AS anyone who watches the Academy Awards knows, diamonds are still the most glamorous of gemstones. But as laboratory techniques for synthesizing diamonds improve, the stones may one day be found not only on movie stars, but also in lasers, light-emitting diodes, integrated circuits and other nondecorative but highly practical applications.
That's because many diamonds can be grown today in low-pressure chambers where carbon from a methane-hydrogen mixture is coaxed into collecting and forming single crystals around tiny starter diamonds. The process yields large, rapidly created diamonds that may one day find a use in, among other things, semiconductor devices in high-temperature environments.
''Everybody is growing diamonds,'' said John C. Angus, a professor of engineering at Case Western Reserve University who was a pioneer in developing the technique of creating diamonds from gases, called chemical vapor deposition.
At the Carnegie Institution of Washington, researchers have now adapted the technique to make thick single crystals of diamonds that not only grow extremely rapidly but also turn out to be considerably harder than natural diamonds.
''We can't quantify how hard the diamond is, because it tends to damage the instruments used to measure it,'' said Russell J. Hemley, a senior staff scientist at Carnegie.
The research group, which began looking into the vapor deposition method four years ago, has created diamonds as thick as about one-fifth of an inch and as wide as two-fifths of an inch, Dr. Hemley said.
Dr. Hemley, a member of the institution's Geophysical Laboratory, said his interest in diamonds was related to basic research in the behavior of materials at extreme pressures. ''We need large, perfect diamonds to make high-pressure devices for our research,'' he said. But diamonds like the ones the group has grown will have many other uses, including electronics, he said.
Apollo Diamond, a Boston company, is also growing large, single crystal diamonds by using a version of the chemical vapor deposition method, said Robert C. Linares, a founder of the company.
Researchers have long sought ways to use diamonds as a more durable alternative to silicon, which does not stand up as well to high temperatures and stress. But many early diamonds made by vapor deposition were poorly suited to electronic applications because they emerged in the form of a film with a jumble of diamond crystals oriented in varying ways, leading to defects that could trap electrons.
The researchers at Carnegie grew their diamonds from a gaseous mixture heated to high temperatures to produce the carbon that condensed on a diamond kernel. ''We start with a seed, and the carbon atoms then rain out from the plasma, arranging themselves as a single crystal rather than as a film,'' Dr. Hemley said. Afterward the diamonds are heated to more than 3,600 degrees Fahrenheit and put under pressure to harden them further.
Semiconductor devices are one of several areas in which the new generation of synthetic diamonds may find use. Currently most transistors, diodes and integrated circuits are based on silicon, which is ''doped'' with impurities to alter the flow of electrons.
Diamond has a crystal structure similar to that of silicon and shares many of its properties.
But turning diamonds into semiconductors has proved a tough job, primarily because of the difficulties in doping diamonds, which are natural insulators, to improve their electrical properties. Doping diamonds with boron has worked well to turn them into a type of semiconductor called a p-type or p-diamond, for the positive charges that carry current.
But transistors and diodes also need a second kind of doped semiconductor material, called n-type, and that diamond has turned out to be hard to devise.
''The major outstanding problem for diamond semiconductor electronics is the lack of a good n-type doping agent,'' said James E. Butler, a research chemist at the Naval Research Laboratory who has conducted diamond research for 17 years, primarily working on improving the chemical vapor deposition process. ''Without it, diamond electronics will be seriously limited.''
N-type diamonds have been developed, including some that use phosphorus, he said, but none of the materials are entirely satisfactory. Last year Dr. Butler and colleagues reported that they had created a boron-doped diamond grown by vapor deposition that was then treated with deuterium.
''It's an n-type and it's reproducible,'' Dr. Butler said. ''But we don't yet understand the fundamentals.''
At Case Western, Dr. Angus and his colleagues have been making progress, although their solution is far from perfect, he said. Working with a doctoral student, Sally Eaton-Magana, now a postdoctoral associate at the Naval Research Laboratory, he doped vapor-produced diamonds with both boron and sulfur. ''We added two elements at the same time to achieve n-type behavior,'' he said. It works, he added, but the electrons don't move fast enough.
Dr. Angus says the problem might be that the doping seems to work only in the near surface region rather than uniformly throughout the diamond, a necessity for controllable properties. ''You don't want the electrical properties to vary willy-nilly throughout the semiconductor,'' he said.
Dr. Butler said that synthetic diamonds might find their niche not in microprocessors but in high-current high-voltage applications -- for instance, in switching devices for high-speed trains. These trains work at 10,000 volts or so, he said, and use semiconductors to help control the power. Currently the cars use big semiconductor wafers and related heavy gear that add up to roughly a ton per railcar.
''But in the future diamond could be used to take that ton of electronics and bring it down to a hundred pounds,'' he said.
Despite the problems that remain to be solved, many researchers are hopeful that the new generation of synthetic diamonds will play a role in computers. ''Chips are getting hotter and hotter, the more transistors you add,'' said Jimmy L. Davidson, a professor of electrical and computer engineering at Vanderbilt University who has long worked in diamond research. Silicon stops working at about 200 degrees Fahrenheit, he said, but diamond has internal properties that allow it to work at 1,000 degrees Fahrenheit.
''When we put diamonds in computers to draw off heat,'' he said, ''no fans will be needed.''
Photo: RESILIENT -- A synthetic single-crystal diamond created from gases in a technique known as chemical vapor deposition. (Photo by Physica Status Solidi)