The Application of Ultra-High Resolution Surface Analysis Techniques to the Study of Glass Corrosion Processes

S Fearn, E. Fabre and D.S.McPhail
Imperial College, London

Ion beam based analysis techniques such as Secondary Ion Mass Spectrometry (SIMS), Focused Ion Beam (FIB) SIMS and Low Energy Ion scattering (LEIS) can yield vital information on the chemistry of the surface layers of a glass. In this paper we will discuss various applications of these techniques in glass science and technology. SIMS yields information on the atomic make up of the sample with parts-per-million sensitivity. Depending upon the operating conditions it’s possible to achieve a depth resolution of ~1nm or a lateral resolution of 5nm. By studying glass surfaces with SIMS as a function of time we can build up information on reaction mechanisms and kinetics and this approach may be optimised by using stable isotopes as tracers (18O2 or D2O). This approach has been used to study the corrosion of vessel glass from the V&A museum and we are also beginning to use it to study contaminants on display cabinets. In focused ion beam SIMS a gallium ion beam can be focused down to a spot size of 5nm, and this beam can be used both for ion milling and for SEM and SIM analysis. That sample preparation and sample analysis can be conducted sequentially in the same instrument without breaking the vacuum. In LEIS the ion beam is scattered off the sample surface yielding information on the chemistry of the very surface layer itself. This technique can be non-destructive if the conditions of analysis are carefully controlled; it yield true monolayer resolution analysis of the glass surface and can provide information on how that surface is terminated. For example it is possible to cross-section a particle on the sample surface and then image it. In introducing these techniques we will describe our new IONTOF TOF SIMS – LEIS instrument and our FIB-SIMS instrument.