Dielectrophoretic integration of single- and few-layer graphenes

The dielectrophoretic integration of single- and few-layered graphenes from three distinct graphene suspensions is presented, enabling the parallel assembly of individual two-dimensional nanostructures at predefined locations. The first suspension is an aqueous solution of graphene oxide, the second is ultrasonically exfoliated pristine graphene in N-methyl-pyrrolidone (NMP), and the third is exfoliated graphene in surfactant-stabilized 1 wt % aqueous SDBS solutions. The most crucial aspect for the successful thin flake deposition is the solution quality of the exfoliated graphene. After dielectrophoresis, single-layer graphene oxide is placed between the electrodes, which, while initially insulating, recovers its electrical conductivity following thermal reduction. From the chemically unmodified graphene-NMP solutions, the directed assembly of electrically active few-layer graphene flakes is realized, with flake thicknesses in the range 8-30 nm. Liquid phase exfoliation in water-surfactant solutions yields significantly thicker flake dimensions from 50 to several 100 nm due to the higher enthalpy of mixing in the dispersion. To achieve single-layer pristine graphene dielectrophoretic deposition, higher solution qualities must be available, consisting largely of single-layer graphene sheets. The reported research provides an important framework for parallel fabrication approaches of graphene-based devices.