Surface tracks on ultra-thin polymer films.

In this work, crater formation by single 20 MeV Au ions on ultra-thin poly(methyl methacrylate) (PMMA) films was systematically investigated as a function of the thickness t of the layers (2 nm< t <100 nm). The samples were bombarded at grazing angles of incidence (79°and 84° to the surface normal) and morphological changes analyzed employing scanning force microscopy in the tapping mode. For thicknesses from 100 nm down to approximately 20 nm no major changes were observed in the size and morphology of the impact features. For t<20 nm rims (hillocks) start to diminish, but crater hole size showed very little changes even for very thin samples of ∼ 8 nm. Similar results were observed for both impact angles. The results indicate a different depth of origin for crater and ridge formation due to a fast ion impact. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]