Fei helios g3 uc

Scanning Electron (SE)-images were taken with a Zeiss Supra VP55 (Zeiss, Germany) at 1.5 kV, 10 µm aperture size, in high vacuum mode, and using the ETD detector. Specimens were mounted on a Scanning Electron Microscope (SEM) sample holder using Silver glue (Acheson Silver DAG 1415 M). SEM- Energy-Dispersive X-ray Spectroscopy (EDX) measurements were performed at 20 kV and 0.8 nA on a FEI Helios G3 UC (FEI, USA) equipped with an Oxford X-MAX 80 mm² SDD. The samples were coated with gold prior to the EDX measurements. A FIB lamella for TEM-EDX was prepared using a standard liftout procedure using the above-mentioned FEI Helios G3 (FEI, USA) system. As a support grid, an EMtec copper liftout grid was used. Final thickness of the lamella is estimated to be around 60 nm. TEM-EDX was performed at 200 kV and 1 nA on a FEI Talos F200X (FEI, USA) equipped with a four quadrant Super-X EDX System. Spectrum image size: 256 × 256 pixels. Pixel-size: 765 pm. Dispersion: 5 eV. Dwell-time: 5 µs. Overall measuring time: 60 minutes with drift compensation. For the characterization of the supercrystals, obtained SAXS measurements were performed by scanning a line along the samples and using the same parameters and post-processing as stated before.

Enamel slices were cut from the labial or palatal sections of the teeth for FIB (Focused Ion Beam) specimens using a Buehler Isomet 4000 precision saw (Buehler, Esslingen, Germany) while the teeth were irrigated with water. Following that, smaller pieces were cut as described in “Results”. Conductive silver was used to bond the samples to electron microscope stubs. After grinding the specimen with SiC papers ranging from 1200 to 4000, the surfaces were vacuum dried, and sputter coated with a thin gold layer for 60 nm. The lamellae were created using a dual-beam FIB system (FEI Helios G3 UC, FEI Deutschland GmbH, Frankfurt/Main, Germany) by cutting the enamel prisms perpendicular to the lamella. The lamella electron was then transparent after several thinning steps with currents of 0.79 nA, 0.23 nA, 80 pA, and finally 40 pA. STEM images were captured using collected inelastic and elastic scattered electrons and a high angle annular dark-field (HAADF) detector (FEI Deutschland GmbH, Frankfurt/Main, Germany).