Download or read book All Electron and Full Potential Positron Annihilation Calculations for Intrinsic and Defective Zinc and Zinc Oxide written by Taojun Zhou 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, "All-electron and Full-potential Positron Annihilation Calculations for Intrinsic and Defective Zinc and Zinc Oxide" by Taojun, Zhou, 周濤俊, 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 ALL-ELECTRON AND FULL-POTENTIAL POSITRON ANNIHILATION CALCULATIONS FOR INTRINSIC AND DEFECTIVE ZINC AND ZINC OXIDE submitted by ZHOU Tao Jun for the Degree of Doctor of Philosophy at The University of Hong Kong in January 2008 Positron annihilation spectroscopy (PAS) is a useful experimental method for studying the electronic structure of materials. To achieve its full poten- tial, however, theoretical methods must be used to interpret PAS results. The studies performed in this work have involved the development of a high ac- curacy positron package capable of theoretically predicting positron-electron momentum distributions and positron lifetimes. The package is based on the WIEN2k package, which utilizes a full potential linearized augmented plane wave (FLAPW) formalism to obtain accurate electron densities. The positron packagewasdevelopedusingthetwocomponentdensityformalismandiscapa- ble of dealing not just with positron annihilation from a bulk crystal state, but also for positrons that are localized in crystal defects. This type of defect studyuses a large sized super-cell. The relaxation of a defect under the inuence of a localized positron has been incorporated into the package. It is shown that experimental data such as Coincidence Doppler Broadening Spectroscopy(CDBS), AngularCorrelationofAnnihilationRadiation(ACAR), andPositronAnnihilationLifetimeSpectroscopy(PALS), canbewellsimulated using this package. The ecacy of the positron package has been demonstrated with respect to two material systems; namely zinc (Zn)/copper (Cu) and zinc oxide (ZnO), with vacancy type defects being considered in both cases. For the transition metal Zn, the local density approximation (LDA), gen- eralized gradient approximation (GGA) and the state-dependent scheme are applied. The GGA value for the positron lifetime is found to be 157ps. The positron-electron momentum spectrum of Zn is compared with that of Cu. The simulationsshow, ingoodagreementwithexperiment, thatthesetwotransition metals of similar electronic structure, have markedly di(R)erent shapes for their positron-electronmomentumdistributions. Reasonsforthisarediscussedbased upon the nature of the 3d electron wavefunctions. The positron package gives a GGA positron lifetime of 191ps for the Zn monovacancy which is in reasonable agreement with experiment. When the positron package is applied to ZnO a GGA positron lifetime of 162ps is obtained which is within the present experimental range. In the GGA approximation, the positron lifetime of the oxygen vacancy is 165ps while that of the Zn vacancy is 220ps - values which are both well within the experimental range. Positron-electron momentum distributions were obtained and compared with experiment. These studies clearly demonstrate the positron package is reliable and useful in the analysis of the experimental results. DOI: 10.5353/th_b3963416 Subjects: Positron annihilation Electron spectroscopy Zinc Zinc oxide
Download or read book All electron and Full potential Positron Annihilation Calculations for Intrinsic and Defective Zinc and Zinc Oxide written by Taojun Zhou and published by . This book was released on 2007 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Positron Annihilation Spectroscopic Studies of Undoped N Type Zinc Oxide Single Crystal written by Chun-Wai Hui 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, "Positron Annihilation Spectroscopic Studies of Undoped N-type Zinc Oxide Single Crystal" by Chun-wai, Hui, 許俊偉, 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 POSITRON ANNIHILATION SPECTROSCOPIC STUDIES OF UNDOPED N-TYPE ZINC OXIDE SINGLE CRYSTAL submitted by HUI CHUN WAI for the Degree of Master of Philosophy at The University of Hong Kong in August 2006 Positron lifetime spectroscopy and coincidence Doppler broadening spectroscopy (CDBS) were used to study the defects in two pieces of hydrothermal (HT) grown ZnO single crystal samples (HT1 and HT2) obtained from two different companies, namely University Wafer, US, and MaTecK, Germany. Single component model could offer good fitting to the lifetime spectra of HT1 and HT2 at temperatures ranging from 25K to 285K. The room temperature positron lifetimes of HT1 and HT2 were found to be 191ps and 181 ps, respectively. The observation was associated with saturated positron trapping into two different Zn-vacancy related defects existing in the two samples. For HT1, the lifetime was observed to be temperature independent. However for HT2, the lifetime had constant value with temperature higher than 200K. It then decreased with decreasing temperature and reached the value of 172ps at 30K. This temperature dependence of lifetime could be explained by the presence of an additional positron shallow trap. Positron-electron autocorrelation function (AF) was extracted from the CDBS spectra. The obtained AF mappings of HT1 and HT2 at room temperature confirmed that the defects existing in HT1 and HT2 should have different microstructures. Positron lifetime spectroscopy was also performed on undoped pressurized melted grown n-type ZnO single crystal. Two-component model was required to give good description to the lifetime spectra. The two lifetime components were found to have temperature independent values of 181ps and 366ps, which were attributed to saturated positron trapping into two defects, V related defect and vacancy cluster respectively. Zn DOI: 10.5353/th_b3857339 Subjects: Positron annihilation Zinc oxide Compound semiconductors - Spectra
Download or read book Positron Annihilation written by A.T. Steward and published by Elsevier. This book was released on 2012-12-02 with total page 455 pages. Available in PDF, EPUB and Kindle. Book excerpt: Positron Annihilation focuses on the process of positron annihilation in different environments. Partitioned into two parts with 42 chapters, the book contains the contributions of authors who have done research on the annihilation of positrons, which brought about valuable information on the properties of matter. The first part of the book deals with lengthy review articles, including a survey of the physics of positron annihilation; positron annihilation in metals and the theory involved in the process; and positron annihilation in alkali halides and ionic crystals. Positronium formation and interaction in gases, molecular substances, and ionic crystals are also given attention. Gaseous positronics and positron annihilation in condensed gases and liquids are also discussed. The second part of the book focuses on developments on positron annihilation and the direction of research on this field. The studies concentrate on positron annihilation in various crystals, metals, mercury, liquefied gases, helium, and metal oxides. Numerical representations and analyses are presented to support the processes involved. The book can best serve the interest of those who want to explore further the annihilation of positrons.
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: This dissertation, "Defect Studies of Single Crystal and Thin Film Zinc Oxide by Positron Annihilation Spectroscopy and Cathodoluminescence" by Chun-kit, To, 杜俊傑, 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. DOI: 10.5353/th_b4608955 Subjects: Zinc oxide - Defects Positron annihilation Electron spectroscopy Cathodoluminescence
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:
Download or read book Positron Annihilation ICPA 10 written by Yuan Jin He and published by Trans Tech Publications Ltd. This book was released on 1994-11-24 with total page 1104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Positron Annihilation - ICPA-10 presents new results and ideas of researchers who seek more profound understanding of the nature of positron annihilation. All these scientific and technological thoughts are included in these two-volume proceedings, which contain 7 review talks, 203 contributed papers (among them, 20 are invited), and 3 summary talks. The volume is complete with keyword and author indices.
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
Download or read book Positron Annihilation in Chemistry written by Ole E. Mogensen and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: The only critical discussion available on the chemistry of the two "strange" light particles, the positron and positronium, with much space devoted to the excess electron. Positron annihilation allows the investigation of many unusual phenomena in the reaction kinetics of the positron, positronium, and excess electron, and in radiation chemistry and physics, while also providing important information on defects in solids.
Download or read book Electron Positron Annihilation Physics written by Brian Foster and published by CRC Press. This book was released on 1990 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed introduction to the main topics in e +e - annihilation, with particular emphasis on experimental work. Invaluable to both graduate students studying high-energy physics & scientists entering the field.
Download or read book Positron Annihilation in an Interacting Electron Gas written by J. P. Carbotte and published by . This book was released on 1965 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Intrinsic Point Defects in Zinc Oxide written by Paul Erhart and published by . This book was released on 2006 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Positron Annihilation written by and published by . This book was released on 1967 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Briefs written by and published by . This book was released on 1992 with total page 950 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Positron annihilation Characteristics in Real Solids Including Many body Enhancement Effects written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A density functional scheme has been developed for incorporating electron-positron correlation effects into band-structure calculations of positron-annihilation characteristics. The electron and positron densities are determined from a self-consistent set of equations based on a generalized Kohn-Sham scheme. Application of this formalism to defect-free aluminum is described. The results for a two-dimensional angular-correlation spectrum and the positron lifetime show very good agreement with experiment. The method is of general applicability and can be used with any existing self-consistent band-structure scheme.
Download or read book Positron Annihilation Spectroscopic Studies of Undoped N type Zinc Oxide Single Crystal written by Chun-wai Hui and published by . This book was released on 2006 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Positron Annihilation written by Wayne State University and published by . This book was released on 1967 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
