Low energy MeV SIMS yield measurements of various inorganic samples

The low energy range (a few 100 keV to a few MeV) primary ion mode in MeV Secondary Ion Mass Spectrometry (MeV SIMS) and its potential in exploiting the capabilities of conventional (keV) SIMS and MeV SIMS simultaneously was investigated. The aim is to see if in this energy range both types of materials, inorganic and organic, can be simultaneously analyzed. A feasibility study was conducted, first by analyzing the dependence of secondary ion yields in Indium Tin Oxide (ITO – In2O5Sn) and leucine (C6H13NO2) on various primary ion energies and charge states of Cu beam, within the scope of equal influence of electronic and nuclear stopping. Expected behavior was observed for both targets (mainly nuclear sputtering for ITO and electronic sputtering for leucine). MeV SIMS images of samples containing separate regions of Cr and leucine were obtained using both keV and MeV primary ions. Based on the image contrast and measured data, the benefit of a low energy beam is demonstrated by Cr+ intensity leveling with leucine [M+H]+ intensity, as opposed to a significant contrast at higher energy. It is estimated that by lowering the energy, leucine [M+H]+ yield efficiency lowers roughly 20 times as a price for gaining about 10 times larger efficiency of Cr+ yield, while leucine [M+H]+ yield still remains sufficiently pronounced.