Sanghoon Bae1 Jaewoo Shim1 Wei Kong1 Kuan Qiao1 Doyoon Lee1 Ruike Zhao1 Suresh Sundram2 Xin Li2 Jagadeesh Moodera1 Xuanhe Zhao1 Chris Hinkle3 Abdallah Ougazzaden2 Jeehwan Kim1

1, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
2, Georgia Institute of Technology, Metz, , France
3, The University of Texas at Dallas, Dallas, Texas, United States

Heterostructures formed by weak van der Waals interactions between 2D materials have revealed novel physics and device functionalities. However, it is challenging to precisely control the number of layer at wafer scale. The tape mechanical exfoliation method has been used as main method to obtain few monolayer 2D flakes from various bulk crystals, which allows stacking of multiple 2D materials. The method relies on trial-and-error based operation, which lead substantial time-consuming. In addition, the typical size of stacked heterostructures is only limited to hundreds of microns. An effort to avoid these issues focuses on direct growth of 2D materials on wafers. However, it has been noted that controlling nucleation of 2D layers via growth is even more challenging because of easy-additonal nulei formation on top of the initial nuclei. Accordingly, it has been required to develop alternative way.
Here we report a layer-resolved splitting (LRS) for 2D materials that permits precise control of the number of layer of 2D materials. It produces multiple monolayers of wafer-scale 2D materials from one multilayer 2D material growth. We grow thick 2D materials, such as WS2, hBN, WSe2, and MoSe2, and precisely split them into multiple monolayers. We study the underlying mechanics of LRS for the 2D material multilayers into many individual monolayers. The wafer-scale monolayer of transition metal dichalcogenides after LRS exhibits substantial photoluminescence enhancement uniformly across a 2-inch wafer which maybe related to indirect-to-direct band gap transition. Through this LRS approach, we successfully demonstrate van der Waals heterostructures with single-atom resolution. We strongly believe LRS will open up new venue for 2D material research community.