| ZnO nanobelts are a group of quasi-one-dimensional nanostructures that have a unique rectangle-like cross section, with typical widths of several hundred nanometers, width-to-thickness ratios of 1 to 10, and lengths of tens to hundreds of micron meters. They are the promising candidates for nanoscale ultrahigh frequency resonator, nanosensors and nanoactuators due to their well-defined geometry, prefect single crystallinity and excellent piezoelectric properties. In this study, we revealed the following unique nanomechanical and electromechanical properties of a single ZnO nanobelt using Atomic Force Microscopy. (i) Elastic modulus, hardness and fracture toughness of the ZnO nanobelt are much smaller than its bulk counterpart. (ii) Strong photoinduced elastic effect is observed in ZnO nanobelt, while there is no effect in its bulk counterpart. (iii) The effective piezoelectric coefficient, d33, of ZnO nanobelt is frequency dependent and much higher than that of its bulk counterpart. These unique properties cannot be accounted for using macroscale theory such as continuum mechanics, while they may be related to surface effects thanks to the high surface to volume ratio of ZnO nanobelt. One of the consequences of our findings is that these properties are fundamental to the real applications and may be universal phenomena in quasi-one-dimensional semiconducting nanostructures, which are becoming building blocks of MEMS (Micro Electromechanical Systems) and NEMS (Nano Electromechanical Systems). |
