Layer-by-layer characterization of ultrathin films with secondary ion mass spectrometry

We demonstrate the capability of cluster secondary ion mass spectrometry on characterization of multi-layer ultrathin films assembled by electrostatic adsorption of oppositely charged polyelectrolytes. The samples consisting of layers of polyethylenimine, PEI, and polystyrene sulfonate, PSS, were bombarded with 19 keV (CsI)Csþ and 21 keV Au3þ projectiles with secondary ions identified by time-of-flight mass spectrometry. The data show the high sensitivity of cluster SIMS to the physicochemical characteristics of the two topmost layers. # 2004 Elsevier B.V. All rights reserved