Graphene Functionalization by O<sub>2</sub>, H<sub>2</sub>, and Ar Plasma Treatments for Improved NH<sub>3</sub> Gas Sensing
Sogo Iwakami, Shunya Yakushiji, Tomonori Ohba
Abstract
High Resolution Image Download MS PowerPoint Slide Graphene-based materials have gained attention for their promise in various applications owing to their two-dimensional structure. Functionalizing the graphene surface can help realize materials with noble properties. In this study, graphene was functionalized by plasma treatment in O 2, H 2, and Ar environments, and the effects on the NH 3 gas-sensing performance were evaluated. The O 2 plasma treatment induced oxidation of the graphene (i.e., graphoxide), while the H 2 plasma treatment induced hydrogenation (i.e., graphane). Raman scattering spectroscopy suggested that graphoxide had vacancy-type defects and graphane had sp 3 -type defects, while Ar-treated graphene had both types of defects. Graphane had the highest sheet resistance followed by graphoxide, Ar-treated graphene, and pristine graphene, which can be attributed to the large bandgap of 3.0 eV for graphane. In contrast, graphoxide had the best NH 3 gas-sensing performance, which indicates that NH 3 gas interacts more strongly with vacancy-type defects than with sp 3 -type defects. The results showed that functionalizing the graphene structure generated noble materials with a superior NH 3 gas-sensing performance compared with pristine graphene.