<span>This invention may be used by or on behalf of the United States Government without the payment of any royalties therefor. The invention relates as indicated to a modified low-pressure process for the growth of diamonds from diamond seed crystals which is characterized by using a mixture of a boron or aluminum compound or lithium vapor with a monocarbon atom source of carbon for diamond deposition. Inclusion of such material (hereinafter called a "doping agent") in the diamond deposition gas results in the production of diamond crystals including boron, aluminum or lithium in the crystal lattice. These elements impart color to the diamond rendering them useful in the gemstone field and also impart semiconducting properties to the diamond crystals. The resulting synthetically grown diamonds may also be used in the manufacture of industrial abrasive tools. The manner of using such materials as are produced by the process herein described is within the skill of artisans in the gemstone, electronics, and abrasive tool fields. The term "low pressure" insofar as it is applied to the production of diamond contemplates anything below 40,000 p.s.i. One "low pressure" process (Hibshman U.S. Pat. No. 3,371,996) contemplates pressures of from 1 to 2000 atmospheres, and temperatures which are limited to 1,100.degree. C. or less. This process is characterized by utilization of a platinum catalyst to promote the production of carbon from carbon monoxide. The present improvements contemplate very </span><span>much lower pressures, preferably a hydrocarbon source for the carbon and an absence of metallic catalysts. Another process (Eversole U.S. Pat. Nos. 3,030,187 and 3,030,188) contemplates temperatures in the range of from 600.degree. to 1600.degree. C. and pressures of from 0.03 mm. Hg to 10 atmospheres. A special type of low-pressure carbon transport process is taught by Brinkman U.S. Pat. No. 3,142,539 which contemplates temperatures in the range of from 1000.degree. C. to 1800.degree. C. and a molten metallic medium for transporting carbon to the seed crystals. Brinkman in U.S. Pat. No. 3,175,885 discloses another carbon transport process utilizing a vapor transport for carbon evaporated from pure graphite at very high temperatures, distinguished by maintaining the seeds and carbon source at different temperatures. As an example of an extremely high-pressure process, reference may be had to U.S. Pat. No. 3,334,968 to Ishizuka who contemplates pressures of 75,000 atmospheres. Also reference may be had to the patent of Wentorf U.S. Pat. No. 3,297,407 which utilizes seed crystals but extremely high pressures on the order of 75,000 atmospheres. There are quite a few other patents which contemplate high-pressure equilibrium processes and these are exemplified by the patents to Darrow U.S. Pat. No. 3,310,501; Strong U.S. Pat. No. 3,303,053; Wentorf U.S. Pat. No. 3,142,595; Wentorf U.S. Pat. No. 3,148,161; Wentorf U.S. Pat. No. 3,181,933 and others.http://www.google.com/patents?vid=USPAT3607061</span>
