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Defect Study Of Zinc Oxide Bulk Materials By Positron Lifetime Spectroscopy
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Book Synopsis Defect Study of Zinc Oxide Bulk Materials by Positron Lifetime Spectroscopy by : 蘇振強
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
Book Synopsis Defect Study of Zinc Oxide Bulk Materials by Positron Lifetime Spectroscopy by : Chun-keung So
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:
Book Synopsis DEFECTS AND OPTOELECTRONIC PROPERTIES OF ZINC OXIDE by : Naresh Adhikari
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.
Book Synopsis All-Electron and Full-Potential Positron Annihilation Calculations for Intrinsic and Defective Zinc and Zinc Oxide by : Taojun Zhou
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
Book Synopsis Defect Studies of Single Crystal and Thin Film Zinc Oxide by Positron Annihilation Spectroscopy and Cathodoluminescence by : Chun-Kit To
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:
Book Synopsis Defect Studies of Single Crystal and Thin Film Zinc Oxide by Positron Annihilation Spectroscopy and Cathodoluminescence by : Chun-kit To
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:
Book Synopsis Defects in ZnO Investigated by Positron Lifetime Spectroscopy and Cathodoluminescence by : Jianguo Zhong
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:
Book Synopsis Characterization of Single Defects in Zinc Oxide by : Yun-Yi Pai
Download or read book Characterization of Single Defects in Zinc Oxide written by Yun-Yi Pai and published by . This book was released on 2014 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis summarizes my work on characterizing isolated defects in zinc oxide (ZnO). In chapter 1, I will briefly review the major strength of quantum information processing over classical computation. I will then review the basic properties of nitrogen-vacancy centers, the most-studied point defect species in diamond, and how they motivate the search for defects of similar properties in other semiconductor materials for defect-based quantum information processing. In chapter 2, I will describe our initial study on the optical properties of successfully isolated defects in ZnO: their fluorescence spectra, excited state lifetimes, and their photodynamics including blinking. In chapter 3, I will detail my work on extending the capability of an atomic force microscope to include simultaneous imaging in a confocal geometry. In chapter 4, I will discuss possible directions for our defect studies.
Book Synopsis Studies of Oxygen Implantation Induced Deep Level Defects in Zinc Oxide Single Crystal by : Ziran Ye
Download or read book Studies of Oxygen Implantation Induced Deep Level Defects in Zinc Oxide Single Crystal written by Ziran Ye 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, "Studies of Oxygen Implantation Induced Deep Level Defects in Zinc Oxide Single Crystal" by Ziran, Ye, 叶自然, 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 wide band gap semiconductor which has attracted great attention because of its wide applicability. In order to obtain semiconductor devices with stable and reproducible properties further study of deep level defects is essential. DLTS (Deep level Transient Spectroscopy) is a direct and straightforward techniqueto determine the energy level of the deep level defects. Other information such as activation energy and capture cross section of the defect can also be obtained through this method. In our study ZnO single crystal samples were implanted by oxygen with the energy of 150keV. After the pretreatment of hydrogen peroxide, Schottky contacts were fabricated with Au film deposited by thermal evaporation. Deep level defects were studied by deep level transient spectroscopy (DLTS). Single peak spectra were observed in the as-implanted sample and samples anneal at 350oC, 650oC and 750oC with the corresponding activation energy decreasing with the annealing temperature from 0.29eV as found in theas-implanted sample. Three peaks were identified in the DLTS spectra of the 900oC sample, with the activation energies of 0.11eV, 0.16eV and 0.37eV respectively.After analysis in detail we found some peaks in the DLTS spectra were the combination of two other peaks, dominated in different temperature range. The thermal evolutions of the deep levels up to the temperature of 1200oC were also investigated. DOI: 10.5353/th_b4715385 Subjects: Zinc oxide - Defects Deep level transient spectroscopy Ion implantation
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2540 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positron Annihilation Spectroscopic Studies of Undoped N-Type Zinc Oxide Single Crystal by : Chun-Wai Hui
Download or read book Positron Annihilation Spectroscopic Studies of Undoped N-Type Zinc Oxide Single Crystal written by Chun-Wai Hui 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, "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
Book Synopsis Computational Techniques for Analytical Chemistry and Bioanalysis by : Philippe B. Wilson
Download or read book Computational Techniques for Analytical Chemistry and Bioanalysis written by Philippe B. Wilson and published by Royal Society of Chemistry. This book was released on 2020-12-10 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work will serve as a definitive overview of the field of computational simulation as applied to analytical chemistry and biology, drawing on recent advances as well as describing essential, established theory for graduates and postgraduate researchers.
Book Synopsis Zinc Oxide and Related Materials: Volume 957 by : Jürgen H. Christen
Download or read book Zinc Oxide and Related Materials: Volume 957 written by Jürgen H. Christen and published by . This book was released on 2007-04-05 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners. The topics covered in this volume, first published in 2007, include devices, defects, spintronics and magnetism, growth, optical properties and nanostructures, and doping and processing TFTs.
Book Synopsis Defect Sensitivity and Resolvability Limits in Positron-Lifetime Spectroscopy by : 錢匡裕
Download or read book Defect Sensitivity and Resolvability Limits in Positron-Lifetime Spectroscopy written by 錢匡裕 and published by . This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positrons in Solids by : P. Hautojärvi
Download or read book Positrons in Solids written by P. Hautojärvi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: In condensed matter initially fast positrons annihilate after having reached equi librium with the surroundings. The interaction of positrons with matter is governed by the laws of ordinary quantum mechanics. Field theory and antiparticle properties enter only in the annihilation process leading to the emergence of energetic photons. The monitoring of annihilation radiation by nuclear spectroscopic methods provides valuable information on the electron-positron system which can directly be related to the electronic structure of the medium. Since the positron is a positive electron its behavior in matter is especially interesting to solid-state and atomic physi cists. The small mass quarantees that the positron is really a quantum mechanical particle and completely different from any other particles and atoms. Positron physics started about 25 years ago but discoveries of new features in its interac tion with matter have maintained continuous interest and increasing activity in the field. Nowadays it is becoming part of the "stock-in-trade" of experimental physics.
Book Synopsis Positron Annihilation Spectroscopic Studies of Undoped N-type Zinc Oxide Single Crystal by : Chun-wai Hui
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 Metals Abstracts written by and published by . This book was released on 1994 with total page 1620 pages. Available in PDF, EPUB and Kindle. Book excerpt:
