The absence of a D-band (at 1340 cm -1 ) indicates the defect-free graphene in hBN/G and hBN/non-F-G. For F-G, the D and D' peaks appear in the Raman spectra. A uniform functionalization with an average ID/IG of 2.2 is indicated, representing that the functionalization degree is around 1%. After functionalization of hBN/G, mechanically exfoliated 1L-MoS2 was directly transferred on the top of the hBN/G to form the areas of hBN/F-G/MoS2 and hBN/non-F-G/MoS2 (Figure and). Afterwards, hBN/(non-)F-G/MoS2 was annealed in vacuum at 200 °C for 2h to enhance the interlayer contact since low-weight molecular contaminants are known to be eliminated from the interior. The AFM image of hBN/(non-)F-G/MoS2 is displayed in on hBN/G is uniform, although the MoS2 Raman signal on hBN (hBN/MoS2), as marked in region I, is slightly increased owing to the electric neutral characteristic of hBN. (1.88 eV), respectively, due to the p-doping effect of phenyl-groups (Figure ). In addition, laser-induced effects can be excluded, since the laser radiation didn't generate PL changes for pristine MoS2 and MoS2/G, respectively (Figure and Figure ). Moreover, the potential BPO residues on the surface cannot vary the PL properties of MoS2 under the operational laser energy, as reference experiments revealed (Figure ). Thus, the measured PL enhancement consequently results from the effect induced by F-G. In Figure and, two peaks, the in-plane E 1 2g (385.4 cm -1 ) and the out-of-plane A1g (404.1 cm -1 ) appear in the Raman spectrum of the hBN/MoS2 layer. The frequency difference between E 1 2g and A1g is 18.7 cm -1 , confirming the monolayer characteristic of the MoS2 flake. The heterojunction areas display the typical vibration modes of 1L-MoS2 and 1L-graphene, which indicates the effective formation of the heterostructure. The magnified Raman spectra of MoS2 in the range of 300-500 cm -1 are shown in Figure . It has been reported that the A1g mode is sensitive to charge-doping and the E 1 2g mode is sensitive to lattice distortions or strain in MoS2. The frequency difference between E 1 2g and A1g in hBN/non-F-G/MoS2 is 20.9 cm -1 , which is 2.2 cm -1 higher than the value of hBN/MoS2 due to the electron donation from graphene to MoS2. However, after the functionalization, the E 1 2g and A1g modes in hBN/F-G/MoS2 with a difference of 18.7 cm -1 have no obvious shift compared to the hBN/MoS2. We deduce that there are two possible reasons: On the one hand, the weak electron-withdrawing effect from the phenyl groups cannot generate a large shift of the A1g Raman mode of MoS2. On the other hand, the phenyl functional groups effectively separate the graphene basal plane and MoS2 interface with an increased interlayer distance, which impairs the electron transfer from the carbon plane to MoS2. The MoS2 in hBN/F-G/MoS2 is mainly supported by the phenyl groups instead of the graphene surface, resulting in partly free-standing MoS2. Compared to the electron-withdrawing groups in GO, such as hydroxyl, epoxy, and organosulfates, the phenyl groups have a very weak electron-withdrawing effect.