Sapphire jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics (especially integrated circuits and GaN-based LEDs). Sapphire is the birthstone for September and the gem of the 45th anniversary.
Silicon on sapphire Silicon on sapphire Silicon on sapphire (SOS) is a hetero-epitaxial process for integrated circuit manufacturing that consists of a thin layer (typically thinner than 0.6 µm) of silicon grown on a sapphire (AlO) wafer. SOS is part of the Silicon on Insulator (SOI) family of CMOS technologies. Typically, high-purity artificially grown sapphire crystals are used. The silicon is usually deposited by the decomposition of silane gas (SiH) on heated sapphire substrates. The advantage of sapphire is that it is an excellent electrical insulator, preventing stray currents caused by radiation from spreading to nearby circuit elements. SOS faced early challenges in