Although ZnO nanowires with the [0001] growth direction have potential applications as piezoelectric diodes, the performance of these nanodevices is low because the on/off current ratio is only about 9.3 even if there is a large deformation of the ZnO nanowire. Furthermore, because the applied forces have not been quantified in the reported nanodevices, it is difficult to select the proper applied force in practical applications of these nanodevices.

Now, a research group in China, led by Yue Zhang from the University of Science and Technology Beijing, has managed to improve the performance of the device by using single polar-surface-dominated ZnO nanobelts. The team's diode exhibits a high on/off current ratio of about 1.6 × 104 and a low threshold force of about 180 nN at 4.5 V bias.

"We used a Schottky contact instead of an Ohmic contact to depress the off current and used polar-surface-dominated ZnO nanobelts instead of ZnO nanowires with the [0001] growth direction to enhance the on current under the small applied forces induced by an AFM tip" Yue Zhang told

Currently, ZnO nanomaterials, such as nanowires, nanobelts, nanosprings, nanocombs and tetraleg ZnO nanorods, have been successfully synthesized by the team. The next task is to fabricate and evaluate various nanodevices based on these nanostructures. These investigations pave the way for the application of ZnO nanomaterials as nanoscale electric and electromechanical devices.

The researchers presented their work in Nanotechnology.