Growth of single-crystalline zirconium diboride thin film on sapphire

Conducting and reflecting thin film of ZrB_2, which has lattice mismatch of only 0.6% to GaN, was grown epitaxially on sapphire substrate [α-Al_2O_3(0001)] via thermal decomposition of Zr(BH_4)_4. In situ reflection high energy electron diffraction and ex situ x-ray diffraction analyses indicate that the epitaxial relationship is singular, i.e., ZrB_2[0001]∥Al_2O_3[0001] and ZrB_2[110]∥Al_2O_3[100]. X-ray photoelectron spectroscopy and scanning tunneling microscopy revealed that the oxide-free surface could be recovered by heating the film at approximately 750 °C under ultrahigh vacuum, which demonstrates its suitability as a template for the growth of nitride semiconductors