Research: U.S. And Japan Sparkle In Diamond Thin Film Research

Diamonds are turning out to be industry's best friend these days, and, in a reversal of the old adage, the smaller the diamond, the better. In fact, thin films of tiny diamonds applied to mundane substances, such as iron, are revolutionizing businesses that make products as diverse as drills and cutting tools, stereo loudspeaker tweeters, heat sinks, sunglasses, prosthetic devices, and components for scientific instruments. The United States and Japan are the leading players in this rapidly growing technology, which takes advantage of the diamond's unique properties. Diamond is the hardest known substance; it conducts heat more quickly than copper; it has a surface similar to Teflon; it carries sound at high velocity; and it resists most chemical substances. Diamond is not an abundant material, however, so to take best advantage of its exceptional qualities it is combined with less unusual and less expensive substances. Country Percentage* United States 41.7 Japan 25.0 United Kingdom 7.8 Federal Republic of Germany 6.8 Italy 3.0 * These five countries account for nearly 85 percent of the 1988 documents included in ISI's 1988 research front on diamond thin films. According to the 1988 Research Front database of the Philadelphia-based Institute for Scientific Information (ISI), the U.S. and Japan are preeminent in current research on diamond thin films (see Table 1). A research front, or specialty area, consists of a group of "core," or highly cited, articles from any year and the papers published in a specific year (in this case, 1988) that consistently cited these core documents. Titled by ISI as "Diamond films; microwave plasma chemical vapor-deposition; rapid growth" (chemical vapor deposition is one of the methods currently used to "grow" diamond on other substances), this specialty contains 42 core articles published between 1918 and 1987. Twelve of these core articles were published in 1986, 1987, or 1988, which gives this specialty a three-year immediacy index of nearly 29 percent. Immediacy measures how hot or current a field is -- the average immediacy is 15 percent. As a group, the 42 core publications were referenced by 251 papers published in 1988. Table 1 shows that close to 42 percent of the 1988 citing papers listed author addresses in the U.S., while 25 percent listed Japan. For Japan, this percentage is three times greater than its overall contribution (7.1 percent) to ISI's 1988 Research Front database. By contrast, the overall U.S. contribution (41 percent) is essentially the same as its contribution to diamond thin film research. The United Kingdom, Federal Republic of Germany, and Italy round out the list, ranking third, fourth, and fifth, respectively. These three countries produced 7.8, 6.8, and 3.0 percent of the papers in diamond thin film research. These countries' contributions to diamond thin film research are on par with what they contribute to science in general (8.7 percent for the U.K., 5.7 percent for the Federal Republic of Germany, and 2.7 percent for Italy). Japanese researchers lead in the development of new applications, as opposed to basic research. In fact, Japanese companies have applied for more than 200 patents concerning diamond films since 1985. These companies include Sumitomo Electric, which is working with Japanese Victor Co. (JVC) on diamond films for stereo speaker tweeters. Sumitomo is also researching coating prosthetic devices and biosensors with diamond films, in an effort to produce devices and sensors that are compatible with biological tissue. Mitsubishi Metals, another Japanese industrial power, is devel- oping tool inserts coated with diamond thin films: The hard polycrystalline coating provides a sharp and wear-resistant cutting edge. As mentioned, U.S. institutions contributed more papers than any other country in the 1988 diamond film research front. U.S. efforts in diamond thin film technology are focused on basic research. Among the U.S. players, Pennsylvania State University topped the list (see Table 2). Penn State, which contributed 5.8 percent of the 251 papers, is part of a 30-member industry-university consortium that was formed in the 1980s to develop commercial applications for diamond thin film technology in the U.S. FILM RESEARCH Institution Percentage Pennsylvania State University 5.8 Princeton University 4.0 Oak Ridge National Laboratory 2.7 Sandia National Laboratories 2.5 KFA Julich GMBH, W.Germany 2.5 Source: ISI's 1988 Research Front The remaining institutions in Table 2 are also U.S. based, with the exception of KFA Julich GMBH, which is in the Federal Republic of Germany. Princeton University, Oak Ridge National Laboratory, and Sandia National Laboratories, along with KFA, each contributed at least 2.5 percent of the papers. Researchers have been creating diamond thin films since the early 1950s. In 1954, scientists at General Electric synthesized artificial diamonds from graphite; in 1955, the company reported the development of a method involving high pressures and high temperatures to grow synthetic diamond crystals on a metal substance, such as iron, nickel, or chromium. This method is still used today. The film it produces is usually used as an abrasive agent or applied to tools for cutting. Another technique, in which thin diamond films are grown under low pressure, was developed by Soviet scientists Boris V. Derjaguin and Dimitri V. Fedoseev at the Institute of Physical Chemistry of the Academy of Sciences of the USSR, Moscow, in 1956. They received a patent for this method in 1980. More often today, industries use chemical vapor deposition methods to create diamond thin films. Developed in the early 1980s by Japanese scientists, these techniques usually involve the use of a hot filament (or microwave radiation) to heat hydrogen and methane gases over a substrate such as silicon or nickel. The carbon in the gas then condenses over the substrate (which is cooler), while the more reactive types of carbon combine with atomic hydrogen and are released, leaving behind a layer of pure diamond crystals. Future applications for diamond thin films rely in part on the ability of researchers to further reduce the temperatures used in these methods. Until then, less heat-resistant materials, such as some plastics, cannot be efficiently and effectively coated with diamond films. Another drawback concerns the quality of the diamond film produced. Potential uses, such as in high-temperature transistors or electronic computer chips, require a single-crystal diamond film deposited on a nondiamond substrate. Most films produced today are polycrystalline. The technology to produce a one-crystal film does not yet exist. Scientists are hopeful that a solution is just around the corner. But Russell Messier of the Materials Research Laboratory at Penn State, who heads the 30-member consortium there, warns that it may be 10 years before science refines the currently available techniques to produce the single-crystal diamond films required to create a diamond microchip. Diamond thin film researchers will gather this summer in Italy to share their knowledge and expertise at a conference sponsored by NATO. The Advanced Study Institute on Diamond and Diamond-Like Films will take place from July 22 to August 2 in Castelvecchio Pascoli. Abigail Grissom is a freelance science writer based in Philadelphia.

Research: U.S. And Japan Sparkle In Diamond Thin Film Research

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