Epitaxial (100) iridium on A-plane sapphire: A system for wafer-scale diamond heteroepitaxy

Large-scale heteroepitaxial growth of diamond depends critically on the development of a suitable lattice-matched buffer layer and substrate system. Epitaxial (100) iridium films have been grown on terraced, vicinal a-plane (112̄0) α-Al2O3 (sapphire) by electron-beam evaporation. The epitaxial relationship, Ir(100)//Al2O3(112̄0) with Ir[011]//Al2O3[11̄00], was determined by x-ray diffraction and electron backscattering diffraction analysis. For a 300-nm thickness of Ir, a (200) rocking curve yielded a linewidth of 0.21°, and the film exhibited a macrostepped surface with low pinhole density. This Ir/sapphire system provides a basis for large-area growth of (100) heteroepitaxial diamond.