Core-level photoelectron spectroscopy study of interface structure of hydrogen-intercalated graphene on n-type 4H-SiC(0001)

The interface structure of hydrogen-intercalated graphene/SiC(0001), formed by annealing SiC substrates with the buffer layer at high temperature under atmospheric molecular hydrogen, was investigated by core-level photoelectron spectroscopy. The investigation of C 1s spectra, captured before and after the annealing at various temperatures in a vacuum, indicates that residual materials (hydrocarbon and hydrogen) stayed at the interface on the as-treated sample and remained there until annealing at around 700 degrees C. These residual materials would cause distortion of the graphene. The analysis of Si 2p photoelectron spectra reveals insufficient termination of Si-dangling bonds at the interface by hydrogen and that significant interface states remained. The interface states of Si dangling bonds are plausible origins of Fermi level pinning and would act as charged impurities. These distortion and charged impurities should degrade the electronic performance of graphene in this system.