Soon thereafter, GE researchers reported their own successful diamond synthesis in Nature. Like Gemesis, both teams used conditions that mimic the pressures and temperatures under which diamonds are thought to form naturally. But these companies marketed their synthetic stones as heat sinks for electronics or used them solely for research purposes. Gemesis, on the other hand, is growing diamonds for jewelry. And because Gemesis' yellow lab-grown diamonds are visually indistinguishable from their mined counterparts, some in the gem industry have expressed concern that the lab-grown diamonds could be passed off as naturals.
In addition, he says trace amounts of nickel left in the diamond from the metal catalyst cause a short-lived phosphorescence after exposure to intense ultraviolet light--a characteristic not shared by most natural diamonds. He also points out that differences in the spatial distribution of nitrogen defects between natural and Gemesis-grown diamonds can be detected by Fourier transform infrared spectroscopy and X-ray absorption spectroscopy.
But Gemesis' business plan only begins with gems. Diamond has an extraordinary range of materials properties: It is the hardest and stiffest material known; is an excellent electrical insulator; has the highest thermal conductivity of any material yet barely expands when heated; is transparent to UV, visible, and infrared light; and is chemically inert to nearly all acids and bases.
Diamond's superlative properties are fine-tuned by impurities found in the carbon lattice--the same impurities that produce colors in naturally occurring diamond. Diamonds having a perfect carbon crystal lattice without defects or substitutions are colorless. Such diamond has a large band gap--meaning that the energy required to free an electron so it can move through the diamond lattice is high--and therefore is an excellent electrical insulator.
But replacing some of the carbon atoms in the diamond lattice with boron--an impurity that produces the pretty blue color in some rare diamonds, including the famed Hope Diamond --transforms diamond into a p-type semiconductor. That's because boron has only three outer-shell electrons and can make only three of four bonds that carbon normally does in the diamond lattice.
The result is a missing electron or "hole" that can move freely through the crystal, allowing the diamond to conduct positive charge. For materials applications that take advantage of these remarkable properties, natural diamonds have obvious flaws: They are prohibitively expensive and limited in size.
Butler, who is spearheading attempts to study, grow, and use diamond at the U. Naval Research Laboratory. As a consequence, Gemesis and many others are eager to create large synthetic diamonds with carefully selected impurities--for instance, boron-doped semiconducting diamonds that could be used to fabricate diamond-based electronic devices that could stand up to heat and chemical attack.
But high-pressure, high-temperature methods of synthesizing diamond like Gemesis' offer limited control of impurities and produce diamonds of limited size, Butler says.
Apollo Diamond , a start-up company in Boston, thinks that a low-pressure technique called chemical vapor deposition CVD could be the answer. Butler agrees. Apollo is using CVD to grow single-crystal diamond wafers big enough to be cut into diamond gemstones of a carat of more.
Apollo's method can grow larger diamonds and is less expensive than high-pressure, high-temperature methods, notes Robert C. Linares, Apollo's founder and chairman. CVD allows finer control of impurities than do high-pressure, high-temperature methods, Linares says.
This enables Apollo to produce a wider variety of colored diamonds--including colorless, pink, blue, honey brown, and even black. Like Gemesis, Apollo inscribes its larger lab-grown gems to aid detection. Eversole of Union Carbide. Back then, "there was a great deal of skepticism that one could grow diamond at low pressures because diamond is thermodynamically unstable with respect to graphite," recalls John C. You were thought to be a fool or a fraud if you proposed this," he says.
Union Carbide subsequently abandoned the project. But a small band of Russian and American scientists, including Angus, pushed forward. By the late s, Angus managed to prove that diamond growth by CVD was indeed feasible. The method was further refined into a viable commercial process in the s by scientists at the National Institute for Research in Inorganic Materials in Tsukuba, Japan. Hydrogen is the key to growing diamond and not graphite under these conditions, Angus' early work showed.
At the surface, the carbon lattice of diamond is decorated with "dangling bonds" that can potentially cross-link to reorganize the surface into more stable graphite. Monthly payments will appear on your credit card statement, but the remaining amount on hold will not show up as debt. Choose a. Shape Round. Advanced Options. Clear Filters.
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