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A New Technology Makes the Micro Components of Diamond Film.

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Mechanical Engineering 123(02), 63 (Feb 01, 2001) (1 page) doi:10.1115/1.2001-FEB-7

Abstract

A new process developed at the Argonne National Laboratory in Argonne, Illinois, for growing diamond films promises to bring the superior mechanical and thermal properties of diamond to the rapidly expanding field of microelectromechanical systems (MEMS). Many of the visionary applications of MEMS, such as tiny weather satellites and deep-space craft, require moving mechanical assemblies that can operate for years or decades. Diamond films acquire an adsorbed surface layer of hydrogen or oxygen, and- if the film is smooth enough- this layer serves as a lubricant. Films produced by other methods than that used at Argonne are rough, and the surface irregularities negate the effect of the adsorbed antifriction layer. The Argonne scientists have developed an ultrananocrystalline technology that makes the MEMS components of diamond film that has the smoothness, detail, and structural stability necessary for practical use. The laboratory scientists are now working on a multilayer deposition method to allow the complete fabrication of full devices without the need for them to be assembled manually.

Article

A new process developed at the Argonne National Laboratory in Argonne, Ill. , for growing diamond films promises to bring the superior mechanical and thermal properties of diamond to the rapidly expanding field of micro electromechanical systems.

MEMS are tiny mechanical devices such as sensors, valves, gears, n1irrors, and actuators, with features measured in micrometers. A MEMS device, which is much too small to be seen with the human eye, contains microcircuitry on the tiny silicon chip into which some mechanical device, such as a mirror or a sensor, has been manufactured.

Argonne National Lab uses a new process to create diamond film with the strength and smoothness needed for use in a tiny, moving MEMS device.

Grahic Jump LocationArgonne National Lab uses a new process to create diamond film with the strength and smoothness needed for use in a tiny, moving MEMS device.

In the new market for MEMS, many potential applications for these microscopic devices aren't really practical because the properties of the material currently used-silicon-aren't suitable. This is especially true for devices that require extensive sliding and rolling contact, such as micromotors for aerospace applications, because silicon wears too quickly. The exceptional physical properties of diamond-hardness, wear resistance, low coefficient of friction comparable with that of Teflon, and thermal and chemical stability-would expand the range of MEMS applications.

Many of the visionary applications of MEMS, such as tiny weather satellites and deep-space craft, require moving mechanical assemblies that can operate for years or decades. Because of their size, such devices must rotate at speeds as high as 400,000 rotations per minute to do useful work. At such high speeds, silicon components wear out in minutes. Diamond is hard enough to withstand this wear. Also, because atomic forces begin to dominate at this scale, such devices must operate without external lubricants.

Diamond films acquire an adsorbed surface layer of hydrogen or oxygen, and- if the film is smooth enough- this layer serves as a lubricant. Films produced by other methods than that used at Argonne are rough, and the surface irregularities negate the effect of the adsorbed antifriction layer. Furthermore, conventionally produced diamond films are so rough that they quickly abrade any nondiamond component in contact with it.

The Argonne scientists have developed an ultrananocrystalline technology that makes the MEMS components of diamond film that has the smoothness, detail, and structural stability necessary for practical use. Ultrananocrystalline diamond films are deposited by a chemical vapor deposition method developed at Argonne and patterned by using photolithography and other techniques Common in the semiconductor industry.

Argonne's patented method was developed using fullerenes, which are spherical molecules of pure carbon containing 60 carbon atoms. Subsequent work at the lab showed that the same result can be achieved by introducing methane into an argon plasma as long as little or no additional hydrogen is present.

The result is freestanding diamond structures as little as 300 nanometers thick with features as small as 100 nanometers and friction coefficients as low as 0.01.

The laboratory scientists are now working on a multilayer deposition method to allow the complete fabrication of full devices without the need for them to be assembled manually. These devices could be micronscale pinwheels gears, turbines, and micromotors.

Copyright © 2001 by ASME
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