Nitrogen, A Major Impurity in Common Type I Diamond

Abstract

Common type I diamonds (as classified by Robertson et al.) have additional absorption in the infrared and ultraviolet. It is shown that the strongest absorption band in the infrared at 7.8 μ and the ultraviolet absorption at 3065 A are proportional to the nitrogen concentration of the crystal. A corresponding increase in lattice constant is found to be as high as 0.01% for a nitrogen content of 0.2%. Concentration, X-ray, and density data suggest that nitrogen occupies a substitutional position in the diamond lattice. The infrared absorption bands at 7.8, 8.3, 9.1, and 20.8 μ are considered to be C-N molecular vibrations. Several optical, electrical, and thermal properties of diamond are discussed in view of our findings.