Development of a Practicable Digital Pulse Read-Out for Dark-Field STEM. (February 2021)

• Record Type: Journal Article
• Authors: Mullarkey, Tiarnan; Downing, Clive; Jones, Lewys
• Is Part Of: Microscopy and microanalysis. Volume 27:Number 1(2021)
• Page Start: 99
• Page End: 108
• Publication Date: 2021-02
• Subjects: annular dark-field (ADF) imaging, -- electron counting, -- low-dose imaging, -- scanning transmission electron microscopy; Microscopy -- Periodicals; Microchemistry -- Periodicals; 502.82
• DOI: 10.1017/S1431927620024721
• Languages: English
• ISSNs: 1431-9276

Abstract

Abstract: Abstract : When characterizing beam-sensitive materials in the scanning transmission electron microscope (STEM), low-dose techniques are essential for the reliable observation of samples in their true state. A simple route to minimize both the total electron-dose and the dose-rate is to reduce the electron beam-current and/or raster the probe at higher speeds. At the limit of these settings, and with current detectors, the resulting images suffer from unacceptable artifacts, including signal-streaking, detector-afterglow, and poor signal-to-noise ratios (SNRs). In this article, we present an alternative approach to capture dark-field STEM images by pulse-counting individual electrons as they are scattered to the annular dark-field (ADF) detector. Digital images formed in this way are immune from analog artifacts of streaking or afterglow and allow clean, high-SNR images to be obtained even at low beam-currents. We present results from both a ThermoFisher FEI Titan G2 operated at 300 kV and a Nion UltraSTEM200 operated at 200 kV, and compare the images to conventional analog recordings. ADF data are compared with analog counterparts for each instrument, a digital detector-response scan is performed on the Titan, and the overall rastering efficiency is evaluated for various scanning parameters.