 Solution

Use high-resolution transmission electron microscopy with a coherent, well-aligned beam and an objective aperture admitting the direct beam and the spatial frequencies required at the interface. Orient a crystalline region near a suitable zone axis so that useful lattice fringes are excited; minimize drift, vibration and astigmatism. Choose defocus and aberration correction to transfer the target frequencies, rather than treating the image as a direct map of atoms at arbitrary defocus.

An aberration-corrected scanning transmission electron microscopy probe with high-angle annular dark-field imaging can instead resolve an interface with more directly interpretable atomic-number contrast. A nominal $150\mathrm{nm}$ thickness may be too great for clean atomic-resolution interpretation: thin the interface further if necessary, finish focused ion beam milling at lower ion energy to reduce damaged surface layers, and check for curtaining and implantation. The best mode depends on crystallinity and damage sensitivity; an amorphous interface calls for resolving its boundary and composition rather than inventing lattice fringes.