Suchergebnisse

Ultraviolet (UV) photodetection has drawn a great deal of attention in recent years due to a wide range of civil and military applications. Because of its wide band gap, low cost, strong radiation hardness and high chemical stability, ZnO are regarded as one of the most promising candidates for UV photodetectors. Additionally, doping in ZnO with Mg elements can adjust the bandgap largely and make it feasible to prepare UV photodetectors with different cut-off wavelengths. ZnO-based photoconductors, Schottky photodiodes, metal–semiconductor–metal photodiodes and p–n junction photodetectors have been developed. In this work, it mainly focuses on the ZnO and ZnMgO films photodetectors. We analyze the performance of ZnO-based photodetectors, discussing recent achievements, and comparing the characteristics of the various photodetector structures developed to date.

In the study, the correlation of optical and photocatalytic properties of ZnO nanorods and ZnO/Ag nanocomposite materials were investigated. ZnO nanorods were synthesized at low temperatures by the hydrothermal method, and Ag nanoparticles were synthesized using the polyol method. When the surface of ZnO nanorods was coated with Ag nanoparticles, the integral intensity of the PL spectrum of ZnO nanorods decreased by 2 times. However, it was observed that the degradation efficiency of the organic dye of ZnO/Ag nanocomposite materials was 2.2 times higher than that of ZnO nanorods. It was found that the migration of charge carriers through the interfaces of ZnO nanorods and silver nanoparticles was caused by a decrease in PL integral intensity and an increase in photocatalytic properties after the surface of ZnO nanorods was coated with Ag nanoparticles.

Ultraviolet (UV) photodetection has drawn a great deal of attention in recent years due to a wide range of civil and military applications. Because of its wide band gap, low cost, strong radiation hardness and high chemical stability, ZnO are regarded as one of the most promising candidates for UV photodetectors. Additionally, doping in ZnO with Mg elements can adjust the bandgap largely and make it feasible to prepare UV photodetectors with different cut-off wavelengths. ZnO-based photoconductors, Schottky photodiodes, metal–semiconductor–metal photodiodes and p–n junction photodetectors have been developed. In this work, it mainly focuses on the ZnO and ZnMgO films photodetectors. We analyze the performance of ZnO-based photodetectors, discussing recent achievements, and comparing the characteristics of the various photodetector structures developed to date.

The financial support of research grants ERA.NET RUS_ST20170-051 and SFERA II project "Transnational Access activities" (EU 7th Framework Programme Grant Agreement N312643). This work was partly supported by the Russian Foundation for Basic Research, project no. 18-52-76002. ; ZnO nanocrystals, undoped and doped with Iridium or Indium were prepared by solar irradiation in Heliotron reactor in PROMES CNRS facilities, France. The comparative analysis of the excitonic spectra of ZnO single crystal and ZnO nanocrystals (NCs) doped with In and Ir was performed. It is shown that the excitonic processes in Ir doped nanocrystals coincide well with electronic processes in undoped NC and single crystal; however, the electronic processes in In-doped nanocrystals are significantly different from those in single crystal. The radioluminescence spectra of ZnO:In was analysed and additional luminescence band at ∼3.18 eV was detected due to In-doping. The luminescence decay time depends on In concentration in nanocrystals and is significantly less in ZnO:In compared with undoped nanocrystals. The fast scintillation of ZnO:In makes this material promising for application. ; Russian Foundation for Basic Research 18-52-76002; Seventh Framework Programme N312643; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

This research was funded by the Latvian Scientific Council grant LZP-2018/2-0083. Institute of Solid State Physics, University of Latvia, as the Center of Excellence, has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under Grant Agreement No. 739508, project CAMART2. ; Transition metal dichalcogenide (TMD) MoS2 and WS2 monolayers (MLs) deposited atop of crystalline zinc oxide (ZnO) and graphene-like ZnO (g-ZnO) substrates have been investigated by means of density functional theory (DFT) using PBE and GLLBSC exchange-correlation functionals. In this work, the electronic structure and optical properties of studied hybrid nanomaterials are described in view of the influence of ZnO substrates thickness on the MoS2 @ZnO and WS2 @ZnO two-dimensional (2D) nanocomposites. The thicker ZnO substrate not only triggers the decrease of the imaginary part of dielectric function relatively to more thinner g-ZnO but also results in the less accumulated charge density in the vicinity of the Mo and W atoms at the conduction band minimum. Based on the results of our calculations, we predict that MoS2 and WS2 monolayers placed at g-ZnO substrate yield essential enhancement of the photoabsorption in the visible region of solar spectra and, thus, can be used as a promising catalyst for photo-driven water splitting applications. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.--//-- Published under the CC BY 4.0 licence. ; Latvian Scientific Council grant LZP-2018/2-0083; Institute of Solid State Physics, University of Latvia, as the Center of Excellence, has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under Grant Agreement No. 739508, project CAMART2.

We report on the synthesis of thin films of ZnCo 2O 4 and ZnMn 2O 4 spinels, as well as pure Co 3O 4 and Mn 3O 4 spinels, by means of electrodeposition. Spinel thin films have been analyzed by energy dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy. We show that under determined deposition conditions the initial wurtzite structure of Co- and Mn-doped ZnO develops into spinel structures when the Co and Mn concentration in the films is above the solubility limit of these ions in the typical ZnO-wurtzite structure. © 2012 Elsevier Ltd. All rights reserved. ; This work was supported by Spanish Government through MICINN grants MAT2009-14625-C03-03, MAT2010-21270-C04-04 and MALTA CSD2007-0045. Financial support by the European Commission through NanoCIS project (PIRSES-GA-2010-269279) is gratefully acknowledged. Finally, we also want to acknowledge the support of Vicerrectorado de Investigacion y Desarrollo de la Universitat Politecnica de Valencia through projects UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11. ; Tortosa Jorques, MD.; Manjón Herrera, FJ.; Mollar García, MA.; Marí Soucase, B. (2012). ZnO-based spinels grown by electrodeposition. Journal of Physics and Chemistry of Solids. 73(9):1111-1115. https://doi.org/10.1016/j.jpcs.2012.04.002 ; S ; 1111 ; 1115 ; 73 ; 9

5wt% copper doped zinc oxide (Cu-ZnO) nanostructures were prepared via the hydrothermal technique at different temperatures of 70, 100, 130, 160 and 190oC. UV spectroscopy, FE-SEM microscopy, XRD crystallography, and EDS measurements were used for nanostructure characterization. UV spectroscopy indicated a red shift for the absorption peaks, and hence a blue shift for the energy gap values, as temperature increased from 70 to 190oC. FE-SEM microscopy showed an increase in the average lengths and diameters of the nanostructures following a similar increase in temperature. XRD crystallography indicated decent structural patterns for Cu-ZnO nanostructures with an increase in crystallite size upon temperature increase. Interestingly, three unprecedented extra indices appeared in the structural pattern at 190oC, which might indicate a configuration of hexagonal crystallite with three extra planes. EDS measurements indicated the sole presence of Cu, Zn and O.

Optical properties of ZnO-based single nanorods are probed by cathodoluminescence (CL) measurements at T=5 K. We observe a variation of the ZnO near band edge CL by three orders of magnitude along the nanorod axis, accompanied by a spectral blueshift of 10-30 meV. This indicates a rather poor structural quality of the nanorod bottom part, close to the substrate. ZnO/ZnMgO quantum wells grown on top of ZnO nanorods are found to exhibit much stronger confinement effects as compared to their two-dimensional counterparts, suggesting a reduced spontaneous and piezoelectric polarization effects. ; We acknowledge supports from the France-Korea Associated International Laboratory "Center for Photonics and Nanostructures" (CPN), the European Union projects STREP FP6-016924 "NANDOS" and HPRN-CT-2002-00298 "Photon Mediated Phenomena in Semiconductor Nanostructures".

We report on hybrid films based on ZnO/organic dye prepared by electrodeposition using tetrasulfonated copper phthalocyanines (TS-CuPc) and Eosin-Y (EoY). Both the morphology and porosity of hybrid ZnO films are highly dependent on the type of dyes used in the synthesis. High photosensitivity was observed for ZnO/EoY films, while a very weak photoresponse was obtained for ZnO/TS-CuPc films. Despite a higher absorption coefficient of TSCuPc than EoY, in ZnO/EoY hybrid films, the excited photoelectrons between the EoY levels can be extracted through ZnO, and the porosity of ZnO/EoY can also be controlled. © 2011 Moya et al. ; This study was supported by the Spanish Government through MCINN grant MAT2009-14625-C03-03, the Generalitat Valenciana through programme PROMETEO/2009/063, and the Fundacao para a Ciencia e a Tecnologia (Portugal). Thanks are due to Susie Pannell for critically reading the manuscript and providing invaluable suggestions. ; Moya Forero, MM.; ANURA SAMANTILLEKE; Mollar García, MA.; Marí Soucase, B. (2011). Nanostructured hybrid ZnO thin films for energy conversion. Nanoscale Research Letters. 6:384-389. https://doi.org/10.1186/1556-276X-6-384 ; S ; 384 ; 389 ; 6 ; ZHENG, H., PAN, Y., & XIANG, X. (2007). Oxidation of acidic dye Eosin Y by the solar photo-Fenton processes. Journal of Hazardous Materials, 141(3), 457-464. doi:10.1016/j.jhazmat.2006.12.018 ; Qazi, S. J. S., Rennie, A. R., Cockcroft, J. K., & Vickers, M. (2009). Use of wide-angle X-ray diffraction to measure shape and size of dispersed colloidal particles. Journal of Colloid and Interface Science, 338(1), 105-110. doi:10.1016/j.jcis.2009.06.006

AbstractA facile solution processing strategy has been developed for the formation of Ag-modified ZnO microneedles at various calcination temperatures such as 300, 500, and 700 °C (AZ3, AZ5, and AZ7 respectively). Due to the heavy doping of AgNO3, Ag+ ions have been incorporated in to the crystal lattice of ZnO in all the Ag-ZnO samples, which facilitated the formation of Ag-ZnO microneedle morphology with minimized defect states, and obviously, the plasmon peaks were observed due to Ag modification. These Ag-ZnO microneedle structures have been evaluated for their photocatalytic performance using methylene blue as model target contaminant and their activity was compared with the commercially available titania P25 photocatalyst. The photoactivity of all the Ag-ZnO microneedle structures was significantly higher than that of the commercially available P25 photocatalyst with the most active Ag-ZnO material having a photocatalytic activity ~ 1.4 times greater than that of P25 titania.

Ministry of Science and Technology, Taiwan (104-2221-E-110-012-MY3, 107-2221-E-110-004-MY3); National Natural Science Foundation of China (51602309, U1605245). ; The temperature-dependent polarized photoluminescence spectra of nonpolar ZnO samples were investigated by 263 nm laser. The degree of polarization (DOP) of m-plane quantum wells changes from 76% at 10 K to 40% at 300 K, which is much higher than that of epilayer. The strong anisotropy was presumably attributed to the enhanced confinement effect of a one-dimension confinement structure formed by the intersection of quantum well and basal stacking fault. The polarization of laser beam also has an influence on the DOP. It is assumed that the luminescence polarization should be affected not only by the in-plane strains but also the microstructural defects, which do modify the electronic band structure. ; Ministry of Science and Technology, Taiwan 104-2221-E-110-012-MY3,107-2221-E-110-004-MY3; National Natural Science Foundation of China U1605245,51602309; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

The authors gratefully acknowledge the financial support for this work from research grant ERA.NET RUS Plus Nr.609556 and from the SFERA II project Transnational Access activities (EU 7th Framework Programme Grant Agreement no 312643) for supporting ZnO nanopowders preparation. ; Two types of ZnO ceramics were fabricated and characterized by XRD, SEM methods. The radioluminescence spectra were measured within the 300–550 K range. The defect luminescence band peaking at ~2.35 eV is the dominant one in radioluminescence spectra in both of the fabricated ceramics. The thermostimulated luminescence (TSL) glow-curves were measured after X-ray irradiation at 300 K. It was concluded that the complex overlapping peak within the 320–450 K temperature range consists of two components (~360–375 K and 400–420 K). The ratio of component intensities differs in both ceramics. The positions of high temperature TSL components (480–520 K) also differ in both samples; therefore not only sintering conditions but also the properties of the initial powder are very important for characteristics of TSL. A linear dependence of peak intensity on irradiation dose was observed up to ~3 kGy for ceramic 1 and up to 9 kGy for ceramic 2. ; Seventh Framework Programme 312643; Seventh Framework Programme 312643; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²