Investigation of the influence of defects on the nanomechanical properties of graphene by multifrequency atomic force microscopy

在这个项目中，将开发一种方法，可视化的机械样品属性直接出平面和平面内。因此，将实现基于扫描力显微镜的多频技术，其中用于形貌采集的反馈参数是类似于间歇接触模式的悬臂梁的弯曲本征模式的振幅。此外，光热激发第二弯曲和扭转振荡。弹性和耗散的相互作用可以从各自模式的频移和激励振幅中提取。该方法将用于石墨烯上，以确定这种非凡材料的基面上的纳米机械特性。研究的对象是人工缺陷对材料力学性能的影响。特别地，应该解决以下问题：石墨烯的局部弹性模量如何通过引入sp3缺陷和空位而改变。在石墨烯的纳米级和微观力学性能之间建立经验关系是否可行？这对于评估石墨烯是否适合作为电子和机械设备的组件特别重要。此外，还应研究缺陷的纳米力学性能是否会因某些环境中的老化而随时间变化。

In this project, a method will be developed that visualizes mechanical sample properties directed out-of-plane and in-plane. Thus, a scanning force microscopy based multifrequency technique will be realized where the feedback parameter for the topographical acquisition is the amplitude of the flexural eigenmode of the cantilever similar as for the intermittent contact mode. In addition, a second flexural and a torsional oscillation is photothermally excited. The elastic and dissipative interactions can be extracted from the frequency shift and excitation amplitude of the respective modes. The method will be employed on graphene to determine the nanomechanical properties across the basal plane of this extraordinary material. The change of the mechanical properties with artificially induced defects is the object of investigation. In particular the following question should be addressed: How does the local elastic modulus of graphene change by the introduction of sp3-defects and vacancies. Is it feasible to establish an empirical relationship between nanoscopic and microscopic mechanical properties of graphene? This is particularly important to assess if graphene is suitable as component for electronic and mechanical devices. Additionally, it should be investigated if the nanomechanical properties of defects change with time due to aging in certain environments.