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We demonstrate graphene-on-diamond field effect transistor (FET) actions modulated by optically excited charge state of nitrogen-vacancy (NV) centers in diamond. Palladium (Pd) metal contacts on graphene serve as the source and the drain. Negative charge state NVcenter in diamond serves as the gate with diamond being the gate dielectric and produces an electric field to enhance the hole concentration in the graphene channel. The conductivity of graphene varies with negative charge state NVcenter, resulting in differential conductance. The negative gate bias is removed when a NVcenter is converted to an NV o center. P-type graphene channel exhibits positive differential conductance under illumination by a blue (405 nm) laser beam while on the contrary negative differential conductance by a red (633 nm) laser beam. Furthermore, by simultaneous illumination of both blue and red laser beams, effects on differential conductance decrease according to the relative intensity of the two laser beams. Graphene FETs with wavelength dependent multiple optical inputs and one electrical output in response to the charge state of NV centers in diamond has been reported.

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