Transmission Kikuchi diffraction and transmission electron forescatter imaging of electropolished and FIB manufactured TEM specimens

• The transmission imaging and diffraction techniques are emerging in scanning electron microscopy (SEM) as promising new field of materials characterization.
• The manuscript titled: “Transmission Kikuchi Diffraction and Transmission Electron Forescatter Imaging of Electropolished and FIB Manufactured TEM Specimens” documents how different specimen thinning procedures can effect efficiency of transmission Kikuchi diffraction and transmission electron forescatter imaging.
• The abilities to make precision crystallographic orientation maps and dark-field images in transmission was studied on electropolished versus focus ion beam manufactured TEM specimens.
• Depending on the need, electropolished and focused ion beam technique may produce suitable specimens for transmission imaging and diffraction in SEM.
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We present a study of the efficiency of the utility of scanning electron microscope (SEM)-based transmission methods for characterizing grain structure in thinned bulk metals. Foils of type 316 stainless steel were prepared by two methods commonly used for transmission electron microscopy — double-jet electropolishing and focused ion beam milling. A customized holder allowed positioning of the foils in a configuration appropriate for both transmission electron forward scatter diffraction, and for transmission imaging by the use of a forescatter detector with two diodes. We found that both crystallographic orientation maps and dark-field transmitted images could be obtained for specimens prepared by either method. However, for both methods, preparation-induced artifacts may affect the quality or accuracy of transmission SEM data, especially those acquired by the use of transmission Kikuchi diffraction. Generally, the quality of orientation data was better for specimens prepared by electropolishing, due to the absence of ion-induced damage.