SPONTANEOUS DESORPTION - FIELD ASSISTED ION INDUCED DESORPTION MASS-SPECTROMETRY

Spontaneous desorption (SD) has been studied as a function of field strengths and sputtering energies. Accordingly, the mechanism of SD is proposed to be a two step process. The first step is the field desorption of ions from a grid or aperture. This step is evidenced by the dependence of the electron count rate versus the electric field strength. The first step is also the 'rate determining step'. The second step is the sputtering of the sample surface by the field desorbed ions. This step is evidenced by the large difference in ion yields at the same field strength but different incident ion energies. The SD effect is also present in other techniques that rely on a potential difference between the sample and a grid to extract desorbed or ionized particles. © 1990.