HIGH-RESOLUTION CHARACTERZATION OF LOW-DIMENSIONAL DEFECTS IN SrTiO3

i Acknowledgements . ii Outline . iv List of Figures . viii List of Tables . xi List of Abbreviations . xii List of Softwares . xiv Chapter One Introduction . 1 Chapter Two Literature Review . 5 2.1 Defects in Oxides: An Opportunity for Future Devices . 6 2.2 Surface Defects: Reconstructed SrTiO3 Surface . 7 2.2.1 Surface Patterns . 8 2.2.2 TEM Studies . 9 2.3 Bulk Defects: (Pr, Al) Implanted SrTiO3 . 10 2.3.1 Emission Mechanism of SrTiO3:Pr 3+ . 11 2.3.2 Increased Efficiency Mechanisms . 13 2.3.3 Introduction of RE ions in SrTiO3 . 15 2.4 Challenges in Characterization of Defects and Low-Dimensional Structures . 19 2.4.1 STEM Mode . 20 2.4.2 TEM Mode . 21 2.4. 3 Spectroscopy . 22 Ph.D. Thesis G. -Z. Zhu; McMaster University Materials Engineering v Chapter Three Specimen Synthesis and Characterization Techniques . 23 3.1 Synthesis of Reconstructed Oxide Surfaces . 24 3.2 Synthesis of Implanted Oxides . 24 3.2.1 Ion Implantation . 24 3.2.2. Post-implantation Treatment . 27 3.3 Luminescence of Implanted Oxides . 28 3.4 TEM Characterization . 28 3.4.1 Sample Preparation for TEM . 28 3.4.2 Conventional Transmission Electron Microscopy . 30 3.4. 3 High-Resolution Imaging . 31 3.4. 4 Electron Energy-Loss Spectroscopy . 32 3.5 Simulation . 33 3.5.1 Multislice Method. 33 3.5.2 Multiplet Method . 34 Chapter Four The Extraction of Weak Signals . 36 4.1 Images . 37 4.1. 1 Invisible Z-contrast from Heavy Atoms . 37 4.1. 2 Directly Imaging Light Atoms within a Heavier Lattice . 39 4.2 EEL Spectra. 40 4.2.1 Experimental Design: A Thickness Series . 41 4.2.2 Step I: Background Subtraction . 42 4.2.3 Step II: Spectra Alignment and Normalization . 44 4.2.4 Step III: Thickness Evaluation . 44 4.2. 5 Step IV: Signal Extraction . 46 Ph.D. Thesis G. -Z. Zhu; McMaster University Materials Engineering vi Chapter Five Results: (001)-Oriented SrTiO3 Reconstructed Surfaces . 47 5.1 Formation of Surface Reconstruction . 48 5.1. 1 (2x1) Surface Pattern . 48 5.1. 2 c(4x2) Surface Pattern . 49 5.2 High-Resolution Profile Images . 50 5.2.1 (2x1) Surface Pattern . 50 5.2.2 c(4x2) Surface Patterns . 52 5.3 Surface Spectra . 54 5.3.1 Spectra from a Thickness Series . 54 5.3.2 Thickness Measurement . 56 5.3.3 Surface Spectra . 56 5.3.4 Multiplet Simulation . 57 Chapter Six Results: Low-dimensional Defects within Ion-implanted SrTiO3 . 61 6.1 Photoluminescence . 62 6.1. 1 The Effect of Aluminum. 62 6.1. 2 The Associated Crystal Field around Pr 3+ . 65 6.2 Recrystallization . 67 6.2.1 Thermal-Induced Recrystallization . 68 6.2.2 Electron-Beam-Associated Recrystallization . 75 6.3 Nano-Clusters . 77 6.3.1 Detectability of Dopants . 80 6.3.2 Associated Electronic Structures . 81 6.3.3 Electron-Beam Damage Behaviors . 82 6.4 Electronic Structures . 83 Ph.D. Thesis G. -Z. Zhu; McMaster University Materials Engineering vii 6.5 Linear Defects within Implantation Regions . 88 6.4.1 Dislocation Loops . 89 6.4.2 Dislocation Cores . 91 Chapter Seven Conclusions . 97 Appendix 1 Parameter Estimation for Inverse Power-law Background Model . 100 A1.1 Hypotheses and Variance of Each Count . 100 A1.2 Least Square Fitting . 102 A1.3 Weighted Least Square Fitting . 103 A1.4 Maximum Likelihood . 105 A1.5 Variances of the Signal . 106 A1.6 Signal-to-noise Ratio . 107 Appendix 2 MATLAB Codes . 108 A2.1 Maximum Likelihood Background Fitting . 108 A2.2 Singular Value Decomposition . 111 A2.3 Dimension Calibration for a Scanned Diffraction Film . 113 Appendix 3 The Visibility of Pr wihin the SrTiO3 lattice .