Heteroepitaxy of single crystal diamond on Ir buffered KTaO₃ (001) substrates

The heteroepitaxy of a single crystal diamond has been carried out in the KTaO₃ substrate using Ir as a buffer layer. KTaO₃ has a perovskite lattice structure and displays a face-centered cubic structure. Its lattice constant is 3.98 Å, which is only 3% mismatched with the lattice constant of Ir of 3.84 Å, and also, its thermal expansion coefficient is 4.031 × 10⁻⁶/K, which is nearly close to that of diamond 3.85 × 10⁻⁶/K (at 1223 K), making it to be regarded as an alternate substrate of the heteroepitaxy of a single crystal diamond. The magnetron sputtering technique was used to deposit Ir thin films with a high orientation in the (001) direction on a KTaO₃ (001) substrate. Thereafter, bias enhanced nucleation on Ir surface was grown by direct current chemical vapor deposition (CVD) methods. At last, a single crystal diamond with a size of 10 × 10 × 0.78 mm³ has been grown, whose (004) rocking curve FWHM is 183 arc sec, which testifies to the excellent crystalline quality of the heteroepitaxial diamond film.