Fig. 4

Evaluation of depth resolution. a–g Reconstructed phase using seven slices from a 21-slice reconstruction with a step of 6 nm along the optical axis and h–n, corresponding power spectra. Lattice fringes, (0002) with a spacing of 0.34 nm and their corresponding reflections fade outside a sample height range from −12 to 12 nm. This confirms a depth resolution of about 24–30 nm for the spatial frequency corresponding to the 0.34 nm lattice spacing. The 2 nm scale bar is the same for a–g. The values in h–n are defined as the distance from the focus plane of the lower CNT, which is at depth of 197 nm