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Copper Doping of Zinc Oxide by Nuclear Transmutation Matthew .C Recker

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Copper Doping of Zinc Oxide by Nuclear Transmutation Matthew .C Recker Air Force Institute of Technology AFIT Scholar Theses and Dissertations Student Graduate Works 3-14-2014 Copper Doping of Zinc Oxide by Nuclear Transmutation Matthew .C Recker Follow this and additional works at: https://scholar.afit.edu/etd Recommended Citation Recker, Matthew C., "Copper Doping of Zinc Oxide by Nuclear Transmutation" (2014). Theses and Dissertations. 658. https://scholar.afit.edu/etd/658 This Thesis is brought to you for free and open access by the Student Graduate Works at AFIT Scholar. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of AFIT Scholar. For more information, please contact [email protected]. Copper Doping of Zinc Oxide by Nuclear Transmutation THESIS Matthew C. Recker, Captain, USAF AFIT-ENP-14-M-30 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio DISTRIBUTION STATEMENT A APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED The views expressed in this document are those of the author and do not reflect the official policy or position of the United States Air Force, the United States De- partment of Defense or the United States Government. The company, product, and service names used in this document are for identification purposes only. All trade- marks are property of their respective owners. Use of these trademarks does not imply endorsement. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. AFIT-ENP-14-M-30 COPPER DOPING OF ZINC OXIDE BY NUCLEAR TRANSMUTATION THESIS Presented to the Faculty Department of Engineering Physics Graduate School of Engineering and Management Air Force Institute of Technology Air University Air Education and Training Command in Partial Fulfillment of the Requirements for the Degree of Master of Science Matthew C. Recker, BS Captain, USAF March 27th, 2014 DISTRIBUTION STATEMENT A APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED AFIT-ENP-14-M-30 COPPER DOPING OF ZINC OXIDE BY NUCLEAR TRANSMUTATION Matthew C. Recker, BS Captain, USAF Approved: //signed// 27 February 2014 John W. McClory, PhD (Chairman) Date //signed// 27 February 2014 James C. Petrosky, PhD (Member) Date //signed// 27 February 2014 Robert L. Hengehold, PhD (Member) Date AFIT-ENP-14-M-30 Abstract This research verifies that neutron irradiation of zinc oxide leads to Cu-doping of the material by nuclear transmutation. When irradiated, the zinc atoms in ZnO can absorb a neutron resulting in four unstable isotopes (65Zn, 69Zn, 69mZn and 71Zn) which will decay according to their half-lives. 71Zn has a very short half-life and 69Zn decays via a non-gamma emitting β-emission, so neither of these isotopes were detected with gamma spectroscopy. However, both 65Zn and 69mZn were detected and positively identified. 65Zn was visible at all times and 69mZn was visible when the samples were measured within a few days of irradiation. All decay paths of 65Zn lead to 65Cu and the detection of the 1115.5 keV characteristic γ-ray from this decay clearly indicated that 65Cu was being created. Previous electron paramagnetic resonance (EPR) spectroscopic results were repli- cated to determine the spectrum of copper impurities in ZnO as well as the corre- sponding spacing between signals for the two stable isotopes of copper. This hyperfine 65 63 ± spacing was found to be 1015±1 G for Cu and 947 1 G for Cu. The separation between the signals for the irradiated samples was found to be 1013 ±1 G confirming the creation of only 65Cu, as predicted by theory. One motivator for this research was to produce p-type ZnO material through the introduction of copper atoms. The copper EPR signal detected in this research was visible without light stimulation at 6 K, indicating the copper atoms created by trans- mutation are in the Cu2+ state. This implies that these copper atoms exist above the Fermi level. However, there is not enough evidence to determine the position within the band gap and its suitability for p-type material remains undetermined. iv AFIT-ENP-14-M-30 This thesis is dedicated to my family. Thank you for your love, support and understanding throughout my research! v Acknowledgements I would like to thank Dr. John McClory for serving as the chair of my Thesis Committee as well as providing support through valuable insight and guidance. I’d like to thank my committee members: Dr. Petrosky and Dr. Hengehold. I thank Dr. Halliburton for suggesting this research topic and his full support in all of the EPR aspects. I thank Capt Shamaun Holston for all of his help in the EPR lab. Finally, I thank Kevin Herminghuysen and everyone at the Ohio State University Research Reactor for their time and expertise. Matthew C. Recker vi Table of Contents Page Abstract........................................... ................... iv Acknowledgements .................................... ................. vi ListofFigures........................................ ................. ix ListofTables......................................... ................. xi I. Introduction...................................... .................1 1.1 Motivation ......................................... ...........1 1.2 PreviousStudies .................................... ...........2 1.2.1 Korea University (2003) ............................. ......2 1.2.2 Washington State University (2011) . .....2 1.3 Zinc Oxide Applications . ........3 1.4 Thesis Objectives................................... ............3 II. Theory.......................................... ..................5 2.1 ZincOxide .......................................... ..........5 2.1.1 Properties and Characteristics. .......5 2.2 Neutron Interaction................................ .............5 2.3 Radioactive Growth and Decay.......................... .........8 2.3.1 Oxygen Isotopes.................................. ....... 10 2.3.2 ZincIsotopes ..................................... ...... 11 2.3.2.1 64Zn ...........................................11 2.3.2.2 68Zn and 70Zn...................................12 2.3.3 Impurity Isotopes ................................. ...... 15 2.3.3.1 Copper......................................... 15 2.3.3.2 Effect of Other Impurities ........................ 17 2.4 Gamma Spectroscopy ................................ .......... 17 2.4.1 GammaDetection ................................... .... 17 2.4.2 Expected Spectral Features ........................ ....... 18 2.4.3 Peak Identification and Activity Determination . 20 2.5 Mathematica Model .................................. ......... 22 2.5.1 Assumptions...................................... ...... 22 2.5.2 Predicting the Spectrum and Calculating Activity............................................. ... 24 2.6 EPR Spectroscopy.................................. ........... 27 2.6.1 ZeemanEffect ..................................... ..... 27 2.6.2 Hyperfine Splitting . .... 29 2.6.3 EPR Spectrometer System........................... ..... 31 2.7 Selecting Samples forNTD .............................. ....... 31 vii Page III. Experiment...................................... ................. 33 3.1 Material .......................................... ........... 33 3.2 ReactorFacility..................................... .......... 34 3.3 Equipment ......................................... .......... 36 3.3.1 Canberra High-Purity Germanium (HPGe) GammaDetector...................................... .. 36 3.3.2 Bruker EPR Spectrometer ........................... ..... 36 3.4 Irradiation Procedure ............................... ........... 37 3.4.1 ShortIrradiation .................................. ...... 37 3.4.2 LongIrradiation................................... ...... 38 3.5 Gamma Spectroscopy Procedure....................... .......... 41 3.6 EPR Spectroscopy Procedure ......................... .......... 42 IV. Results andAnalysis................................. .............. 43 4.1 Gamma Spectroscopy ................................ .......... 43 4.1.1 Long Irradiation Results . ..... 43 4.1.1.1 Identification of 511 keV Annihilation Peak........................................... 45 4.1.1.2 Identification of 1115 keV 65ZnPeak ............... 46 4.1.1.3 Backscatter Peak and Compton Edge .............. 48 4.1.2 Short Irradiation Results . ..... 49 4.1.2.1 Identification of 438 keV 69mZnPeak ............... 50 4.1.3 Analysis of Sample Activities . 51 4.1.3.1 Comparison of Measured Counts to Model Predictions ............................... 53 4.1.4 Calculation of the 65Cu Concentration...................... 56 4.2 EPR Spectroscopy.................................. ........... 57 4.2.1 Spectrum Processing............................... ...... 58 4.2.2 Spectra of Pre-Annealed Samples ...................... .... 59 4.2.3 Spectra of As-Grown Samples ......................... .... 62 V. Conclusions ........................................ .............. 64 5.1 SummaryofResults .................................. ......... 64 5.2 FutureWork....................................... ........... 67 5.2.1 Verifying the Fermi Level............................ ..... 67 5.2.2 Verifying the Ferromagnetic Behavior of Cu-dopedZnO........................................ .. 67 5.2.3 Understanding the Native Copper ...................... ... 67 5.2.4 Irradiation of Other Semiconductor Materials . .. 68 Bibliography .......................................... ................ 69 viii List of Figures Figure Page 1. Cross-section data for 64Zn.......................................8
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