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

Ken Harada,Hiroyuki Shinada,Kodai Niitsu,Tetsuya Akashi,Yoshimasa A Ono,Keiko Shimada,Daisuke Shindo,Shigeo Mori

doi:10.1038/s41598-018-19380-4

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.

Highlights

Recent state-of-the-art technologies on electron microscopes (EMs) have provided us an advanced EM system equipped with generation of coherent electron beams, their precise operations during the propagation, and single electron detection
In the present double-slit experiments, we used the following technologies and methods to clarify these ambiguities: (1) highly coherent electron beams from a recently developed 1.2-MV field-emission transmission electron microscope (FE-TEM)[18,19], (2) asymmetric double slits having slit widths that can be varied by using a biprism, and (3) measurements under a pre-Fraunhofer condition at distances shorter than those in the Fraunhofer condition
This analysis confirms that the camera system on the microscope can detect single electron positions

Summary

Introduction

Recent state-of-the-art technologies on electron microscopes (EMs) have provided us an advanced EM system equipped with generation of coherent electron beams, their precise operations during the propagation, and single electron detection. When spatial spreads of existence probabilities of electrons, which depend on Heisenberg’s uncertainty principle, become larger than the double-slit size, it becomes possible to precisely carry out double slit experiments, which indicate wave-particle duality of electrons. In the present double-slit experiments, we used the following technologies and methods to clarify these ambiguities: (1) highly coherent electron beams from a recently developed 1.2-MV field-emission transmission electron microscope (FE-TEM)[18,19], (2) asymmetric double slits having slit widths that can be varied by using a biprism, and (3) measurements under a pre-Fraunhofer condition at distances shorter than those in the Fraunhofer condition. We used these three interference patterns to distinguish three types of electron: electrons passing through only one of the asymmetric slit; electrons passing through both slits simultaneously; and electrons passing through only the other slit

Methods

Results

Discussion

Conclusion