High-yield fabrication of monolayer and twisted bilayer freestanding hexagonal boron nitride

Hexagonal boron nitride (h-BN), which supports a uniquely large bandgap, has gained interest in its dielectric properties and as a host for quantum emitters. Resolving the atomic structures of emitters in h-BN poses a significant challenge, and monolayer samples provide the best opportunity for such investigations. Meanwhile, the electronic and excitonic properties of freestanding monolayer h-BN itself continue to be a subject of debate. One of the main bottlenecks for resolving these challenges is a lack of transfer method for reliably producing high-yield freestanding monolayer h-BN. Here, we present a layer-by-layer transfer protocol for preparing large-area h-BN samples, including fully suspended monolayer and randomly twisted multilayer forms. The fabrication method should greatly facilitate the study of the intrinsic optical, chemical, and mechanical properties of h-BN, advance the atomic structure study of BN-based quantum emitters, and provide a versatile single-atom-thick insulating substrate for materials imaging.