Study of molecular surface diffusion by imaging static secondary ion mass spectrometry (SIMS): polymers on Ag-surfaces

A new technique for the investigation of surface diffusion is described. The method is based upon imaging static SIMS. Provided a well-defined boundary between a covered and an uncovered surface area can be produced by an appropriate procedure, this technique can be applied to any substrate-overlayer combination, including involatile molecular layers, as well as isotopically labelled elemental or molecular layers. We applied this technique to study the surface diffusion of polystyrene (PS), polydimethylsiloxane (PDMS), polymethylmethacrylate (PMMA), and the perfluorinated polyether Krytox on etched Ag-substrates at room temperature. For PDMS and Krytox, we found a considerable surface diffusion with diffusion coefficients in the range of 10(-7)-10(-6) cm(2)/s. In contrast, for PMMA and PS, no surface diffusion was observed at room temperature. (C) 1998 Elsevier Science B.V. All rights reserved.