Improved Nanoscale Electron Diffraction Gratings and Electron Interferometric Measurements

Modern aberration-corrected transmission electron microscopes (TEMs) achieve atomic-resolution imaging, which has become essential in fields such as material science, microbiology, and genetics. Nano-fabricated electron diffraction gratings have introduced coherent beam splitting, and wave-function sculpting to the TEM. An electron Mach Zehnder Interferometer has been constructed in a standard TEM, with nanoscale diffraction gratings as beam splitters [1]. Utilizing the interferometer, proof of principle interaction free measurements, spatial mapping of plasmon modes, and mapping of electrostatic potentials were carried out. The quality of the interferometric measurements is inherently limited by the quality of the beam splitting diffraction gratings. Focused ion beam (FIB) milling is the main technique used to fabricate electron diffraction gratings, but for optimal diffraction nanometer depth precision is required. Here we present work on improving the depth resolution of FIB milled diffraction gratings, and utilizing this new control in holography and interferometric measurements.

[1] C. W. Johnson, A. E. Turner, and B. J. McMorran, Scanning two-grating free electron

mach-zehnder interferometer, Phys. Rev. Res. 3, 043009 (2021)