Controlled growth of in-plane graphene/h-BN heterostructure on a single crystal Ge substrate

Highlights: • In-plane Graphene/h-BN heterostructure (GBN) is synthesized by using chemical vapor deposition. • An elementary semiconductor Ge catalyst plays a crucial role in the growth of both graphene and h-BN, as well as in recycling process. • The area ratio of graphene in GBN can be tuned from 22% to 95% by adjusting size and density of h-BN domains. • Electrical conductance of GBN is changed based on the ratio of conducting graphene and insulating h-BN, which conforms to the Percolation theory of 2D materials. In this study, we successfully demonstrate the growth of an in-plane graphene/h-BN (GBN) heterostructure on a single crystal Ge (1 1 0) substrate. A group IV semiconductor Ge is an appropriate catalyst for the epitaxial growth of both graphene and h-BN. Thus, by sequentially introducing ammonia borane (NH₃-BH₃) and methane using two-zone low-pressure chemical vapor deposition (LPCVD), we obtained an in-plane GBN heterostructure. Based on microscopic and spectroscopic analyses, we confirmed that the edge of the pre-synthesized h-BN domains provides plentiful nucleating sites for the lateral epitaxial growth of graphene. Furthermore, we systematically controlled the area and density of h-BN domains in GBN and observed a change in the electrical conductivity of GBN based on the ratio of conducting graphene and insulating h-BN. This result conforms to the percolation theory of two-dimensional materials (2DMs). We believe that our synthetic approach could be a practical method for large-scale synthesis and property control of in-plane heterostructures and can be applied to various types of 2D heterostructures—potentially useful in a wide range of electronic applications.