Direct electron detection for atomic-resolution spectroscopic mapping under cryogenic and signal-limited conditions

Area of Science:

• Materials Physics
• Biological Systems
• Solid-Liquid Interfaces

Background:

• Spectroscopic mapping using STEM-EELS at cryogenic temperatures is expanding into new research fields.
• Signal limitations due to sample sensitivity or acquisition time can hinder these experiments.
• Direct electron detectors (DEDs) offer advantages over traditional charge-coupled devices (CCDs), including higher detective quantum efficiency and better signal-to-noise ratios.

Purpose of the Study:

• To compare the performance of a Gatan K2 Summit DED with a Gatan UltraScan 1000 CCD for signal-limited EELS experiments.
• To evaluate the suitability of DEDs for cryogenic atomic-resolution elemental mapping.

Main Methods:

• Comparative performance analysis of a DED and a CCD in STEM-EELS experiments.
• Evaluation of energy resolution, signal-to-noise ratio, and atomic column contrast.
• Demonstration of atomic-resolution elemental mapping at cryogenic temperatures using DEDs.

Main Results:

• The DED achieved comparable energy resolution to the CCD at a 5x lower dispersion, enabling a broader energy range.
• DEDs facilitated low-signal experiments, including rapid mapping of minor and high-energy edges.
• Elemental maps acquired with DEDs exhibited increased atomic column contrast at low dwell times compared to CCDs.

Conclusions:

• DEDs significantly enhance cryogenic STEM-EELS by overcoming signal limitations.
• The improved performance of DEDs enables advanced low-signal experiments and rapid atomic-resolution elemental mapping.
• This advancement opens new possibilities for research in materials physics, biological systems, and interface science.