Regularly branched InN nanostructures: zinc-blende nanocore and polytypic transition

Regularly branched InN nanostructures were controllably grown on c-plane sapphire substrates by using hydride vapor phase epitaxy. On the basis of the crystallographic analysis of these InN tetrapods, it is proposed that (i) each tetrapod consists of four nanorods in the wurtzite phase protruding from a truncated tetrahedral nanocore in the zinc-blende phase and that (ii) branching occurs at the four {111} faces of the truncated tetrahedral nanocore. Our work suggests that the branching regularity of InN tetrapods is attributed to the polytypic transition at these four faces.