凯发

Graphene/h-BN has been a very hot topic for fundamental research as well as novel device applications, with many exciting results demonstrated. However, such samples were always made by mechanical exfoliation with no scalability. We have carried out series work on the controlled synthesis of graphene on single crystalline h-BN flakes by low pressure chemical vapor deposition (LPCVD). CH4 or C2H2 were used as carbon precursors and Ar/H2 as carrier gases. Typical growth temperature is around 12000C with growth time of several hours. Experimental results show that graphene domains nucleated preferentially at screw dislocation sites with an obvious competition between the 2D and 3D growth. On the graphene/h-BN hetero-structure, moiré patterns are detectable by scanning probe microscopy. With the help of moiré interferometry and atomic resolution imaging, it is found that, when well controlled, the graphene grains align precisely with the h-BN with an uncertainty of rotation angle less than 0.05°. The edges of the grains are derived to be mainly of armchair configuration, conformal to theoretical predictions on non-catalyst substrate. We will also present our latest development: by introducing a gaseous catalyst, the growth speed can be increased by two-three orders of magnitude, yielding largest single crystalline grain size up to 20 m. The results may stimulate further research on the graphene/h-BN hetero-structure and graphene/h-BN super-lattice, which may have profound impact on graphene research in the future.