Intercalation of Cs through wrinkles of epitaxial graphene

Interclation of alkali atoms is a straightforward route for the chemical doping of epitaxial graphene (G). This has been demonstrated for graphene on SiC [1] as well as for graphene on metals [2], where dopings/shifts of the Dirac cone at the K-point near the Fermi level have been followed by angle-resolved photoemission spectroscopy (ARPES). However, ARPES is area-averaging technique which does not provide a clear picture on the process of the penetration of alkali atoms to a position between graphene layer and its support. Our ARPES studies for intercalation of Li, Na, K, and Cs to G/Ir(111) have indicated that dynamics of alkali intercalation depend on the size of the alkali atom and we have focused to the intercalation of large alkali atom, Cs. By the combination of ARPES, scanning tunneling microscopy and low- energy electron microscopy we reveal two different doping effects from Cs on top and intercalated compact layer which is formed by a diffusion of Cs atoms through wrinkles network of graphene. [1] J. L. McChesney, et al., Phys. Rev. Lett. 104, 136803 (2010). [2] M. Bianchi, et al., Phys. Rev. B 81, 041403(R) (2010).