Omniprobe lift out grids

Samples were prepared for TEM imaging using Ga focused ion beam (FIB) on Quanta dual beam SEM/FIB (FEI, Hillsboro, OR). Lamellas were lifted out with OmniProbe 200 (Oxford Instruments, Abingdon, United Kingdom) and attached on Omniprobe Lift-out grids (TED PELLA, INC., CA, USA) on the V position to minimize bending of the foil. An ion beam accelerating voltage of 5 keV with a beam current 16 pA was used for the final polish. The average thick ness of each TEM sample is ~50 nm, confirmed by SEM. TEM samples were imaged with a transmission electron microscope (TEM) [Philips CM-20, Hillsboro, OR] with 200 keV using a LaB₆ beam source. Some of the images are taken at a high magnification and patched together to make a montage to retain high enough resolution to resolve dislocation loops. Multiple TEM samples were prepared and observed with different tilts for the composite materials. Dislocation loop areal concentration at each depth was calculated from TEM images (~5 × 5 μm²) divided into 200 × 1800 nm² sections with random tilts. Standard deviation was generated from the accumulated concertation from each section.