Chuang Meng-Hsi, Chen Chun-An, Liu Po-Yen, Zhang Xin-Quan, Yeh Nai-Yu, Shih Hao-Jen, Lee Yi-Hsien
Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan.
Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu, 30013, Taiwan.
Nanoscale Res Lett. 2022 Mar 14;17(1):34. doi: 10.1186/s11671-022-03670-y.
Moiré lattice in artificially stacked monolayers of two-dimensional (2D) materials effectively modulates the electronic structures of materials, which is widely highlighted. Formation of the electronic Moiré superlattice promises the prospect of uniformity among different moiré cells across the lattice, enabling a new platform for novel properties, such as unconventional superconductivity, and scalable quantum emitters. Recently, epitaxial growth of the monolayer transition metal dichalcogenide (TMD) is achieved on the sapphire substrate by chemical vapor deposition (CVD) to realize scalable growth of highly-oriented monolayers. However, fabrication of the scalable Moiré lattice remains challenging due to the lack of essential manipulation of the well-aligned monolayers for clean interface quality and precise twisting angle control. Here, scalable and highly-oriented monolayers of TMD are realized on the sapphire substrates by using the customized CVD process. Controlled growth of the epitaxial monolayers is achieved by promoting the rotation of the nuclei-like domains in the initial growth stage, enabling aligned domains for further grain growth in the steady-state stage. A full coverage and distribution of the highly-oriented domains are verified by second-harmonic generation (SHG) microscopy. By developing the method for clean monolayer manipulation, hetero-stacked bilayer (epi-WS/epi-MoS) is fabricated with the specific angular alignment of the two major oriented monolayers at the edge direction of 0°/ ± 60°. On account of the optimization for scalable Moiré lattice with a high-quality interface, the observation of interlayer exciton at low temperature illustrates the feasibility of scalable Moiré superlattice based on the oriented monolayers.
二维（2D）材料人工堆叠单分子层中的莫尔晶格有效地调节了材料的电子结构，这一点已得到广泛关注。电子莫尔超晶格的形成有望实现晶格中不同莫尔晶胞之间的均匀性，从而为诸如非常规超导性和可扩展量子发射器等新特性提供一个新平台。最近，通过化学气相沉积（CVD）在蓝宝石衬底上实现了单层过渡金属二硫属化物（TMD）的外延生长，以实现高度取向单分子层的可扩展生长。然而，由于缺乏对排列良好的单分子层进行必要的操作以获得清洁的界面质量和精确的扭转角控制，可扩展莫尔晶格的制造仍然具有挑战性。在此，通过使用定制的CVD工艺在蓝宝石衬底上实现了可扩展且高度取向的TMD单分子层。通过在初始生长阶段促进类核域的旋转来实现外延单分子层的可控生长，从而在稳态阶段实现排列的域以进一步进行晶粒生长。通过二次谐波产生（SHG）显微镜验证了高度取向域的全覆盖和分布。通过开发清洁单分子层操作方法，制备了异质堆叠双层（外延WS/外延MoS），其中两个主要取向的单分子层在边缘方向以0°/±60°的特定角度排列。由于对具有高质量界面的可扩展莫尔晶格进行了优化，低温下对层间激子的观测说明了基于取向单分子层的可扩展莫尔超晶格的可行性。
