Patent ID: 7964280

Claim:
A method of forming a CVD diamond, the method comprising: (i) providing a substrate; (ii) providing a CVD synthesis atmosphere in which there exists a gas comprising nitrogen at a concentration greater than 300 ppb, calculated as molecular nitrogen; and (iii) adding into the CVD diamond synthesis atmosphere a gas comprising boron or silicon, wherein the boron or silicon is added in a controlled manner into the CVD diamond synthesis atmosphere to reduce a detrimental effect on color of the single crystal CVD diamond caused by nitrogen so as to produce a single crystal CVD diamond in which a majority volume of at least 80% of the single crystal CVD diamond has at least one of the following features (a) to (e): (a) an absorption spectrum measured at room temperature such that the color of a standard 0.5 ct round brilliant would be better than K on the Gemological Institute of American (GIA) gem diamond color scale; (b) an absorption coefficient at 270 nm measured at room temperature which is less than 2.9 cm −1 ; (c) an absorption coefficient at 350 nm measured at room temperature which is less than 1.5 cm −1 ; (d) an absorption coefficient at 520 nm measured at room temperature which is less than 0.45 cm −1 ; and (e) an absorption coefficient at 700 nm measured at room temperature which is less than 0.18 cm −1 , wherein the single crystal CVD diamond has a thickness of greater than 0.1 mm, wherein a concentration of nitrogen in the majority volume of the single crystal CVD diamond is greater than 5×10 15 atoms/cm 3 , and wherein a concentration of boron or silicon in the majority volume of the single crystal CVD diamond is greater than 10 14 atoms/cm 3 .