After attaching a few µm of Pt protection layer a 20x12x10 µm cross section was cut with FIB using a 20 nA beam current, reduced to 4 nA and 600 pA for final polishing on a cross-beam SEM from Zeiss (AURIGA® -CrossBeam workstation). The Image in Fig. was taken with an acceleration voltage of 2kV and performed in backscattered electron mode. The equivalent circuits used to fit the arcs are shown in the top right corner. The second semicircle is attributed to the 650 nm amorphous layer which is detrimental to ionic transport as shown in previous literature.