Detection of Ultraviolet Light by Graphene Oxide Derived from Epitaxial Graphene on SiC and Graphite

Because of their tunable band gap, flexibility, and high surface-to-volume ratio, two-dimensional materials have appeared as the most promising materials for ultraviolet (UV) light sensors. Here, we report the detection of UV light by oxidized epitaxial graphene (EG) formed on the Si-face of the SiC substrate and graphene oxide (GO) produced by Hummer oxidation of graphite. Both epitaxial graphene oxide (EGO) and GO were characterized by Raman and X-ray photoelectron spectroscopy, and the devices were made simply by placing two parallel copper electrodes onto the graphene oxide layers. Irradiation of UV light onto the graphene oxides was realized by the real-time current measurements between two electrodes at a fixed bias of 1 V. The sudden upward jump of the current (Ids) upon UV light irradiation was observed in both EGO- and GO-based devices, which were returned to the original value, while the UV source was turned OFF. The photocurrent (I _ph), the magnitude of the current jump by the UV irradiation, for EGO, was estimated at 8 mA with a channel distance of 2 mm and UV power of 80 mW/cm². The I _phlinearly increases with UV power. In the case of GO, I _phwas estimated at 0.2 nA with a similar setup. The photoresponse time and responsivity for EGO are ∼11 s and 5.6 A/W, respectively, which are higher than those of GO. The quantum efficiencies (η) for EGO and GO are calculated as 1907 and 2.3 × 10^-6 %, respectively, with an incident power of UV light at 9 mW/cm^-2. Because of the advantages of the EG on SiC concerning the stability and wafer scale growth, the present study is expected to lead the development of lab-on-chip-based ultrasensitive UV sensors.