## 3 Results and Discussion
These results indicate the production of a higher-quality gallium nitride with a smooth surface morphology on FLG. Figure 6 shows SEM images of the surface of GaN grown on an AlN/graphene/SiO\({}_{2}\)/Si substrate. One can trace the difference between GaN growth on the SLG (Figure 6a,b) and FLG (Figure 6c) regions. The SEM images clearly show areas of different contrast (Figure 7a), differing in the quality of the epitaxial layers and surface morphology (Figure 6b,c). These areas correlate well with areas of single-layer and few-layer graphene (Figure 2d,e) before PA-MBE growth. Figure 6d shows a general AFM scan of the GaN/AlN film on SLG and FLG. Figure 6e,f shows AFM scans of GaN/AlN films on the SLG  
Figure 5: **(a,d)** Images of RHEED patterns from the GaN surface during PA-MBE growth on FLG (**a**) and MLG (**d**) at azimuthal angles \(\varphi\) = 0\({}^{\circ}\). (**b,e**) Intensity profiles for azimuthal angles \(\varphi\) = 0\({}^{\circ}\) for the GaN layer growing on FLG (**b**) and MLG (**e**), respectively. (**c,f**) Structures of RHEED reciprocal spaces of the GaN layer grown on different graphene buffer layers: FLG (**c**) and MLG (**f**). In the PA-MBE process, epitaxial GaN/AlN layers grow directly on the graphene-coated regions; in other places, the nitride layers are polycrystalline. The formation of polycrystalline GaN/AlN occurs due to the low surface mobility of the adatom and rare nucleation sites. These regions possess increased reactivity and therefore facilitate nucleation of AlN. The improvement in the quality of the GaN layers in the sections of FLG indicates that the density of AlN cores correlates with the density of defects in graphene and its root-mean-square roughness. This correlates well when comparing the growth of GaN/AlN on graphene with different numbers of layers (Figure 6). The thickness of the graphene significantly affects the selectivity of the growth of layers of III nitrides. Figure 6 confirms this conclusion for all the samples studied. A particularly clear contrast is observed in Figure 2e, where FLG regions are present. The contrast is due to the different number of graphene layers. The light and dark areas in the figure  
Figure 6: SEM and AFM images of the surface of GaN/AlN (0001) film grown on SLG (**a,b,d,e**) with regions of FLG (**c,f**) and on MLG (**g–i**) in random regions of the samples. correspond to small and large numbers of graphene layers, respectively. Epitaxial layers of nitrides of the best quality are formed only in the darker regions (few-layer graphene), while in the light regions (low-layer graphene) the nucleation of nitrides is worse, as can be seen from Figure 6a-f. We assume that the role of graphene _n_-layers can be explained by differences in surface potential or chemical reactivity. In the case of the growth of nitrides on multilayer graphene, epitaxial layers are characterized by a developed surface morphology with the presence of a large number of structural defects (Figure 6g-i). There are also distinctly traced areas of a circular shape (Figure 6i), where bubbles with liquid were presumably present after the transfer of multilayer graphene to the surface of the amorphous substrate (Figure 2g-i). The surface of the bubbles was characterized by a convex shape (Figure 2i), which led to the formation of a polycrystalline layers of nitrides on its surface (Figure 6i). EDX analysis (Figure S6f) of nitride film on MLG indicates the presence of a small amount of copper, which confirms the nature of the observed bubbles due to fluid residues during the liquid transfer of graphene to the amorphous substrate. By mapping Raman spectra and determining the intensity of the graphene and nitride peaks, we can identify regions of SLG and FLG graphene after PA-MBE of the III-nitride layers. Figure 7 shows the Raman maps for the obtained experimental samples.