Cross-sectioning photovoltaic polymer blends with advanced gas-ion microscopy

Focused ion beams (FIBs) are commonly used to prepare samples for cross-sectional imaging in the electron microscope. When working with polymeric or other soft materials, however, conventional metal-ion FIBs can cause significant sample damage and destroy features of interest. In this work, we demonstrate how He+ and Ne+ gas-ion beams can be used as a more suitable alternative by fabricating and imaging high quality cross-sections of polymer films used for organic photovoltaics. We first cryo-cleave polymer films before using a gas-ion beam to fabricate a high-quality cross-sectional sample, and reveal nanostructure in the film cross-section after a brief plasma treatment. We discuss some of the practical nuances of the technique and compare the relative strengths of He+ and Ne+ beams for nanofabrication. Finally, we image the cross-section with the He+ beam, demonstrating the impressive capabilities of the gas-ion microscope as a combined tool for nanofabrication and imaging.