Polar-surface dominated ZnO nanobelts and the electrostatic energy induced nanohelixes, nanosprings, and nanospirals

We report the controlled synthesis of free-standing ZnO nanobelts whose surfaces are dominated by the large polar surfaces. The nanobelts grow along the a axis, their large top/bottom surfaces are the ±(0001) polar planes, and the side surfaces are (011̄0). Owing to the positive and negative ionic charges on the zinc- and oxygen-terminated ±(0001) surfaces, respectively, the nanobelts form multiloops of nanohelixes/nanosprings/nanospirals for the sake of reducing electrostatic energy introduced by the polar surfaces as well as balancing the difference in surface tension. The polar surface dominated ZnO nanobelts are likely to be an ideal system for understanding piezoelectricity and polarization induced phenomena at nanoscale.