On the Origin of Nonclassical Ripples in Draped Graphene Nanosheets: Implications for Straintronics

Abstract

Ever since the discovery of graphene and subsequent explosion of interest in single-atom-thick materials, studying their mechanical properties has been an active area of research. Atomistic length scales often necessitate a rethinking of physical laws, making such studies crucial for understanding and ultimately utilizing material properties. Here, we report on the investigation of nanoscale periodic ripples in suspended, single-layer graphene sheets by scanning tunneling microscopy and atomistic scale simulations. Unlike the sinusoidal ripples found in classical fabrics, we find that graphene forms triangular ripples, where bending is limited to a narrow region on the order of a few unit cell dimensions at the apex of each ripple. This nonclassical bending profile results in graphene behaving like a bizarre fabric, which regardless of how it is draped, always buckles at the same angle. Investigating the origin of such nonclassical mechanical properties, we find that unlike a thin classical fabric, both in-plane and out-of-plane deformations occur in a graphene sheet. These two modes of deformation compete with each other, resulting in a strain-locked optimal buckling configuration when draped. Electronically, we see that this in-plane deformation generates pseudo electric fields creating a ∼3 nm wide pnp heterojunction purely by strain modulation.

Modeling and simulations for 2D materials: a ReaxFF perspective

“…Comparisons between flat and rippled graphene on copper surface showed that the binding of copper atoms is more favored by rippled graphene. The examples showing the good agreement in describing graphene bending, ripple formation as well as binding characteristic for copper surface were recently reported [29,317]. With the use of previously published parameter set where C-Cu interactions were optimized for Cu-metal surface catalysis [318], the authors were able to reproduce experimentally measured graphene draping and rippling angle at the copper step edges and also show better binding properties of the rippled graphene.…”

“…2D materials exhibit many unique properties and play a pivotal role in a wide range of research areas such as sensors [319,320], desalination membranes [34,317,321,322], energy storage [323,324] and biomedical applications [325][326][327]. However, the mechanical properties of 2D materials cannot be accurately inferred from the chemical composition.…”

Mechanical, electronic, optical, piezoelectric and ferroic properties of strained graphene and other strained monolayers and multilayers: an update

“…Triangular periodic ripples in suspended graphene were found in another work. There, bending was limited to a region few unit cells wide [94]. Triangular ripples are unlike the sinusoidal ripples found in fabrics.…”

Transport Property of Wrinkled Graphene Nanoribbon Tuned by Spin-Polarized Gate Made of Vanadium-Benzene Nanowire

“…Governed by the supernal flexibility of graphene, using the surface topographical corrugations like wrinkles [24,25], ripples [26][27][28][29][30][31][32][33], folds [34], or crumples [35][36][37][38] to exploit exceptional properties is an amazing technique in experiments. In particular, high-quality conformal wrinkles in graphene can be controllably fabricated with expected orientations, wavelengths, and amplitudes by using various simple methods, which is of paramount importance for potential applications in flexible electrodes, sensors, and actuators [39][40][41][42][43][44].…”