2,317 research outputs found
The effect of the interlayer design on the electroluminescence and electrical properties of n-ZnO nanorod/p-type blended polymer hybrid light emitting diodes
No full textHybrid light emitting diodes (LEDs) based on n-ZnO nanorods and blended polymers were fabricated and characterized. The blended polymers consisted of a blue emitting polymer and a charge transport polymer. The effect of the interlayer design on the electrical and electroluminescent characteristics of these hybrid LEDs was investigated. We demonstrated that by adding a calcium (2) acetylacetonate [Ca(acac)(2)] layer between the blended polymer layer and the ZnO nanorods, an increase in device performance was observed. The purpose of the extra layer was to act as a band offset stepping layer (offset divider). Moreover, the effect of the stepper layer thickness for this offset stepping layer was studied. The results indicate that LED performance is greatly affected by the presence and thickness of this band offset stepping layer.Original Publication:Amal Wadesa, Omer Nour and Magnus Willander, The effect of the interlayer design on the electroluminescence and electrical properties of n-ZnO nanorod/p-type blended polymer hybrid light emitting diodes, 2009, NANOTECHNOLOGY, (20), 6, 065710.http://dx.doi.org/10.1088/0957-4484/20/6/065710Copyright: Institute of Physicshttp://www.iop.org
Size-controlled growth of well-aligned ZnO nanorod arrays with two-step chemical bath deposition method
No full textWell-aligned ZnO nanorod arrays (ZNAs) with different sizes in diameter were fabricated on Si substrates by two-step chemical bath deposition method (CBD), i.e. substrate pre-treatment with spin coating to form ZnO nanoparticles layer and CBD growth. The effects of substrate pre-treatments, pH, angel (θ) between substrate and beaker bottom and growth time (t) on the structure of ZNAs were investigated in detail by X-ray diffraction (XRD), field emission scan electronic microscope (SEM) and photoluminescence (PL). The results show that substrate pre-treatment, pH, θ and t indeed have great influence on the growth of ZNAs, and their influence mechanisms have been, respectively, explained in detail. The introduction of a ZnO nanoparticle layer on the substrate not only helps to decrease the diameter but also has a strong impact on the orientation of ZNAs. Under the growth condition of pH 6, θ = 70° and t = 2 h, the well-aligned ZnO nanorod arrays with 50 nm diameter was obtained on the pre-treated Si substrates. And only a strong UV peak at 385 nm appears in room temperature PL spectrum for this sample, which indicates that as-synthesized ZnO nanorods have a perfect crystallization and low density of deep level defects.Original Publication:LiLi Yang, Qingxiang Zhao and Magnus Willander, Size-controlled growth of well-aligned ZnO nanorod arrays with two-step chemical bath deposition method, 2009, Journal of Alloys and Compounds, (469), 1-2, 623-629.http://dx.doi.org/10.1016/j.jallcom.2008.08.002Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com
Effective way to control the size of well-aligned ZnO nanorod arrays with two-step chemical bath deposition
No full textThe diameter of well-aligned ZnO nanorod arrays (ZNAs) grown on Si substrates has been well controlled from 150nm to 40nm by two-step chemical bath deposition method (CBD), i.e. substrate pretreatment with spin coating to form ZnO nanoparticles seed layer and CBD growth. The effects of ZnO nanoparticles density and diameter on size and alignment of ZNAs were investigated in detail by atomic force microscope (AFM), X-ray diffraction (XRD), scan electronic microscope (SEM), transmission electron microscope (TEM) and photoluminescence (PL). The results indicate that both diameter and density of ZnO nanoparticles which were pre-coated on the substrates will influence the size and alignment of ZNAs, but the density will play a key role to determine the diameter of ZNAs when the density is higher than the value of 2.3×108cm-2. Moreover, only a strong UV peak at 385 nm appears in room temperature PL spectrum for these samples, which indicates that as-synthesized ZnO nanorods have a perfect crystallization and low density of deep level defects.Original Publication:Li-Li Yang, Qingxiang Zhao, Magnus Willander and J.H. Yang, Effective way to control the size of well-aligned ZnO nanorod arrays with two-step chemical bath deposition, 2009, Journal of Crystal Growth, (311), 4, 1046-1050.http://dx.doi.org/10.1016/j.jcrysgro.2008.12.028Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com
Chemically fashioned ZnO nanowalls and their potential application for potentiometric cholesterol biosensor
No full textChemically fashioned zinc oxide (ZnO) nanowalls on aluminum wire have been characterized and utilized to fabricate a potentiometric cholesterol biosensor by an electrostatic conjugation with cholesterol oxidase. The sensitivity, specificity, reusability, and stability of the conjugated surface of ZnO nanowalls with thickness of similar to 80 nm have been investigated over a wide logarithmic concentrations of cholesterol electrolyte solution ranging from 1x10(-6)-1x10(-3) M. The presented biosensor illustrates good linear sensitivity slope curve (similar to 53 mV/decade) corresponding to cholesterol concentrations along with rapid output response time of similar to 5 s.Original Publication:M.Q. Israr, J.R. Sadaf, Omer Nur, Magnus Willander, S. Salman and B. Danielsson, Chemically fashioned ZnO nanowalls and their potential application for potentiometric cholesterol biosensor, 2011, Applied Physics Letters, (98), 25, 253705.http://dx.doi.org/10.1063/1.3599583Copyright: American Institute of Physicshttp://www.aip.org
Memorandum : betr. die Sicherung und Erschliessung der Quellen zur juedischen Kulturgeschichte und Familienkunde.
No full textDocument about the proposed establishment of a center for German Jewish culture and genealogy in Berlin or HamburgdigitizedThe manuscript has been removed from the ‘Lehranstalt fuer die Wissenschaft des Judentums Collection’, AR 11844Born in Hamburg on February 26, 1896, Erna Magnus was a social worker who was engaged in an historical study of the Jewish community of Hamburg during the 1930s. She emigrated to the United States in 1939, where she held various social work and teaching position
Effective Suppression of Surface Recombination in ZnO Nanorods Arrays during the Growth Process
No full textZnO nanorods arrays are respectively prepared under different vapor pressures with opening (OZN) or sealing (SZN) of the beaker. The results from time-resolved photoluminescence measurements indicate that sealing the beaker during the growth process can effectively suppress the surface recombination of ZnO nanorods, and the suppression effect is even better than a 500 degrees C post-thermal treatment or OZN samples. The results from X-ray photoelectron spectroscopy measurements reveal that the main reason for this phenomenon is that the surfaces of the SZN samples are attached by groups related to NH3 instead of the main surface recombination centers such as OH and groups in the OZN samples. The ammonia surface treatment on both OZN and SZN samples further testifies that the absorption of the groups related to NH3 does not contribute to the surface recombination on the ZnO nanorods.This document is the Accepted Manuscript version of a Published Work that appeared in final form in CRYSTAL GROWTH and DESIGN, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: Li-Li Yang, Qingxiang Zhao, Magnus Willander, Xianjie Liu, Mats Fahlman and J H Yang, Effective Suppression of Surface Recombination in ZnO Nanorods Arrays during the Growth Process, 2010, CRYSTAL GROWTH and DESIGN, (10), 4, 1904-1910. http://dx.doi.org/10.1021/cg100017b Copyright: The American Chemical Society http://pubs.acs.org/</p
The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes
No full textIn this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600 degrees C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (O-i) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (V-o) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.The original publication is available at www.springerlink.com:Naveed Ul Hassan Alvi, Kamran Ul Hasan, Omer Nur and Magnus Willander, The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes, 2011, NANOSCALE RESEARCH LETTERS, (6), 1, 130.http://dx.doi.org/10.1186/1556-276X-6-130Licensee: Springer Science Business Mediahttp://www.springerlink.com
Study of luminescent centers in ZnO nanorods catalytically grown on 4H-p-SiC
No full textHigh-quality ZnO nanorods (NRs) were grown by the vapor-liquid-solid (VLS) technique on 4H-p-SiC substrates. Heterojunction light emitting diodes (LEDs) were fabricated. Electrical characterization including deep level transient spectroscopy (DLTS) complemented by photoluminescence (PL) is used to characterize the heterojunction LEDs. In contrast to previously published results on n-ZnO thin films on p-SiC, we found that the dominant emission is originating from the ZnO NRs. Three luminescence lines have been observed; these are associated with blue (465 nm) and violet (446 nm) emission lines from ZnO NRs emitted by direct transition/recombination of carriers from the conduction band to a zinc vacancy (V-Zn) radiative center and from a zinc interstitial (Zn-i) radiative center to the valance band. The third green-yellow (575 nm) spectral line is emitted due to a transition of carriers from Zn-i to V-Zn. The superposition of these lines led to the observation of strong white light which appears as a wide band in the room temperature PL.Original Publication:Nargis Bano, I Hussain, Omer Nour, Magnus Willander, P Klason and Anne Henry, Study of luminescent centers in ZnO nanorods catalytically grown on 4H-p-SiC, 2009, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, (24), 12, 125015.http://dx.doi.org/10.1088/0268-1242/24/12/125015Copyright: Iop Publishing Ltdhttp://www.iop.org
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