Universal mechanical exfoliation of large-area 2D crystals
Yuan Huang, Yuhao Pan, Rong Yang, Lihong Bao, Lei Meng, Hailan Luo, Yongqing Cai, Guodong Liu, Wenjuan Zhao, Zhang Zhou, Liangmei Wu, Zhili Zhu, Ming Huang, Liwei Liu, Lei Liu, Peng Cheng, Kehui Wu, Shibing Tian, Changzhi Gu, Youguo Shi, Yanfeng Guo, Zhi Gang Cheng, Jiangping Hu, Lin Zhao, Guanhua Yang, Eli Sutter, Peter Sutter, Yeliang Wang, Wei Ji, Xingjiang Zhou, Hong-Jun Gao
Abstract
Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.