Status and Applications of Diamond and Diamond-Like Materials An Emerging Technology (1990) / Chapter Skim
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4 Applications
4 Applications
Pages 73-90
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From page 73... ...
TABLE 4-1 Mechanical and Thermal Applications of Superhard Materials Application Property Utilized Material Bearings, journals ABCDEF 23456 Barrier coatings BC F 3456 Heat sinks Ft 123456 Cutting tools AB DEE, 123456 Surgical blades' A D 1 3456 microtomes Knives, AB DE 1 3456 cutting blades Abrasives A F 23 56 Medical implants ABC E 34 Wire drawing dies AB DEF 123 5 Legend A- Hardness B - Chemical stability C - Permeability D - Young's modulus E - Friction coefficient F - Thermal conductivity 1 - Diamond, single-crystal 2 - Diamond, polycrystalline composite 3 - Diamond, polycrystalline film 4 - Diamond-like materials 5 - Silicon carbide 6 - Cubic boron nitride 73
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From page 74... ...
Finally, CVD deposition of polycrystalline bulk material, as opposed to thin film material, requires high deposition rates. Although high deposition rates have been reported in the literature, uniform deposition of high-quality material over large areas has not yet been achieved.
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From page 75... ...
K - Electrically insulating L- Semiconductivity M - Dielectric strength N - Carrier ~relocity\mobility O - Refractive index MECHANICAL APPLICATIONS Bearings and Journals: Coatings and Monolithic 1 - Diamond, single-crystal 2 - Diamond, polycrystall~ne composite 3 - Diamond, polycrystalline film 4 - Diamond-like material 5 - Silicon carbide 6 - Cubic boron nitride Single-crystal diamonds have been used as bearings and wear-resistant surfaces (as for phonograph needles) and more prominently for wire-drawing dies.
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From page 76... ...
Barrier Coatings Nonreactivity in corrosive environments, at high temperature, and in the presence of ionizing radiation may make it possible to use some superhard materials as protective barrier coatings in adverse environments. Their low permeability would prevent diffusion of reactive species to the substrate material, thus preventing substrate degradation.
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From page 77... ...
The potential of CVD diamond for abrasive grain is now being evaluated by various manufacturers. It will probably find a unique niche in the market by virtue of its purity, shape (i.e., flakes and sheets are possible)
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From page 78... ...
, formulated by Johnson, applies to the evaluation of semiconductors for performance as high-power microwave and millimeter-wave amplifier materials. Its principal parameters are the saturated charge carrier velocity (he., the velocity at which charge carriers move through the semiconductor at very high electric fields)
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From page 79... ...
Other areas of major potential impact of superhard materials are electrical insulators, hightemperature transistors, negative electron affinity cathodes (Himpse} et al., 1979) , electronic heat sinks, advanced projection photolithography, clirect-write microelectronics, transistors resistant to ionizing radiation, and coatings for magnetic rlisks and magnetic read-write heads for protection from head crashes.
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From page 80... ...
These very short channel lengths lead to electric field strengths of 50,000 volts/cm in logic devices and even greater fields in analog devices. Since the superhard materials have lower atomic mass than more conventional semiconductors, the energies of the optical phonons that scatter the charge carriers are much higher.
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From page 81... ...
The combination of radiation hardness and high-temperature capability of superhard materials may make electronics practical within or near nuclear reactors. High-Voltage Electronics High-voltage electronics made from superhard semiconductor materials would have greater reliability than vacuum tubes, the components most likely to fail in high-voltage circuits.
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From page 82... ...
Unlike copper, the superhard heat sinks are generally electrically insulating in nature and can be used for removing heat without the complicating requirement of an additional electrically insulating layer. The high heat-removal capability of these materials should permit the fabrication of integrated circuits with significantly increased component densities.
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From page 83... ...
Coating of disks and heads with DLC has been the subject of extensive study, and a considerable payoff in saved data may be realized (Tsai and Bogy, 1987~. Additional Technological Impacts Additional advantages of superhard electronic materials include in situ electronic sensing and signal processing in chemical reactors, automobile engines, engines in heavy industrial equipment, rocket engines, nuclear reactors, etc.; low-cost microwave ovens; higher-speed supercomputers; nuclear radiation dosimeters and detectors with great potential for use in radiation biology and medicine; and thermistors.
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From page 84... ...
c ( l ~ ) cxE where RT = figure of merit of ~ fracture strength arc = thermal conductivity c' = Poisson's ratio = linear thermal expansion coefficient E = Young's modulus The use of CVD diamond as an optical film material has the limitation of requiring high substrate temperatures (greater than 600 °C)
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From page 85... ...
, high-speed optically activated electronic switches, ultraviolet detectors, optical waveguides, and fiber optic coatings. Monolithic Windows and Lenses The ability to deposit high-optical-quality CVD diamond at high deposition rates will make it possible to produce winclows and lenses for the infrared, visible, and ultraviolet that are durable in extreme environments.
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From page 86... ...
in impurity ions within the diamond or within a heterojunction pen junction. Ultraviolet lasers made of superhard materials offer greater storage density capability on compact disks because the laser light could be focused to smaller spot sizes.
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From page 87... ...
Optical Coatings High-Power Laser Mirrors Laser mirrors are subject to degradation from a variety of sources: They are subject to intense optical radiation, which causes a form of dielectric breakdown owing to the high optical electric fields present; they are subject to thermal shock and degradation as a result of heating by the intense optical radiation; they are subject to attack by reactive species such as fluorine in excimer lasers; they are subject to plasma erosion in lasers with gas discharges; and they are subject to environmental degradation from dust and moisture when they act as the output coupler to the external environment. Furthermore, many lasers operate in the ultraviolet.
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From page 88... ...
Additional Technological Impacts Additional advantages that may arise from the application of superhard materials to optics include environmentally stable interference filters; missile detection sensors; and detectors resistant to ionizing radiation. REFERENCES Adamson, A
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From page 89... ...
1986. Thermal conductivity of diamond films synthesized by microwave plasma CVD.
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From page 90... ...
9o Tsai, H
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