Atomic-scale characterization of the interfacial phonon in graphene/SiC



Emi Minamitani, Ryuichi Arafune, Thomas Frederiksen, Tetsuya Suzuki, Syed Mohammad Fakruddin Shahed, Tomohiro Kobayashi, Norifumi Endo, Hirokazu Fukidome, Satoshi Watanabe, and Tadahiro Komeda



Epitaxial graphene on SiC that provides wafer-scale and high-quality graphene sheets on an insulating substrate is a promising material to realize graphene-based nanodevices. The presence of the insulating substrate changes the physical properties of free-standing graphene through the interfacial phonon, e.g., limiting the mobility. Despite such known impacts on the material properties, a complete and microscopic picture is missing. Here, we report on atomically resolved inelastic electron tunneling spectroscopy (IETS) with a scanning tunneling microscope for epitaxial graphene grown on 4H-SiC(0001). Our data reveal a strong spatial dependence in the IETS spectrum, which cannot be explained by intrinsic graphene properties. We show that this variation in the IETS spectrum originates from a localized low-energy vibration of the interfacial Si atom with a dangling bond via ab initio electronic and phononic state calculations. This insight may help advancing graphene device performance through interfacial control.




Physical Review B: