Plan-view SEM using a conventional secondary detector instead of an in-lens secondary detector allowed a more in-depth analysis on the formation of regular hexagonal pits at the surface of Sample 3 (see Figure ). The formation of both pits and inclusions results in increased surface roughness which in turn forces the basal planes of BN to bend in order to follow the surface, as can be seen on the bottom corner of FIG5a. We suggest that lower temperature or silane-free processes for sp 2 -BN epitaxy may improve the quality of the BN films on ZrB2.