Atomistic Mechanisms of Ultralarge Bending Deformation of Single-Crystalline TiO2-B Nanowires

Titanium dioxide (TiO2) nanowires (NWs) are usually considered to be brittle semiconductor materials, which limits their use in strain-related applications, even though they are already widely applied in various fields. Based on observations using an in situ transmission electron microscopy method, we find, for the first time, that individual crystalline TiO2 NWs with a bronze phase (TiO2-B) can exhibit an ultralarge elastic bending strain of up to 18.7%. Using an in situ atomic-scale study, the underlying mechanisms of the ultralarge bending deformation of TiO2-B NWs under the ⟨111⟩{100} system are revealed to be governed by lattice shear and rich dislocation movements; the lattice shearing is supported by numerical simulations. Locally, large-scale sheared lattices with a shear strain of up to 10.7% can be observed in a bent NW. It is believed that the large-scale lattice shearing deformation offers the NW the ability to absorb a large bending energy so that fast dislocation aggregation and propagation are avoided. Therefore, the TiO2-B NWs can endure an ultralarge bending strain without crack formation or amorphization. However, it is found that the lattice shear-governed bending mechanism is not applied in the ⟨010⟩{100} system. These results are able to provide more opportunities for the strain engineering of TiO2 NWs and also help promote the potential applications of TiO2 NW-based flexible devices.