Capacitive micromachined ultrasonic transducer (CMUT) with graphene membrane

This paper presents fabrication methods using graphene as a membrane that was thermally bonded on top of the CMUT cavity formed by patterned photoresist. The impedance measurement result showed graphene CMUT exhibit high resonance frequency when membrane size remains large. Previously we had also reported such a graphene CMUT with stiction problem caused by a graphene transfer technique. In the newly fabricated CMUT, different methods are used to protect the graphene membrane and stiction problem was solved by bonding in air. The resonant frequencies of the fabricated graphene CMUT with membrane sizes of 500µm and 90µm are found to be 45MHz and 63MHz respectively in air.