Fig. 3

FESEM in-operando observation of the evolution of APT-specimen geometry during final low-keV milling at the investigated temperatures and Ga-concentration in the resulting APT-specimens utilising a Pt-protection layer. a FESEM-SE screen-grabs from during the final low-keV APT-specimen milling step utilising 5 keV ion accelerating voltage and 16 pA FIB current. The dashed lines mark the respective Pt–Sn interfaces. The specimen evolution during the final milling step is shown at 25 °C, -30 °C and -60 °C for four timesteps. The respectively last panels show the final APT-specimens for each milling temperature. Scale bar of 500 nm is valid for all images. b 3D Ga-concentration distributions from the APT reconstructions for specimens prepared at 25 °C, -30 °C and -60 °C, alongside the respective Ga-concentration profiles along the direction of evaporation. The correspondence of datapoints in the Ga-concentration profiles with the Ga-concentration distributions is exemplarily sketched for the 25 °C-specimen. Scale bars of 100 nm are valid for all images. The Ga-concentration distributions are scaled from 0.0 to 2.0 at.% Ga.