Applications of ZnO Nanostructures

ZnO nanobelts were also considered for applications as nanosensors and tianoac-tuators. The piezoelectric coefficient of a ZnO nanobelt was measured using AFM with a conductive tip [54]. For this purpose, ZnO nanobelts were dispersed on a (10 0) Si wafer coated with Pd. The nanobelts were then coated with 5 nm layer of Pd. It was ensured that the top and bottom surfaces of the nanobelts were not short ircuited. The effective piezoelectric coefficient d33 for the (0001) surface of the nanobelts was measured by piezoresponse force microscopy. The d33 coefficient was found to vary from 26.7 to 14.3 pm with increasing frequency from 30 to 150 kHz. These 

Microelectromechanical systems (MEMS) have already transitioned to a new realm with much improved sensitivity and functionality. Further improvements are assumed within reach with nanostructures. For example, by combining MEMS technology with self-assembled nanobelts, cost-effective cantilevers with much improved sensitivity may be produced for a range of devices and applications such as force, pressure, mass, and thermal, biological, and chemical sensors. 

Semiconducting nanobelts are ideal candidates for cantilever applications, because they are structurally defect-free single crystals and provide a significant improvement in the cantilever sensitivity due to their reduced dimensions. Individual ZnO nanobelts could be aligned on Si chips to have a range of lengths and therefore resonance frequencies [3], 

In conclusion, it is clear that a wide variety of nanostructures can be produced with ZnO using relatively simple synthesis methods. These nanostructures can certainly be used for studying fundamental physics in nanoscale. Even though devices have already been demonstrated using ZnO nanostructures (see also Chapter 8), whether the advancements in technology and materials science will allow their applications to real-life devices is not yet clear. However, it is dear that ZnO is very favorable as compared to other semiconductors in that this material lends itself well to the production of nanostructures from which functional devices have already been fabricated. 

3 Wang, Z.L. (2004) Journal of Physics Condensed Matter, 16, R829. 

---

Possible applications of ZnO nanostructures are UV lasers (up to now only with optical excitation) [84], chemical sensors [85], or transparent substrates for thin film solar cells, e.g. as an alternative to Ti02 in injection type solar cells or in organic solar cells [79,86,87]. In the latter two applications the increased effective surface of arrays of ZnO nanowires leads to... 

---