Oxide-on-graphene field effect biosensors

Nanoelectronics-based detection schemes offer fast and label-free alternatives to bioanalysis. Here we report on the design, fabrication, and operation of ion-sensitive field-effect biosensors using large-area graphene sheets synthesized by chemical vapor deposition. The graphene transducer channel has a high carrier mobility of approximately 5000cm$^{2}$/Vs. Our oxide-on-graphene design uses thin HfO$_{2}$ and SiO$_{2}$ films to passivate the graphene channel and electrodes from electrolyte and uses the top SiO$_{2}$ surface for sensing and linker chemistry. The pH sensitivity of the bare SiO$_{2}$ is measured to be 46mV/pH, in good agreement with literature results. We demonstrate the silanization of the SiO$_{2}$ surface with aminopropyl-trimethoxysilane (APTMS). The pH sensitivity of the APTMS-functionalized SiO$_{2}$ is measured to be 43mV/pH. By applying the solution gate voltage in pulse, we eliminate hysteresis in the transfer curve of the graphene channel, which is a common challenge in achieving high-solution detection using nanostructure-based field effect sensors. The amine-functionalized SiO$_{2}$ surface can be further functionalized with bio-probes to perform the detection of specific binding events such as DNA hybridization.