Diamond is the hardest natural material known. It conducts heat five times faster than copper, and can withstand the harshest environmental conditions, including chemical and radioactive forces. It is an excellent insulator or conductor, meaning it can either allow electricity to pass through it – or block it. Perhaps amongst its most interesting qualities; diamond can be placed inside a human body without triggering an immune response.
What makes diamond the choice material to use?
Well, most people are familiar with the beauty of diamonds because of its application as a gemstone, but they’re not aware of all the other superlative properties of diamond. For example, it is the material with the highest thermal conductivity of any material, either man-made or synthetic. Sound travels faster through diamond than it does through any other medium. Of course, most people are familiar with it being the hardest material, but this list of properties where diamond truly excels is quite long, and so it finds application where people need truly superior performance from a material and can afford diamond in that application.
Can you give us a little background on the synthetic diamond industry and what areas or industries synthetic diamond is applied?
It probably sprang up during and just after World War II because of the difficulty in United States, primarily, in getting access to diamond to use in machining applications in the war effort. Most people realized that you don’t find diamond in North America. And so all sources, primary sources at the time were in South Africa, which was an Axis-leaning country. As you might expect, the United States didn’t want to be caught in this bind again. So there was an effort to synthesize the material. It was in the mid-‘50s that a group at General Electric was successful.
So the technique they used was a high-pressure, high-temperature technique where you grow seeds, very small particles of diamond, by adding carbon to it in a diffusion process. And it wasn’t long, perhaps within the next five or ten years, that De Beers became active in the area and Sumitomo in Japan became active. Those three companies today are probably the biggest producers of synthetic diamond, primarily abrasives for grinding and cutting applications. The bits that are being used to drill the rescue tunnel to the Chilean miners, I’m sure, are diamond tipped. Diamond saw blades are used to remove the top layer of the highways that you see as you drive around, prior to them being resurfaced.
Your dentist drills out that nasty cavity using a diamond-coated bit, a diamond burr, so there’s a lot of diamond abrasive being made today, perhaps somewhere between 1 and 2 billion carats a year of this are being made. In fact, it’s one of those materials that’s being supported by the Chinese government and the Chinese industry is starting to bring prices of that material down to commodity levels.
The high-pressure, high-temperature process is similar to the way a diamond develops naturally. When was the chemical vapor deposition process developed to synthesize diamonds?
The chemical vapor deposition, of course, is a lower temperature, lower pressure technique of growing diamonds from carbon that’s in the gas phase. And I suppose this was first done in the ‘60s in Russia, but it really became much more popular in the late ‘80s as academic researchers in Japan, the Americas, and Europe became interested in growing polycrystalline diamond in a wafer form, mostly hoping to use diamonds’ interesting and unique properties as a new substrate to replace silicon in microprocessor manufacturing.
Because it’s cheaper or better?
Because it’s better. It’s not necessarily cheaper, at least at the levels of production that they were using at that time and are still being used today. It’s not quite become as cheap as they would like, especially for such a mass market application.
Can you explain how a synthetic diamond is made using chemical vapor deposition?
This chemical vapor deposition technique is not unlike what’s done to deposit other materials on substrates. We take a substrate and put it under a vacuum. We then fill the chamber with a carrier gas, which, in our case, is hydrogen, and a carbon-containing gas, which, in our case, is methane. We then energize these molecules, and that can be done a number of ways, from something as simple as a flame to something a little more exotic, such as microwaves or creating an arc jet. This breaks apart the hydrogen and the methane, the carbon deposits on your substrate as diamond, graphite, and soot, and hydrogen etches away the graphite and soot much faster than it etches away the diamond.
What is left behind is a very large number of very small diamond crystals all growing. The end result, of course, is a thick layer, millimeters thick, perhaps, but a thick layer of diamond on your substrate, which you can then process and create a wide variety of products. More recently, people have put single crystal diamond substrates in these systems and added carbon to them in order to grow larger single crystals of diamond. This technique provides you the benefits of being able to engineer the material to add specific quantities of specific contaminants in order to tailor the properties of the diamond that you make.
What industries have used your materials?
Diamond used for its
thermal conductivity
and high electrical resistivity
There’s a variety of industries. Diamond is still used extensively in the metal cutting industry, so we’ve made pieces of this polycrystalline and diamond material, which can be put on tool bits for milling or turning or drilling, these kinds of things. Higher quality material can often be used in optical applications, optical elements for infrared spectrophotometers or other analytical instruments. Beam conditioning components for X-ray beam lines and experimental facilities. A variety of high technology applications.
We use the high thermoconductivity of diamond to remove the heat from higher-power electronic devices, so small diamond heat spreaders are being used in laser diode packages in the telecommunications industry or in the cutting laser industry. And we’re finding more and more uses for the thermal property of diamond in higher-power electronics for power conversion and other forms of communication in military and satellite applications.
What was the most common application for one of your synthetic diamonds? Can you cite a particularly uncommon or challenging application?
Targets for short-pulse,
high-power lasers
use very thin diamond
Diamond seems to be fairly well accepted as a heat spreader in these microelectronic applications. So I would suggest that that’s a pretty common, pretty well-understood application for this chemical vapor deposit of diamond. Some of the more unusual things that we’re getting involved with involve making thinner and thinner coatings or membranes of diamond. At the moment, we’ve been successful at making these membranes or exposed areas of diamond down to about 30 nanometers thick.These are used as targets for short-pulse, high-power lasers in generating carbon ion beam, which have some interesting potential applications in tumor treatment, as well as some applications in containment of fusion. These are a little different and have presented some challenges.
Often times, it’s in failed attempts to produce a material that other materials of interest are created or breakthroughs are made; I was wondering if you’ve ever experienced a time where a failed project actually led you to another discovery that forwarded your study or spurred on another use of synthetic diamond?
As we try to make things for our customers, we often discover or learn how to do certain things to the diamond, which then can be applied in the future to resolve other customer problems. Probably the most direct response to this question has to do with the Nobel Prize in physics that was awarded this year, to fellows who discovered graphene, which is a single-molecule or single-atom thick sheet of carbon atoms.
This was an offshoot of people doing experiments with various forms of carbon molecules, whether it’s graphite or fullerenes, which is a spherical assembly of carbon atoms or carbon nanotubes, which is a cylindrical assembly of carbon atoms.
Carbon Nanotube You’re talking about Andre Geim and Konstantin Novoselov who won the Nobel prize for Physics this year for their experiments on the two-dimensional material graphene?
Yeah. And that’s an offshoot of this increasing interest in carbon science that’s taken place since the advent of chemical vapor deposition of diamonds and forms of diamond.
Andre and Konstantin also won the IgNobel Award. The IgNobel awards highlight the silly yet thought-provoking experiments going on behind the serious stuff. They used a magnet to levitate a frog.
Will synthetic diamond replace natural diamond in the future? Can you grow a better diamond than, say, a gem quality natural diamond?
Yes, we can grow a better diamond than a gem-quality natural diamond and we can grow a diamond that’s got less than one part per billion of contamination in it, where the vast majority of natural diamonds have a couple hundred parts per million of just nitrogen, let alone other forms of contaminants in them. So the question of replacement really has to do with you, Laurie. I mean if you were to get engaged would you be as happy with your new fiancé if he presented you with a synthetic engagement ring, as opposed to a natural engagement ring?
Maybe that’s not a fair question to ask of you. You have an interest in the science and would probably appreciate the synthetic diamond even more; but it’s the emotional attachment we have to the gem 'diamond' which would have to shift in order to appreciate a purer synthetic diamond.
Where do you think synthetic diamond will go from here? Obviously, it’s gonna move into other industries as it becomes easier to make and we see more applications?
Optical grade diamond
for IR applications
The indications from the research that’s being done today, in terms of applications, involves the development of electronic devices made out of diamond, whether it’s detectors for various forms of radiation or biological agents, substrates for doing electrochemistry, or the substrates themselves for transistors which can handle higher power loading. This would be a real benefit to power conversion applications.
Power conversion is the technology that’s used to create or to change the current that’s produced by your solar cells into the alternating current that’s used by your toaster or the alternating current that’s generated by the wheels on your car into the direct current that’s stored by your car battery and vice-versa. And so as the power in those systems is increased, the necessity for electronics to handle that increased power goes up and diamond is a natural fit for those kind of applications.
With its unique properties, and because the demand constantly moves toward smaller, lighter, faster devices, industry will find synthetic diamond a valuable material for future applications. Scientists like Joe Tabeling use the extraordinary properties of diamond to solve the challenges of these demanding applications. We want to thank Joe for taking the time to talk to us today.
