Dynamic scan shaping: overcoming coil hysteresis for high-speed STEM

Scanning transmission electron microscopy (STEM) has a number of benefits over conventional parallel illumination transmission electron microscopy, such as the ability to simultaneously perform a range of imaging and spectroscopy techniques. However, one distinct disadvantage is the slow imaging speeds, a consequence of the sequential nature of the pixel acquisition, limiting imaging speeds to a few frames per second (fps). This reduces dose-rate control, increases the effect of distortions, and hinder the ability to capture dynamic events for in-situ experiments. The main obstacle to faster framerates is the inductance and hysteresis of the scanning coils that has previously only been addressable with the addition of entirely new hardware coils. Here we demonstrate a predictive scan shaping approach using conventional scanning systems, where scan input is determined based on where the beam will be instead of where the beam should be. We use this new approach to acquire fully sampled 512x512 images at 60 ns per pixel, giving a framerate of 41 fps.