A Transfer-Free Approach for Preparation of Edge-Exposed Multilayer Graphene Micromesh and Study on Its NO₂ Sensing Performance

Abstract

Two-dimensional (2D) graphene holds enormous potential as a future candidate for gas sensors, not only coming from its vast surface area, but also contributed by the highly active edges, which have promptly become a research hotspot. In this work, we developed a novel transfer-free approach to prepare chemical vapor deposited (CVD) edge-exposed multilayer graphene micromeshes by pre-patterning the molybdenum (Mo) catalyst through photolithography. Our facile and efficient approach provides fewer steps, higher accuracy, and virtually unrestricted patternable features. It is also semiconductor manufacturing compatible with precise alignment and positioning for wafer-scale mass production. Graphene micromeshes with different thicknesses were prepared and studied for NO₂ (∼1 ppm) gas sensing. Despite the reduction in the surface area, the micromeshes still delivered an enhancement of the overall response (for 20 min CVD graphene, from 0.692% to 0.744%). Based on our proposed calculation model, which hypothetically separates the response from the surface and edges, thinner multilayer graphene edges exhibited exceptionally high sensitivity compared to the surface due to higher reactivity and edge-facilitated gas adsorption. Our pre-patterning method and study of graphene micromesh-based prototype gas sensors provide insights into the role of the edges of multilayer graphene, which could potentially be a vital part for future high-performance gas sensors.