Photoelectron Diffraction Imaging of Microcrystallites on the Surface of a NiPolycrystal

The applicability of the forward scattering of photoelectrons in electron microscopy is demonstrated for the characterization and investigation of the polycrystalline substrates. The well-resolved images of individual microcrystallites on the surface of Ni polycrystal have been obtained by using the Ni2p3/2photoelectrons(Ekin= 635eV)collected at a widely variable direction of emission. By using the forward scattering approach, not only crystallites resolved by an optical microscope but also the microcrystallites, which were not distinguished by the optical method, have been easily identified through the photoelectron diffraction contrast. This contrast amounted to almost 50% of the whole intensity scale and could be observed directly during the acquisition of the images. Crystallographic information on the orientation of the microcrystallites constituting the polycrystal was obtained: some crystallites with the low index surfaces were identified, some microcrystallites with the same orientation were recognized, and the symmetry of the surfaces of the individual crystallites was partly controlled. An approximate identification of the crystallographic orientation of several individual microcrystallites in the investigated Ni polycrystal has been achieved.