A nanofabricated amplitude-division electron interferometer in a transmission electron microscope

Abstract

Wavefront-division electron interferometry with the electron biprism has enabled many applications such as electron holography, exit-wave reconstruction, and demonstration of the Aharonov-Bohm effect. However, wavefront-division interferometry is limited by the requirement of high source coherence. Amplitude-division electron interferometers, first demonstrated by Marton and co-workers in 1954, can overcome this limitation. The implementation of these interferometers is hindered by the precise rotational and translational alignment required. This thesis develops a self-aligned, monolithic electron interferometer consisting of two 45 nm thick silicon layers separated by 20 gm and fabricated from a single crystal silicon cantilever on a transmission electron microscope grid by gallium focused ion-beam milling. Using this interferometer, beam path-separation and interference fringes of lattice periodicity and a maximum contrast of 15% in an unmodified 200 kV transmission electron microscope was demonstrated. This interferometer design can potentially be scaled to millimeter-scale and used in electron holography. It can also be applied to perform fundamental physics experiments such as interaction-free measurement with electrons, with the aim of significantly reducing the damage suffered by biological samples during high-resolution microscopy. Thus, the interferometer can serve as a proof-of-concept of the recently proposed 'Quantum Electron Microscope'.