Detection of electron vortex beams : Using a scanning transmission electron microscope

Abstract: Electron vortex beams (EVBs) are electron beams with a doughnut-like intensity profile, carrying orbital angular momentum due to their helical phase shift distribution. When employed in an electron microscope, they are expected to be efficient for the detection of magnetic signals. In this report I have investigated high angle annular dark field (HAADF) images obtained using EVBs. This was done for 300 K and 5K. For 5 K,  I also compared HAADF images from an ordinary electron beam with HAADF images from an electron vortex beam. What was found was that EVBs produced doughnuts around the atomic columns. However, when taking the size of the electron source into account, this phenomena could no longer  be observed. When comparing images from EVBs with images from ordinary electron beams, I found that the intensity of scattered electrons around atomic columns was broader for EVBs. This was persistent even after taking the source size into account.