Very-High Dynamic Range, 10,000 Frames/Second Pixel Array Detector for Electron Microscopy

Area of Science:

• Materials Science
• Electron Microscopy
• Physics

Background:

• Quantitative scanning transmission electron microscopy (STEM) methods like ptychography require precise dose control for accurate mapping of electric, magnetic, and strain fields.
• High beam currents and sensitive signal detection are crucial for efficient data acquisition in STEM.
• Existing detectors face limitations in dynamic range and speed, impacting the quality and timeliness of STEM data.

Purpose of the Study:

• To introduce and evaluate the second-generation Electron Microscope Pixel Array Detector (EMPAD-G2) for advanced STEM applications.
• To demonstrate the EMPAD-G2's capability to overcome limitations of previous detectors in terms of speed, dynamic range, and data quality.
• To present a new metric, maximum usable imaging speed (MUIS), for characterizing detector performance.

Main Methods:

• Development and implementation of the EMPAD-G2, a hybrid pixel array detector with advanced capabilities.
• Continuous imaging at frame rates up to 10 kHz with a wide dynamic range (single electrons to >180 pA/pixel).
• Testing across electron energies from 80 to 300 keV, including ptychographic reconstructions and strain/polarization mapping.

Main Results:

• The EMPAD-G2 achieves high-speed imaging (up to 10 kHz) with exceptional dynamic range at 300 keV.
• It enables simultaneous collection of comprehensive diffraction information, from bright-field disks to Kikuchi bands.
• Experimental results showcase successful ptychographic reconstructions and accurate mapping of strain and polarization fields.

Conclusions:

• The EMPAD-G2 significantly advances quantitative STEM by enabling rapid, high-quality data acquisition.
• Its performance characteristics allow for precise mapping of material properties, even with challenging beam conditions.
• The introduction of MUIS provides a standardized method for assessing detector performance in electron-starved or saturated regimes.