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

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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.