10 - Surface and interface effects: properties of nanostructured ZnO

Abstract

This chapter presents a comprehensive overview of the current research addressing the surface and interface effects on the various properties of ZnO nanostructures and their potential applications. The impact of surface and interfaces in controlling materials’ properties is significant in the case of nanostructured confined systems due to the large enhancement of surface-to-volume ratio. To achieve the advanced applications of ZnO nanostructures utilizing the surface/interface effect, it is essential to understand how the materials’ properties are being influenced by the reduction of their dimensions. Various properties of ZnO nanostructures are described in detail, especially the surface energy, surface and interface chemistry, along with the use of surface defects in controlling its electronic structure, optical, and transport properties, which have a strong influence on the behavior at heterointerfaces (or heterojunctions) of the system. In this context, the important role of the different native defects at the surfaces and interfaces of ZnO nanostructures, to produce the distinct visible emissions, has been discussed elaborately. Based on the discussions on various experimental and theoretical analyses, it turns out that the impact of defects and surface states can crucially affect the inherent electronic and optical properties of ZnO nanostructures, thus influencing the properties of heterointerfaces between ZnO nanostructures and other active materials in devices, and in turn the device efficiency. Overall, suitable surface/interface modification manifests alteration and tuning of optical, electrical, and electronic properties of ZnO nanostructures, thus indicating potential applications in light-emitting devices, photodetectors, solar cells, batteries, gas sensors, photocatalysis, etc.