Lattice Orientation Heredity in the Transformation of 2D Epitaxial Films

Abstract

9999999% has enabled the rapid development of modern information technologies within the last 70 years. [1,2] To meet the more complicated requirement in the coming 5G and big-data era, many other advanced electronic materials have been developed with promising applications in high-level multifunctional chips. They include GaN, [3,4] SiC, [5] diamond, [6] AlN, [7] ZnO, [8] 2D van der Waals (vdW) layered materials, [9] and perovskites. [10] However, preparing highly crystalline mono-oriented films or crystals with minimized defects is still a major bottleneck for these applications. [11][12][13][14][15] Direct epitaxial (Epi) growth has been widely explored to prepare highly oriented or monocrystal thin films in many material systems. The well-demonstrated examples include epitaxial wide bandgap semiconducting nitrides by metal-organic chemical vapor deposition (MOCVD), [4,16] epitaxial oxides (e.g., ZnO, In 2 O 3 , and Ga 2 O 3 ) by pulsed laser deposition (PLD) [17] or molecular beam epitaxy (MBE), [18] and 2D vdW-layered epitaxial films (e.g., graphene, [19] h-BN, [20] MoS 2 , [21] and WS 2 [22] ) by (MO)CVD. Generally, direct epitaxial deposition can be divided into three steps: 1) mono-oriented nucleation, 2) grain enlargement, and 3) formation of highly oriented continuous film. [21,[23][24][25] The epitaxial growth process has a strict requirement not only on the growth atmosphere, but also on the substrate. Well-designed MOCVD, PLD, and MBE systems could provide a precisely controlled atmosphere, but the highly oriented film can only be grown on single-crystal substrates with minor lattice mismatch. [26] For vdW-layered 2D materials, metal substrates are usually needed. For example, graphene and h-BN are usually grown on singlecrystal Cu substrate, [19,20] and single-crystal MoS 2 was recently demonstrated to grow on mono-oriented Au(111) surface. [21] However, these films must be transferred to fabricate devices, which raises a big concern about metal residue contamination. [27] Therefore, these traditional direct epitaxial growth techniques still have many limitations.This manuscript presents a unique process called "lattice orientation heredity" (LOH) for preparing various highlyoriented films, including 2D materials. Our process ensures that the lattice orientation of product films can be inherited by chemical conversion of precursor oxide films. Our process takesThe ability to control lattice orientation is often an essential requirement in the growth of both 2D van der Waals (vdW) layered and nonlayered thin films. Here, a unique and universal phenomenon termed "lattice orientation heredity" (LOH) is reported. LOH enables product films (including 2D-layered materials) to inherit the lattice orientation from reactant films in a chemical conversion process, excluding the requirement on the substrate lattice order. The process universality is demonstrated by investigating the lattice transformations in the carbonization, nitridation, and sulfurization of epitaxial MoO 2 , ZnO, and In 2 O 3 thin films....

Heteroepitaxial Growth, Degenerate State, and Superconductivity of Perovskite-Type LaWN3 Thin Films

“…In contrast, in the case of LaWN 3 [101̅0] || α-Al 2 O 3 [112̅0], the difference between the interplanar spacings of the LaWN 3 (101̅0) plane (4.911 Å) and the α-Al 2 O 3 (112̅0) plane (4.747 Å) is low at ∼3%. This rotational epitaxial relation is also observed in other compounds such as ZnO on α-Al 2 O 3 and should stabilize the heteroepitaxial interface.…”

“…Figure 1g schematically illustrates the in-plane heteroepitaxial relationship. The crystallographic orientation is LaWN 3 [101̅ 0] || α-Al 2 O 3 [112̅ 0]: i.e., the inplane domain of LaWN 3 is rotated by 30°with respect to that of α-Al 2 O 3 , which was confirmed from the angle difference as 25 and should stabilize the heteroepitaxial interface. Next, we examined the electronic transport properties for the LaWN 3 epitaxial film grown at the optimized conditions.…”

Growth of 2D Materials at the Wafer Scale

“…Reproduced with permission. [ 180 ] Copyright 2021, Wiley‐VCH. j–l) 2D metal (Al, Ga, and In) nitrides grown by graphene encapsulation: j) Schematic of growing non‐vdW 2D layer by graphene encapsulation.…”

“…However, our group recently discovered a lattice orientation heredity (LOH) phenomenon in the chemical transformation of epitaxial MoS 2 films. [ 180 ] LOH‐grown non‐vdW 2D films can be used to support 3D film epitaxial growth on a disordered substrate surface, as shown in the schematic in Figure 23e. Figure 23f illustrates how we use LOH process to prepare the mono‐oriented 2D MoN film on an amorphous substrate.…”

“…However, lattice orientation heredity in the transformation of TMDC films can help to synthesis mono‐oriented stable metal nitride and carbide films, which can then support GaN epitaxial growth. [ 180 ] For remote epitaxial growth, only monolayer or bilayer graphene has been verified as the transparent layer in remote compound epitaxial growth. [ 184 ] It has no requirement on the graphene lattice orientation since 3D film growth is only confined by the 3D substrate.…”