Investigation on the ion-gel dielectric characteristics for graphene transistor toward flexible and transparent devices

We systematically investigated the effect of chemical property of ion-gel on the graphene FET performances in terms of on/off ratio, Dirac point voltage, and transconductace. The chemical property of ion-gel was controlled by the various UV-crosslinking conditions for ion gel formation. Our experiments revealed that UV exposure time and composition ratio for the ion-gel dielectric play important roles in modulating graphene FET characteristics. At an optimized condition, our device showed not only very high on/off ratio (~20), but low operable gate-source voltage range (< 2 V). Besides, by taking advantages of elastic and transparent properties of our ion-gel, we demonstrated the fabrication of flexible and transparent ion-gel top-gated graphene FET on plastic substrate with high performances.