Monoatomically Thin Films: Nonlinear Mechanical Response and Mechanical-Electrical Coupling

这项建议描述了一项将实验和理论相结合的计划，以扩大对石墨烯和其他二维材料在超高应变下的机械性能和电子结构的理解。这一建议建立在两个PI最近发表在《科学》杂志上的工作基础上，在该工作中，在破坏之前获得了前所未有的大弹性应变，约为25%。拟议的工作包括三个建立在这些结果基础上的实验推进。首先，通过对已知晶格取向的石墨烯纳米带进行纳米压痕测试，将测量石墨烯的方向相关非线性力学性能，直至超高应变。其次，这些技术将被推广到其他二维材料上。第三，研究了这些材料在超高应变下的电学性质。横切的理论推力将探索从头算理论预测这些结果的能力，从头算结果将被用于对连续介质模型进行参数化。超高应变态既是科学和技术的前沿。鉴于石墨烯正在被研究的许多潜在应用，从太空电梯到电子电路，这项研究的结果可能会有广泛的应用。此外，这些二维材料的简单性使它们成为从原子水平到连续介质的多尺度建模的主要试验台。这项工作将资助两名研究生，他们将学习广泛的技能，包括纳米制造、纳米材料合成、纳米机械测试和理论。此外，这项工作对本科生和高中生来说非常方便：在助学金期间，私人投资机构将支持两名本科生和至少一名高中生。最后，PIS将开发模拟和动画，以在国家纳米科学与工程学习与教学中心维护的NanoEd资源门户网站上建立教学模块。

This proposal describes a plan for combined experimental and theoretical efforts to expand the understanding of mechanical properties and electronic structure of graphene and other two-dimensional materials under ultrahigh strain. This proposal builds upon recent work published in Science by two of the PIs, in which unprecedentedly large elastic strains of approximately 25% were obtained prior to failure. The proposed work includes three experimental thrusts that build on these results. First, the directionally-dependent nonlinear mechanical properties of graphene will be measured up to ultrahigh strains by performing nanoindentation tests of graphene nanoribbons with known lattice orientation. Second, these techniques will be carried over to other two-dimensional materials. Third, the electronic properties of these materials will be studied under ultrahigh strain. A crosscutting theoretical thrust will explore the ability of ab-initio theory to predict these results, and the ab-initio results will be used to parameterize a continuum model.Ultrahigh strain strain states are both a scientific and technological frontier. Given the many potential applications for which graphene is being studied, ranging from space elevators to electronic circuits, the results from this study will likely have widespread applications. Furthermore, the simplicity of these two-dimensional materials makes them a prime testbed for multi-scale modeling, ranging from the atomic level to the continuum. This work will sponsor two graduate students, who will learn a broad range of skills, including nanofabrication, nanomaterials synthesis, nanomechanical testing, and theory. In addition, the work is highly accessible to undergraduate and high school students: the PIs will support two undergraduates during the period of the grant, and at least one high school student. Finally, the PIs will develop simulations and animations to build a teaching module on the NanoEd resource portal maintained by the National Center for Learning and Teaching in Nanoscale Science and Engineering.