Penetration of alkali atoms throughout graphene membrane: theoretical modeling

TL;DR

This paper models and experimentally investigates how different alkali atoms penetrate graphene membranes, revealing varying energy barriers and migration behaviors for Li, Na, Rb, and Cs.

Contribution

It provides a comparative theoretical and experimental analysis of alkali atom penetration through graphene, highlighting differences based on atomic species and substrate effects.

Findings

Li can penetrate graphene at room temperature.

Na penetrates at 100°C, Rb and Cs do not penetrate.

Energy barriers vary significantly among alkali atoms.

Abstract

Theoretical studies of penetration of various alkali atoms (Li, Na, Rb, Cs) throughout graphene membrane grown on silicon carbide substrate are reported and compared with recent experimental results. Results of first principles modeling demonstrate rather low (about 0.8 eV) energy barrier for the formation of temporary defects in carbon layer required for the penetration of Li at high concentration of adatoms, higher (about 2 eV) barrier for Na, and barriers above 4 eV for Rb and Cs. Experiments prove migration of lithium adatoms from graphene surface to the buffer layer and SiC substrate at room temperature, sodium at 100{\deg}C and impenetrability of graphene membrane for Rb and Cs. Differences between epitaxial and free standing graphene for the penetration of alkali ions are also discussed.