Interference experiment with asymmetric double slit by using 1.2-MV field emission transmission electron microscope

Abstract

Advanced electron microscopy technologies have made it possible to perform precise double-slit interference experiments. We used a 1.2-MV field emission electron microscope providing coherent electron waves and a direct detection camera system enabling single-electron detections at a sub-second exposure time. We developed a method to perform the interference experiment by using an asymmetric double-slit fabricated by a focused ion beam instrument and by operating the microscope under a “pre-Fraunhofer” condition, different from the Fraunhofer condition of conventional double-slit experiments. Here, pre-Fraunhofer condition means that each single-slit observation was performed under the Fraunhofer condition, while the double-slit observations were performed under the Fresnel condition. The interference experiments with each single slit and with the asymmetric double slit were carried out under two different electron dose conditions: high-dose for calculation of electron probability distribution and low-dose for each single electron distribution. Finally, we exemplified the distribution of single electrons by color-coding according to the above three types of experiments as a composite image.

The Young-Feynman controlled double-slit electron interference experiment

“…In the final stage of the review process, we became aware of a recently published paper by Harada et al . 31 on interference experiments with asymmetric double slits, which were aimed at categorisation of the electrons. As their experiments were carried out using a 1.2 MV field emission electron microscope, the biprisms that were used as slits were not completely opaque to the electrons, as required in the experiments reported in the present work, in which the required opacity was achieved only at a very low accelerating potential of 60 kV.…”

Interference and interferometry in electron holography

“…Figure 4 shows an example of the double-slit interference fringe formation processes, i.e. a ‘single-electron buildup’ experiment [ 38 ]. Each bright spot in the figures shows an arrival point of a single electron.…”

Electron holography on Fraunhofer diffraction

“…In this paper, we propose electron holography on Fraunhofer diffraction utilizing an asymmetric double slit created by a biprism from a symmetric double slit placed at the specimen position [22]. A Fraunhofer diffraction wave from a wider slit can work as an objective wave interfering with a plane-wave-like wave from an extremely narrower slit acting as a reference wave.…”

“…Figure 1 shows an illustration for explaining the concept of this study and ‘pre-Fraunhofer condition’ [22]. An asymmetric double-slit, which has one narrow opening and other slightly wider opening, is positioned at the upstream of a coherent electron wave.…”