*2.5. Optical Profilometry*

A Zeta-20 Optical Profilometer (KLA Instruments, Milpitas, CA, USA) was used to undertake analysis of the craters that were produced as a result of sputtering during the ToFSIMS depth profiling experiments. The profile of each crater was measured using a 20 × lens with a z range of 44 μm, 400 steps with a step size of 0.111 μm across 10-line profiles at a working distance of 3.1 mm. The FOV with the high resolution 0.35 × coupler 2/3" camera was 1169 × 876 μm2.

### *2.6. Scanning Electron Microscopy Experimental Parameters*

SEM analysis of the samples was carried out using a Dual Beam Quanta 200 3D (FEI, Hillsboro, UK). Prior to imaging the surface, it was coated (~12–17 nm) in gold-palladium to reduce surface charge effects. The sample surface was sputter coated with gold-palladium using an Emitech K500X SEM preparation sputter system. The images contained in this work were collected at an accelerating voltage of 10 kV and a working distance of 8–15 mm. The average pore area, number of pores, and Feret's diameter of the pores in each sputter deposited thin film were calculated using ImageJ software (Version 1.8.0) (National Institute of Health, Bethesda, MD, USA). In total, 3 areas were analysed from each sample.
