Semicircular-aperture illumination scanning transmission electron microscopy

TL;DR

This paper introduces a semicircular aperture in STEM that enhances phase contrast transfer, offering a cost-effective and noise-free alternative to traditional phase plates for high-resolution imaging of various samples.

Contribution

The study presents a novel semicircular aperture design in STEM that improves phase contrast transfer without charge accumulation or background noise, reducing costs compared to existing methods.

Findings

Enhanced phase contrast transfer with semicircular aperture

No charge accumulation or background noise observed

Effective imaging of polymer, biological, and magnetic samples

Abstract

Scanning transmission electron microscopy (STEM) provides high-resolution visualization of atomic structures as well as various functional imaging modes utilizing phase contrast. In this study we introduce a semicircular aperture in STEM bright field imaging, which gives a phase contrast transfer function that becomes complex and includes both lower and higher spatial frequency contrast transfer. This approach offers significant advantages over conventional phase plate methods, having no charge accumulation, degradation, or unwanted background noise, which are all problematic in the phase plate material. Also compared to the differential phase contrast or ptychography equipment, this semicircular aperture is far less costly. We apply this approach to visualization of polymer, biological and magnetic samples.