Sub-100 nanosecond temporally resolved imaging with the Medipix3 direct electron detector

Abstract

Detector developments are currently enabling new capabilities in the field of Transmission Electron Microscopy (TEM). We have investigated the limits of a hybrid pixel detector, Medipix3, to record dynamic, time varying, electron signals.Operating with an energy of 60 keV, we have utilised electrostatic deflection to oscillate electron beam position on the detector. Adopting a pump-probe imaging strategy we have demonstrated that temporal resolutions three orders of magnitude smaller than available for typically used TEM imaging detectors are possible. Our experiments have shown that energy deposition of the primary electrons in the hybrid pixel detector limits overall temporal resolution. Through adjustment of user specifiable thresholds or the use of charge summing mode, we have obtained images composed from summing 10,000s frames containing single electron events to achieve temporal resolution less than 100 ns. We propose that this capability can be directly applied to studying repeatable material dynamic processes but also to implement low-dose imaging schemes in scanning transmission electron microscopy.

Quantifying the Performance of a Hybrid Pixel Detector with GaAs:Cr Sensor for Transmission Electron Microscopy

“…One class of experiments where high-Z sensors are likely to be particularly useful are time-resolved experiments. By reducing the lateral spread in the signal produced by the primary electrons, the temporal resolution of HPDs should be also be improved at high energies, as the scattering of incident electrons over multiple pixels means they can be counted in multiple frames when using short frames times [12]. Other experimental modes that would benefit from the use of HPDs with high-Z sensors include 4D-STEM modes that depend on precise measurement of the deflection of disks in the diffraction pattern due to either transmitted or Bragg-diffracted electrons.…”

“…On-pixel signal processing circuitry makes them capable of high (typically kHz) frame-rates and electron counting at MHz rates [8,9]. This makes them highly effective sensors for capturing fast (1ms) dynamics in a conventional transmission electron microscope (TEM) [10], and they show the potential to record processes at timescales of ≤ 1 µs [11,12]. Their ability to maintain a linear response even when subjected to high (≥ 1000 e/pixel/s) electron flux means they are suitable for use in a variety of diffractionbased experiments [9].…”

Fast Pixelated Detectors in Scanning Transmission Electron Microscopy. Part I: Data Acquisition, Live Processing, and Storage

“…This makes the detector capable of noiseless operation by the setting of an appropriate threshold for counting, and the detector is thus able to detect individual electrons. As a consequence, the Medipix3 detector is of potential use in time-resolved electron microscopy experiments, where sub-100 ns time resolution has been recently demonstrated (Paterson et al, 2020 a ).…”

Angular dependence of fast-electron scattering from materials

“…2(a) and 2(c), were acquired using a probe C S -corrected microscope at 300 kV accelerating voltage [21]. The instrument is equipped with a Merlin Medipix 3 detector for recording diffraction patterns on a 256 × 256 array of pixels [22]. Diffraction projection, detector gain correction factors, and the frequency modulation transfer function have been carefully calibrated to enable accurate modeling of diffraction patterns by multislice simulations.…”