Temperature-dependent transport properties of graphene decorated by alkali metal adatoms (Li, K)

We report the electrical transport properties of graphene for dilute alkali metal decoration (n ∼ 2 × 1012 cm−2) at cryogenic temperatures. Upon deposition of K and Li atoms at T = 20 K, graphene devices are doped with electrons, and the charge carrier mobility is decreased. As temperature is increased, the number of electrons donated to the graphene and the number of charged scatterers are reduced, and the mobility of the metal decorated graphene is increased. This differs from the typical temperature-dependent transport in undecorated graphene, where the mobility decreases with increasing temperature. To investigate the kinetic behavior of adatoms on graphene, we estimate the hopping time of the Li and K adatoms on graphene based on the migration barrier in the low concentration regime of the metal adatoms by Density Functional Theory calculations. The calculations reveal that these adatoms are mobile even at cryogenic temperatures and become more mobile with increasing temperature, allowing for cluster...