw dislocations drive the growth of layered materials in a different way from the typical layer-by-layer growth and can influence the vertical stacking configurations and overall crystal symmetry to yield complex morphologies as well as varied physical properties. − , Screw dislocations combined with non-Euclidean surfaces also provide a pathway to introduce interlayer twists rationally . Although dislocations are commonly observed in layered materials, the studies on the structures of screw dislocations and their formation process have been limited.…”

“…In addition to the monolayer or layer-by-layer structures, screw dislocation growth has been observed frequently in 2D materials growth, ,− and they influence the vertical stacking configurations of MX 2 materials. , Screw dislocated MX 2 nanoplates can be categorized by the number of layers and the orientation of each layer in the repeating stacking sequence, which correlate with the distinct shape of the nanoplates caused by the assembled Wulff construction of each individual layer. MX 2 spiral nanoplates exhibit three classes of shapes caused by three stacking configurations: triangular spirals have a [+] (3R-like) stacking, hexagonal spirals have a [+ – ] (2H) stacking, and truncated triangular shapes consist of mixed repeating stacking sequence such as [+ – + ]. , Here, in the square brackets, the orientation of a layer is represented by “+” (0° or ±120°) or “–” (±60° or 180°) signs.…”

“…In layered materials, it typically shears along the out-of-plane direction, connects layers into one continuous helicoid, and results in a spiral morphology. 24,43 Screw dislocation growth has been observed in CVD grown 2D materials, such as graphene, 25 h-BN, 26 MoS 2 , 27,28 WS 2 , 12,28−31 WSe 2 , 32,33 SnS 2 , 34 SnSe 2 , 35 SnS, 36 and GeS, 37,38 as well as Bi 2 Se 3 and Sb 2 Te 3 grown via solution synthesis and molecular beam epitaxy. 39−42 Screw dislocations drive the growth of layered materials in a different way from the typical layer-bylayer growth and can influence the vertical stacking configurations and overall crystal symmetry to yield complex morphologies as well as varied physical properties.…”

Theoretical Study of Chemical Vapor Deposition Synthesis of Graphene and Beyond: Challenges and Perspectives

“…Figure 9i shows the formation of biscrew dislocations from the coalescence of antiparallel hBN crystals. 170 When two antiparallel hBN islands meet each other, there is a chance of forming an "X" configuration at the interface. Further growth of the "X" shaped interface leads to the formation of biscrew dislocations.…”

Building Functional Memories and Logic Circuits with 2D Boron Nitride

“…[ 136 ] At the boundaries of merged spiral domains, the shear strain was dependent on the broadcasting directions of screw dislocations located at the coalescence boundary. [ 137 ] As elucidated in Figure 5c, at the beginning of the epitaxy, nuclei attached at the boundaries of Cu (110) surface, and then grew to be single‐crystal domains. Due to the multinuclei growth mechanism, the neighboring domains had a lot of chances to meet and merge into one part.…”