High quality sapphire crystal by advanced chemical transport process

Single crystal sapphire was synthesized by chemical transport of Al-O generated by the reaction of polycrystalline Al2O3 ceramic and carbon. Using C-axis oriented polycrystalline Al2O3 ceramics as a seed crystal in the deposition temperature range, a C-axis sapphire crystal (Φ5xL35 mm) was grown at a temperature range of 700–1000 °C, and the growth rate in the C-axis direction was about 3.5 mm/h. The transmittance in the visible to infrared region of the synthesized sapphire is a theoretical value (transmission loss is lower than 0.1 %/cm), and the absorption edge was less than 200 nm (the band gap is 6.2 eV), which is shorter than the absorption edge (240 nm) of the commercially available single crystal (band gap 5.2 eV) synthesized by the Czochralski method. The dislocation density in this material was extremely low, and it was confirmed by lattice image observation that it was a high-quality single crystal with very few defects.