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After the successful synthesis of graphene using chemical vapor deposition in 2009, the large-area/defect-free transfer method still remains a critical issue for implementing high-performance graphene-based electronic devices. Here, for the first time, we demonstrated a specially prepared water-soluble amorphous WO3 intermediate layer to effectively protect the graphene surface from immediately after its synthesis to transfer and final unit processing. Moreover, using the photodetector to which the proposed protection method was applied, the performance improvement was quantitatively verified. Compared with the control device, the surface-protected photodetector recorded a higher photoresponsivity of 1.74 times and faster temporal photoswitching response time of 4 s or more. The graphene surface protection method using the WO3 intermediate layer allows the reversibility in transfer process and performance enhancement of graphene-based electronic devices.

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.