2D–3D heterointerface regulation of van der Waals epitaxy of AlN on graphene for wafer-scale exfoliation

In this work, we present a three-step van der Waals epitaxy method to grow a transferable single-crystalline AlN membrane on untreated bilayer graphene by using two-dimensional (2D)/three-dimensional heterointerface regulation. Ultra-low V/III ratio in the first step greatly enables rapid mergence of quasi-2D AlN to protect the graphene from the damage in high-temperature and ammonia environments. Cyclic growth with different V/III ratios is introduced to release the strain in the second step, effectively alleviating the cracking problem of the subsequent AlN epilayer. Furthermore, we demonstrate the mechanical exfoliation of wafer-scale AlN epilayers and reveal the mechanism behind their controlled delamination. This work provides an effective strategy to realize free-standing AlN membrane on graphene with high quality and controllable delamination, laying a solid foundation for flexible deep ultraviolet device applications.