Challenges of low-temperature synthesized ZnO nanostructures and their integration into nano-systems

From the multitude of nanostructures under active research, Zinc Oxide (ZnO) nanowires (NWs) have attracted enormous attention due to the materials’ unique electrical, optical, mechanical and piezoelectric properties. Since 10 years, piezoelectric nanocomposites based nanogenerators (NGs) have gained extensive attention for their applications in mechanical energy harvesters and self-powered tactile sensors. Other emerging applications of ZnO single-crystalline NWs are high performance field-effect transistors (FETs) targeting low power applications, or highly sensitive FET based biosensors. A possible route to reduce the price of these devices is using low cost manufacturing over large-area substrates, and hydrothermal synthesis appears as a promising solution. First we will present here a facile, cost-effective and industrially scalable process flow for the fabrication of high performance stretchable nanogenerators (SNG) on polydimethylsiloxane (PDMS) substrate. The SNG device exhibits excellent performance with a 35 µW peak output power achieved from a 8 cm2 device under a pressure of 100 kPa. Moreover, we investigated ZnO nanostructures for FETs on both conventional rigid (Si/SiO2) and unconventional flexible substrates (polyethylene terephthalate PET). The electrical characterization results (field-effect mobility, on/off current ratio, sub-threshold swing) reveal the potential of the present nanomaterials for high performance electronics. The key issues of efficient NGs and FETs will be presented, taking into account the technological constraints. This opens horizons for integrating high quality ZnO nanostructures as active semiconducting elements for autonomous flexible electronic circuits.