Monolayer two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides (TMDCs), provide a versatile platform for exploring novel physical phenomena at the 2D limit, and show great promise for next-generation electronic, optoelectronic, and quantum devices. To overcome the weak van der Waals interaction in the bulk layered crystal and achieve high quality single-crystal monolayers is a crucial task in top-down mechanical exfoliation. Tape exfoliation has long been the dominant approach to obtain single-crystal monolayers with high quality. More recently, there has been a fast development of using metals as an intermediate to enhance monolayer area and exfoliation yield. This review will provide a survey of mechanical exfoliation strategies of tape and metal-assisted exfoliations, particularly for the most popular graphene and TMDC materials. The interfacial interaction and lateral strain between monolayer and other materials such as oxides and metals play a crucial role in monolayer selectivity and yield. The challenges and opportunities will be highlighted for future development of exfoliating procedures to achieve large-area and high-quality 2D material monolayers and artificial stacks.

单层二维 (2D) 材料，如石墨烯和过渡金属二硫属化物 (TMDC)，为探索二维极限处的新物理现象提供了一个多功能平台，并在下一代电子、光电和量子器件方面显示出巨大的前景。克服块状层状晶体中弱的范德华相互作用并获得高质量的单晶单层是自上而下机械剥离的关键任务。长期以来，胶带剥离一直是获得高质量单晶单层的主要方法。最近，使用金属作为中间体来提高单层面积和剥离产率的发展迅速。本综述将对胶带和金属辅助剥落的机械剥落策略进行调查，特别是对于最流行的石墨烯和 TMDC 材料。单层与其他材料（如氧化物和金属）之间的界面相互作用和横向应变对单层选择性和产量起着至关重要的作用。未来去角质程序的发展将面临挑战和机遇，以实现大面积和高质量的二维材料单层和人工堆叠。