EXAMINATION OF DEFORMATION DEFECTS IN BULK CRYSTALS USING ELECTRON CHANNELING CONTRAST IMAGING

摘要

The crystallographic characterization of dislocations and deformation twins associated with plastic deformation is commonly carried out by thin foil examination in transmission electron microscopy (TEM) using diffraction contrast analysis. However, the thin foil approach has some limitations including difficulties in sample preparation, relatively small viewable areas, artifacts associated with thin foils, and difficulties in carrying out in-situ studies. As an alternative approach, electron channeling contrast imaging (ECCI) offers the ability to image and characterize crystallographic defects in the near surface region of bulk specimens by using a field emission gun scanning electron microscope (FEG-SEM). In this method, selected area channeling patterns (SACPs) are used to set up imaging conditions in a manner analogous to using selected area diffraction patterns in TEM. This paper reviews the electron channeling phenomena and image formation in ECCI, and outlines the experimental parameters necessary to image dislocations and microtwins. A number of examples are presented that illustrate the capabilities and advantages of using ECCI for defect imaging and analysis.