Ytterbium Intercalation of Epitaxial Graphene Grown on Si-Face SiC

Somsakul Watcharinyanon¹, Leif I. Johansson¹, Chao Xia¹, Jan Ingo Flege², Axel Meyer², Jens Falta², Chariya Virojanadara¹

¹Department of Physics, Chemistry, and Biology, Linkoping University, Linkoping, Sweden.
²Institute of Solid State Physics, University of Bremen, Bremen, Germany.

DOI: 10.4236/graphene.2013.22010                

Abstract

The rare-earth metal, ytterbium (Yb), was deposited on graphene grown on Si-face SiC, kept at room temperature. Yb was not found to intercalate, destroy or dope the graphene layer before subsequent heating, unlike alkali metals such as Li and Na. Our photoemission results reveal that heating to 300^oC promotes Yb intercalation into the graphene-substrate interface. Real-time low energy electron microscopy (LEEM) measurements indicated intercalation to start at a sample temperature of around 220^oC. In the intercalation process, Yb penetrates through the graphene and buffer layer and forms bonds to the silicon in the topmost SiC substrate bilayer, as indicated by the shifted components observed in the C 1s, Si 2p, and Yb 4f spectra. The Yb intercalation decouples the buffer layer from the substrate and transforms it into another graphene layer as manifested by the absence of buffer layer spots in the μ-LEED pattern and the appearance of an additional π band in the ARPES spectra, respectively. Moreover, the observed shift of the Dirac point down from the Fermi level by 1.9 eV indicates electron doping of the graphene layer upon Yb intercalation. The Yb intercalated graphene sample was found to be thermodynamically stable up to temperatures around 700^oC.

Keywords

Epitaxial Graphene; SiC; Ytterbium; Intercalation; PES; ARPES; LEEM

Conflicts of Interest

The authors declare no conflicts of interest.

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