Fig. 4
High-resolution TEM images of selected cubic diamond polycrystals extracted from the DP 0–0.05 powder (a, b) and typical images of the simple twinning boundaries, of several nanometres in length, found occasionally in the sample (c, d). Panels (a, b): scale bar—4 nm. Different crystallites are highlighted in different colours in (a). Arrows in panels (c) and (d) mark the selected clearly distinguishable twinning boundaries