LAUSR

The so-called buffer layer (BL) is a carbon rich reconstructed layer formed during the sublimation of SiC (0001). The existence of covalent bonds between some of the carbon atoms in this layer and the underlying silicon atoms makes it different from epitaxial graphene. We report a systematical and statistical investigation of the BL signature and its coupling with epitaxial graphene by Raman spectroscopy. Three different kinds of BLs are studied: bare buffer layer obtained by direct growth (BL 0), interfacial buffer layer situated between graphene and SiC (c-BL 1) and the interfacial buffer layer without graphene above (u-BL 1). To obtain the latter, we develop a mechanical exfoliation of graphene by depositing and subsequently removing an epoxy-based resin or nickel layer. The observed BLs are ordered-like on the whole BL growth temperature range. BL 0 Raman signature may vary from sample to sample but also forms patches on the same terrace. u-BL 1 share similar properties with BL 0 , albeit with more variability. These BLs have a strikingly larger overall intensity than BL with graphene on top. The signal onset on the high frequency side upshifts upon graphene coverage, that cannot be explained by a simple strain effect. Two fine peaks situated at 1235 and 1360 cm-1 are present for epitaxial monolayer while absent for BL and transferred graphene. These findings point to a coupling between graphene and BL.