Electric lamp and discharge devices – Discharge devices having a thermionic or emissive cathode
Reexamination Certificate
1999-12-06
2003-09-09
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Discharge devices having a thermionic or emissive cathode
C313S311000, C313S495000
Reexamination Certificate
active
06617773
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron-emitting device, an electron source using the electron-emitting devices, an image-forming apparatus, such as display devices or the like, constructed using the electron source, and methods for producing them.
2. Related Background Art
The conventionally known electron-emitting devices are roughly classified under two types; thermionic cathodes and cold cathodes. The cold cathodes include field emission type (hereinafter referred to as “FE type”) electron-emitting devices, metal/insulator/metal type (hereinafter referred to as “MIM type”) electron-emitting devices, surface conduction type electron-emitting devices, and so on.
Examples of the known FE type devices include those disclosed in the following: W. P. Dyke & W. W. Dolan, “Field emission,” Advance in Electron Physics, 8, 89 (1956); C. A. Spindt, “Physical Properties of thin-film field emission cathodes with molybdenum cones,” J. Appl. Phys., 47, 5248 (1976); M. W. Geis, “Electron field emission from diamond and other carbon materials after H
2
, O
2,
and Cs treatment” Appl. Phys. Lett. 67 (9) (1995); W096/35640; Ken Okano, “Low-threshold cold cathodes made of nitrogen-doped chemical-vapor-deposited diamond,” Nature, Vol. 381, 1996; A. J. Amaratunga, “Nitrogen containing hydrogenated amorphous carbon for thin-film field emission cathodes,” Appl. Phys. Lett., 68 (18) (1996); A. Weber, “Carbon based thin film cathodes for field emission displays,” J. Vac. Sci. Technol. A16 (3) (1998); Eung Joon Chi, “Effects of heat treatment on the field emission property of amorphous carbon nitride,” J. Vac. Sci. Technol. B16 (3) (1998), and so on.
Examples of the known MIM type devices include those disclosed in C. A. Mead, “Operation of Tunnel-Emission Devices,” J. Appl. Phys., 32, 646 (1961), and so on.
Examples of the surface conduction electron-emitting devices include those disclosed in M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965), and so on.
The surface conduction electron-emitting devices utilize such a phenomenon that electron emission occurs when electric current is allowed to flow in parallel to the surface in a thin film of a small area formed on a substrate. Examples of the surface conduction electron-emitting devices reported heretofore include those using a thin film of SnO
2
by Elinson cited above and others, those using a thin film of Au (G. Ditmmer: “Thin Solid Films,” 9, 317 (1972)), those using a thin film of In
2
O
3
/SnO
2
(M. Hartwell and C. G. Fonstad: “IEEE Trans. ED Conf.,” 519, (1975)), those using a thin film of carbon (Hisashi Araki et al.: Shinku (Vacuum), Vol. 26, No. 1, p22 (1983)), and so on.
A typical device configuration of these surface conduction electron-emitting devices is the device structure of M. Hartwell cited above, which is shown in FIG.
18
. In the same drawing, numeral
1
designates an electrically insulative substrate. Numeral
4
denotes an electrically conductive film, which is, for example, a thin film of a metal oxide formed in an H-shaped pattern and in which an electron-emitting region
5
is formed by an energization operation called “forming” described hereinafter. In the drawing the gap L′ is set to 0.5 to 1 mm and the width W′ to 0.1 mm.
In these surface conduction electron-emitting devices, it was common practice to preliminarily subject the conductive film
4
to the energization operation called the forming, thereby forming the electron-emitting region
5
. Namely, the forming is an operation for applying a dc voltage or a very slowly increasing voltage, for example at the increasing rate of about 1 V/min, to the both ends of the conductive film
4
to locally break, deform, or modify the conductive film, thereby forming the electron-emitting region
5
in an electrically higher resistance state than the resistance in the surroundings. In the electron-emitting region
5
a fissure is created in part of the conductive film
4
and electrons are emitted from near the fissure.
In the surface conduction electron-emitting device after the aforementioned forming operation, electrons are emitted from the above-stated electron-emitting region
5
when the current flows in the device with application of the voltage to the conductive film
4
including the electron-emitting region
5
.
On the other hand, for example, as disclosed in Japanese Patent No. 2,836,015, No. 2,903,295, etc., the device after the forming is sometimes subjected to a treatment called an activation operation. The activation operation is a step by which remarkable change appears in the device current If and in the emission current Ie.
The activation step can be performed by repeatedly applying pulse voltage to the device, as in the case of the forming operation, under an ambience containing an organic substance. This operation causes a film mainly containing carbon or a carbon compound to be deposited from the organic substance existing in the ambience onto the electron-emitting region of the device and the vicinity thereof, so as to induce outstanding change in the device current If and in the emission current Ie, thereby achieving better electron emission characteristics.
FIGS. 20A and 20B
are schematic diagrams to show the electron-emitting device disclosed in the above publications. In
FIGS. 20A and 20B
, reference numeral
1
designates an electrically insulating substrate,
2
and
3
electrodes,
4
the aforementioned electrically conductive film,
10
the film mainly containing carbon or the carbon compound, formed by the aforementioned activation operation, and
5
the electron-emitting region.
Since the surface conduction electron-emitting device described above is simple in the structure and easy in the production, it has the advantage of capability of forming an array of many devices across a large area. A variety of applications have been investigated heretofore in order to take advantage of this property. For example, such applications include charged beam sources, display devices, and so on.
An example of the application wherein a lot of surface conduction electron-emitting devices are arrayed is an electron source in which the surface conduction electron-emitting devices are arrayed in parallel and a lot of rows are arranged, each row including the surface conduction electron-emitting devices whose two terminals are connected to respective wires (for example, Japanese Patent Application Laid-Open No. 64-31332, No. 1-283749, and No. 2-257552).
Particularly, in the field of the image-forming apparatus such as the display devices and the like, flat panel display devices using liquid crystals are becoming widespread in recent years, in place of the CRTs, but they are not of a self-emission type. Therefore, they had the problem that a back light or the like was required, for example. Therefore, there were desires for development of the display device of the self-emission type.
When the image-forming apparatus is constructed as a display device in which an electron source comprised of a lot of surface conduction electron-emitting devices is combined with a fluorescent material for emitting visible light with reception of electrons emitted from the electron source, the apparatus, even of the large area, can be produced relatively readily and is the emissive display with excellent quality of display.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a configuration of the surface conduction electron-emitting device capable of realizing highly efficient and stable electron emission characteristics, an electron source and an image-forming apparatus using it, and methods for producing them.
The inventors have been conducted intensive and extensive research in order to solve the above object and came to accomplish the present invention, based on such knowledge that the electron emission efficiency of the surface conduction electron-emitting device varied large, depending upon the quality of the carbon-containing film (carbon film), particularly, depending upon
Arai Yutaka
Tamura Miki
Yamamoto Keisuke
Patel Ashok
Zimmerman Glenn
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