ABSTRACT
Chapter 6 outlined electron microscope instrumentation and methods, giving some of the theoretical background to imaging by diffraction contrast (DC), high-resolution electron microscopy (HREM), and the high-angle annular dark eld (HAADF) method, in the scanning transmission electron
9.1 Introduction ...........................................................................................................................245 9.2 Sample Preparation Methods ................................................................................................246 9.2.1 Crushing and Dispersion in Solvent ..........................................................................246 9.2.2 Evaporation onto Holey Carbon Films ......................................................................246 9.2.3 Chemical Polishing.................................................................................................... 247 9.2.4 Electropolishing......................................................................................................... 247 9.2.5 Ultramicrotomy ......................................................................................................... 247 9.2.6 Ion-Beam Milling ...................................................................................................... 247 9.2.7 Mechanical Polishing ................................................................................................248 9.2.8 Focused Ion-Beam Milling ........................................................................................248 9.3 Calibration of TEM ...............................................................................................................249 9.4 Structural Characterization of Grain Boundaries and Interfaces ......................................... 251 9.4.1 Lattice Misorientation ............................................................................................... 251 9.4.2 Determination of Grain Boundary Misorientation ................................................... 252 9.4.3 Diffraction Effects .....................................................................................................254 9.4.4 Grain Boundary Dislocations ....................................................................................256 9.4.5 Determination of Dislocation Line Directions and Interfacial Plane Indices ........... 259 9.5 Atomic Imaging of Interfaces ...............................................................................................260 9.5.1 Atomic Imaging of GBs Using HREM .....................................................................260 9.5.2 An Example of Interfacial Characterization by HREM ........................................... 262 9.5.3 Example of Atomic Imaging of Segregation Using HAADF-STEM .......................265 9.6 Chemical Characterization of Interfaces ..............................................................................268 9.6.1 Measurement of Grain Boundary Segregation by EDX ............................................268 9.6.2 Interfacial Characterization Using EELS .................................................................. 273 References ...................................................................................................................................... 277
microscopy (STEM). Chemical characterization by energy dispersive x-ray (EDX) analysis and electron energy-loss spectroscopy (EELS) was also discussed. Such information is necessary in order to appreciate the speci c application of transmission electron microscopy (TEM) to the characterization of a grain boundary (GB) or an interface (IF), which is the particular subject of this chapter. After a brief summary of the methods available to generate electron-transparent foils from bulk samples and the TEM parameters that require calibration, procedures are described for the determination of misorientation across a GB/IF using electron diffraction. The imaging and analysis of interfacial dislocations are discussed. For GBs with suitable orientation, HREM and HAADF now enable the direct imaging of atomic structure, interfacial dislocations, and the structural units from which the GB is composed. In the space available it is not possible to acknowledge the many excellent contributions to this subject reported in the literature. However, speci c examples are described in order to illustrate the current state of characterization at the leading edge of this eld. The established area of characterization of interfacial segregation by EDX is then described before considering the rapidly expanding area of EELS characterization by spectroscopy, energy- ltered mapping (energy- ltered TEM [EFTEM]), spectroscopic imaging in STEM (electron energy-loss spectroscopy and imaging [EELSI]), and absorption edge ne structure analysis (energy-loss nearedge structure [ELNES]). Space limitation prevents speci c description of more specialized areas of TEM IF analysis, such as magnetic domain imaging, in situ experiments, and electron holography.
