ABSTRACT
In this book, we mainly reviewed the works performed by our research group. In fact, in its thin-film form, ZnO has been applied to many devices, for example, as the transparent conductor in solar cells, varistors, etc. ZnO research was revitalized about 10 years ago following the works carried out by Z. K. Tang, P. D. Yang, Z. L. Wang, and M. Kawasaki.1-6 As a result of the inspiration from their works, ZnO was highly regarded as a potential optoelectronic material in light-emitting devices. The easy realization of one-dimensional nanowire form triggered the explosive worldwide research on this material. However, we have to admit that most researches focus on the material synthesis/fabrication, but not devices. Thus, it is important and interesting to introduce the readers to the device aspects of ZnO, which is indeed one of the most important functional materials. We hope that in this book, the readers could see a wide range of devices made of ZnO, especially ZnO nanostructures. Most devices discussed in the book make use of the large surface area of ZnO nanostructures. It is worth mentioning that although we could expect quantum confinement effect in the future, so far report in this aspect is still rare. The reason is that ZnO nanowires are generally more than 10 nm in diameter when fabricated (typically a few hundred nanometers in diameter), which makes them bulkier. We would like to suggest the readers that they pay attention to some ZnO nanodevices, including field emission nanodevices, electronic papers, and nanorod light-emitting diodes. These devices
have a good prospect in practical applications in terms of cost and performance. It is also worth mentioning that Z. L. Wang has invented a nanogenerator based on ZnO nanowire, making use of the piezoelectric properties of ZnO.7 With the nanowire form, a so-called research domain of nanopiezotronics can be generated.8 In our opinion, ZnO nanostructure and nanodevice research is a very good example of how future multidisciplinary research needs to be performed. Clearly, we have to involve physics, chemistry, electronics, and photonics in ZnO nano-research. In fact, this has to be the general methodology for future nanotechnology research, i.e., at the nanoscale, the blurred difference between different disciplines. Last, it is worth mentioning that ZnO, as one of the most studied functional materials, would bring us more excitement in the future, as the ZnO nanodevice research is still at its beginning.
