Method of producing diamond of controlled quality

A method of producing a diamond substance of known acceptable quality by chemical vapor deposition, said known acceptable quality being indicated by the cathodoluminescence spectrum of a control diamond substance having said acceptable quality, which method comprises:

• a) providing a substrate in a chemical vapor deposition chamber;
• b) depositing a diamond substance on said substrate by chemical vapor deposition, said depositing comprising:
• i. introducing into said chamber a matrix gas comprising hydrogen and at least one additional gas selected from a hydrocarbon gas and carbon monoxide;
• ii. exciting said matrix gas to create a plasma while heating said substrate to a temperature of least 700.degree. C. to deposit a diamond substance on said substrate, said substance being crystallographically diamond;
• c) terminating said deposition at an early stage after commencing said deposition before a significant mass of said diamond substance has been deposited on said substrate, the amount of deposited diamond substance being sufficient to enable measurement of the luminescence spectrum of said diamond substance by cathodoluminescence measurement;
• d) removing said substrate bearing said diamond substance from said chamber;
• e) subjecting said diamond substance to a cathodoluminescence measurement to determine the luminescence spectrum of said diamond substance;
• f) comparing, utilizing the luminescence measurement of step (e), the luminescence spectrum of said diamond substance to the luminescence spectrum of said control diamond substance of said acceptable quality, the luminescence spectrum of said control diamond substance being indicative of a diamond substance of said acceptable quality whereby the comparison provides an indication of any deviation in said deposited diamond substance from said acceptable quality;
• g) returning said substance bearing said diamond substance, to said chemical vapor deposition chamber;
• h) depositing additional diamond substance on said substance by chemical vapor deposition according to step b);
• i) adjusting, based on the comparison of step f) , one or more of the pressure, substrate temperature, or matrix gas composition prevailing in step h) to compensate for deviation from acceptable quality indicated by the comparison of step f);
• and
• j) repeating steps c) through i) to produce a significant mass of said diamond substance of said acceptable quality.