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(a) Typical energy dispersion at K point for epitaxial graphene. (b) Observed temperature dependence of shift in Fermi edge during ARPES experiment due to charging effect. (c) Plot of shift in Fermi edge vs temperature (dashed line serves as a guide to the eye). Inset shows the magnitude of the shift at 60K vs incident photon energy.
(a) Photoluminescence spectrum at 60 K from epitaxial graphene samples grown on 6H SiC. [(b) and (c)] Temperature dependence of PL spectrum from 15 to 140 K corresponding to gray regions in (a). (d) Plot of relative intensity of nitrogen and H1 peaks against shift in Femi energy from ARPES, all vs temperature (Relative intensities are normalized to H1 peak and dashed lines serve as guides to the eye).
(a) Energy band diagram for freestanding graphene and SiC crystal (not in thermal equilibrium). (b) Epitaxial graphene and 6H SiC as-grown (thermal equilibrium). Due to band bending ( from ARPES measurements) the gap from the top of the valence band of SiC to the Fermi level of graphene is at the junction. (c) Schematic of charging effect due to D1 PL.
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