Transport measurement of Li doped monolayer graphene

Lithium adatoms on monolayer graphene have been predicted to induce superconductivity with a critical temperature near 8 K [1], and recent experimental evidence by ARPES indicates a critical temperature nearly that high [2]. Encouraged by these results, we investigated the effects of lithium deposited at cryogenic temperatures on the electronic transport properties of epitaxial and CVD monolayer graphene down to 3 K. The change of charge carrier density due to Li deposition was monitored both by the gate voltage shift of the Dirac point and by Hall measurements, in low and high doping regimes. In the high doping regime, a saturation density of 2\texttimes 10$^{\mathrm{13}}$ cm$^{\mathrm{-2}}$ was observed independent of sample type, initial carrier density and deposition conditions. No signatures of superconductivity were observed down to 3 K. [1] G. Profeta, et al., Nat Phys 8, 131 (2012). [2] B. M. Ludbrook, et al., PNAS 112 (38), 11795--11799 (2015).