Scanning Electron Microscopy and X-Ray Microanalysis

1. Introduction.- 1.1. Evolution of the Scanning Electron Microscope.- 1.2. Evolution of the Electron Probe Microanalyzer.- 1.3. Outline of This Book.- 2. Electron Optics.- 2.1. Electron Guns.- 2.1.1. Thermionic Emission.- 2.1.2. Tungsten Cathode.- 2.1.3. The Lanthanum Hexaboride (LaB6) Cathode.- 2.1.4. Field Emission Gun.- 2.2. Electron Lenses.- 2.2.1. General Properties of Magnetic Lenses.- 2.2.2. Production of Minimum Spot Size.- 2.2.3. Aberrations in the Electron Optical Column.- 2.3. Electron Probe Diameter, dp, vs. Electron Probe Current i.- 2.3.1. Calculation of dmin and imax.- 2.3.2. Measurement of Microscope Parameters (dp, i, ?).- 2.3.3. High-Resolution Scanning Electron Microscopy.- 3. Electron-Beam-Specimen Interactions.- 3.1. Introduction.- 3.2. Scattering.- 3.2.1. Elastic Scattering.- 3.2.2. Inelastic Scattering.- 3.3. Interaction Volume.- 3.3.1. Experimental Evidence.- 3.3.2. Monte Carlo Calculations.- 3.4. Backscattered Electrons.- 3.4.1. Atomic Number Dependence.- 3.4.2. Energy Dependence.- 3.4.3. Tilt Dependence.- 3.4.4. Angular Distribution.- 3.4.5. Energy Distribution.- 3.4.6. Spatial Distribution.- 3.4.7. Sampling Depth.- 3.5. Signals from Inelastic Scattering.- 3.5.1. Secondary Electrons.- 3.5.2. X-Rays.- 3.5.3. Auger Electrons.- 3.5.4. Cathodoluminescence.- 3.6. Summary.- 4. Image Formation in the Scanning Electron Microscope.- 4.1. Introduction.- 4.2. The Basic SEM Imaging Process.- 4.2.1. Scanning Action.- 4.2.2. Image Construction (Mapping).- 4.2.3. Magnification.- 4.2.4. Picture Element (Picture Point).- 4.2.5. Depth of Field.- 4.2.6. Image Distortions.- 4.3. Stereomicroscopy.- 4.4. Detectors.- 4.4.1. Electron Detectors.- 4.4.2. Cathodoluminescence Detectors.- 4.5. The Roles of Specimen and Detector in Contrast Formation.- 4.5.1. Contrast.- 4.5.2. Atomic Number (Compositional) Contrast (Backscattered Electron Signal).- 4.5.3. Compositional Contrast (Secondary-Electron Signal).- 4.5.4. Contrast Components.- 4.5.5. Topographic Contrast.- 4.6. Image Quality.- 4.6.1. Signal Quality and Contrast Information.- 4.6.2. Strategy in SEM Imaging.- 4.6.3. Resolution Limitations.- 4.7. Signal Processing for the Display of Contrast Information.- 4.7.1. The Visibility Problem.- 4.7.2. Signal Processing Techniques.- 4.7.3. Combinations of Detectors.- 4.7.4. Beam Energy Effects.- 4.7.5. Summary.- 5. X-Ray Spectral Measurement: WDS and EDS.- 5.1. Introduction.- 5.2. Wavelength-Dispersive Spectrometer.- 5.2.1. Basic Design.- 5.2.2. The X-Ray Detector.- 5.2.3. Detector Electronics.- 5.3. Energy-Dispersive X-Ray Spectrometer.- 5.3.1. Operating Principles.- 5.3.2. The Detection Process.- 5.3.3. Artifacts of the Detection Process.- 5.3.4. The Main Amplifier and Pulse Pileup Rejection.- 5.3.5. Artifacts from the Detector Environment.- 5.3.6. The Multichannel Analyzer.- 5.3.7. Summary of EDS Operation and Artifacts.- 5.4. Comparison of Wavelength-Dispersive Spectrometers with Energy-Dispersive Spectrometers.- 5.4.1. Geometrical Collection Efficiency.- 5.4.2. Quantum Efficiency.- 5.4.3. Resolution.- 5.4.4. Spectral Acceptance Range.- 5.4.5. Maximum Count Rate.- 5.4.6. Minimum Probe Size.- 5.4.7. Speed of Analysis.- 5.4.8. Spectral Artifacts.- Appendix: Initial Detector Setup and Testing.- 6. Qualitative X-Ray Analysis.- 6.1. Introduction.- 6.2. EDS Qualitative Analysis.- 6.2.1. X-Ray Lines.- 6.2.2. Guidelines for EDS Qualitative Analysis.- 6.2.3. Pathological Overlaps in EDS Qualitative Analysis.- 6.2.4. Examples of EDS Qualitative Analysis.- 6.3. WDS Qualitative Analysis.- 6.3.1. Measurement of X-Ray Lines.- 6.3.2. Guidelines for WDS Qualitative Analysis.- 6.4. X-Ray Scanning.- 7. Quantitative X-Ray Microanalysis.- 7.1. Introduction.- 7.2. ZAF Technique.- 7.2.1. Introduction.- 7.2.2. The Absorption Factor, A.- 7.2.3. The Atomic Number Factor, Z.- 7.2.4. The Characteristic Fluorescence Correction, F.- 7.2.5. The Continuum Fluorescence Correction.- 7.2.6. Summary Discussion of the ZAF Method.- 7.3. The Empirical Method.- 7.4. Quantitative Analysis with Nonnormal Electron Beam Incidence.- 7.5. Analysis of Particles and Rough Surfaces.- 7.5.1. Geometric Effects.- 7.5.2. Compensating for Geometric Effects.- 7.5.3. Summary.- 7.6. Analysis of Thin Films and Foils.- 7.6.1. Thin Foils.- 7.6.2. Thin Films on Substrates.- 7.7. Quantitative Analysis of Biological Material.- 7.7.1. Introduction.- 7.7.2. Mass Loss and Artifacts during Analysis.- 7.7.3. Bulk Samples.- 7.7.4. Thick Sections on Bulk Substrates.- 7.7.5. Thin Samples.- 7.7.6. The Continuum Method.- 7.7.7. Thick Specimens on Very Thin Supports.- 7.7.8. Microdroplets.- 7.7.9. Standards.- 7.7.10. Conclusion.- Appendix A: Continuum Method.- Appendix B: Worked Examples of Quantitative Analysis of Biological Material.- Notation.- 8. Practical Techniques of X-Ray Analysis.- 8.1. General Considerations of Data Handling.- 8.2. Background Shape.- 8.2.1. Background Modeling.- 8.2.2. Background Filtering.- 8.3. Peak Overlap.- 8.3.1. Linearity.- 8.3.2. Goodness of Fit.- 8.3.3. The Linear Methods.- 8.3.4. The Nonlinear Methods.- 8.3.5. Error Estimation.- 8.4. Dead-Time Correction.- 8.5. Example of Quantitative Analysis.- 8.6. Precision and Sensitivity in X-Ray Analysis.- 8.6.1. Statistical Basis for Calculating Precision and Sensitivity.- 8.6.2. Sample Homogeneity.- 8.6.3. Analytical Sensitivity.- 8.6.4. Trace Element Analysis.- 8.7. Light Element Analysis.- 9. Materials Specimen Preparation for SEM and X-Ray Microanalysis.- 9.1. Metals and Ceramics.- 9.1.1. Scanning Electron Microscopy.- 9.1.2. X-Ray Microanalysis.- 9.2. Particles and Fibers.- 9.3. Hydrous Materials.- 9.3.1. Soils and Clays.- 9.3.2. Polymers.- 10. Coating Techniques for SEM and Microanalysis.- 10.1. Introduction.- 10.1.1. Specimen Characteristics.- 10.1.2. Alternatives to Coating.- 10.1.3. Thin-Film Technology.- 10.2. Thermal Evaporation.- 10.2.1. High-Vacuum Evaporation.- 10.2.2. Low-Vacuum Evaporation.- 10.3. Sputter Coating.- 10.3.1. Ion Beam Sputtering.- 10.3.2. Diode or Direct Current Sputtering.- 10.3.3. Cool Diode Sputtering.- 10.3.4. Sputtering Techniques.- 10.3.5. Choice of Target.- 10.3.6. Coating Thickness.- 10.3.7. Advantages of Sputter Coating.- 10.3.8. Artifacts Associated with Sputter Coating.- 10.4. Specialized Coating Methods.- 10.4.1. High-Resolution Coating.- 10.4.2. Low-Temperature Coating.- 10.5. Determination of Coating Thickness.- 10.5.1. Estimation of Coating Thickness.- 10.5.2. Measurement during Coating.- 10.5.3. Measurement after Coating.- 10.5.4. Removing Coating Layers.- 11. Preparation of Biological Samples for Scanning Electron Microscopy.- 11.1. Introduction.- 11.2. Compromising the Microscope.- 11.2.1. Environmental Stages.- 11.2.2. Nonoptimal Microscope Performance.- 11.3. Compromising the Specimen.- 11.3.1. Correlative Microscopy.- 11.3.2. Specimen Selection.- 11.3.3. Specimen Cleaning.- 11.3.4. Specimen Stabilization.- 11.3.5. Exposure of Internal Surfaces.- 11.3.6. Localizing Areas of Known Physiological Activity.- 11.3.7. Specimen Dehydration.- 11.3.8. Specimen Supports.- 11.3.9. Specimen Conductivity.- 11.3.10. Heavy Metal Impregnation.- 11.3.11. Interpretation and Artifacts.- 12. Preparation of Biological Samples for X-Ray Microanalysis.- 12.1. Introduction.- 12.1.1. The Nature and Enormity of the Problem.- 12.1.2. Applications of X-Ray Microanalysis.- 12.1.3. Types of X-Ray Analytical Investigations.- 12.1.4. Types of Biological Specimens.- 12.1.5. Strategy.- 12.1.6. Criteria for Satisfactory Specimen Preparation.- 12.2. Ambient Temperature Preparative Procedures.- 12.2.1. Before Fixation.- 12.2.2. Fixation.- 12.2.3. Histochemical Techniques.- 12.2.4. Precipitation Techniques.- 12.2.5. Dehydration.- 12.2.6. Embedding.- 12.2.7. Sectioning and Fracturing.- 12.2.8. Specimen Supports.- 12.2.9. Specimen Staining.- 12.2.10. Specimen Coating.- 12.3. Low-Temperature Preparative Procedures.- 12.3.1. Specimen Pretreatment.- 12.3.2. Freezing Procedures.- 12.3.3. Movement of Elements within a Given Cellular Compartment.- 12.3.4. Postfreezing Procedures.- 12.3.5. Frozen-Hydrated and Partially Frozen-Hydrated Material.- 12.3.6. Freeze Drying.- 12.3.7. Freeze Substitution.- 12.3.8. Sectioning.- 12.3.9. Fracturing.- 12.3.10. Specimen Handling.- 12.4. Microincineration.- 13. Applications of the SEM and EPMA to Solid Samples and Biological Materials.- 13.1. Study of Aluminum-Iron Electrical Junctions.- 13.2. Study of Deformation in Situ in the Scanning Electron Microscope.- 13.3. Analysis of Phases in Raney Nickel Alloy.- 13.4. Quantitative Analysis of a New Mineral, Sinoite.- 13.5. Determination of the Equilibrium Phase Diagram for the Fe-Ni-C System.- 13.6. Study of Lunar Metal Particle 63344,1.- 13.7. Observation of Soft Plant Tissue with a High Water Content.- 13.8. Study of Multicellular Soft Plant Tissue with High Water Content.- 13.9. Examination of Single-Celled, Soft Animal Tissue with High Water Content.- 13.10. Observation of Hard Plant Tissue with a Low Water Content.- 13.11. Study of Single-Celled Plant Tissue with a Hard Outer Covering and Relatively Low Internal Water Content.- 13.12. Examination of Medium Soft Animal Tissue with a High Water Content.- 13.13. Study of Single-Celled Animal Tissue of High Water Content.- 14. Data Base.- Table 14.1. Atomic Number, Atomic Weight, and Density of Metals.- Table 14.2. Common Oxides of the Elements.- Table 14.3. Mass Absorption Coefficients for K? Lines.- Table 14.4. Mass Absorption Coefficients for L? Lines.- Table 14.5. Selected Mass Absorption Coefficients.- Table 14.6. K Series X-Ray Wavelengths and Energies.- Table 14.7. L Series X-Ray Wavelengths and Energies.- Table 14.8. M Series X-Ray Wavelengths and Energies.- Table 14.9. Fitting Parameters for Duncumb-Reed Backscattering Correction Factor R.- Table 14.10. J Values and Fluorescent Yield, ?, Values.- Table 14.11. Important Properties of Selected Coating Elements.- References.