Penetration of alkali atoms throughout a graphene membrane: theoretical modeling.
Theoretical studies of penetration of various alkali atoms (Li, Na, Rb, Cs) throughout a graphene membrane grown on a silicon carbide substrate are reported and compared with recent experimental results. Results of first principles modeling demonstrate a rather low (about 0.8 eV) energy barrier for the formation of temporary defects in the carbon layer required for the penetration of Li at a high concentration of adatoms, a higher (about 2 eV) barrier for Na, and barriers above 4 eV for Rb and Cs. Experiments prove migration of lithium adatoms from the graphene surface to the buffer layer and SiC substrate at room temperature, sodium at 100 °C and impenetrability of the graphene membrane for Rb and Cs. Differences between epitaxial and free-standing graphene for the penetration of alkali ions are also discussed.
School of Computational Sciences, Korea Institute for Advanced Study (KIAS), Hoegiro 87, Dongdaemun-Gu, Seoul, 130-722, Korean Republic. danil@kias.re.kr
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Boukhvalov
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Virojanadara