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This work contributes to the understanding of focused ion beam (FIB) technology for polymers. The conditions of treatment are varied, in particular by etching under ‘dry’ ultra-high vacuum conditions or in the presence of water vapour. For a glassy epoxy network, the changes in chemistry and morphology are characterised. Energy-dispersive X-ray analysis reveals that gallium is always implanted in the epoxy but the content is higher in the case of ‘dry’ FIB milling. According to attenuated total reflection infrared micro-spectroscopy, new chemical structures form in the surface region of the epoxy during FIB milling with or without water vapour. Scanning electron microscopy and scanning force microscopy were used to image the topography of the etched epoxy surfaces. Quite smooth surfaces result under ‘dry’ etching conditions. In the presence of water vapour, rough surfaces with a sub-micrometre globular morphology are obtained. This is an indication of the heterogeneous morphology of the epoxy polymer. As compared to ‘dry’ conditions, the introduction of water vapour during FIB milling increases the milling yield significantly. As a result, the FIB treatment changes the chemistry and the structure of the epoxy network not only at the very surface but also in some significant surface layer of the sample. It can be expected that such a modified zone will also form on other cross-linked polymers. Copyright © 2009 John Wiley & Sons, Ltd.

For poly(methyl methacrylate) (PMMA) as a representative of amorphous thermoplastic polymers, the milling effects, and the chemical changes due to ion bombardment with a focused ion beam (FIB) at normal incidence are studied with scanning force microscopy (SFM), scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), and infrared (IR) spectroscopy for varying conditions of Ga+ treatment, including the effect of partial water pressure. Stopping and Range of Ions in Matter (SRIM) simulation results for 30 keV Ga+ at normal incidence show that the zone of primary ion–polymer interaction extends ca 100 nm into the PMMA. Accordingly, this interaction region is much wider than the original beam diameter. The width of the region where the recoiled ions interact strongly with the polymer chains is larger. Secondary processes, such as fragment diffusion and phonon transport, are expected to extend even farther into the polymer. SEM and SFM reveal distinct topologies of areas milled without or in presence of water vapour. Water vapour–assisted FIB milling produces more roughness and defects. The infrared attenuated total reflection spectroscopy (IR-ATR) spectra indicate that ion milling in PMMA damages methacrylate side groups in particular. In contrary to metals, an increase in the degree of milling is found when the beam spot overlap parameter increases. Copyright © 2009 John Wiley & Sons, Ltd.