Collision target-gas effects during the tandem secondary-ion mass-spectrometric analysis of polymers

Abstract

A triple-quadrupole secondary-ion mass spectrometer has been designed in order to study the fragmentation of secondary ions ejected from solid surfaces under low primary beam flux conditions (static SIMS). This system has been used to study the fragmentation of some simple polymers in order to identify some of the key parameters controlling the collisionally activated dissociation (CAD) process for secondary ions and to make comparison with observations made for conventional mass spectrometers. A variety of collision targets have been employed, including argon, xenon, sulphur hexafluoride and oxygen and the effects of target pressure and collision energy have been studied, for cluster ions generated from polytetrafluoroethylene (PTFE). Xenon provided the most complete fragmentation patterns. It has proved possible to construct complex fragmentation patterns and to observe ion–molecule reactions between fluorocarbon parent ions and oxygen and sulphur hexafluoride targets.