36th International Field Emission Symposium

J. Phys. Colloques 50 (1989) C8-541-C8-545
DOI: 10.1051/jphyscol:1989893

TIME FOCUSING IN A FIELD PULSED ATOM-PROBE WITH A REFLECTRON

W. DRACHSEL¹, L.v. ALVENSLEBEN² et A.J. MELMED<sup>3, 4

1</sup>  Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-1000 Berlin 33, F.R.G.
²  Institut für Metallphysik, Universität Göttingen, Hospitalstrasse 3-5, D-3400 Göttingen, F.R.G.
³  National Institutes of Standards and Technology, Gaithersburg, MD 20899, U.S.A.
⁴  Custom Probes Unlimited, Box 3938, Gaithersburg, MD 20878, U.S.A.

Abstract
The poor termination of a tip in the discharge line of an atom-probe and the field ionization of the species at different times during the voltage pulse cause a broadening in the kinetic energy of the ions, thus deteriorating the ToF-spectra. To improve the resolution of the atom-probe, the Poschenrieder-filter was introduced quite early. Despite the elaborate designs so far in use, the simpler design of a reflectron, as is commonly in use with other ToF-techniques, was never tried in this context. To test this idea, a reflectron with an acceptance angle of 1.5° for a 0.8 m ToF-length was constructed. The time focusing is of first order (as with a Poschenrieder filter), which gives an improvement at an assumed ΔE/E = 10 % from Δt/t = 0.05 to Δt/t = 0.001 with compensation. The instrument was tested with a field pulsed atom-probe and an improvement of m/Δm from ~30 to > 400 was achieved.