Mechanical exfoliation using adhesive tapes remains a widely adopted method for producing high-quality atomic layers of two-dimensional (2D) materials. However, conventional commercial tapes often exhibit poor yield and reproducibility, particularly for brittle transition metal dichalcogenides (TMDs), and require additional processing such as plasma treatment or polymer-assisted transfer. Here, we report a specially engineered adhesive tape─referred to as the Flat and Hard Backing (FHB) tape─designed to improve exfoliation performance through simultaneous optimization of three structural elements: adhesive surface flatness, backing rigidity, and in-plane thermal expansion behavior. The FHB tape enables direct exfoliation of WSe2 monolayers and bilayers onto untreated SiO2/Si substrates with high yield and uniformity, under ambient conditions and without auxiliary treatments. Comparative evaluation shows that the FHB tape achieves more than an order of magnitude larger flake area and higher frequency of large-area flakes than two widely used commercial tapes. The enhanced performance is attributed to a combination of surface morphology control, mechanically stabilized stress fields, and thermal-mechanical coupling during the exfoliation process. Our results highlight the critical role of tape architecture in 2D crystal exfoliation and offer a robust and scalable approach for fabricating large-area monolayers, particularly for a class of semiconducting TMDs, rather than a universally applicable exfoliation method.
Onodera et al. (Fri,) studied this question.