Maintaining the genuine structure of 2D materials and catalytic nanoparticles at atomic resolution

Abstract

The recent development of atomic resolution, low dose-rate electron microscopy allows investigating 2D materials as well as catalytic nano particles without compromising their structural integrity. For graphene and a variety of nanoparticle compositions, it is shown that a critical dose rate exists of <100e−/Å2s at 80keV of electron acceleration that allows maintaining the genuine object structures including their surfaces and edges even if particles are only 3nm large or smaller. Moreover, it is demonstrated that electron beam-induced phonon excitation from outside the field of view contributes to a contrast degradation in recorded images. These degradation effects can be eliminated by delivering electrons onto the imaged area, only, by using a Nilsonian illumination scheme in combination with a suitable aperture at the electron gun/monochromator assembly.