Growth of cubic InN on r-plane sapphire

InN has been grown directly on $r$ -plane sapphire substrates by plasma-enhanced molecular-beam epitaxy. X-ray diffraction investigations have shown that the InN layers consist of a predominant zinc blende (cubic) structure along with a fraction of the wurtzite (hexagonal) phase which content increases with proceeding growth. The lattice constant for zinc blende InN was found to be $\text{a=4.986\hspace{0.17em}Å.}$ For this unusual growth of a metastable cubic phase on a noncubic substrate an epitaxial relationship was proposed where the metastable zinc blende phase grows directly on the $r$ -plane sapphire while the wurtzite phase arises as the special case of twinning in the cubic structure.