Research on in-situ oxidation of the copper covered by graphene

Graphene-based photodetector with ultra-high responsivity is an important research field of low dimensional optoelectronics applications. A number of hybrid graphene/quantum dots photodetectors with high responsivity have been developed. In this paper, the in-situ oxidation of the copper covered by monolayer graphene was studied under the oxygen-rich condition. It is found that the oxidation process first occurs at the grain boundary of graphene and the oxide is Cu2O. The intensity ratio of 2D band and G band of graphene is ~3, and the defect D peak is absent, which indicates that the quality of graphene is not damaged during the oxidation process. The hybrid transfer-free graphene/Cu2O photodetector is fabricated by in-situ copper oxidation. Under 450 nm laser illumination, the responsivity of the photodetector is 3.8×106 A/W at 0.2 V. The gain is up to 1.1×107 , which is due to the modulation of Fermi level of graphene by Cu2O quantum dots. The photodetector exhibits the specific detectivity of 3.6×1011 Jones. This work opens a feasible pathway to develop transfer-free graphene/semiconductor photodetector with high responsivity.