On-axis TKD for orientation mapping of nanocrystalline materials in SEM

A new configuration for Transmission Kikuchi Diffraction (TKD) in SEM was recently developed, with a scintillator perpendicular to the electron beam. This configuration, “on-axis” TKD, makes grains and twins below 10 nm well visible in orientation maps and with high indexation rate, as demonstrated with an electrodeposited nanocrystalline Ni. This high lateral spatial resolution is achieved by combining high accelerating voltage and low sample thickness to reduce the interaction volume. Among the advantages of the on-axis TKD, orientation mapping of particularly thin samples can be realized thanks to the advantageous axial position of the detector. Indeed, the reduction of the solid angle of the transmitted intensity around the beam axis with decreasing sample thickness is much less of a problem with an axial detector than with an off-axis detector. With an on-axis detector, the only condition for production of an orientation map is that the sample must be thick enough to produce Kikuchi diffraction in addition to spots.