Aberration-Corrected Analytical Transmission Electron Microscopy

Professor R.M.D. (Rik) Brydson is based in the School of Process, Environmental and Materials Engineering at the University of Leeds, UK. He is a committee member for the European Microscopy Society as well as the Electron Microscopy and Analysis Group (Institute of Physics).

• List of Contributors xi Preface xiii1 General Introduction to Transmission Electron Microscopy (TEM) 1Peter Goodhew1.1 What TEM Offers 11.2 Electron Scattering 31.2.1 Elastic Scattering 71.2.2 Inelastic Scattering 81.3 Signals which could be Collected 101.4 Image Computing 121.4.1 Image Processing 121.4.2 Image Simulation 131.5 Requirements of a Specimen 141.6 STEM Versus CTEM 171.7 Two Dimensional and Three Dimensional Information 172 Introduction to Electron Optics 21Gordon Tatlock2.1 Revision of Microscopy with Visible Light and Electrons 212.2 Fresnel and Fraunhofer Diffraction 222.3 Image Resolution 232.4 Electron Lenses 252.4.1 Electron Trajectories 262.4.2 Aberrations 272.5 Electron Sources 302.6 Probe Forming Optics and Apertures 322.7 SEM, TEM and STEM 333 Development of STEM 39L.M. Brown3.1 Introduction: Structural and Analytical Information in Electron Microscopy 393.2 The Crewe Revolution: How STEM Solves the Information Problem 413.3 Electron Optical Simplicity of STEM 423.4 The Signal Freedom of STEM 453.4.1 Bright-Field Detector (Phase Contrast, Diffraction Contrast) 453.4.2 ADF, HAADF 453.4.3 Nanodiffraction 463.4.4 EELS 473.4.5 EDX 473.4.6 Other Techniques 483.5 Beam Damage and Beam Writing 483.6 Correction of Spherical Aberration 493.7 What does the Future Hold? 514 Lens Aberrations: Diagnosis and Correction 55Andrew Bleloch and Quentin Ramasse4.1 Introduction 554.2 Geometric Lens Aberrations and Their Classification 594.3 Spherical Aberration-Correctors 664.3.1 Quadrupole-Octupole Corrector 694.3.2 Hexapole Corrector 704.3.3 Parasitic Aberrations 724.4 Getting Around Chromatic Aberrations 744.5 Diagnosing Lens Aberrations 754.5.1 Image-based Methods 774.5.2 Ronchigram-based Methods 804.5.3 Precision Needed 854.6 Fifth Order Aberration-Correction 854.7 Conclusions 865 Theory and Simulations of STEM Imaging 89Peter D. Nellist5.1 Introduction 895.2 Z-Contrast Imaging of Single Atoms 905.3 STEM Imaging Of Crystalline Materials 925.3.1 Bright-field Imaging and Phase Contrast 935.3.2 Annular Dark-field Imaging 965.4 Incoherent Imaging with Dynamical Scattering 1015.5 Thermal Diffuse Scattering 1035.5.1 Approximations for Phonon Scattering 1045.6 Methods of Simulation for ADF Imaging 1065.6.1 Absorptive Potentials 1065.6.2 Frozen Phonon Approach 1075.7 Conclusions 1086 Details of STEM 111Alan Craven6.1 Signal to Noise Ratio and Some of its Implications 1126.2 The Relationships Between Probe Size, Probe Current and Probe Angle 1136.2.1 The Geometric Model Revisited 1136.2.2 The Minimum Probe Size, the Optimum Angle and the Probe Current 1156.2.3 The Probe Current 1156.2.4 A Simple Approximation to Wave Optical Probe Size 1176.2.5 The Effect of Chromatic Aberration 1176.2.6 Choosing αopt in Practice 1186.2.7 The Effect of Making a Small Error in the Choice of αopt 1196.2.8 The Effect of α On the Diffraction Pattern 1206.2.9 Probe Spreading and Depth of Field 1226.3 The Condenser System 1246.4 The Scanning System 1266.4.1 Principles of the Scanning System 1266.4.2 Implementation of the Scanning System 1286.4.3 Deviations of the Scanning System From Ideality 1286.4.4 The Relationship Between Pixel Size and Probe Size 1306.4.5 Drift, Drift Correction and Smart Acquisition 1316.5 The Specimen Stage 1336.6 Post-Specimen Optics 1356.7 Beam Blanking 1366.8 Detectors 1376.8.1 Basic Properties of a Detector 1376.8.2 Single and Array Detectors 1396.8.3 Scintillator/Photomultiplier Detector 1396.8.4 Semiconductor Detectors 1416.8.5 CCD Cameras 1426.9 Imaging Using Transmitted Electrons 1456.9.1 The Diffraction Pattern 1456.9.2 Coherent Effects in the Diffraction Pattern 1476.9.3 Small Angular Range – Bright Field and Tilted Dark Field Images 1526.9.4 Medium Angular Range – MAADF 1526.9.5 High Angular Range – HAADF 1536.9.6 Configured Detectors 1536.10 Signal Acquisition 154Acknowledgements 1597 Electron Energy Loss Spectrometry and Energy Dispersive X-ray Analysis 163Rik Brydson and Nicole Hondow7.1 What is EELS and EDX? 1647.1.1 Basics of EDX 1647.1.2 Basics of EELS 1667.1.3 Common Features For Analytical Spectrometries 1687.2 Analytical Spectrometries in the Environment of the Electron Microscope 1707.2.1 Instrumentation for EDX 1707.2.2 EELS Instrumentation 1747.2.3 Microscope Instrumentation for Analytical Spectroscopies 1787.3 Elemental Analysis and Quantification Using EDX 1827.4 Low Loss EELS – Plasmons, IB Transitions and Band Gaps 1877.5 Core Loss EELS 1917.5.1 Elemental Quantification 1917.5.2 Near-Edge Fine Structure For Chemical and Bonding Analysis 1957.5.3 Extended-Edge Fine Structure For Bonding Analysis 2007.6 EDX and EELS Spectral Modelling 2017.6.1 Total Spectrum Modelling 2017.6.2 EELS Modelling of Near Edge Structures and also the Low Loss 2017.7 Spectrum Imaging: EDX and EELS 2027.8 Ultimate Spatial Resolution of EELS 2067.9 Conclusion 2078 Applications of Aberration-Corrected Scanning Transmission Electron Microscopy 211Mervyn D. Shannon8.1 Introduction 2118.2 Sample Condition 2128.3 HAADF Imaging 2138.3.1 Imaging of Isolated Atoms 2138.3.2 Line Defects (1-D) 2198.3.3 Interfaces and Extended Defects (2-D) 2208.3.4 Detailed Particle Structures (3-D) 2268.3.5 Low-loss EELS 2308.3.6 Core-loss EELS and Atomic-scale Spectroscopic Imaging 2318.4 Conclusions 2369 Aberration-Corrected Imaging in CTEM 241Sarah J. Haigh and Angus I. Kirkland9.1 Introduction 2419.2 Optics and Instrumentation for Aberration-Corrected CTEM 2439.2.1 Aberration-Correctors 2439.2.2 Related Instrumental Developments 2439.3 CTEM Imaging Theory 2449.3.1 CTEM Image Formation 2449.3.2 The Wave Aberration Function 2469.3.3 Partial Coherence 2529.4 Corrected Imaging Conditions 2539.4.1 The Use of Negative Spherical Aberration 2549.4.2 Amplitude Contrast Imaging 2569.5 Aberration Measurement 2569.5.1 Aberration Measurement From Image Shifts 2569.5.2 Aberration Measurement from Diffractograms 2579.5.3 An Alternative Approach to Aberration Measurement 2589.6 Indirect Aberration Compensation 2589.7 Advantages of Aberration-Correction for CTEM 2599.8 Conclusions 259Acknowledgements 260Appendix A: Aberration Notation 263Appendix B: General Notation 267Index 275

“This book is essential for microscopists involved in nanoscale and materials microanalysis especially those using scanning transmission electron microscopy, and related analytical techniques such as electron diffraction x-ray spectrometry (EDXS) and electron energy loss spectroscopy (EELS).”  (Imaging & Microscopy, 1 March 2012)