2.2. Charged particle beam microscopy
HIM measurements were performed using an ultra-high vacuum (UHV) Orion Plus helium ion microscope from Zeiss [16].The microscope is equipped with an Everhardt–Thornley (ET) detector
for Secondary Electron (SE) detection. A micro-channel plate situ-ated below the last lens just above the sample allows the qualitative analysis of Backscattered Helium (BSHe). This detector yields images in which dark areas correspond to light elements—having a low backscatter probability—and bright areas—with a high backscatteryield—correspond to heavy elements in the specimen.High Resolution Scanning Electron Microscopy (HRSEM) mea-surements were performed using a Merlin Field Emission SEM