JPH0797474B2 - Electron-emitting device and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electron-emitting device used as an electron-emitting source, and more particularly to an electron-emitting device exhibiting voltage-controlled negative resistance characteristics and a method for manufacturing the same. .

[Prior Art] Conventionally, as an electron-emitting device capable of emitting electrons with a simple structure, for example, MI Elinson (MIElinso)
n) and other known cold cathode devices are known [Radio Engineering Electron Phys., Vol. 10, 1290-1296].
P., 1965].

This utilizes a phenomenon in which electrons are emitted from a thin film having a small area formed on a substrate by flowing an electric current in parallel to the film surface, and is generally called a surface conduction electron-emitting device.

This surface conduction electron-emitting device uses not only the SnO ₂ (Sb) thin film announced by Elinson et al., But also an Au thin film [Gee Ditmer: "Sin Solid.
Films ”(G.Dittmer:“ Thin Solid Films ”), 9
Vol., P. 317, (1972)], by ITO thin film [M Hartwell & C. G. Fonstad: "I-E-E-Trans-E-D-Dee Conf" (M .Hartwell and CGFonstad: “IEEE Tr
ans.ED Conf. ") 519, (1975)], by carbon thin film [Haraki Araki et al.," Vacuum ", Vol. 26, No. 1, p. 22,
(1983)] etc. have been reported.

The typical device configuration of these surface conduction electron-emitting devices is described in Section 7.
Shown in the figure. In the figure, 1 and 2 are electrodes for obtaining electrical connection, 3'is a conductive thin film formed of an electron emission material,
Reference numeral 4 indicates an electron emitting portion, and 5 indicates a substrate.

In each of the surface conduction electron-emitting devices described above, electrodes 1 and 2 are provided on a substrate 5 provided with a conductive thin film 3 ', a voltage is applied between the electrodes 1 and 2, and an energization process called forming is performed. The electron emitting portion 4 is formed. That is, electrode 1,
The thin film 3'is energized by applying a voltage between the two, and the thin film 3'is locally destroyed, deformed or altered by the Joule heat generated thereby, and the electron emitting portion 4 in an electrically high resistance state is formed. By being formed, it has an electron emission function.

The above-mentioned electrical high resistance state means that a part of the thin film 3'is 0.5μ.
It means that there is a crack of m to 5 μm and the inside of the crack is a discontinuous state film having a so-called island structure. The discontinuous state film having an island structure generally means that particles having a diameter of several tens of angstroms to several microns are present on the substrate 5, and the particles form a spatially discontinuous and electrically continuous film. Say

[Problems to be Solved by the Invention] However, the conventional forming process by electric current, which is indispensable for manufacturing the surface conduction electron-emitting device, is essentially a partial destruction or deterioration of the film due to Joule heat of electric current. There is such a problem.

1) Since it is impossible to design an island structure that serves as an electron-emitting portion, it is difficult to control the characteristics, and variations among elements are likely to occur.

2) The island structure has a short life and is poor in stability, and element damage is likely to occur due to external electromagnetic wave noise.

3) The materials for the islands are limited to gold, silver, SnO ₂ , ITO, etc., and materials with a small work function cannot be used, so a large current cannot be obtained.

Due to the above problems, the surface conduction electron-emitting device has not been positively applied industrially although it has an advantage that the device structure is simple.

The present invention has been made in view of the above-mentioned problems of the conventional surface conduction electron-emitting device, has a quality equal to or higher than that of the conventional surface conduction electron-emitting device, has a small variation in characteristics, and can control the characteristics. (EN) Provided is a surface conduction electron-emitting device having a novel structure capable of controlling the position of an electron-emitting portion.

[Means for Solving the Problems] Means taken in the present invention for solving the above problems will be described with reference to FIG. 1 corresponding to one embodiment of the present invention. In the present invention, a pair of electrodes 1, A thin film conductor 3 containing fine particles is provided between the two, and an electron emission portion is formed in a part of this thin film conductor 3, and a voltage control type negative resistance is provided between the device voltage and the device current. (VCNR: Voltage Controlle
d Negative Resistance) A surface conduction electron-emitting device that exhibits characteristics is taken.

Electrodes 1 and 2 and thin film conductor 3 containing fine particles in the present invention
Are provided on the substrate 5 similarly to the conventional one. As a material for the substrate 5, for example, an insulating material such as glass or quartz is used.

The electrodes 1 and 2 are provided so as to face each other, and can be formed by a commonly used method such as a vacuum film forming process and a photolithography process. The materials of the electrodes 1 and 2 are general conductive materials, and for example, metals such as Ni, Al, Cu, Au, Pt, and Ag, and oxides such as SnO ₃ and ITO can be used.

The thickness of the electrodes 1 and 2 is preferably several hundred Å to several μm.
The electrodes 1 and 2 are opposed to each other, and the relative distance L is preferably several hundred Å to several tens of μm, and the opposing width W is several μm to each other.
A few mm is preferable. However, these ranges are approximate, and may be out of this range depending on the usage conditions of the element.

The fine particles in the present invention include a normal cathode material having a low work function, a high melting point and a low vapor pressure, a material forming the electron emitting portion 4 by a conventional forming treatment, and a material having a high secondary electron emitting efficiency. Are preferable, and the particle size thereof is preferably several tens of to several μm.

Specifically, for example, boride such as LaB ₆ , CeB ₆ , YB ₄ , CdB ₄ ,
Carbide such as TiC, ZrC, HfC, TaC, SiC, WC, nitride such as TiN, ZrN, HfN, Nb, Mo, Rh, Hf, Ta, W, Re, Ir, Pt, Ti, Au, Ag, Cu , Cr, A
Metals such as l, Co, Ni, Fe, Pb, Pd and Cs, metal oxides such as In ₂ O ₃ , SnO ₂ and Sb ₂ O ₃ , semiconductors such as Si and Ge, and fine particles such as carbon, Ag and Mg Examples thereof may be mentioned, and one kind thereof or a mixture of two or more kinds may be used.

The thin film conductor 3 containing fine particles has a structure of a continuous fine particle film in which the fine particles are densely distributed and has an electric resistance of about several Ω / □ (sheet resistance). Further, even if a part of the continuous fine particle film has discontinuity of fine particles, no problem occurs.

If the thin-film conductor 3 containing fine particles can be surely attached between the facing portions of the electrodes 1 and 2, even if the thin-film conductor 3 is attached after the electrodes 1 and 2 are attached to the substrate 5, the electrodes 1 and 2 are attached before the attachment. You may attach it. In the structure shown in FIG. 1, the electrodes 1 and 2 are attached, and then the thin film conductor 3 is attached thereto.

The attachment of the thin film conductor 3 can be carried out as follows, for example, in addition to gas deposition or vacuum deposition (state of initial film).

First, fine particles of the above-mentioned material or a compound containing the above-mentioned material and, if necessary, additives are added to an organic dispersion medium and stirred to prepare a fine-particle dispersion liquid in which fine particles are almost uniformly dispersed. Then, this fine particle dispersion is applied to the surface of the substrate 5 (before or after attaching the electrodes 1 and 2) by, for example, a method such as dipping or spin coating so that the dispersion medium can be removed by evaporation. Firing is performed at a temperature and for a time that can decompose this.

By doing as described above, the thin-film conductor 3 containing fine particles is formed between the facing portions of the electrodes 1 and 2 (interval L shown in FIG. 1).
Location). When the thin film conductor 3 is provided after the attachment of the electrodes 1 and 2, for example, as shown in FIG. 1, the thin film conductor 3 tends to be attached to the electrodes 1 and 2 other than between the facing portions of the electrodes 1 and 2. However, since a voltage is not substantially applied to the thin film conductor 3 other than between the facing portions of the electrodes 1 and 2, there is no problem.

The organic dispersion medium may be any as long as it can disperse the fine particles without degrading them, and for example, butyl acetate, alcohols, methyl ethyl ketone, cyclohexane, and mixtures thereof can be used, depending on the type of the fine particles. And select it.

The additive promotes dispersion of fine particles, and for example, a well-known dispersion auxiliary agent such as a surface active agent can be used.

The baking temperature and time are different depending on the type of organic dispersion medium used, the coating amount, etc.
It takes about 1 hour.

The solid content concentration of the fine particle dispersion liquid and the number of times of application (application amount) are the desired characteristics of the thin film conductor 3, and thus the desired electron emission portion 4.
Adjust according to the characteristics of. That is, the solid content concentration and the coating amount of the fine particle dispersion may be determined within a range where the thin film conductor 3 having an electric resistance of less than the above-mentioned several Ω / □ (sheet resistance is obtained. If the solid content concentration and the coating amount are too large, If the electric resistance of the thin film conductor 3 becomes too low, and conversely the solid content concentration and the coating amount are too small, the electric resistance of the thin film conductor 3 becomes too high, and in each case a good surface conduction electron-emitting device is obtained. It gets harder.

The electron-emitting portion 4 in the present invention is a portion of the thin film conductor 3 between the electrodes 1 and 2 in which the contained fine particles become islands and become a discontinuous state film by the energization process, that is, the forming process. The whole thin film conductor 3 between the two may be the electron emitting portion 4, or a part thereof may be the electron emitting portion 4.

The energization treatment may be performed in the atmosphere, but it is preferably performed under vacuum or under an inert gas in order to prevent element damage. Further, it is preferable that the voltage applied during the energization treatment is adjusted according to the desired characteristics of the surface conduction electron-emitting device.

This surface conduction electron-emitting device has a voltage-controlled negative resistance (VCNR) between the device voltage and the device current.
It is necessary to show a gative resistance characteristic. The VCNR characteristic is a characteristic that the element current decreases as the element voltage increases.

[Operation] In the present invention, the fact that the electron-emitting portion 4 is formed by the energization treatment of the thin film conductor 3 containing fine particles serves to control the VCNR characteristics of the obtained surface conduction electron-emitting device. .

By the way, although the VCNR characteristic is also shown in some conventional surface conduction electron-emitting devices, the generation mechanism thereof has not been clarified at present, and therefore, the VCNR characteristic is not controlled.

Also in the present invention, by any mechanism, VCNR
It is unclear whether the characteristics are brought and controllable, but it is considered to be due to the fact that the thin film conductor 3 containing fine particles is used.

[Example] Example 1 A surface conduction electron-emitting device having the structure shown in FIG. 1 was produced as follows. The element shape is W 200 μm,
L was set to 20 μm.

As the fine particle dispersion liquid, the following material was stirred together with glass beads for 24 hours on a paint shaker.

Fine particles SnO ₂ (particle size 1000 Å or less) 1.0 g Organic dispersion medium MEK (methyl ethyl ketone): cyclohexane = 3: 1 800 cc First, on a quartz substrate 5 that has been sufficiently degreased and washed, a Ni film is formed by vacuum deposition and photolithography. Electrodes 1 and 2 were provided.

Next, the fine particle dispersion liquid was applied onto the substrate 5 by a spin coating method and baked at 250 ° C. for 10 minutes repeatedly to form a thin film conductor 3 containing fine particles and having an electric resistance of 150Ω or less. After that, under a vacuum of 1 × 10 ^-5 torr, change the voltage boost rate to 1V / 10 seconds (1V boost for 10 seconds, the same applies below), 1V / 100 seconds, 1V / 1 second. Then, a voltage is applied to each of the electrodes 1 and 2, and the thin film conductor 3 between the electrodes 1 and 2 is energized to form the electron emitting portion 4.

The characteristics of the surface conduction electron-emitting device obtained as described above were measured by an apparatus as shown in FIG. In the figure, 6 is a power source for applying a voltage to the surface conduction type emission device, 7 is an ammeter for measuring a current flowing through the surface conduction type emission device, and 8 is an emission from the surface conduction type emission device. , An anode electrode for measuring electrons ^- e, 9 is a power source for applying a voltage to the anode electrode 8, and 10 is an emission current I _e.
The same reference numerals as those in FIG. 1 indicate the same members.

A voltage V _f is applied to the surface conduction electron-emitting device by the power source 6 to cause electrons to be emitted from the device, and a current I _f flowing through the surface conduction electron-emitting device is measured by the ammeter 7 and the ammeter 10
The emission current I _e was measured by.

The voltage Va applied to the power source 9 may be an appropriate voltage, but in this measurement, it was fixed at 1000V. Also, this measurement is 1 x 1
It was performed under a vacuum of 0 ^-5 torr or more.

In Fig. 3, Fig. 4 and Fig. 5, the boost rate is 1V / 1.
It is a current-voltage characteristic (IV characteristic) of the present surface conduction electron-emitting device manufactured at 0 seconds, 1V / 100 seconds, and 1V / 1 second.

The the I-V characteristic, as shown in Figure 3, is monotonically increasing region I (V _f to the device current I _f increases increasing the element voltage V _f 0V to
13V region) and a voltage control type negative resistance region II ( _Vf is 13V or later) in which the device current _If decreases when the device voltage _Vf increases.

That is, the IV characteristic shown in FIG. 4 has a clear VCNR characteristic, and the IV characteristic shown in FIG. 5 does not have a clear VCNR characteristic.

Further, as is clear from FIGS. 3 to 5, the device exhibiting the VCNR characteristic has a high emission current I _e and the electron emission efficiency I _e / I
_{f is} also high.

In this way, the VCNR characteristics can be controlled by changing the step-up of the voltage applied to the element when the thin film conductor 3 containing the fine particles is energized.

Incidentally, the degree of VCNR characteristic, the maximum value of the device current I _f, when raising the voltages 3V, the value to decrease the element current I _f (% indication)
It was evaluated by.

Example 2 FIG. 6 is a graph showing the IV characteristics measured in this example.

In the surface conduction electron-emitting device of this embodiment, W is 200 μm and L is 5 μm, and the boost rate of the voltage applied during the energization process is
It was manufactured in the same manner as in Example 1 except that 1 V / 10 seconds.

As can be seen from FIGS. 3 and 6, the VCNR characteristic can be controlled by changing the element shape, and the smaller the distance L between the electrodes 1 and 2, the greater the degree of the VCNR characteristic.
The emission current I _e was large and the electron emission efficiency I _e / I _f was also high.

Example 3 Electrodes 1 and 2 were formed on a quartz substrate 5 by the method described in Example 1. W was 10 mm and L was 50 μm.

Next, the thin film conductor 3 is formed of silver fine particles of 0.1 μm or less by the gas deposition method (“Powder and Industry” Vol. 19, No. 5, 1987), which is widely known as a method for forming ultrafine particles. did.

The gas deposition method can form a film with extremely small particles having a particle size of 0.1 μm or less, and as a material, various metal materials such as gold, copper, and nickel can be used in addition to silver.

The width of the thin film conductor 3 (the direction parallel to the gap between the electrodes) was set to 2 mm.

Next, when an appropriate energization process was performed, a good electron emission was obtained with a VCNR characteristic in the relationship between the device current and the electron voltage. The electron emitting portion 4 after the energization treatment was composed of a discontinuous film having silver particles as islands.

[Effects of the Invention] As described above, the surface conduction electron-emitting device of the present invention is
Not only is it possible to select the island material for the discontinuous film, and it is effective not only in improving the variation and element deterioration, but also by controlling the VCNR, it is greatly effective in improving the emission current.

[Brief description of drawings]

FIG. 1 is an explanatory view of a surface conduction electron-emitting device according to an embodiment of the present invention, FIG. 2 is an explanatory view of a characteristic measuring device used in the embodiment, and FIGS. 3 to 5 are measurement results of the first embodiment. FIG. 6 is a graph showing the results, FIG. 6 is a graph showing the measurement results of Example 2, and FIG.
The figure is an explanatory view of the prior art. 1,2: Electrode 3: Thin film conductor 4: Electron emission part

Front Page Continuation (72) Inventor Toshihiko Takeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References Japanese Patent Publication No. 44-28009 (JP, B1)

Claims (6)

[Claims] 1. A thin film conductor containing fine particles is provided between a pair of electrodes, an electron emitting portion is formed in a part of the thin film conductor, and the thin film conductor is provided between a device voltage and a device current. An electron-emitting device having a voltage-controlled negative resistance characteristic. 2. The fine particles have a particle size of several tens of Å to several μm.
The electron-emitting device according to claim 1, which is a fine particle of 3. The electron emitting device according to claim 1, wherein the electron emitting portion is a discontinuous portion formed in a part of the thin film conductor. 4. A method of manufacturing an electron-emitting device, comprising a step of energizing a thin-film conductor containing fine particles, which is arranged between a pair of electrodes, to form an electron-emitting portion, the step-up rate of voltage during energization. Is controlled to control the voltage-controlled negative resistance characteristic between the device voltage and the device current. 5. The fine particles have a particle size of several tens of Å to several μm.
The method for producing an electron-emitting device according to claim 4, wherein the particles are fine particles. 6. The method of manufacturing an electron-emitting device according to claim 4, wherein the electron-emitting portion is a discontinuous portion formed in a part of the thin film conductor.