Electron microscopy is a core characterization technique that is commonly used in materials research. This technique uses high-energy electrons to obtain high-resolution images and chemical information about materials, allowing for the creation of structure-property relationships. Electron microscopy provides higher resolution compared to optical microscopy, which uses light as a source. Electron microscopy can be divided into three main groups: scanning electron microscopy (SEM), focused ion beam processing microscopy (FIB-SEM), and transmission electron microscopy (TEM).
SEM typically uses secondary electrons that are created through inelastic scattering between the electrons and the sample. FIB-SEM uses a focused ion beam to scan the surface of the sample and create an SEM image. The elemental distribution within the sample and the crystal structure-orientation information of the sample can be obtained using attached energy dispersive x-ray spectroscopy (EDS) and electron backscattered detector (EBSD), respectively.
The FIB system uses a focused beam of ions (usually Ga3+ ions) to create an image or etch the surface of the sample. The energy of the ion and the position of the beam are precisely controlled to perform the desired processes. TEM sample preparation and cross-section imaging of semiconductors for reverse engineering are well-known applications of FIB-SEM.
TEM is used to analyze the structure and chemical composition of nanomaterials. The ideal sample thickness for TEM is 100 nm or less. High-resolution TEM images are created using transmitted electrons that are generated through the interaction of high-energy electrons and the sample. TEM has the advantage of providing various types of information about the sample. In STEM mode, TEM can provide imaging data and spectroscopic mapping simultaneously. Selected area electron diffraction (SAED) provides crystallographic information about the material, while electron energy loss spectroscopy (EELS) and energy dispersive x-ray spectroscopy (EDX) provide chemical information about the material.