Fully Suspended Reduced Graphene Oxide Photodetector with Annealing Temperature-Dependent Broad Spectral Binary Photoresponses

A series of fully suspended reduced graphene oxide (RGO) photodetectors were fabricated based on free-standing thermally reduced graphene oxide (GO) thin films with various annealing temperatures (from 200 to 1000 degrees C). A new phenomenon was found that under ultraviolet (375 nm) to near-infrared (1064 nm) lasers irradiations, the photodetector consisting of fully suspended thermally reduced graphene oxide thin film and Au interdigital electrodes possess positive or zero or negative response depending on the annealing temperature of GO. This may originate from the competition between annealing temperature-dependent the positive photoresponse from RGO and the negative photoconductivity of Au interdigital electrodes. The annealing temperature-dependent wide spectral binary photoresponse offers a good thinking for designing RGO-based light triggered logic devices. Moreover, upon visible (405 nm) to near-infrared (1064 nm) irradiations, all fully suspended RGO detectors prepared at various annealing temperatures exhibit fast photoresponse, that is, rise time is only tens of milliseconds, which are 1-4 orders of magnitude faster than the reported photodetectors based on supported RGO film and are on the same order of magnitude as the supported CVD-grown and supported mechanically exfoliated graphene photodetectors. The fast photoresponse originates from the fully suspended construction of device and the thin thickness of film, which provides a new design idea for fast response RGO-based device.