Comparison of the measurement of beam-current densities in an electron microscope using a Faraday cup and solid-state detector

A Faraday cup has been constructed which is capable of accurately measuring beam-current densities in the image plane of an electron microscope. This device has been employed to calibrate a solid-state detector typical of those often used to measure such small electron intensities. The ability of the solid-state detector to distinguish single electrons was found to be a sensitive function of the incident electron intensity. Important applications of this work include investigations of radiation damage in beam-sensitive materials, e.g., biological specimens