Extended Data Fig. 2: Background subtraction and comparison of vibrational signals between STO and graphene films.

a, A HAADF STEM image at the edge of STO film. The dark region is graphene, while the bright region is STO supported by graphene. b, Raw dark-field vibrational spectra at STO and graphene regions as marked by black and red dots in (a). Both spectra were obtained by summing 200 frames of 1 s exposure spectra. The spectrum collected at the graphene region contains two broad peaks at 60–100 and 140–200 meV, in agreement with previous studies^11,12. c, Background-subtracted spectra at STO and graphene regions. In the energy range of 10–80 meV energy range, the vibrational signals of graphene are negligible compared to those of STO. In the energy range of 80–120 meV, the intensity of vibrational signals of STO is about six times that of graphene. The broad peak in 140–200 meV originates from phonon modes in graphene or other residual contamination. Therefore, we can ignore the bulk phonon modes of graphene and residual contamination in the energy range of interest for STO and BTO. d, Background-subtracted spectrum containing STO phonon structure in the energy range of 10–110 meV. The spectrum is used in Fig. 1b. e, Background-subtracted spectrum containing vibrational states of graphene and residual contamination in the energy range of 140–200 meV. The raw spectrum is duplicated from the black curve in (b). The blue dots are fitting windows, while the black dashed lines are the fitted backgrounds using a power law function.