Therefore, atom probe tomography (APT) analyses were performed at the peak implantation depth, around 700 nm, as well as after the peak damage, depth of 1300 nm. The noise level of the mass spectra under the chosen analysis conditions does, however, not allow to detect the low Ag content (around 0.003 at% at the peak of implantation based on SRIM simulation). In Figure the 3D reconstruction of one of the three datasets obtained from a depth of 700 nm is shown which is representative for all of them. The atoms are homogeneously distributed throughout the needle and no grain boundaries are visible, meaning only a single grain was investigated. The chemical composition, shown in Supplementary Table is close to the nominal composition of Li6.4La3Zr1.4Ta0.6O12. Although, LLZTO is intended to be single phase (see XRD, SEM, and TEM analysis) the 3D reconstruction from a depth of 1300 nm on the other hand shows a clearly visible grain boundary, a grain with the same composition as in the previous dataset and a lithium deficient grain on top of it (Figure ). The lithium content in the upper grain is around 10.4 ± 2.0 at.%, see Supplementary Table , while still having a homogeneous distribution of atoms. A proxigram from the grain boundary, Supplementary Figure shows the transition in lithium content. There is also a dataset only containing a lower lithium content. The Li-poor extra phase could be related to minor extra phases which have already been present in the sample or to a lithium loss in the high vacuum conditions during the APT analysis, which has been recently demonstrated. Finally, we used FIB-SEM with correlative TOF-SIMS to find evidence for the presence of Ag ions in the implanted zone. Figure depicts the spots where the TOF SIMS measurements were taken and a slight peak, at 106.8 mass to charge ratio is visible in the first 0.9 µm diameter spot, which can be attributed to the 107 Ag implanted into this region. This peak vanishes in the other two spots confirming that the Ag is implanted into the desired depth. Attempts to, at least qualitatively, confirm the implantation profile using larger spots, shown in Supplementary Figure dropped the signal below the threshold where it is distinguishable from noise.