Local-strain-induced charge carrier separation and electronic structure modulation in zigzag ZnO nanotubes: Role of built-in polarization electric field

By use of first-principles calculations, we examine the effects of uniaxial strain and radial deformation on electronic properties of zigzag ZnO nanotubes. Our results show that local strain or deformation can cause significant reduction of the band gap owing to quantum-confined Stark effect induced by the built-in electric polarization. Driven by this polarization field, the charge carriers are separated with hole and electron states localized on the opposite ends of the tube. In sharp contrast, uniform tensile strain tends to widen the band gap while compressive strain and radial deformation have negligible effects on the band gap, although they can produce considerable shifts in edge-state energies. The present results reveal the key role of local strain as an effective tool in tuning the properties of zigzag ZnO nanotubes. Such local-strain-induced electronic structure modulation suggests an effective approach to design and implementation of ZnO nanotubes in nanoscale devices.