High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy

TL;DR

This paper introduces a high dynamic range pixel array detector for electron microscopy that enables rapid, detailed imaging with single electron sensitivity and the ability to analyze full diffraction patterns for comprehensive sample characterization.

Contribution

The paper presents a novel hybrid pixel array detector with high dynamic range, fast framing, and full diffraction pattern capture for enhanced electron microscopy imaging.

Findings

Achieved 1,000,000:1 dynamic range within a single frame.

Enabled rapid data collection at 1.1 kHz framing rate.

Demonstrated capability to analyze full scattering distributions.

Abstract

We describe a hybrid pixel array detector (EMPAD - electron microscope pixel array detector) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128 x 128 pixel detector consists of a 500 um thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit (ASIC). The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition (DAQ) system, and preliminary results from experiments with 80 to 200 keV electron beams.