Atomistic mechanisms of van der Waals epitaxy and property optimization of layered materials

Abstract

Since the first isolation of graphene from graphite in 2004, atomically thin or layered materials have been occupying the central stage of today's condensed matter physics and materials sciences because of their rich and exotic properties in two dimensions (2D). Many members of the ever-expanding 2D materials family, such as graphene, silicene, phosphorene, borophene, hexagonal boron nitride, transition metal dichalcogenides, and even the strong topological insulators, share the distinct commonality of possessing relatively weak van der Waals (vdW) interlayer coupling, whereas each member may invoke its own fabrication approaches, and is characterized by its unique properties. In this review article, we first discuss the major atomistic processes and related morphological evolution in the epitaxial growth of vdW layered materials, including nucleation, diffusion, feedstock dissociation, and grain boundaries. Representative systems covered include the vdW epitaxy of both monolayered 2D systems and their lateral or vdW-stacked heterostructures, emphasizing the vital importance of the vdW interactions in these systems. We also briefly highlight on some of the recent advances in the property optimization and functionalization of the 2D materials, especially in the fields of optics, electronics, and spintronics. /compmolsci 6 7 8 FIGURE 1 | Binding energies of C-C dimers on flat metal (111) surfaces with respect to the C-C distance (a) and the preference of C-C dimer formation on close-packed transition metal surfaces (b). The inset in (a) shows the top view of a C-C dimer on a closepacked metal surface. (Reprinted with permission from Ref 42.FIGURE 4 | Minimum energy paths of C diffusion within and between the different regions on (a) Cu(111) and (b) Ni (111). Here, Sub(1) and Sub(2) represent the first and second subsurface sites, respectively. The numbers in the horizontal axes correspond to the routes shown in the inset of (a). (

Band gap measurements of monolayer h-BN and insights into carbon-related point defects

“…Therefore, in vdW epitaxial heterostructures, an atomically sharp interface is obtained, where chemical doi:10.1088/2053-1583/ac0d9c bonds are absent and only vdW interactions are present between the sample and the substrate. [45][46][47][48][49] The region at the interface is usually referred to as vdW gap, such as illustrated in Figure 1(a). Since the vdW interaction is weak, it is expected that each material in the heterostructure preserves most of its electronic properties.…”

Applications of Phosphorene and Black Phosphorus in Energy Conversion and Storage Devices

“…Later, phosphorene, a monolayer sheet of black phosphorus, was afterward successfully experimentally exfoliated in 2014 by Zhang and co‐workers as well as Ye and co‐workers in which they implemented the scotch‐tape microcleavage method, which is well known for graphene isolation. After these pioneering works, numerous 2D research teams began rapidly exploiting this new material over the previously intensively studied 2D materials such as graphene, transition metal dichalcogenides, hexagonal boron nitride, MXenes, and silicene …”

Strain‐Driven and Layer‐Number‐Dependent Crossover of Growth Mode in van der Waals Heterostructures: 2D/2D Layer‐By‐Layer Horizontal Epitaxy to 2D/3D Vertical Reorientation

“…[14][15][16][17] The dangling bond free basal planes of 2D TMD layers enable the vdW assembly of structurally distinguishable 2D materials by relaxing the lattice match constraints demanded in conventional heterojunctions growths. [18][19][20][21][22][23] A large family of 2D vdW heterostructures has recently been developed through various chemical routes, [24][25][26] and one of the most explored material systems is 2D molybdenum/tungsten disulfides (MoS 2 /WS 2 ) in vertical stacks. [23,[27][28][29][30][31] In order to leverage their desired functionalities, it is essential to tailor the morphological variables of 2D layers during their growth stages, which would only be possible once their underlying growth mechanism is clarified.…”