Atomic Scale Characterization and First-Principles Studies of Si3N4 Interfaces (eBook)

Supervisor’s Foreword 6
Acknowledgments 9
Contents 10
1 Silicon Nitride Ceramics 13
1.1…Introduction 13
1.2…Overview of Previous Studies on Si3N4 14
1.3…Overview of the Present Study 15
References 17
2 Theoretical Methods and Approximations 23
2.1…Born Oppenheimer Approximation 23
2.2…Density Functional Theory 24
2.3…Approximations for the Exchange-Correlation Energy Functional 26
2.4…Periodic Systems: Bloch’s Theorem 27
2.5…k-Point Sampling 28
2.6…Plane Waves, Pseudopotentials, and the Projector Augumented Wave Method 29
2.7…Aperiodic Structures 30
2.8…DFT+U 31
References 32
3 Overview of Experimental Tools 34
3.1…Conventional Transmission Electron Microscope 34
3.2…High-Resolution TEM 35
3.3…Image Simulations 37
3.4…Z-Contrast Imaging in STEM 38
3.5…Annular Bright-Field Imaging in STEM 40
3.6…Probe Formation 40
3.7…Electron Energy-Loss Spectroscopy/Energy-Filtered STEM 44
3.8…Aberration Correctors 47
3.9…Microscopes Used 49
3.10…Multivariate Statistical Analysis 50
References 51
4 Structural Energetics of beta -/bf{Si}_3/hbox{N}_4(10/overline{1}0) Surfaces 55
4.1…Introduction 55
4.2…Computational Methods and Parameters 56
4.3…Silicon Nitride in the Presence of Oxygen 57
4.3.1 /Uptheta={/frac{1}{4}} ML Coverage 59
4.3.2 /Uptheta={/frac{1}{2}} ML Coverage 60
4.3.3 /Uptheta={/frac{3}{4}} ML Coverage 63
4.3.4 /Uptheta=1 ML Coverage 65
4.3.5 Phase Diagram of /varvec /beta-/bf{Si}_3/hbox{N}_4/,(10/overline{1}0) Surface 66
4.3.6 Summary 69
4.4…Silicon Nitride in the Presence of Cerium 70
4.5…Silicon Nitride in the Presence of Oxygen and Rare-Earth Elements 72
4.5.1 Summary 74
References 74
5 Atomic-Resolution Study of the Interfacial Bonding at Si3N4/CeO2minus delta Grain Boundaries 76
5.1…Experimental Setup 76
5.2…Z-Contrast Images of Si3N4/CeO2minusdelta Interfaces 77
5.3…EELS Experiments 79
5.4…Summary 81
References 82
6 Atomic-Resolution Study of {/varvec /beta}-/bf{Si}_3/bf{N}_4//bf{SiO}_2 Interfaces 83
6.1…Introduction 83
6.2…Methods 84
6.3…Imaging of the /bf{Si}_3/bf{N}_4//bf{SiO}_2 Interface 84
6.3.1 Spectroscopy 87
6.4…Thicker Intergranular Films 93
6.5…Discussion of the Results and Conclusions 95
References 96
7 Imaging Bulk alpha -Si3N4 98
7.1…Introduction 98
7.2…Experimental Setup 99
7.2.1 Imaging alpha -Si3N4 99
7.2.2 DFT Calculations 100
7.2.3 EELS Experiments 102
7.3…Summary 102
References 103
8 Conclusions and Future Work 104
References 107
Appendix A Projector Augmented Wave Method 108
Appendix B Incoherent Imaging 111
Index 113