Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
1999-07-20
2001-03-13
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C445S051000
Reexamination Certificate
active
06200183
ABSTRACT:
TECHNICAL FIELD
The present invention is generally directed to electron emission materials. More particularly, the present invention is directed to the use of diamond as an electron emission material.
BACKGROUND ART
There has been great interest in fabricating cold cathodes using wide-band-gap semiconductors. Such material has been used as coatings on metallic tips, as tip materials, and as thin-film cold cathodes. Materials of current interest include among others diamond, nitrides, disordered carbon forms, and others.
Electron emission is achievable in many ways from a variety of materials and several mechanisms have been proposed to explain the phenomenon. For example, a disordered tetrahedral carbon thin-film device using a diode configuration has been successfully demonstrated in applications for such purposes. (To this purpose see the article by B. L. Weiss, A. Badzian, L. Pilione, T. Badzian, and W. Drawl, Appl. Phys. Lett. 71, 794 (1997).) This material seems to satisfy the provide the following qualities:
(i) electronic structure characteristics of wide-band-gap semiconductors;
(ii) high dielectric breakdown;
(iii) n-type electrical conductivity;
(iv) favorable emission surface properties, including negative electron affinity and/or emission enhancement by adsorbed specific atoms; and
(v) durability under a high electrical field, including longevity in thousands of hours.
In general, diamond material fulfills these conditions as is demonstrated in the extensive electron emission art. Examples include: U.S. Pat. No. 3,947,716, issued on Mar. 30, 1976, to Fraser, Jr. et al.; U.S. Pat. No. 3,970,887, issued on Jul. 20, 1976, to Smith et al.; U.S. Pat. No. 4,307,507, issued on Dec. 29, 1981, to Gray et al.; U.S. Pat. No. 4,685,996, issued on Aug. 11, 1987, to Busta et al.; U.S. Pat. No. 4,955,636, issued on Aug. 8, 1989, to Busta et al.; U.S. Pat. No. 4,964,946, issued on Oct. 23, 1990, to Gray et al.; and U.S. Pat. No. 5,703,435, issued Dec. 30, 1997.
According to some of the teachings of the art, chemical vapor deposition (CVD) methods were used in the fabrication of emission devices because of their versatility.
Of these requirements, the most difficult to achieve is the n-type diamond, preferably as a shallow donor material. However, n-type diamond was reported as a result of P (phosphorous) doping of (
111
) homoepitaxial thin films. In this investigation, Hall measurements were taken and an activation energy of 0.46 eV was calculated. (See S. Koizumi, M. Kamo, Y. Sato, H. Ozaki, and T. Inuzuka, Appl. Phys. Lett. 71 (1997) at 1065.)
While providing arguable improvements in the art, the prior art fails to provide a practical method of providing a diamond suitable for providing electron field emission. Such a method remains wanting.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide for the use of a material which is generally satisfactory as an electron emission material.
It is an additional object of the present invention to provide for the use of such a material which provides an electronic structure characteristics of wide-band-gap semiconductors.
Still a further object of the present invention is to provide for the use of such a material which demonstrates high dielectric breakdown.
Yet an additional object of the present invention is to provide for the use of such a material which demonstrates n-type electrical conductivity.
A further object of the present invention is to provide for the use of such a material which demonstrates favorable emission surface properties, including negative electron affinity and/or emission enhancement by adsorbed specific atoms.
Still a further object of the present invention is to provide for the use of such a material which demonstrates durability under a high electrical field, including longevity in thousands of hours.
These and other objects are provided in the present invention through the use of diamond as an electron emission material. Satisfactory measurements were conducted on diamond coatings deposited on WC-Co alloy by a multiple pulsed laser process. The electron emission was measured in a diode configuration with a diamond surface-anode spacing of 20 and 50 &mgr;m in vacuum at P=10
−7
Torr. Current densities of 6 mA/cm were calculated at an applied voltage of 3000 V (for 20 &mgr;m). Analysis proved that electron field emission provided by a diamond grown by a multiple pulsed laser process proved to satisfactorily meet the specified demands.
REFERENCES:
patent: 4685976 (1987-08-01), Schachameyer et al.
patent: 5154945 (1992-10-01), Baldwin et al.
patent: 5308651 (1994-05-01), Ohta et al.
patent: 5445550 (1995-08-01), Xie et al.
patent: 5643641 (1997-07-01), Turchan et al.
patent: 5891522 (1999-04-01), Olson
Badzian Andrzej R.
Badzian Theresa
Drawl William R.
Mistry Pravin
Roy Rustum N.
Harness & Dickey & Pierce P.L.C.
QQC, Inc.
Ramsey Kenneth J.
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