Optimising low-dose Focused Ion Beam milling in polymer membranes

Session

Poster Session One

Authors

Dr Ofentse Makgae (1), Dr Martha Briceno (1)

Affiliations

1. Johnson Matthey Technology Centre

Keywords

FIB, membranes, soft materials

Abstract text

A focused ion beam (FIB) is a technique in which accelerated (Ga) ions spatter material away upon interaction.¹ This technique is used mainly for electron-transparent transmission electron microscopy sample preparation, FIB tomography or cross-sectional analysis of materials such as semiconductors, ceramics, metals, polymer thin films and biological specimens.¹ Unlike conductive materials such as ceramics and metals, polymer membranes are non-conductive and thus susceptible to beam-induced heating during ion beam milling.² Ion beam-induced heating in polymer membranes creates ‘melt-like’ artefacts that smear the pristine structural details of the membrane along the cross-section. In addition, it is also shown that accelerated Ga ions can result in the chemical alteration of the membrane’s chemical structure, which affects the properties of the membrane.^2,3 These ion-beam-induced damage is typically circumvented by dose-controlled milling or lowering the specimen temperature via cryogenics.^2,3 Here, we aim to optimise the milling parameters for polymer membrane cross-section milling by determining the optimum current, accelerating voltage and dwell time required to minimise beam-induced heating in polymer membranes. Preliminary results show that reducing the dwell time at low milling currents and high voltage reduces the beam-induced artefacts in the membrane cross-sections. The results of this study will help understand the pristine microstructure of polymer membranes in a standardised and reproducible routine cross-sectional analysis.

References

1. L.A. Giannuzzi, F.A. Stevie., Micron 30 (1999) 197–204

2. S. Kim et al., Ultramicroscopy 111 (2011) 191–199

3. R.J. Bailey et al., Micron 50 (2013) 51–56