Invited Paper AS-TuM3
Three-dimensional Sputter Depth Profiling of Molecular Structures: Prospects and Limitations

Tuesday, October 21, 2008, 8:40 am, Room 207

The use of cluster ions as projectiles in Secondary Ion Mass Spectrometry (SIMS) has opened the door to sputter depth profile analysis of molecular solids. In particular, it is found that molecular information contained in the mass spectrum of material released from the surface by cluster ion impact is retained even if the ion bombarded surface is macroscopically eroded up to micrometers in depth. In combination with finely focused beam probes, high-resolution three-dimensional chemical analysis of molecular structures becomes feasible.¹ This type of experiments, which are virtually impossible using atomic primary ions, bear great implications with respect to biological applications of the SIMS technique. From a number of test studies performed on various model systems, the fundamental principles behind molecular depth profiling are beginning to emerge. The combination of experimental data with phenomenological models and theoretical simulations of the sputter erosion process allows to gain insight into the role of different parameters governing the efficiency of different projectiles for this type of analysis. The talk will briefly summarize the present status of this rapidly evolving field and discuss possible prospects and limitations of the technique.

¹A. Wucher, J. Cheng, N. Winograd, Anal. Chem. 79 (2007), 5529.