A novel in-lens detector for electrostatic scanning LEEM mini-column

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.