Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is a highly sensitive analytical technique that describes the chemical composition and distribution of a sample surface. It uses a range of incident ion sources to impact on solid surfaces and generate secondary ions that can be analysed by a time of flight (or OrbitrapTM) mass spectrometer to determine the surface chemistry of that surface or layer.
Right: The new and unique 3D OrbiSIMS at the University of Nottingham
Image Courtesy of Vladimir Korolkov
ToF-SIMS uses a pulsed primary ion beam (Bin+, Cs+, Ar+, etc.) to impact on a sample surface and induce a fragmentation cascade. The result is the desorption of neutrals, secondary ions (+/-) and electrons from the first few monolayers of the sample. The secondary ions can then be accelerated into a "flight tube" and their mass is determined by measuring the exact time at which they reach the detector (i.e. time-of-flight). A single secondary ion mass spectrum can be used to describe the constituents of one point on a surface. Alternatively if the incident beam is rastered across several points within a given surface area, it is possible to build a chemical image map of that surface. Using incident ions such as Cs+, Arn+ C60+ in a dual beam approach it is also possible to sputter through the top layers of the inorganic or organic surfaces respectively while monitoring the incidence profile of elemental or molecular species (i.e. depth profiling).
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