This result is similar to van der Waals epitaxial growth of MoS2 on graphene  and perhaps originates from the higher boundary effect of the Evofosfamide ic50 narrower graphene belt after mechanical exfoliation . Besides, the triangular h-BN nanosheets on graphene showed different in-plane orientations from each other. Raman spectroscopy provided a useful means of gleaning
information about the lattice vibration modes of graphene and h-BN. After being transferred to SiO2/Si by the Scotch tape mechanical exfoliation method, the graphene was generally aligned with the (002) lattice plane parallel to the surface of the SiO2/Si wafer [1, 2]. The existence of graphene was shown by Raman spectra in Figure 3, in which the I 2D/I G ratio of graphene was less than 0.5, indicating the multilayer structure of the graphene. Moreover, a weak D peak of graphene at 1,350 cm-1 was observed from the Raman spectra (Figure 3), indicating a small number of defects in the graphene, which may have originated from the original HOPG or the mechanical exfoliation process. For the sample examined after CVD, a peak much stronger than the D peak of graphene appeared at 1,367 cm-1, indicating the E 2g vibration mode of h-BN, which was consistent with the reported values [5, 6, 13–19]. Interestingly, the 2D and G
peaks for graphene diminished in intensity after CVD, and this may have originated from the partial buy Staurosporine coverage of the graphene by h-BN. As shown in Figure 3b,c, the G peaks of graphene for the graphene substrate and h-BN/graphene were fitted with Lorentz curves (solid lines). The fitting data were well fitted with the raw data, while the Raman frequency and full width at half maximum (FWHMs) for G bands were almost equal to each other. These results are comparable with the reported values of graphene  and graphite [27, 28], showing the high quality
of graphene Selleck BIBW2992 before and after CVD and indicating that the synthesis of h-BN nanosheets on graphene in our Phosphatidylinositol diacylglycerol-lyase manuscript does not cause a degradation of graphene. Figure 3 Raman spectra. (a) Raman spectra of graphene before CVD (lower plot) and h-BN/graphene after CVD (upper plot). G peaks fitting with Lorentz curves (solid lines) for graphene substrate (b) and h-BN/graphene (c) are shown with their FWHMs, respectively. According to previous reports , the gas-phase nucleation for h-BN was absent at growth temperatures lower than 1,000°C; hence, the growth of h-BN nanosheets on graphene was dominated by the surface nucleation during our CVD process at 900°C. Moreover, the surface topography of the substrate is vital to the surface nucleation . Consequently, the nucleation of the h-BN nanosheets on the graphene substrate was regulated by the surface morphology of graphene in our work.