Secondary Ion Mass Spectrometry of Small Molecules Held at Cryogenic Temperatures

In recent years more emphasis has been placed on the analytical potential of Secondary Ion Mass Spectrometry (SIMS) for the study of organic materials [1,2,3]. We wish to report on static SIMS experiments on a few simple mole-cules condensed on a copper substrate held at low temperatures. For the experiments we used an Extranuclear Inc., quadrupole massfilter equipped with a Bessel box type energy filter. The bandwidth of the ions accepted in the massfilter was set at 1 eV. Our ion gun is differential pumped and during the experiments a pressure in the 10-9 torr range could easily be maintained in the main chamber. Our primary ion beam current density was between 1 and 10 nA/cm2 and the beam energy was varied between 500 and 5000 eV. As primary Fig.1 SIMS spectrum of neat methane at 15°K using 1 keV Ne+ ion