  Scanning electron microscopy (SEM) is a versatile technique used to image
samples at the nanoscale. Conventional imaging by this technique relies on
finding the average intensity of the signal generated on a detector by
secondary electrons (SEs) emitted from the sample and is subject to noise due
to variations in the voltage signal from the detector. This noise can result in
degradation of the SEM image quality for a given imaging dose. SE count
imaging, which uses the direct count of SEs detected from the sample instead of
the average signal intensity, would overcome this limitation and lead to
improvement in SEM image quality. In this paper, we implement an SE count
imaging scheme by synchronously outcoupling the detector and beam scan signals
from the microscope and using custom code to count detected SEs. We demonstrate
a ~30% increase in the image signal-to-noise-ratio due to SE counting compared
to conventional imaging. The only external hardware requirement for this
imaging scheme is an oscilloscope fast enough to accurately sample the detector
signal for SE counting, making the scheme easily implementable on any SEM.
