Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1998-11-13
2002-10-29
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S304000, C313S306000, C313S311000
Reexamination Certificate
active
06472814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron-emitting device and a production method thereof and, more particularly, to an electron-emitting device having a lower electrode, an insulating layer having pores, and an upper electrode stacked in this order on a substrate, and a method for producing the electron-emitting device.
2. Related Background Art
The conventionally known electron-emitting devices are generally classified under two kinds, thermionic emission devices and cold cathode emission devices. The cold cathode emission devices include field emission type (FE type) devices, metal/insulator/metal type (MIN type) devices, surface conduction electron-emitting devices, and so on.
The FE type devices are disclosed, for example, in W. P. Dyke & W. W. Dolan, “Field emission,” Advance in Electron Physics, 8, 89 (1956) or in C. A. Spindt, “PHYSICAL Properties of thin-film field emission cathodes with molybdenum cones,” J. Appl. Phys., 47, 5248 (1976).
The tip of an electron-emitting body of the field emission type electron-emitting devices is one called a cone having the three-dimensionally sharp-pointed shape and an electron beam is emitted from the tip of the cone by placing a strong electric field between a gate electrode with an aperture, disposed above the cone, and an electron-emitting region.
In order to overcome the problem in the production method of the above field emission devices, which is the need for complicated steps and expensive apparatus for forming a recessed portion for formation of the electron-emitting region, Japanese Laid-open Patent Applications No. 5-298252 and No. 5-211029 describe examples in which holes of an anodic oxide film of aluminum are used as apertures of the gate electrode and in which electron-emitting regions are formed in the holes of the anodic oxide film. These conventional examples will be described referring to
FIGS. 32 and 33
.
FIG. 32
is a sectional view of the electron-emitting device in Japanese Laid-open Patent Application No. 5-198252.
FIG. 33
is a sectional view of the electron-emitting device in Japanese Laid-open Patent Application No. 5-211029. In
FIG. 32
, reference numeral
161
designates an insulating substrate,
162
an electroconductive layer,
163
an insulating film,
164
through holes,
165
the gate electrode, and
166
cathodes. The insulating film
163
is the anodic oxide film of aluminum and the tip of the cathodes
166
is of the cone shape similar to that of the electron-emitting body of the field emission devices. In
FIG. 33
, reference numeral
171
designates a metal layer,
172
the Al anodic oxide film,
172
a
micropores, and
173
cylindrical electrodes. The application describes that in
FIG. 33
the distance can be made constant between the cylindrical electrodes
173
and the gate electrode or between the needlelike electrodes and the anode electrode, so as to make electron emission efficiency constant.
The MIM type devices are disclosed, for example, in C. A. Mead, “Operation of Tunnel-Emission Devices,” J. Appl. Phys., 32, 646 (1961).
Recent researches on the MIM type are seen in Toshiaki Kusunoki, “Fluctuation-free electron emission from non-formed metal-insulator-metal (MIM) cathodes fabricated by low current anodic oxidation,” Jpn. J. Appl. Phys. vol. 32 (1993) pp L1695, Mutsumi Suzuki et al., “An MIM cathode array for cathode luminescent displays,” IDW '96 (1996) p529, and so on.
An MIM type electron-emitting device according to Kusunoki or Suzuki et al. described above will be described referring to FIG.
34
.
FIG. 34
is a schematic sectional view of the MIM type electron-emitting device. In the same figure, reference numeral
1
denotes a substrate,
2
a lower electrode,
3
an insulating layer, and
4
an upper electrode. The electron-emitting device is made by a production method for first forming SiO
2
on the Si substrate by sputtering, depositing Al as the lower electrode, further forming an anodic oxide film of high quality in the thickness of 5.5 nm while controlling oxidation rates, using ethylene glycol and tartaric acid, and thereafter forming Au of the upper electrode in the thickness of 9 nm. It is described that good electron emission characteristics were achieved by applying voltage between the anode of the upper electrode and the cathode of the lower electrode thus formed. Specifically, according to Kusunoki et al., negative resistance does not appear in the device current flowing against the voltage applied to the device. The “negative resistance” herein is a phenomenon in which the device current decreases as the device voltage increases. In addition, fluctuation does not occur in the emission current. Here, the “fluctuation” means temporal change of the emission current. It is also described that dependence of the emission current on the device voltage varies depending upon the thickness of the insulating layer and that the thicker the insulating layer, the higher the device voltage that has to be applied. It is further described that with anodic oxide films made at high oxidation rates, the negative resistance appears in the electron emission characteristics and the fluctuation occurs large.
An example of the surface conduction electron-emitting device with improved electron emission characteristics is described in Japanese Laid-open Patent Application No. 9-82214. This will be described referring to
FIGS. 35A and 35B
. In the figures, reference numeral
191
denotes a substrate,
192
an electron-emitting region,
193
an electroconductive film,
194
a cathode device electrode,
195
an anode device electrode,
196
a fissure, and
197
a field correcting electrode. In the surface conduction electron-emitting device of this example, electrons emitted move in an electric field established by the cathode and the anode and a singular point of the electric field above the anode device electrode affects the ratio of electrons reaching the anode electrode, provided to sandwich a vacuum with the electron emitting element i.e., the electron emission efficiency. This device is an example in which the field correcting electrode is provided outside the device electrodes in order to improve the electron emission efficiency.
SUMMARY OF THE INVENTION
According to the studies by Spindt et al., the conventional FE type electron-emitting devices, however, had a problem of a spread of the electron beam, which was hindrance against enhancement of definition. In the example of application of the holes of the anodic oxide film to the apertures of the gate electrode, there remained a problem of poor repeatability in formation of the cone of the electron-emitting region. In the example in which the electron-emitting regions were formed in the cylindrical shape, there also arose problems of poor repeatability of the electron emission characteristics and high driving voltage. In the surface conduction electron-emitting device provided with the correcting electrode, the electron emission efficiency was increased, but the potential of the correcting electrode was high, which was a problem in driving.
In the conventional MIM type electron-emitting devices, first, the thickness of the insulating layer was thin, several nm, and the thickness greatly affected the electron emission characteristics. In an electron source equipped with many devices, variations in the thickness of the insulating layer are directly bound to variations in the emission current, so that control of variations is difficult. When an image pickup device or an image forming device is constructed using the electron source; there will arise a problem of degradation of image quality. Second, the quality of the insulating layer did not affect only the electron emission characteristics, but also affected the device current. In the case of the electron source equipped with many devices, variations in the quality of the insulating layer are directly bound to variations in the emission current. Particularly, in the case of a large area, control of variations is diffic
Kawate Shinichi
Tsukamoto Takeo
Yamanobe Masato
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