Buffer layer free graphene on SiC(0001) via interface oxidation in water vapor

Abstract

Intercalation of various elements has become a popular technique to decouple the buffer layer of epitaxial graphene on SiC(0001) from the substrate. Among many other elements, oxygen can be used to passivate the SiC interface, causing the buffer layer to transform into graphene. Here, we study a gentle oxidation of the interface by annealing buffer layer and monolayer graphene samples in water vapor. X-ray photoelectron spectroscopy demonstrates the decoupling of the buffer layer from the SiC substrate. Raman spectroscopy is utilized to investigate a possible introduction of defects. Angle-resolved photoemission spectroscopy shows that the electronic structure of the water vapor treated samples. Low-energy electron microscopy (LEEM) measurements demonstrate that the decoupling takes place without changes in the surface morphology. The LEEM reflectivity spectra are discussed in terms of two different interpretations.

Robust Phonon-Plasmon Coupling in Quasifreestanding Graphene on Silicon Carbide

“…However, compared to optical measurements [31], HREELS measures at a rather large momentum transfer thus suggesting a momentum dispersion of the effective mass. The mobility values show reasonable agreement with values determined by transport measurements [7,17,18]. Note that transport properties are determined by the long wave length limit of the effective mass.…”

“…1(d) two different simulations which were carried out with (red curve) and without (blue curve) including these additional modes. While the presence of the SiO x related features is expected [18], the presence of C-H bonds has not been observed before. Considering the large density of defects observed by Raman spectroscopy [18] the presence of C-H bonds in quantities below the detection limit of x-ray photoelectron spectroscopy is reasonable.…”

“…1(d)]. This is due to a higher damping of the plasmon which is caused by the low charge carrier mobility of O-QFMLG as compared to MLG or H-QFMLG [17,18] and which reflects itself in a strong broadening of the modes. The latter also applies to the higher lying mode ω + .…”

“…The static dielectric constant was estimated by the average of the dielectric constants of the SiC substrate and vacuum resulting in a value of 5. n was taken from the literature [7,17,18], where it was gathered from Hall effect measurements. ω Pl and Γ were adjusted to optimize the agreement between the measured and the calculated loss spectra.…”

“…H-QFMLG was obtained by annealing the buffer layer in molecular hydrogen [16,17], while O-QFMLG was prepared by annealing in water vapor [18]. Quasi-freestanding bilayer graphene (H-QFBLG) on Hterminated SiC(0001) was prepared by annealing MLG in hydrogen [16,19].…”