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Author : Jianguo Zhong
Publisher :
ISBN 13 :
Total Pages : 156 pages
Book Rating : 4.:/5 (181 download)
Download or read book Defects in ZnO Investigated by Positron Lifetime Spectroscopy and Cathodoluminescence written by Jianguo Zhong and published by . This book was released on 1992 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : 蘇振強
Publisher :
ISBN 13 : 9781374666856
Total Pages : pages
Book Rating : 4.6/5 (668 download)
Download or read book Defect Study of Zinc Oxide Bulk Materials by Positron Lifetime Spectroscopy written by 蘇振強 and published by . This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Defect Study of Zinc Oxide Bulk Materials by Positron Lifetime Spectroscopy" by 蘇振強, Chun-keung, So, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled DEFECT STUDY OF ZINC OXIDE BULK MATERIALS BY POSITRON LIFETIME SPECTROSCOPY submitted by So Chun Keung for the Degree of Master of Philosophy at The University of Hong Kong in January 2008 Vacancy type defects in ZnO bulk materials grown by different methods from various companies were studied by positron lifetime spectroscopy. Hydrothermal grown ZnO samples from University Wafers Company contained a single 193 ps positron lifetime component, attributed to a zinc vacancy related defect. Upon electron irradiation, a single 185 ps positron lifetime was identified which was explained by the formation of another zinc vacancy related defect. This defect remained stable after isochronal annealing of the sample up to 1200C. Samples from the same company but of different batches contained a 180 ps single lifetime component. In addition, hydrothermal grown ZnO single crystals from Altramet Company and MaTecK Company also demonstrated the 180 ps single lifetime component. Two batches of ZnO single crystals grown by pressurized melt grown method from Cermet company were studied. Data analyses on the older batch samples revealed 1the existence of a 257 ps lifetime component, tentatively attributed to Zn+O divacancy defect. This defect was not detected in more recently grown samples. Instead, a 166 ps single component was found, of which the nature of it could not be unambiguously determined. Vapour phase grown as-grown and 900C annealed ZnO samples were studied. Single lifetime component of 175 ps was identified. Nevertheless, the exact nature of it required further investigation. In the present study, positron lifetimes in different ZnO samples were found. The kinds of open volume vacancy-type defects were believed to be dependent on the growing methods. In addition, production of ZnO single crystals with high and consistent qualities was yet to be achieved at present. 2 DOI: 10.5353/th_b3955869 Subjects: Zinc oxide Materials - Defects Positrons - Spectra
Author : Chun-Kit To
Publisher :
ISBN 13 : 9781361277133
Total Pages : pages
Book Rating : 4.2/5 (771 download)
Download or read book Defect Studies of Single Crystal and Thin Film Zinc Oxide by Positron Annihilation Spectroscopy and Cathodoluminescence written by Chun-Kit To and published by . This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Chun-kit To
Publisher :
ISBN 13 :
Total Pages : 372 pages
Book Rating : 4.:/5 (739 download)
Download or read book Defect Studies of Single Crystal and Thin Film Zinc Oxide by Positron Annihilation Spectroscopy and Cathodoluminescence written by Chun-kit To and published by . This book was released on 2010 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Chun-keung So
Publisher :
ISBN 13 :
Total Pages : 124 pages
Book Rating : 4.:/5 (226 download)
Download or read book Defect Study of Zinc Oxide Bulk Materials by Positron Lifetime Spectroscopy written by Chun-keung So and published by . This book was released on 2008 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : David J. Fisher
Publisher : Trans Tech Publications Ltd
ISBN 13 : 3038262609
Total Pages : 214 pages
Book Rating : 4.0/5 (382 download)
Download or read book Diffusion and Defects in ZnO written by David J. Fisher and published by Trans Tech Publications Ltd. This book was released on 2013-09-04 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lanthanum hexaboride is useful because it possesses a high melting point (2210C), a low work function, one of the highest known electron emissivities, and is stable in vacuum. This volume summarises the extant data on the properties of this material, including the: bulk modulus, conductivity, crystal structure, Debye temperature, defect structure, elastic constants, electronic structure, emissivity, Fermi surface, hardness, heat capacity, magnetoresistance, reflectivity, resistivity, specific heat, surface structure, thermal conductivity, thermoelectric power, toughness and work function. The issue also includes original research papers on: the Pitting Resistance of 316 Stainless Steel in Ringers Solution, the Effect of Different Modifiers on the Microstructure and Strength of Locally Developed A356 Al-Si Alloy, the Site Preference of Zr in NiAl Dislocation Cores and its Effects on Bond Character, the Effect of Different Combinations of Salt Modifier on the Mechanical Properties and Microstructure of A356 Al-Si Alloy, Quasicrystalline Phase Formation in High Frequency Induction Melted Al80Cu14Fe6 Alloy, Numerical Investigation of the Effect of Sprue Base Design on the Flow Pattern of Aluminum Gravity Castings, the Evaluation of Surface Preparation Techniques for Steel Substrates Prior to Coating, Thermal Desorption of Hydrogen from AISI 316L Stainless Steel and Pure Nickel, Structural and Concentration Heterogeneities during the Formation of Silicide Phases in the Ti(5nm)/Ni(24nm)/Si(001)Thin-Film System, Studies of the g-Factor and Hyperfine Structure Constant for Ir4+ in CdO, Theoretical Studies of the Local Structures and Spin Hamiltonian Parameters for the Cu2+ Centers in Alkali Barium Borate Glasses, Study of the Properties of CR-39 Polymer Irradiated with Alpha Particles, Review of Diffusion and Interfacial Reactions in Sandwich Thin-Film Couples and the Correlation Coefficient between Vickers Hardness and Nuclear Techniques.
Author : Naresh Adhikari
Publisher :
ISBN 13 :
Total Pages : 53 pages
Book Rating : 4.:/5 (111 download)
Download or read book DEFECTS AND OPTOELECTRONIC PROPERTIES OF ZINC OXIDE written by Naresh Adhikari and published by . This book was released on 2019 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zinc oxide (ZnO) is a compound semiconductor with a direct wide band gap of 3.4 eV with a high exciton binding energy of 60 meV at room temperature. It is a widely investigated semiconductor due to its high potential for optoelectronic applications in the UV region, especially, for light-emitting diodes and lasers. In these applications of ZnO, native point defects play key roles. The understanding of these defects will help us to realize and control the performance of ZnO in these applications. Also, it will help us to realize p-type doping in ZnO, which will open a way for oxide semiconductor based bipolar devices. Due to the reproducibility of high-quality ZnO crystals and their interesting properties, it is preferred for extensive research over other wide band gap semiconductors. So far, as research points out, native point defects are not well understood. In our work, we will present electrical and optical characterization studies done on ZnO single crystals as well as on polycrystals, and we will relate these measurements to defect studies using Positron Annihilation Lifetime Spectroscopy (PALS) and Coincident Doppler Broadening Spectroscopy (CDBS). It was found that the increase in well-known green luminescence is associated with a decrease in conductivity and charge carrier concentration. Positron lifetime spectroscopy measurements were carried out to reveal the origin of defects responsible for decreasing the conductivity and enhancing the green luminescence. Lastly, it was interesting to observe the decrease in the ratio between green luminescence to near band emission as the laser power increased.
Author : Helmut Heinrich
Publisher :
ISBN 13 :
Total Pages : 724 pages
Book Rating : 4.X/5 (2 download)
Download or read book Proceedings of the 17th International Conference on Defects in Semiconductors written by Helmut Heinrich and published by . This book was released on 1994 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Reinhard Krause-Rehberg
Publisher : Springer Science & Business Media
ISBN 13 : 9783540643715
Total Pages : 408 pages
Book Rating : 4.6/5 (437 download)
Download or read book Positron Annihilation in Semiconductors written by Reinhard Krause-Rehberg and published by Springer Science & Business Media. This book was released on 1999 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive book reports on recent investigations of lattice imperfections in semiconductors by means of positron annihilation. It reviews positron techniques, and describes the application of these techniques to various kinds of defects, such as vacancies, impurity vacancy complexes and dislocations.
Author : Zsolt Kajcsos
Publisher :
ISBN 13 :
Total Pages : 700 pages
Book Rating : 4.X/5 (2 download)
Download or read book Positron Annihilation written by Zsolt Kajcsos and published by . This book was released on 1992 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Zilan Wang
Publisher : Open Dissertation Press
ISBN 13 : 9781361378779
Total Pages : pages
Book Rating : 4.3/5 (787 download)
Download or read book Defect Emission of Zno and Its Related Origins written by Zilan Wang and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Defect Emission of ZnO and Its Related Origins" by Zilan, Wang, 王子蘭, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Zinc oxide (ZnO) is a promising material for ultra-violet optoelectronics applications due to its direct band gap and large exciton binding energy. Defect in semiconductor plays an important role in determining the optical and electrical properties. It is thus crucial to understand the defects‟ performance for realizing the device fabrication. Green luminescence (GL) having the peak at 2.4-2.5 eV is a defect related emission band commonly found in the luminescence spectra of many of the ZnO materials. Despite of the effort devoted for several decades, its origin and emission mechanism remain controversial. In this thesis, the origin of the GL emitted from the ZnO films grown by pulsed laser deposition (PLD) is studied using a comprehensive spectroscopic approach, including the Hall effect measurement, photoluminescence (PL), Raman spectroscopy, positron annihilation spectroscopy (PAS), and secondary ion mass spectroscopy (SIMS). ZnO thin films are grown by PLD method with the growth parameters (namely the substrate temperature and oxygen pressure during the growth) systemically varied. Annealing studies in argon atmosphere reveal the correlation between the free electron concentration and the hydrogen concentration in the samples. Two oxygen deficient defect related Raman modes are also identified and they anneal out after annealing at high temperature. We have investigated the introduction the GL systematically grown by different growth parameters, undergone different post-growth annealing treatment, and different methods of growth. Two kinds of GL's are identified. The first kind of GLs has peak at 2.47 eV without the fine structure, and the other has the peak at 2.45 eV having the fine structure of separation of 0.07 eV. The GL with the fine structure is originated from the surficial region of the ZnO film. The GL without the fine structure is introduced after the annealing 900℃ irrespective of the initial growth conditions. PAS results show a strong correlation between the thermal introductions of a kind of Zn-vacancy and the GL without the fine structure. Moreover, a donor-acceptor-pair (DAP) emission is induced in the low temperature PL spectrum after the same annealing temperature of 900℃. The GL and the DAP emissions are thus associated with the involvement of the VZn. Furthermore by comparing the photon energies of the GL and DAP with the previous first principle calculated results, the GL is ascribed to the conduction band to the (-/2-) acceptor level of VZn, and the DAP involves the (0/-) acceptor level of VZn The presence of the conduction band to the (0/-) level transition is compatible with the results of the photoluminescence excitation (PLE) study. Subjects: Zinc oxide - Defects
Author : Gordon Davies
Publisher : Trans Tech Publications Ltd
ISBN 13 : 3035705240
Total Pages : 1932 pages
Book Rating : 4.0/5 (357 download)
Download or read book Defects in Semiconductors 19 written by Gordon Davies and published by Trans Tech Publications Ltd. This book was released on 1997-12-11 with total page 1932 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern Technology depends upon silicon chips, and life as we know it would hardly be possible without semiconductor devices. Control over a given semiconductor's electronic properties is achieved via defect engineering, and the scientific and technical challenges in this field are manifold. Volume is indexed by Thomson Reuters CPCI-S (WoS).
Author :
Publisher :
ISBN 13 :
Total Pages : 712 pages
Book Rating : 4.E/5 ( download)
Download or read book Diffusion and Defect Data written by and published by . This book was released on 2004 with total page 712 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (96 download)
Download or read book Controlled Synthesis and Understanding of Growth Mechanism - Parameters for Atmospheric Pressure Hydrothermal Synthesis of Ultrathin Secondary ZnO Nanowires written by and published by . This book was released on 2015 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We measured luminescence and scintillation in ZnO single crystals by photoluminescence and X-ray-induced luminescence (XRIL). XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. In the origin of green emission, the dominant trap emission in ZnO, was investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials or the surroundings. Moreover, the measurements showed the absence of positron traps in the crystals and yielded a bulk positron lifetime value that is in complete agreement with the predicted theoretical value = thereby confirming the advantage of the GIPS method. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE.
Author : Vijay Kumar
Publisher : Elsevier
ISBN 13 : 0323903592
Total Pages : 758 pages
Book Rating : 4.3/5 (239 download)
Download or read book Metal Oxide Defects written by Vijay Kumar and published by Elsevier. This book was released on 2022-11-19 with total page 758 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal Oxide Defects: Fundamentals, Design, Development and Applications provides a broad perspective on the development of advanced experimental techniques to study defects and their chemical activity and catalytic reactivity in various metal oxides. This book highlights advances in characterization and analytical techniques to achieve better understanding of a wide range of defects, most importantly, state-of-the-art methodologies for controlling defects. The book provides readers with pathways to apply basic principles and interpret the behavior of metal oxides. After reviewing characterization and analytical techniques, the book focuses on the relationship of defects to the properties and performance of metal oxides. Finally, there is a review of the methods to control defects and the applications of defect engineering for the design of metal oxides for applications in optoelectronics, energy, sensing, and more. This book is a key reference for materials scientists and engineers, chemists, and physicists. Reviews advances in characterization and analytical techniques to understand the behavior of defects in metal oxide materials Introduces defect engineering applied to the design of metal oxide materials with desirable properties Discusses applications of defect engineering to enhance the performance of materials for a wide range of applications, with an emphasis on optoelectronics
Author : Raul Mugabe Peters
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (79 download)
Download or read book Studies of Surface States in Zinc Oxide Nanopowders written by Raul Mugabe Peters and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The surface of ZnO semiconductor nanosystems is a key performance-defining factor in numerous applications. In this work we present experimental results for the surface defect-related properties of ZnO nanoscale systems. Surface photovoltage spectroscopy was used to determine the defect level energies within the band gap, the conduction vs. valence band nature of the defect-related transitions, and to probe key dynamic parameters of the surface on a number of commercially available ZnO nanopowders. In our experimental setup, surface photovoltage characterization is conducted in high vacuum in tandem with in situ oxygen remote plasma treatments. Surface photovoltage investigations of the as-received and plasma-processed samples revealed a number of common spectral features related to surface states. Furthermore, we observed significant plasma-induced changes in the surface defect properties. Ex situ positron annihilation and photoluminescence measurements were performed on the studied samples and correlated with surface photovoltage results. The average positron lifetimes were found to be substantially longer than in a bulk single crystalline sample, which is consistent with the model of grains with defect-rich surface and subsurface layers. Compression of the powders into pellets yielded reduction of the average positron lifetimes. Surface photovoltage, positron annihilation, and photoluminescence spectra consistently showed sample-to-sample differences due to the variation in the overall quality of the nanopowders, which partially obscures observation of the scaling effects. However, the results demonstrated that our approach is efficient in detecting specific surface states in nanoscale ZnO specimens and in elucidating their nature.
Author :
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (16 download)
Download or read book Controlled Synthesis and Understanding of Growth Mechanism {u2013} Parameters for Atmospheric Pressure Hydrothermal Synthesis of Ultrathin Secondary ZnO Nanowires written by and published by . This book was released on 2015 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We measured luminescence and scintillation in ZnO single crystals by photoluminescence and X-ray-induced luminescence (XRIL). XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. In the origin of green emission, the dominant trap emission in ZnO, was investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials or the surroundings. Moreover, the measurements showed the absence of positron traps in the crystals and yielded a bulk positron lifetime value that is in complete agreement with the predicted theoretical value = thereby confirming the advantage of the GIPS method. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE.
