Graphene/diamond (carbon sp2-sp3) heterojunctions are demonstrated as photo-controllable memristors with photoswitchable multiple resistance states and nonvolatile memory functions. The ratio of conductivity change between the higher and lower resistance states of the junctions was ∼103. The junctions exhibit light wavelength selectivity, and the resistance states can be switched only by blue or violet light irradiation. The mechanism for the change in photoconductivity is considered to be caused by oxidation-reduction of the graphene and/or graphene-diamond (sp2-sp3) interfaces through the movement of oxygen ions by bias with photo-irradiation because they have wavelength selectivity and require air exposure for several days to exhibit memristive behavior. These results indicate that graphene-diamond, carbon sp2-sp3 heterojunctions can be used as photo-controllable devices with both photomemory and photoswitching functions.
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