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SIMS21, Poland 2017 - Ichiro Mihara abstract

Ichiro Mihara oral presentation (PB3-Fri2-1-2)

Development of a FIB-TOF-SIMS protocol for hybrid organic-inorganic samples

Ichiro Mihara1,2, Rasmus Havelund2, Mariavitalia Tiddia2,3, Felix Kollmer4, Guido Mula3, Ian S Gilmore2

1 Kuraray CO., LTD., 2045-1, Sakazu, Kurashiki, 710-0801 Okayama, Japan
2 National Physical Laroratory, Hampton Road, TW11 0LW Teddington, United Kingdom
3 Universita degli Studi di Cagliari, S. P. Monserrato - Sestu Km 0.700, 09042 Monserrato CA, Italy
4 ION-TOF Technologies GmbH, Heisenbergstr.15, 48149 Münster, Germany

Focused ion beams (FIBs) are frequently used for sample sectioning for cross-section observation or 3D tomographic analysis. They are mainly used in electron microscopy analysis but also increasingly in combination with SIMS imaging. FIBs can create smooth cross-sections of complex samples and through repeated sectioning and imaging a 3D chemical tomography image with sub-micrometer lateral resolution can be constructed. However, the very high ion doses used for FIB sectioning provides severe chemical damage to organic materials on the exposed cross-section. [1] Consequently, the analysis of organic-inorganic hybrid materials is challenging. Methods are needed to minimize or remove the damage for successful FIB-SIMS analysis.

In this study, we create a reference sample with a well-defined pattern of organic and inorganic regions that enables effects of damage, sputtering rate change and distortion artefacts to be measured. The reference sample consists of a micro channel plate (MCP) which has a regular honeycomb array of tubes of 15 μm diameter. The tubes are completely filled with polystyrene or polymethyl-methacrylate (PMMA) by melting the polymers and pressing them into the tubes in a vacuum oven [2]. This highly regular structure of organic and inorganic phases is suitable for evaluating the lateral resolution, repeatability, reproducibility and reconstruction accuracy.

After the initial FIB milling process, no secondary ion signals on the cross-section were detected from polymer regions owing to carbonization. The organic signals could be recovered as shown in Figure 1 after the polishing by FIB and further cleaning by gas cluster ion beam (GCIB). We investigate the relationship between the FIB dose to mill the crater and the GCIB dose required for the signal recovery quantitatively. Additionally we will discuss the effect of the FIB incident angle and the use of a Bi3+ FIB beam for minimizing damage.