4D-STEM of Beam-Sensitive Materials

ConspectusScanning electron nanobeam diffraction, or 4D-STEM (four-dimensional scanning transmission microscopy), is a flexible and powerful approach to elucidate structure from soft materials that are challenging image in the microscope because their easily damaged by beam. In experiment, converged beam scanned across sample, pixelated camera records diffraction pattern at each scan position. This four-dimensional data set can be mined for various analyses, producing maps of local crystal orientation, structural distortions, crystallinity, different classes. Holding sample cryogenic temperatures minimizes diffusion radicals resulting damage disorder caused The total fluence incident electrons controlled during experiments careful use blanker, steering localized dose, minimizing convergent thus damage. technique applied both organic inorganic known beam-sensitive; they highly crystalline, semicrystalline, mixed phase, amorphous.One common example case many have ?-? stacking polymer chains rings on order 3.4-4.2 A separation. If these aligned some regions, will produce distinct spots (as would other crystalline spacings this range), though may weak diffuse disordered weakly scattering materials. We reconstruct orientation stacking, degree domain size regions. Account summarizes illumination conditions experimental parameters with goal images features beam-sensitive. discuss including cooling, probe shape, fluence, cameras. has been variety materials, not only as an advanced model systems, but beginning microscopist answer science questions. It noteworthy acquisition does require aberration-corrected TEM produced instruments right attention parameters.