Coulomb Scattering Controlled by Ionized Molecules Adsorbed on Graphene

The transport property of graphene is significantly affected by molecular adsorption. When an electron is transferred between graphene and a molecule, charge carriers in graphene are scattered by the ionized molecules to decrease the mobility. The Coulomb scatterer is generally treated as a point charge, and the spatial extent of the molecule has rarely been discussed, although the effect may be important in large molecules. Here, we compare the scattering strengths of various electron-acceptor molecules by depositing them on graphene. As a result, molecules with lower symmetry and larger size enhance the scattering. These molecules can cause backscattering of carriers, increase the scattering cross section, and form aggregates in a random structure, all of which can intensify Coulomb scattering. In addition, the charged molecule does not decrease the mobility in the initial stage of the molecular deposition. The result is explained by the cancellation of the impurity charges in the SiO₂/Si substrate by ionized molecules. Thus, the deposition of suitable molecules enables us to control the electronic properties of the atomic-layered materials.