The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

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A comprehensive review of zno materials and devices

https://www.tandfonline.com/doi/pdf/10.1088/1468-6996/9/3/035004

Enhanced bioactivity of ZnO nanoparticles?an antimicrobial study

Oxygen vacancies in crystal have important impacts on the electronic properties of ZnO. With ZnO2 as precursors, we introduce a high concentration of oxygen vacancies into ZnO successfully. The obtained ZnO exhibits a yellow color, and the absorption edge shifts to longer wavelength. Raman and XPS spectra reveal that the concentration of oxygen vacancies in the ZnO decreased when the samples are annealed at higher temperature in air. It is consistent with the theory calculation. The increasing of oxygen vacancies results in a narrowing bandgap and increases the visible light absorption of the ZnO. The narrowing bandgap can be confirmed by the enhancement of the photocurrent response when the ZnO was irradiated with visible light. The ZnO with oxygen vacancies are found to be efficient for photodecomposition of 2,4-dichlorophenol under visible light irradiation.

Oxygen vacancy induced band-gap narrowing and enhanced visible light photocatalytic activity of ZnO.

Researchers demonstrate a high-efficiency polymer solar cell whose device architecture is compatible with a large-scale roll-to-roll process. Enhanced charge collection in the inverted polymer solar cell design and certified power conversion efficiencies of around 7.4% are reported.

High-efficiency inverted dithienogermole–thienopyrrolodione-based polymer solar cells

Nanostructured oxides in chemistry: characterization and properties.

Effect of confinement is investigated on optical phonons of different symmetries in the nanoparticles of zinc oxide with wurtzite structure using Raman spectroscopy. An optical phonon confinement model is used for calculating the theoretical line shapes, which exhibit different asymmetric broadening and shifts, depending on the symmetries of phonon and their dispersion curves. The best fit to the data is found for particle diameters consistent with those estimated using x-ray diffraction.

Optical phonon confinement in zinc oxide nanoparticles

We report a novel method for the synthesis of stable, OH free zinc oxide quantum dots, using an electrochemical route. The optical properties of these quantum dots were studied at room temperature, by taking the optical absorption and luminescence spectra. The band gap luminescence is predominant in ZnO quantum dots synthesized by the present technique, while the green defect induced luminescence, typical of ZnO, is strongly quenched. The role of defects in photoluminescence emission is discussed.

Spectroscopic and structural characterization of electrochemically grown ZnO quantum dots

ZnO nanoparticles embedded in polymeric matrices

Wet-chemical and electrochemical routes were used to synthesize zinc oxide nanoparticles showing peculiar luminescent properties. ZnO-I are the nanoparticles that show only band gap ultraviolet (UV) emission, whereas ZnO-II type nanoparticles show the defect green luminescence along with the UV emission. Photoluminescence excitation (PLE) spectra of ZnO-I nanocrystals exhibit a single feature located at about 368 nm whereas ZnO-II nanocrystals show two features in PLE: a prominent feature at about 368 nm which is size dependent and a hump at 325 nm. These results are discussed in detail in view of the luminescence behavior in ZnO quantum particles.

B. S. Bendre

Papers

Optical phonon confinement in zinc oxide nanoparticles

Spectroscopic and structural characterization of electrochemically grown ZnO quantum dots

ZnO nanoparticles embedded in polymeric matrices

Luminescence in ZnO quantum particles

Studies on BaO particles in nanosize regime