Comprehensive understanding of water-driven graphene wrinkle life-cycle towards applications in flexible electronics: A computational study

The presence of wrinkles in Graphene Nanoribbons (GNR) and other two-dimensional (2D) materials significantly alter their mechanical, electronic, optical properties, which can be either beneficial or detrimental. Experimentally, it has been observed that during the commonly used growth process of GNR, water molecules, sourced from ambient humidity, can be diffused in between GNR and the substrate. The water diffusion causes wrinkle formation in GNR, which influences its properties. Furthermore, the diffused water eventually dries, creating the alteration not only in the geometry of Wrinkled Graphene Nanoribbons (WGNR) but also its features. Computational analysis of these phenomena can provide an atomistic-level understanding of the phenomena. Therefore, in this work, Molecular Dynamics (MD) simulations are performed to model the water diffusion and evaporation in between GNR and its substrate, and their effect on wrinkle formation and dynamics. Additionally, Density Functional Theory (DFT)-based analysis is used to characterize the difference in the electronic structure of WGNR caused by the change in wrinkle geometry. Our study reveals that the initially distributed wrinkles tend to coalesce to form a localized wrinkle whose configuration depends on the initial wrinkle geometry and the amount of diffused water. The wrinkle configuration changes upon drying, while it remains static until the complete drying. The movement of the localized wrinkle is the combination of three fundamental modes - bending, buckling, and sliding. The stress analysis reveals that the maximum stress is at the base of the wrinkle, and its magnitude is always below the plasticity limit. The DFT results provide insight into the potential of using the wrinkles to control the direction of electron flow for the applications in flexible electronics.
Comment: Main Paper 23 pages, 13 figures