ZnO, aside from TiO2, has been considered as a promising material for purification and disinfection of water and air, and remediation of hazardous waste, owing to its high activity, environment-friendly feature and lower cost. However, their poor visible light utilization greatly limited their practical applications. Herein, we demonstrate the fabrication of different aspect ratios of the ZnO nanorods with surface defects by mechanical-assisted thermal decomposition method. The experiments revealed that ZnO nanorods with higher aspect ratio and surface defects show significantly higher photocatalytic performances.

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Effect of aspect ratio and surface defects on the photocatalytic activity of ZnO nanorods

ZnO is an attractive material for applications in electronics, photonics, acoustics, and sensing In optical emitters, its high exciton binding energy (60 meV) gives ZnO an edge over other semiconductors such as GaN if reproducible and reliable p-type doping in ZnO were to be achieved, which currently remains to be the main obstacle for realization of bipolar devices On the electronic side, ZnO holds some potential in transparent thin film transistors (TFTs) owing to its high optical transmittivity and high conductivity Among the other promising areas of application for ZnO are acoustic wave devices, due to large electromechanical coupling in ZnO, and devices utilizing nanowires/nanorods such as biosensors and gas sensors and solar cells, since it is relatively easy to produce such forms of ZnO nanostructures, which have good charge carrier transport properties and high crystalline quality Despite the significant progress made, there is still a number of important issues that need to be resolved before ZnO can be transitioned to commercial use, not to mention the stiff competition it is facing with GaN, which is much more mature in terms of devices In this paper, recent progress in device applications of ZnO is discussed and a review of critical issues for realization of ZnO-based devices is given

https://doc.rero.ch/record/21182/files/_zg_r_mit_-_ZnO_Devices_and_Applications_A_Review_of_Current_20101229.pdf

ZnO Devices and Applications: A Review of Current Status and Future Prospects

Inorganic semiconductor nanostructures are ideal systems for exploring a large number of novel phenomena at the nanoscale and investigating the size and dimensionality dependence of their properties for potential applications. The use of such nanostructures with tailored geometries as building blocks is also expected to play crucial roles in future nanodevices. Since the discovery of carbon nanotubes much attention has been paid to exploring the usage of inorganic semiconductor nanostructures as field-emitters due to their low work functions, high aspect ratios and mechanical stabilities, and high electrical and thermal conductivities. This article provides a comprehensive review of the state-of-the-art research activities in the field. It mainly focuses on the most widely studied inorganic nanostructures, such as ZnO, ZnS, Si, WO3, AlN, SiC, and their field-emission properties. We begin with a survey of inorganic semiconductor nanostructures and the field-emission principle, and then discuss the recent progresses on several kinds of important nanostructures and their field-emission characteristics in detail and overview some additional inorganic semiconducting nanomaterials in short. Finally, we conclude this review with some perspectives and outlook on the future developments in this area.

Inorganic semiconductor nanostructures and their field-emission applications

Metal oxide semiconductors hold great promise for applications in energy conversion and storage, environmental remediation, optoelectronics, memory, light emission and other areas, but critical factors such as the high rate of charge-carrier recombination and limited light absorption have restricted more practical and viable applications. The remarkable ability of plasmonic noble metals to concentrate and scatter visible light has found a versatile potential in harvesting and converting solar energy. Plasmonic nanostructures of noble metals in combination with semiconductors offer a promising future for the next generation of energy needs. The overlap of the spectral range of the incident photon with absorbance wavelength of the semiconductor and the surface plasmon bands of the plasmonic metal provides a useful tool to predict the enhancement in optical and electrical properties of hybrid semiconductor-noble metal nanostructures. Here we make an attempt to comprehensively review the role of plasmonic noble metals in the enhanced functions for photocatalytic activity, photoenergy conversion in DSSCs, enhanced light emission and photochromatism. We mainly focus on the improvement of performance in TiO2 or ZnO in combination with noble metals on representative photophysical applications. The mechanism behind their interaction with light is discussed in detail in each section.

A study on the mechanism for the interaction of light with noble metal-metal oxide semiconductor nanostructures for various photophysical applications

to improve the structural properties of n- and p-type ZnO compared to previous studies. [7] In addition, a thermal annealing process was carried out to activate the phosphorus dopants in p-type ZnO and improve the electrical and optical properties of the ZnO layers. The LED showed excellent current-rectifying behavior with a threshold voltage of 3.2 V and an EL emission peak at 380 nm at room temperature. The UV EL emission spectrum was in good agreement with the room-temperature photoluminescence (PL) spectrum of the p-type ZnO used in the LED. Furthermore, the near-bandedge emission was increased and the deep-level emission was decreased when (Mg,Zn)O alloy layers were introduced as energy barrier layers between n-type and p-type ZnO films to confine the carrier recombination process to the high-quality n-type ZnO film. A schematic diagram of the p–n homojunction ZnO LED is shown in Figure 1. The gallium-doped n-type ZnO with a thickness of 1.5 lm was grown on a c-Al2O3 substrate. It

Chang-Ku Kang

Papers

UV electroluminescence emission from ZnO light-emitting diodes grown by high-temperature radiofrequency sputtering