Impurities and Optical Properties of Synthetic Diamond.

Pure diamond has no absorption bands in a wide range of wave lengths from ultraviolet to infrared. However, diamond crystals show some colors usually, although most of them are nonattractive yellow or brown. Diamond crystals also give off a variety of luminescence with stimulation from an electron beam, UV light, etc. The colors are produced by the incorporation of impurities. In the case of diamond, the impurities which are incorporated are limited. They are nitrogen, boron, nickel, cobalt, silicon and phosphorus. The color features of high pressure synthetic diamonds are described in terms of the impurities.