Geometrically necessary dislocations in three-point bent Au nanowires studied by in-situ Laue microdiffraction

In the recent past, the mechanical properties of low-dimensional materials have attracted enormous attention. The yield strength for defect free nanostructures was shown to approach the ultimate limit of the respective material. Despite numerous experimental and theoretical works the mechanical behavior and the onset of plasticity at the nanoscale is still not fully understood. To shed additional light on this topic, in situ experimental setups are being designed for monitoring the evolution of the structures during mechanical deformation.

The elastic and plastic deformation of a gold nanowire tested in three-point bending configuration using the custom-built scanning force microscope SFINX was studied in-situ by Laue microdiffraction. A new data treatment method, which bases on the integration of diffraction patterns recorded along the deformed nanostructure, was developed visualizing both movement and shape of the diffraction peaks as a function of the measurement position. Besides bending, torsion is evidenced during the elastic deformation originating from a misalignment of the SFINX-tip of the order of 60 nm with respect to the nanowire center. The plastic deformation was found to be governed by the storage of geometrically necessary dislocations. Analyzing the shape of the diffraction peaks, the activation of two unexpected slip systems is found which does not coincide with the slip systems with the highest resolved shear stress. These unexpected slip systems are probably related to the dislocation nucleation process at the clamping point, which is influenced by the local curvature.