Local strain effects on bandgap energy in flexible <i>h</i> -WO3 nanowires

According to theoretical predictions, local strain in the bent regions of flexible nanowires can alter their electronic structure. However, the experimental validation of such strain-induced effects remains elusive. In this study, we established a clear correlation between local structural deformation and electronic properties in bent hexagonal-WO3 nanowires using four-dimensional scanning transmission electron microscopy and electron energy loss spectroscopy. Although a simple geometric bending model predicts an expansion of the (0001) lattice spacing on the outer side of the bend, our direct observations revealed a larger expansion than predicted. This lattice expansion was accompanied by a significant reduction in bandgap energy. We employed density functional theory calculations and crystal orbital Hamilton population analyses to provide a theoretical framework for these findings. These results provide direct experimental evidence of strain-induced modulation of the electronic structure in metal oxide nanowires.