Buffer layer induced band gap and surface low energy optical phonon scattering in epitaxial graphene on SiC(0001)

The temperature dependent electrical properties of epitaxial graphene grown on Si-face and C-face SiC substrates were investigated by Hall measurements, respectively. Quasi-free-standing epitaxial graphene by H2 intercalation was adopted as the control. Due to a ∼200 meV band gap, the electrical conductivities of graphene on Si-face SiC showed a great increase at temperatures above 350 K compared to the other two. The opened band gap was found attributed to the existent buffer layer. The fitting results of Hall mobility indicates that the buffer layer also limits the carrier transportation of graphene grown on Si-face SiC, as it introduced low energy optical phonon scattering to its epilayer.