We present a review of current research on the optical properties of ZnO nanostructures. We provide a brief introduction to different fabrication methods for various ZnO nanostructures and some general guidelines on how fabrication parameters (temperature, vapor-phase versus solution-phase deposition, etc.) affect their properties. A detailed discussion of photoluminescence, both in the UV region and in the visible spectral range, is provided. In addition, different gain (excitonic versus electron hole plasma) and feedback (random lasing versus individual nanostructures functioning as Fabry-Perot resonators) mechanisms for achieving stimulated emission are described. The factors affecting the achievement of stimulated emission are discussed, and the results of time-resolved studies of stimulated emission are summarized. Then, results of nonlinear optical studies, such as second-harmonic generation, are presented. Optical properties of doped ZnO nanostructures are also discussed, along with a concluding outlook for research into the optical properties of ZnO.

Optical properties of ZnO nanostructures.

ZnO nanostructures for optoelectronics: Material properties and device applications

Recent advances in the field of nanotechnology have led to the synthesis and characterization of an assortment of quasi-one-dimensional (Q1D) structures, such as nanowires, nanoneedles, nanobelts and nanotubes. These fascinating materials exhibit novel physical properties owing to their unique geometry with high aspect ratio. They are the potential building blocks for a wide range of nanoscale electronics, optoelectronics, magnetoelectronics, and sensing devices. Many techniques have been developed to grow these nanostructures with various compositions. Parallel to the success with group IV and groups III–V compounds semiconductor nanostructures, semiconducting metal oxide materials with typically wide band gaps are attracting increasing attention. This article provides a comprehensive review of the state-of-the-art research activities that focus on the Q1D metal oxide systems and their physical property characterizations. It begins with the synthetic mechanisms and methods that have been exploited to form these structures. A range of remarkable characteristics are then presented, organized into sections covering a number of metal oxides, such as ZnO, In2O3, SnO2 ,G a 2O3, and TiO2, etc., describing their electrical, optical, magnetic, mechanical and chemical sensing properties. These studies constitute the basis for developing versatile applications based on metal oxide Q1D systems, and the current progress in device development will be highlighted. # 2006 Elsevier B.V. All rights reserved.

Quasi-one-dimensional metal oxide materials—Synthesis, properties and applications

Zn1–xCoxO (x = 0, 0.05, 0.10, and 0.15) nanoparticles (NPs) were synthesized by a coprecipitation method. The crystalline sizes of synthesized samples were calculated from the powder XRD patterns, which were found to decrease with the increase of cobalt content. The FT-IR spectra confirmed the Zn–O stretching bands at 468, 456, 452, and 461 cm–1 for the respective ZnO NPs. SEM images demonstrated the distinct flowerlike morphology. The photoluminescence spectra of all the samples exhibited a broad emission in the visible range. XPS studies were carried out for Zn0.90Co0.10O NPs. The carriers (donors) bound on the Co sites were observed from the micro-Raman spectroscopic studies. The pure and Co-doped ZnO NPs showed significant changes in the M–H loop where the diamagnetic behavior of ZnO changes to ferromagnetic nature when doping with Co. Oxygen vacancies and zinc interstitials were found to be the main reasons for room-temperature ferromagnetism in the Co-doped ZnO NPs with the support of the results ob...

Effect of Cobalt Doping on Structural, Optical, and Magnetic Properties of ZnO Nanoparticles Synthesized by Coprecipitation Method

Visible light photocatalytic activity of Fe3+-doped ZnO nanoparticle prepared via sol-gel technique

Self-assembled zinc oxide (ZnO) and indium-doping zinc oxide (ZnO:In) nanorod thin films were synthesized on quartz substrates without catalyst in aqueous solution by sol-gel method. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), Raman-scattering spectroscopy, room-temperature photoluminescence (PL) spectra, and temperature-dependent PL spectra measurements. XRD and Raman spectra illustrated that there were no single In2O3 phase in ZnO lattice after indium doping. The PL spectra of ZnO showed a strong UV emission band located at 394nm and a very weak visible emission associated with deep-level defects. Indium incorporation induced the shift of optical band gap, quenching of the near-band-edge photoluminescence and enhanced LO mode multiphonon resonant Raman scattering in ZnO crystals at different temperatures. Abnormal temperature dependence of UV emission integrated intensity of ZnO and ZnO:In samples is observed. The local state emission peak of ZnO:In sam...

Y. W. Chen

Papers

Optical properties of ZnO and ZnO:In nanorods assembled by sol-gel method.