Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 46: Graphene - SiC Substrates and Intercalation (jointly with DS, HL, MA, and O)
TT 46.6: Vortrag
Mittwoch, 13. März 2013, 17:15–17:30, H17
Phonons of graphene on SiC(0001) — Stefan Fryska1, Roland J. Koch1, Felix Fromm1, Alejandro Molina-Sánchez2, •Ludger Wirtz2, Martina Wanke1,3, and Thomas Seyller1,3 — 1FAU Erlangen-Nürnberg — 2University of Luxembourg — 3TU Chemnitz
Epitaxial graphene (EG) on SiC(0001) can be grown on a wafer scale [1] but its charge carrier mobility is considerably lower than that of graphene flakes obstained by mechanical exfoliation. A previous study [2] of the temperature dependence of the mobility suggested that it is determined by remote phonon scattering with phonons of the buffer layer at the interface between EG and SiC(0001). The buffer layer, which is identical to the (6√3×6√3)R 30∘ reconstruction of SiC(0001), consists of a monolayer of carbon atoms in a honeycomb structure. Due to a strong interaction with the substrate, the buffer layer has destorted π-bands and does not exhibit a Dirac cone [3]. In order to learn more about the phonons of the buffer layer we have carried out a study using high-resolution electron energy loss spectrscopy (HREELS) and Raman spectroscopy, accompanied by ab-initio calculations. We observe strong modifications of the phonons of the buffer layer with respect to weakly interacting, quasi-free standing graphene on SiC(0001). In particular, the Kohn anomaly is quenched, which agrees with the lack of a Dirac cone. [1] K. V. Emtsev et al., Nat. Mater. 8 (2009) 203. [2] F. Speck et al., Appl. Phys. Lett. 99 (2011) 122106. [3] K. V. Emtsev et al., Phys. Rev. B 77 (2008) 155303.