Mar 19, 2009
High-performance ZnO nanobelt piezoelectric diodes
Polar-surface dominated ZnO nanobelts can be used to fabricate piezoelectric diodes. The diodes show a high on/off current ratio and a low threshold force. These devices could be used as random access memory units.
Although ZnO nanowires with the  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  growth direction to enhance the on current under the small applied forces induced by an AFM tip" Yue Zhang told nanotechweb.org.
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.
About the author
Y Yang is a PhD student based at the research lab of nanoscale materials and technology led by Prof. Yue Zhang at the department of materials physics, University of Science and Technology Beijing, China. The research lab is currently exploring ZnO nanostructures, together with electrical, optoelectronic and electromechanical measurements, and the application of the resulting nanostructures.