Development of graphene-based ionizing radiation sensors

We present the first steps to develop radiation sensors based on the graphene field effect transistor technology.Such a sensor exploits the ambipolar behavior of graphene near its Dirac point and it is not dependent oncollecting charges, but it senses ionizing radiation trough the change in conductivity of the graphene layerinduced by changes of the electric field. We designed the layout of the sensors with the help of SentaursTCAD. We simulated static operations and the dynamic response to radiation and calculated the source–drain current through the graphene layer with a quasi-analytical model. The transistors were produced at theNational Enterprise for nanoScience and nanoTechnology by depositing high quality graphene on silicon chipsmanufactured by the Fondazione Bruno Kessler foundry. To reduce the high contact resistance between grapheneand aluminum contacts caused by oxidation of the aluminum surface, we used gold/chromium interfaces. Weinvestigated the sensors behavior by mean of electrical measurements, extracting the graphene properties, suchas mobility and doping. We observed modulation of the source–drain current, determined the Dirac point andfound the optimal voltage levels to be sensitive to pulsed IR laser light and훽-particles.