Enhanced electrical properties of reduced graphene oxide multilayer films by in-situ insertion of a TiO2 layer.

Wrinkle-free reduced graphene oxide (rGO)/TiO(2) hybrid multilayer films were directly fabricated using an rGO solution stabilized by a TiO(2) precursor sol applied over a large area by an air spraying method without the use of additional reduction processes. In-situ insertion of the TiO(2) layer between rGO sheets dramatically increased the conductivity and carrier mobility despite the insulating properties of amorphous TiO(2). The TiO(2) situated between rGO sheets also induced significant hole doping. Electrical hysteresis caused by adsorbed water molecules and residual oxidative moieties in the rGO nanosheets vanished due to TiO(2)-assisted screening of charged impurities. These effects decreased the thermal carrier activation energy and increased the density of states at the Fermi level. Ambipolar transport properties were converted into unipolar-like hole transport characteristics by extensive hole doping in the TiO(2) layer.