Diffraction contrast dependence on sample thickness and incident energy in on-axis Transmission Kikuchi Diffraction in SEM

Abstract

Automated orientation mapping in SEM, until now relying on EBSD solely, is currently being improved with the development of the TKD technique. As part of the development of TKD, we introduce a new, TEM-like geometric configuration, with a detector "on-axis" relative to the electron beam, while the detector was "off-axis" in its first form. This new technique produces a wide range of diffraction contrast (spots, lines, bands), varying with sample thickness, incident energy, atomic number and scattering angle. Some of the main trends are identified and discussed. In particular, a model based on the plasmon and phonon scattering is proposed to account for the disappearing of diffraction spots with thickness and incident energy. This work should help experimentalists determine which microscope and sample parameters to use in order to obtain a specific contrast. Finally, the strength and weakness of each diffraction feature for orientation mapping are also reviewed.

Keywords: Bragg spots; Kikuchi lines; On-axis detector; Orientation mapping; SEM; Transmission Kikuchi Diffraction (TKD).