JPH0193024A - Electron emitting element - Google Patents

Abstract

PURPOSE:To obtain the quality equal to or better than the electron emitting element produced by a forming, and to make it possible to control the performance by providing in dispersing minute particles of at least two or more of different substances between electrodes which have a minute interval. CONSTITUTION:Electrodes 2 and 3 which consist of a low resistant substance for applying voltage are provided placing a minute interval, on an insulator of a glass or the like, and between them, a discontinuous electron emitting member 4 in which at least two or more sorts of minute particles are dispersed is formed. By dispersing minute particles 5 of the particle diameter 3000Angstrom or more at the ratio 20% to the whole minute particle numbers, or minute particle of the particle diameter less than 200Angstrom at the ratio 20% to the whole minute particle numbers, the electron emitting efficiency can be further improved, or the driving voltage can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electron-emitting device, specifically a surface conduction type electron-emitting device.

[Conventional technology]

Conventionally, as an element that can emit electrons with a simple structure,
For example, MI Ellingson (M, 1.EIinso
A cold cathode device announced by et al.

[Radio Engineering Electron Physics (Radio Eng, EIectron, Ph
ys, ) Vol. 10, pp. 1290-1296, 1965 This is a method that utilizes the phenomenon of electron emission caused by passing a current parallel to the film surface through a small-area thin film formed on a substrate. It is generally called a surface conduction type emitter.

This surface conduction type emission device uses a 5nO3 (sb) thin film developed by Ellingson et al.
``G. Dittmer's Thin Films''
: “Th1nSolid Fi1ms”), Volume 9, 3
17, (1972), ITO thin film [M. Hartwell and C.F.

Hartwelland C, G, Fonstad: “T.
EEE Trans.

ED Conf"), p. 519, (1975)], and one using a carbon thin film "Hisashi Araki et al.: "Vacuum", Vol. 26, No. 1, p. 22, (1983)].

Typical device configurations of these surface conduction type emitters are shown in the third section.
As shown in the figure. In FIG. 3, 11 and 12 are electrodes for obtaining electrical connection, 13 is a thin film made of an electron-emitting material, 14 is a substrate, and 15 is an electron-emitting portion.

Conventionally, in these surface conduction type emitting devices, an electron emitting portion is formed in advance by an electrical heating process called forming before electron emission is performed.

That is, by applying a voltage between the electrodes 11 and 12, the thin film 13 is energized, and the Joule heat generated thereby locally destroys, deforms, or alters the thin film 13, resulting in a high electrical resistance. By forming the electron emitting portion 15 in the state, the electron emitting function is obtained.

[Problem that the invention is trying to solve] However,
Forming by conventional electrical heating treatment as described above is
Since the manufacturing method itself is unstable and has poor reproducibility, characteristics such as electron emission efficiency vary from device to device, making it almost impossible to control device characteristics.

Furthermore, since the location where the film is destroyed or altered is not constant, the position of the electron emitting portion varies from device to device, making it difficult to design applications for the device.

[Purpose of the invention]

Due to the above-mentioned problems, surface conduction electron-emitting devices have not been actively applied in industry, despite having the advantage of a simple device structure.

The present invention has been made in order to eliminate the drawbacks of the conventional examples as described above, and to produce an electron-emitting device that is equivalent to or higher than the electron-emitting device obtained by the forming process (without performing the conventional process called forming as described above). The object of the present invention is to provide an electron-emitting device having a novel structure with high quality and controllable characteristics.

In particular, the present invention provides an electron-emitting device with improved electron-emitting efficiency and in which the driving voltage of the device can be easily controlled.

[Means and effects for solving the problem] The electron-emitting device of the present invention has at least two
It is characterized by dispersing fine particles of more than one type of substance.

Conventionally, in surface conduction electron-emitting devices, it is said that electrons are emitted from an island-like structure of a thin film between electrodes formed by forming.

However, as a result of intensive studies on the forming process, its structure, and electron emission characteristics, the inventors of the present invention found that forming process can be performed without performing the forming process (by dispersing appropriate fine particles between electrodes having minute intervals). It has been found that an electron emission function equivalent to or better than that obtained can be obtained.

Furthermore, they have discovered that by dispersing fine particles of at least two or more different substances, it is possible to easily control the characteristics of an electron-emitting device, such as electron emission efficiency, stability of emission current, and driving voltage. .

Further, the electron-emitting device of the present invention is characterized in that fine particles having a particle diameter of about 3000 Å or more are dispersed between electrodes having a minute interval, accounting for approximately 20% or more of the total number of fine particles. Alternatively, it is an electron-emitting device characterized in that fine particles having a particle diameter of about 200 Å or less are dispersed by approximately 20% or more of the total number of fine particles.

A detailed description will be given below based on the drawings.

FIG. 1 is a schematic diagram showing a first embodiment of an electron-emitting device according to the present invention.

In the figure, electrodes 2 and 3 made of a low-resistance material for voltage application are provided on an insulator such as glass with a minute interval between them, and at least two types of fine particles 5 are dispersed between them. A high resistance part (electron emission part) 4 is formed. Further, although not shown, an extraction electrode is provided at a spaced interval on the upper surface of the electron emitting portion for extracting emitted electrons. By applying a voltage between the electrodes 2 and 3 in a vacuum, electrons are emitted from the electron emitting section 4 in a direction substantially perpendicular to the plane of the paper.

FIG. 2 is a schematic cross-sectional view in the AB force direction of FIG. 1.

In the figure, at least two or more types of fine particles on the insulator 1 preferably have particle diameters of several 10 to several micrometers, and further, the intervals between the fine particles are preferably formed within the range of several tens of micrometers to several micrometers. Further, the appropriate distance between the electrodes 2 and 3 is usually several hundred to several 10 μm.

The details of the mechanism of electron emission in the electron-emitting device of the present invention are unknown, but since electron emission occurs accompanied by current in the direction of the electrodes 2 and 3, diffraction by the fine particles 5, scattering, secondary electron emission, Emission, thermionic electrons, popping electrons, Auger electrons, etc. can be considered.

The material of the fine particles used in the present invention is very wide, and almost all conductive materials such as ordinary metals, semimetals, and semiconductors can be used. Among them, ordinary cathode materials with low work function, high melting point, and low vapor pressure, thin film materials that form surface conduction electron-emitting devices through conventional forming processing, and materials with large secondary electron emission coefficients. is suitable.

Specifically, LaB 6. CeB 6. YB 4. GdB
borides such as 4, TiC, ZrC, HfC, TaC,
Carbides such as SiC and WC, nitrides such as TiN, ZrN, and HfN, and Nb.

Mo, Rh, Hf, Ta, W,
Re, Ir, Pt, Ti, A
u, Ag, Cu.

Cr, A I , Co, Ni, Fe, Pb, Pd, Cs
, metals such as Ba, MgoIn 203 , SnO2,
Examples include metal oxides such as Sb 203, semiconductors such as Si and Ge, carbon, and AgMg. Note that the present invention is not limited to the above materials.

By appropriately selecting two or more different substances from these materials and using them as fine particles, it is possible to not only cause electron emission but also to easily improve and control the characteristics of the target electron-emitting device. Can be done.

For example, in the electron-emitting device of the present invention, since the current in the direction of the electrode is not necessary for electron emission, the driving voltage of the device can be easily controlled by adding fine particles having relatively low resistance.

Further, by adding fine particles having a large secondary electron emission coefficient, it is effective to stabilize emission efficiency, emission current, and improve lifetime. At this time, if the particle size of the fine particles with a large secondary electron emission coefficient is made larger than the particle size of other fine particles, both the increase in emission efficiency and low voltage driving can be satisfied, which is even more effective.

Specific combinations include metals and metal oxides, or metals and carbides, such as (SnO2).

Pd), (In 203 , Pd) (SnO2, Av
) (In 203.

Av) (SnO2, Pt) (TiC, Pd) (T
aC, Pd).

In addition, the present invention is not limited to the example of fine particles of two or more different substances as described above, but also includes two or more types of fine particles of one type of material that differ only in physical parameters such as average particle size and shape. It is also effective in the case of fine particle composition.

For example, by changing the particle size to two types: one that has a large field emission effect (as small as a hailstorm), and one that is relatively large (more than 3000 Å) that only contributes to conductivity (less than 200 Å), the former can be improved. Although the electron emission amount is increased, low voltage driving can also be achieved with the latter.

In other words, when fine particles with a particle size on the order of several tens to several hundred particles are dispersed, the number of fine particles with a large particle size of approximately several thousand particles, preferably 3000 Å or more, is at least 20% of the total number of particles. Dispersion is very helpful in lowering the drive voltage, which can be easily controlled. (However, the number of fine particles having a large particle size of several thousand angstroms or more does not exceed half of the total.) On the other hand, when fine particles with a particle size of approximately 700 nm to several μm are dispersed, approximately 300 nm is preferable. It was found that when fine particles with a small particle size of 200 Å or less are dispersed at least 20% of the total number of particles, electric field concentration occurs due to the small particle size, contributing to increasing the amount of electron emission.

(However, the number of fine particles with a small particle size of 300 Å or less does not exceed half of the total.) In addition, the two types of different substances described above and the two types with different particle sizes of physical parameters are combined, respectively. Of course, it is also possible to use it. In this case, the effect can be further improved by selecting physical parameters that are optimal for the properties of the material. Specifically, for example, rather than an electron-emitting device having one type of fine particles, it is better to mix and disperse fine particles with higher conductivity and smaller particle size than the fine particles, to reduce the driving voltage and increase the amount of electron emission. Contribute greatly.

Moreover, rather than an electron-emitting device having one type of fine particles, it is better to mix particles with a larger secondary electron emission coefficient than the fine particles.
If the amount of electron emission can be increased, and if the amount of electron emission can be further increased, the amount of electron emission can be further increased if the particle size of the fine particles having a large secondary electron emission coefficient is also larger.

The easiest way to disperse and form fine particles is to apply a dispersion of fine particles of the desired material onto a substrate by spin coating, dipping, or the like, and then remove the solvent, binder, etc. by heat treatment. In this case, the distribution state of the dispersion can be easily controlled by adjusting the particle size, content, application conditions, etc. of the fine particles.

A specific manufacturing method for dispersing fine particles by coating is shown below.

First, on an insulating substrate 1 made of clean glass, ceramics, etc., electrodes 2.3 are formed as low resistance bodies for voltage application. This can be carried out using a normal vacuum deposition method, photolithography method, printing method, or the like.

Common conductive materials such as Au, Pt, and Ag can be used as electrode materials.
In addition to metals such as, oxide conductive materials such as SnO2 and ITO can also be used. The appropriate thickness of the electrodes 2 and 3 is about several hundred to several μm, but the thickness is not limited to this value. In addition, the appropriate electrode spacing is from several hundred people to several tens of micrometers, and the interval width W is from several micrometers to several meters.
A value of about m is appropriate. However, it is not limited to this size.

Next, fine particles 5 are applied between the electrodes. A dispersion of fine particles is used for coating. Fine particles and an additive that promotes the dispersion of the fine particles are added to an organic solvent such as butyl acetate or alcohol, and a dispersion liquid of the fine particles is prepared by stirring or the like.

This fine particle dispersion is applied to the surface of the sample by dipping, spin cording, or the like, and pre-calcined for about 10 minutes at a temperature at which the solvent and the like evaporate, for example, 250°C. As a result, the fine particles 5 are dispersed on the surface of the insulating substrate 1 between the electrodes, and discontinuous electron emitting portions 4 are formed. Of course, the fine particles 5 are arranged over the entire surface of the sample, but since no voltage is substantially applied to the fine particles 5 other than between the electrodes during electron emission, no problem occurs. The arrangement density of the fine particles 5 changes depending on the coating conditions and adjustment of the fine particle dispersion liquid, and the electrode 2,
The amount of current flowing between the two also changes.

Additionally, a chemical method for dispersing and forming fine particles can be used, in which a solvent of an organometallic compound is applied onto a substrate, and then semiconductor metal oxides or metal fine particles are formed by thermal decomposition. . - Examples include tin caprylate (C7H+s COO)2 Sn, diisoacyloxyethoxyantimony C2H5O (Os HlI O
)2 By thermal decomposition of Sb, 5n02. Sb
Examples include forming Pd fine particles from an organic palladium compound and forming Pd fine particles from an organic palladium compound.

For materials that can be vapor deposited, such as metals and semiconductors, fine particles can also be formed directly on the substrate by controlling vapor deposition conditions such as substrate temperature, vapor deposition rate, and vapor deposition time, or by techniques such as mask vapor deposition.

The formation of the electron-emitting portion has been described above, but in any case, a low-resistance portion (electrode) for voltage application can be formed independently of the dispersion of fine particles. The electrode may be formed before or after the formation of the electron emitting region.

Hereinafter, it will be described in more detail with reference to Examples.

In the configuration shown in Figure 1, titanium electrodes with a thickness of 1000 mm, L = 0.8 μm, and W = 300 μm were formed on a glass substrate, and then SnO2 and Pd were dispersed as fine particles between the electrodes. .

The method is to use SnO2 with a primary particle size of 80 to 200 people.
Dispersion liquid (SnO2: 1 g, solvent: MEK (methyl ethyl ketone)/microhexanone-3/1 1000 cc.

Butyral (Ig) was applied using a spin coat (5 times at 300 rpm) and heat treated at 250°C. The Pd fine particles contain an organic palladium compound with a Pd metal equivalent ratio of 0.3%.
Particles of approximately 0.5 μm were obtained by coating and heat treatment in the same manner as described above using a butyl acetate solution (Catapaste CCP-4230 manufactured by Okuno Pharmaceutical Co., Ltd.) containing a certain amount of water. When a voltage of about 10-' Torr was applied in a vacuum between the electrodes of the element thus formed, electron emission started at a threshold voltage of 14V, and an electron emission current of 0.9μ at an applied voltage of 20V.
A was obtained.

Compared to a device using only SnO2 without Pd particles, this device achieves approximately the same electron emission with an applied voltage that is about 10 V lower.

A similar device was formed using fine MgO particles (~several thousand particles) with a large secondary electron emission coefficient in place of the Pd fine particles of Example 1, and the electron emission was measured.

As a result, an electron emission current of 1.5 μA was obtained at an applied voltage of 30 V.

This result was about twice as much electron emission as compared to the case of using SnO2 alone.

"On the tributary" The particle size of the Pd fine particles used in Example 1 ranged from 1OOA to several 1
00 people (organopalladium compound as Pd metal conversion ratio 0)
．． The same experiment as in Example 1 was conducted, except that a butyl acetate solution containing about 1% was applied and heated).

The result was an electron emission current of 1.1 μA at an applied voltage of 25 V.

In the SnO2 dispersion of Example 1, the particle size was
) 100 samples (A) and 0.5 μm samples (B) were prepared, and two types of SnO were prepared in the same manner as in Example 1.
□ were distributed. However, the number of 5n02 in B) is (A)
+(B) was adjusted so that it accounts for over 20% of the total number.

On the other hand, as a comparison, a sample was prepared in which only 100 particles with a particle size of several (7 or 8) were coated and dispersed twice. Its electron emission characteristics were as follows.

By adding large particles in this way, it was possible to lower the driving voltage.

In the SnO3 dispersion of Example 4, a particle size of about 200 to 300 particles (C) was prepared, and in the same manner as in Example 1, the (C) and the above (A) were mixed. , two types of Sn
O2 was distributed. However, the number of 5n02 in C) is (A
) + (C) was adjusted so that it accounted for more than 20% of the total number of fine particles.

As a result, the electron emission current was 1.3 μA at an applied voltage of 30 V.

〔Effect of the invention〕

As explained above, the electron-emitting device of the present invention is constructed by dispersing fine particles of two or more different substances between electrodes at minute intervals, so it is more effective than an electron-emitting device using conventional forming processing. - The manufacturing process is simple and stable - Electron emission characteristics can be easily controlled - Low voltage drive is possible.

・It has the effect of increasing the degree of freedom in element design due to the rich combination of materials and physical shapes.

Furthermore, if 20% or more of the total particles are dispersed with particles having a particle size of 3000 Å or more, the electron emission efficiency or driving voltage can be controlled.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of a first embodiment of an electron-emitting device according to the present invention, FIG. 2 is a schematic cross-sectional view showing an example of an electron-emitting section 4 in this embodiment, and FIG. 3 is a conventional FIG. 2 is a plan view of an electron-emitting device. 1... Insulator 2, 3... Electrode 4.
...Electron emission part 5...Fine particles 11.1
2... Electrode 13... Thin film 14...
... Substrate 15 ... Electron emission efficiency Figure 1 Figure 2

Claims (9)

[Claims] (1) An electron-emitting device characterized in that fine particles of at least two or more different substances are dispersed between electrodes having minute intervals. (2) The electron-emitting device according to claim 1, wherein the different substances have different conductivities. (3) The electron-emitting device according to claim 1, wherein the different substances have different secondary electron emission coefficients. (4) Particles with a particle size of 3000 angstroms or more are placed between the electrodes with a very small interval, at a rate of 2 times the total number of particles.
An electron-emitting device characterized by dispersing more than a certain amount of electrons. (5) An electron-emitting device characterized in that fine particles having a particle diameter of 200 angstroms or less are dispersed between electrodes having minute intervals, by 20% or more of the total number of fine particles. (6) An electron-emitting device in which fine particles of two different substances are dispersed between electrodes having a minute interval, one of the fine particles has a particle size of 3000 angstroms or more, and the fine particles are added to the total number of fine particles. An electron-emitting device characterized by dispersing an electron by 20% or more. (7) The electron-emitting device according to claim 6, wherein the fine particles having a particle size of 3000 angstroms or more have a larger secondary electron emission coefficient than the other fine particles. (8) An electron-emitting device in which fine particles of two different substances are dispersed between electrodes having a minute interval, one of the fine particles has a particle size of 200 angstroms or less, and the fine particles are larger than the whole fine particles. An electron-emitting device characterized by dispersion of 20% or more. (9) The electron-emitting device according to claim 8, wherein the fine particles having a particle size of 200 angstroms or less have a higher electrical conductivity than the other fine particles.