| AVS 63rd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Monday Sessions |
| Session 2D+MI+SA-MoM |
| Session: | 2D Materials Characterization including Microscopy and Spectroscopy |
| Presenter: | Yudi Tu, Kyoto University, Japan |
| Authors: | Y. Tu, Kyoto University, Japan T. Utsunomiya, Kyoto University, Japan T. Ichii, Kyoto University, Japan H. Sugimura, Kyoto University, Japan |
| Correspondent: | Click to Email |
Reducing graphene oxide (GO), a highly oxidized graphene derivatives, by utilizing light irradiation has drawn great attention, due to its flexibility to locally fabricating conductive patterns and tuning the electrical property. We have demonstrated the reduction of GO under the 172 nm vacuum-ultraviolet (VUV) irradiation under high vacuum and combined it with mask photolithography to make reduced graphene oxide (rGO) conductive pattern at sub-μm scale.1,2 The recovery of electrical conductivity at the reduced regions was confirmed by conductive-probe atomic force microscope (CAFM). However, further researches by applying micro Raman spectroscopy (μRS), scanning tunneling microscopy (STM) and CAFM have revealed that the pristine defects induced by the harsh oxidative synthesis of GO is unable to be repaired. On purpose to enhance the electrical conductivity of rGO pattern, generating more conductive paths for the carriers’ transportation is of great importance. In this presentation, we will demonstrate the enhanced electrical conductivity in multilayered rGO sheets. The nanoscale conductive sp2 domains in rGO are connected to construct 3-dimensional conductive paths between the multilayered sheets.
The GO-coated Si substrate was irradiated by the VUV light in the high vacuum (< 10–3 Pa) chamber. The CAFM current mapping revealed that GO and the derived rGO were heterogeneous hybrids of both conductive and insulating domains. Interestingly, besides the nanoscale domains distribution revealed by the previous μRS and STM results, the microscale domains distribution was also observed within the sheets, which was attributed to the uncertainly harsh oxidation synthesis. The CAFM current mapping showed obvious enhancement on the electrical conductivity of bi-layered rGO comparing with the single-layered rGO. A triangle approximate model was applied to estimate the lateral electrical conductivity of rGO sheets. It was found that the tip contact area showed no clear influence on the lateral electrical conductivity. By further measuring the current signals from both bi-layered and single-layered rGO sheets, it was found that the enhancement was not due to the parallel-connection of two rGO sheets but originated from the newly constructed 3-dimensional conductive paths between them.
(1) Tu, Y.; Ichii, T.; Utsunomiya, T.; Sugimura, H. Appl. Phys. Lett.2015, 106, 133105.
(2) Tu, Y.; Ichii, T.; Khatri, O. P.; Sugimura, H. Appl. Phys. Express2014, 7, 75101.