Electronic and geometric structure of graphene/SiC(0001) decoupled by lithium intercalation

Abstract

Graphene formation on top of SiC(0001) by decoupling the carbon buffer layer through lithium intercalation is investigated. Low-energy electron diffraction and core-level photoemission spectroscopy results show that graphene formation already occurs at room temperature, and that the interface morphology is improved after thermal annealing. Angle-resolved photoemission spectroscopy (ARPES) shows that the resulting graphene layer is strongly n-type doped, and in spite of the decoupling by lithium intercalation, a persistent interaction with the substrate imposes a superperiodicity on the graphene band structure that modulates the π band intensity and gives rise to quasi-(2×2) π replica bands. Through a comparison of the ARPES-derived band structure with density-functional-theory calculations, we assign the observed bands to SiC-derived states and interface-related ones; this assignment permits us to establish that the intercalated lithium occupies the T4 site on the topmost SiC layer

Effects of Pb Intercalation on the Structural and Electronic Properties of Epitaxial Graphene on SiC

“…The appearance of this shifted component in the C 1s spectra is an indication of the formation of an intercalation layer through Pb atoms penetration below the interfacial buffer layer. Similar C 1s shifted components have already been reported for other intercalated systems such as H, Si, and Li‐intercalated graphene, and their presence in the C 1s core level spectra has been commonly interpreted in terms of dipole layer formation at the interface due to metal intercalation at the graphene–SiC interface. On the other hand, the disappearance and/or suppression of buffer layer components (S1 and S2) in the C 1s spectra have often been used as a fingerprint to identify the fully and/or partially decoupled graphene layer.…”

Structural and electronic properties of Li-intercalated graphene on SiC(0001)

“…Core-level spectra shows that this dramatic reduction in doping occurs despite evidence that almost half of the Li atoms have not deintercalated or desorbed from the sample. The Li 1s core level spectrum shows that the component assigned to surfaceadsorbed Li essentially disappears while the components assigned to intercalated Li remain, in agreement with earlier observations [13][14][15]24]. We therefore suggest that some Li atoms which were initially adsorbed on the surface, or between FIG.…”

“…In agreement with the results of Refs. [24] and [51], we find that Li intercalation at the interface is sufficient to decouple the carbon buffer layer from the substrate. The Li atom is located at the T4 site on the SiC(0001) surface, breaking the Si-C bonds.…”

“…Bisti et al determined that the Li atoms occupy the T4 site of the topmost SiC bilayer after they intercalate underneath the buffer layer, thereby decoupling it from the substrate [24]. Sugawara et al deposited Li on bilayer graphene at 30 K and reported the appearance of a sharp (…”

Epitaxial graphene/silicon carbide intercalation: a minireview on graphene modulation and unique 2D materials

“…Additionally, a shift of approximately 0.7-2.0eV in bulk SiC C 1s and Si 2p peak positions is often observed in the XPS spectrum as a result of intercalation. 9,15,18,[27][28][29][30][31][32][33][34][35] This shift indicates a change in the charge transfer between SiC and EG caused by the presence of an intercalant layer.…”