Let us consider Haidari et al., 2020, who studied the doping effect in graphene-graphene oxide interlayer. To study "the interlayer coupling effect in combined structures", Haidari and coworkers produced graphene and graphene oxide (GO) heterostructures. In particular, the researchers prepared graphene-, GO-, and graphene/GO areas on a SiO2/Si substrate. The Raman spectra of these three regiones were then obtained. "As shown in Fig. [in Haidari et al., 2020], the distinct Raman spectra for the three defined regions (graphene, GO, and graphene/GO) are clearly identified. For a CVD-fabricated monolayer graphene, the intensity ratio of 2D/G in the Raman spectra is determined to be approximately 3, which indicates that the graphene is crystalized".