Image resolution and sensitivity in an environmental transmission electron microscope

An environmental transmission electron microscope provides unique means for the atomic-scale exploration of nanomaterials during the exposure to a reactive gas environment. Here we examine conditions to obtain such in situ observations in the high-resolution transmission electron microscopy (HRTEM) mode with an image resolution of 0.10 nm. This HRTEM image resolution threshold is mapped out under different gas conditions, including gas types and pressures, and under different electron optical settings, including electron beam energies, doses and dose-rates. The 0.10 nm resolution is retainable for H2 at 1–10 mbar. Even for N2, the 0.10 nm resolution threshold is reached up to at least 10 mbar. The optimal imaging conditions are determined by the electron beam energy and the dose-rate as well as an image signal-to-noise (S/N) ratio that is consistent with Rose's criterion of S/N ≥ 5. A discussion on the electron–gas interactions responsible for gas-induced resolution deterioration is given based on interplay with complementary electron diffraction (ED), scanning transmission electron microscopy (STEM) as well as electron energy loss spectroscopy (EELS) data.

► Aberration-corrected HRTEM in an environmental transmission electron microscope.
► Image resolution and sensitivity versus gaseous and electron-optical settings.
► An image resolution of 0.10 nm in the HRTEM mode of an ETEM.