  When characterising 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 minimise 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 artefacts
including; signal-streaking, detector-afterglow, and poor signal-to-noise
ratios (SNR). In this manuscript 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 analogue artefacts 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 300kV and a Nion
UltraSTEM200 operated at 200kV, and compare the images to conventional analogue
recordings. ADF data are compared with analogue 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.
