Design of a scanning atom probe with improved mass resolution

A design for a high mass resolution scanning atom probe is described, which utilizes a two-conductor microelectrode held at 10-100 mu m from the specimen. Field evaporation pulses are applied to the part of the counter-electrode closest to the specimen, while the output is maintained at ground. If the gap between the two conductors is small, field evaporated ions pass through the microelectrode while the pulse voltage is essentially constant, and thus the resultant spread in ion energies is small and the mass resolution in time-of-flight mass spectrometry is correspondingly improved. Initial results indicate improvements of 4-5 times over the mass resolution obtained with a simple counter electrode. (C) 2000 American Institute of Physics. [S0034- 6748(00)02308-X].