Liquid-cell annular dark-field scanning transmission electron microscopy imaging of single crystal samples on a low-index zone-axis incidence condition

Abstract

In liquid cell (LC) annular dark-field scanning transmission electron microscopy (ADF-STEM), the spatial resolution is limited by the low ratio of signals from samples to background signals from the silicon nitride window membranes and liquid. We report the development of a double-tilt LC holder for atomic-resolution LC-ADF-STEM imaging of single-crystal samples under zone-axis incidence conditions. A SrTiO₃ <001> lamellar sample, approximately 100 nm thick, was prepared using the focused ion beam technique and transferred onto a silicon nitride window membrane of an LC chip via a glass probe pick-up method in air, which avoids Ga ion beam-induced damage to the window membrane. The sample adhered to the high-flatness window membrane and remained immobile, even when embedded in a water droplet. The sample and pure water were enclosed in an LC and observed under <001> zone-axis incidence conditions using aberration-corrected ADF-STEM. Electron channeling along the atomic columns enabled atomic-resolution LC-ADF-STEM imaging with high contrast, sufficiently overcoming background signals from window membranes and liquids. This high-contrast imaging technique could lower the probe current and is expected to mitigate electron-beam-induced radiolysis and minimize undesired sample damage, particularly under high-magnification imaging conditions.