Lightweight, simple and flexible self-powered photodetectors are urgently required for the development and application of advanced optical systems for the future of wearable electronic technology. Here, using a low-temperature reduction process, we report a chemical approach for producing freestanding monolithic reduced graphene oxide papers with different gradients of the carbon/oxygen concentration ratio. We also demonstrate a novel type of freestanding monolithic reduced graphene oxide self-powered photodetector based on a symmetrical metal–semiconductor–metal structure. Upon illumination by a 633-nm continuous wave laser, the lateral photovoltage is observed to vary linfearly with the laser position between two electrodes on the reduced graphene oxide surface. This result may suggest that the lateral photovoltaic effect in the reduced graphene oxide film originates from the built-in electric field by the combination of both the photothermal electric effect and the gradient of the oxygen-to-carbon composition. These results represent substantial progress toward novel, chemically synthesized graphene-based photosensors and suggest one-step integration of graphene-based optoelectronics in the future.
We have demonstrated the dependence of the metal-assisted chemical etching of GaAs on catalyst thickness. For ultra-thin (3~10 nm) Au catalysts, we found that electrochemically generated nano-pinholes in the metal catalyst not only enhance important catalytic effects in redox reactions, but also act as a diffusion pathway for the reactants (H2SO4) and products (Ga3+ and Asn+ ions) for chemical etching oxidized GaAs.
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