A pulsed alkali-ion gun for time-of-flight secondary ion mass spectrometry.

A pulsed alkali-ion gun for use in time-of-flight secondary ion mass spectrometry (TOF-SIMS) has been constructed and tested. The ion pulses are formed by rastering a continuous ion beam from a thermionic emitter source across a 0.13-mm slit. The pulses consist of 100-1000 alkali ions having a full-width-at-half-maximum temporal distribution of less than 2.4 ns and a spot size of approximately 1 × 2 mm. In addition, the angular beam divergence of this ion gun is less than 0.5°, making it also suitable for TOF ion scattering and direct-recoil spectroscopy. The ion gun has been used to obtain a series of cluster ion spectra which show a mass resolution of about 2000 and a mass range of nearly 9000 amu. [ABSTRACT FROM AUTHOR]