A novel principle of an in-lens detector of very slow electrons is describe
d and the detector efficiency discussed. The detector was built into a coax
ial column for a Cylindrical Mirror Analyser for Auger electron microanalys
is. In order to obtain a very low energy scanned imaging, a cathode lens wa
s formed between the final electrode of the column and a negatively biased
specimen. The signal electrons accelerated within the cathode lens field en
ter the column and after being mirrored back impact a micro-channel-plate b
ased detector fitted around the optical axis. The acceptance of the detecto
r, expressed as a ratio of the number of electrons impacting the detector t
o the full emission of a cosine source, was calculated to be 0.86 for 1 eV
and 0.985 for 10 eV electrons. Then, the efficiency of conversion into outp
ut pulses is 0.35 and 0.31, respectively; these parameters are superior to
those of conventional SEM detectors for secondary electrons. Micrographs ta
ken at low energies ranging down to units of eV are presented. (C) 2000 Els
evier Science B.V. All rights reserved.