High-yield fabrication of graphene chemiresistors with dielectrophoresis

We demonstrate a simple, low-cost, but effective approach to deposit graphene on silicon wafers with dielectrophoresis. With a comb-shaped electrode design, graphene sheets can be actively captured between electrodes. Dielectrophoresis proves effective in depositing a large-scale array of graphene on desired locations. The deposition of semiconducting single-walled carbon nanotubes (s-SWNTs) with the same approach is also studied to compare the two forms of carbon-based nanomaterials. The graphene deposition has a lower success rate (approximately 62) than s-SWNTs (100) to cover the comb fingers due to the 2-D sheet structure and larger dimensions of the material. The assembled graphene sheets can successfully bridge over the electrode gap to create functional, ready-to-use electronic devices. The dielectrophoretically deposited graphene is used as the semiconducting material in a liquid-gated field-effect transistor, and it demonstrates p-type characteristics with holes as the majority charge carriers. When used in two-terminal chemiresistors, the deposited graphene demonstrates high sensitivity toward pH values in liquid. The resistance of graphene is inversely proportional to the pH value of the solution in the range of 5-9 with the pH sensitivity of 17.5 /decade. The high-precision, high-yield deposition provides a practical approach for the fabrication of future graphene electronic devices and sensors.