Molecular SIMS for organic layers: new insights

Static SIMS is intensively used for molecular surface characterization. In the case of polymers and organic adsorbates, large characteristic fragments and intact parent ions are detected and used for analytical purpose. However, the exact nature of the mechanisms leading to large molecule emission and ionization is still debated. Recently, owing to comparisons between experiments (ion yields, kinetic energy distributions and disappearance cross-sections) and molecular dynamics (MD) simulations, progress has been made in the understanding of molecular fragment and parent molecule emission under ion beam bombardment. In this paper, we review some of the results obtained in this context. Remarkably, MD simulations allow us to confirm that the emission of large intact molecules can occur via collision cascade mechanisms. This involves a cooperative uplifting process, in which substrate recoil atoms with similar momentum push the molecule upward. (C) 2002 Elsevier Science B.V. All rights reserved.