Plastic and nonmetallic article shaping or treating: processes – Treating shaped or solid article – By a temperature change
Reexamination Certificate
1999-08-18
2001-08-21
Dixon, Merrick (Department: 1774)
Plastic and nonmetallic article shaping or treating: processes
Treating shaped or solid article
By a temperature change
C264S446000, C264S235000, C264S236000, C264S298000, C264S003200, C264S345000, C428S206000
Reexamination Certificate
active
06277318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to devices comprising carbon nanotube films.
2. Discussion of the Related Art
Carbon nanotubes have interesting electronic properties and offer potential for use in electronic devices and in interconnect applications. Carbon nanotubes also feature high aspect ratios (>1000) and atomically sharp tips which make them ideal candidates for electron field emitters. To realize these potential applications, there is a need to process nanotubes into useful forms such as thin films, and, advantageously, patterned thin films.
Carbon nanotubes are currently being produced by a variety of different techniques such as arc-discharge, laser ablation and chemical vapor deposition (CVD). (See S. Iijima,
Nature,
Vol. 354, p. 56 (1991); T. W. Ebbesen and P. M. Ajayan,
Nature,
Vol. 358, p. 220 (1992); and B. I. Yakobson and R. E. Smalley,
American Scientists,
Vol. 85, p. 324 (1997). The as-deposited material, however, is usually in the form of loose powders, porous mats, or films with poor adhesion. These forms of nanotubes do not lend themselves to convenient preparation of robust adherent nanotube thin film structures. The difficulty in preparing an adherent film of nanotubes is believed to be due to the perfect structure associated with carbon nanotubes, which contain essentially no dangling bonds and few defect sites. As a result, nanotube films tend to exhibit poor adhesion, even to the point of being easily removed by contact or by air flow (e.g., an air duster).
Patterned nanotube films have been reported by Fan et al.,
Science,
Vol. 283, p. 512 (1999), and Xu et al.,
Appl. Phys. Lett.,
Vol. 74, p. 2549 (1999). These references describe use of direct deposition techniques such as CVD, in which substrates are selectively patterned with catalyst metals and then nanotubes are grown in the patterned areas. These techniques, however, produce films with poor adhesion. The techniques also expose the substrates to a reactive and high-temperature deposition environment, which is both inconvenient and harmful to actual device structures. In addition, the techniques are limited to the patterned growth of multi-wall carbon nanotubes (MWNTs), because CVD typically produce MWNTs on catalytic substrates.
Thus, there is a desire to develop more convenient and versatile methods for patterning carbon nanotube films with adequate adhesion, to allow formation of more useful and robust device structures.
SUMMARY OF THE INVENTION
The invention provides a method for fabricating adherent, patterned carbon nanotube films. (Adherent indicates that the adhesion strength of the film exceeds scale
2
A or
2
B according to ASTM tape testing method D3359-97.) According to the invention, a substrate is patterned with a carbide-forming material, a carbon-dissolving material, or a low melting point metal (i.e., about 700° C. or less). Carbon nanotubes are then deposited onto the patterned substrate, e.g., by spraying or suspension casting. The nanotubes have relatively poor adhesion to either the substrate material or the patterned material at this stage. The substrate is then annealed, typically in vacuum, at a temperature dependent on the particular patterning material, e.g., a temperature at which carbide formation occurs, at which carbon dissolution occurs, or at which the low melting point metal melts. The annealing thereby provides an adherent nanotube film over the patterned areas, while the nanotubes deposited onto the non-patterned areas are easily removed, e.g., by blowing, rubbing, brushing, or ultrasonication in a solvent such as methanol. This process provides an adherent nanotube film in a desired pattern. The patterned films are useful for a variety of devices, including vacuum microelectronic devices such as flat panel displays, as well as other structures, e.g., nanotube interconnects.
REFERENCES:
patent: 5773921 (1998-06-01), Kessmann et al.
patent: 5872422 (1999-02-01), Xu et al.
patent: WO 98 11588 (1998-03-01), None
Fan, S. et al., “Self-Oriented Regular Arrays of Carbon Nanotubes and their Field Emission Properties”,Science, vol. 283, p. 512 (1999).
Xu et al., “A Method for Fabricating Large-Area, Patterned, carbon Nanotube Field Emitters”,Appl. Phys. Lett., vol. 74, p. 2549 (1999).
Iijima, S.,Nature, vol. 354, p. 56 (1991).
Ebbesen, T. W. et al.,Nature, vol. 358, p. 220 (1992).
Yakobson, B. I.American Scientists, vol. 85, p. 324 (1997).
Fan et al.,Science, vol. 283, p. 512 (1999).
Xu et al.,Appl. Phys. Lett., vol. 74, p. 2549 (1999).
Massalski, T. B.Binary Alloy Phase Diagrams, vol. I, ASM International.
Shelimov, K. B. et al., “Purification of Single Wall Nanotubes by Ultrasonically Assisted Filtration”,Chem. Phys. Lett., vol. 282, p. 429 (1998).
U.S. Patent application Serial No. 09/296572, filed on Apr. 22, 1999.
U.S. Patent application Serial No. 09/351537, filed on Jul. 12, 1999.
Bower Christopher Andrew
Zhou Otto
Zhu Wei
Agere Systems Guardian Corp.
Dixon Merrick
Rittman Scott J.
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