Nanosprings
Scanning electron-microscopy images of nanohelixes of single-crystal piezoelectric ZnO nanobelts. The larger top and bottom surfaces of the nanobelt are dominated by the (0001) polar surfaces. The helical structure is induced to minimize the electrostatic energy of the nanobelt. The nanobelt is ~5 nm thick and 20 nm wide. The diameter of the helixes is ~ 1 µm. Wang and Kong say this is the first report of piezoelectric nanobelts and nanohelixes made from a single crystal.