We are occasionally privileged to welcome distinguished external experts to give seminars to the Group.

  • Dr Masaya Kataoka, National Physical Laboratory
    9th June, 2021

    Electron quantum optics for electrical metrology
  • Dr Jonas Lähnemann, Paul-Drude-Institut für Festkörperelektronik, Berlin
    19th May, 2021

    Revisiting the determination of the carrier diffusion length in GaN from cathodoluminescence spectroscopy
  • Dr Budhika Mendis, Department of Physics, Durham University
    3rd March, 2021

    Towards accurate simulation of EBSD and ECCI signals
    Electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) are two scanning electron microscopy (SEM)-based techniques that provide crystallographic information, such as sample orientation, strain and defects (e.g. dislocations and stacking faults). The techniques rely on the ‘channeling’ phenomenon, where the high energy electron beam is attracted to the positive potential of the atom columns as it propagates through the specimen. During channeling the electrons can also undergo inelastic scattering, such as inner-shell ionisation, as well as phonon and plasmon excitations.

    Standard multislice and Bloch wave simulation methods only take into account elastic and phonon scattering. Recently we have used Monte Carlo techniques to combine multislice calculations with plasmon excitations[1-3]. The significance of this is that plasmons have a relatively large cross-section compared to other energy loss processes. Plasmon multislice simulations have been applied to EBSD and ECCI signals in the SEM[4]. Despite the close similarity of the two techniques, we find that plasmons have an important effect on EBSD, but not ECCI. These results can be explained by considering the effect of plasmon excitation on the intrinsic contrast mechanisms in both EBSD and ECCI.

    [1] BG Mendis, Ultramicroscopy 206 (2019) 112816.
    [2] BG Mendis, Microscopy 69 (2020) 173.
    [3] J Barthel, M Cattaneo, BG Mendis, SD Finlay and LJ Allen, Phys Rev B 101 (2020) 184109.
    [4] BG Mendis, J Barthel, SD Finlay and LJ Allen, Microsc. Microanal. 26 (2020) 1147.