Transport Properties of Graphene Decorated by Li and K adatoms*

We report transport properties of the K and Li decorated graphene (n ~ 2×10¹² cm^-2). Upon deposition of K and Li atoms at T = 20 K, graphene is doped with electrons, and the charge carrier mobility is decreased. As temperature is increased, electrons donated to graphene and 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 by DFT calculations. The calculations reveal that these adatoms are mobile even at cryogenic temperatures and become more mobile with increasing temperature, allowing for cluster formation of adatoms. This indicates that the temperature-dependent transport properties of graphene decorated by Li and K adatoms is due to the decrease of charged scatterers by cluster formation of adatoms.