Enhancement of Underlayer Coverage in Sub-Millimeter Bilayer Graphene by Modifying the Streamline Direction

The growth of large-scale bilayer graphene (bi-graphene) is significantly important for graphene-based device fabrications. Chemical vapor deposition is usually used for the synthesis of high-quality and large-scale thin films including various monolayers and bilayers. However, a major challenge for bi-graphene growth is the so-called limited underlayer coverage, i.e., the faster growth of the top layer than the underlayer. Herein, using the circumfluence chemical vapor deposition, it is demonstrated that the underlayer growth can be greatly enhanced via optimizing the streamline, and high-quality AB-stacking sub-millimeter bi-graphene with underlayer coverage over 93% is achieved successfully. Raman spectroscopy and selected area electron diffraction confirm the high crystalline quality and uniformity of the as-grown bilayers. The as-fabricated field-effect transistor using the bi-graphene as the channel layer exhibits typical semiconductor transfer characteristics and a nonzero bandgap which is required for device applications. It is suggested that the optimized streamline design largely allows a reduction of difference in the edge growth kinetics between the top and bottom layers. Thus, in this work, a promising technical route is presented for the growth of large-scale bi-graphene with high underlayer coverage, beneficial for the development of functional graphene devices. Herein, a high underlayer coverage of sub-millimeter bilayer graphene single crystal is achieved successfully, by modifying the gas flow streamline in the circumfluence chemical vapor deposition, which is attributed to the promotion of carbon sources depositing and absorbing on the copper surface under the vertical streamline.image & COPY; 2023 WILEY-VCH GmbH