CN1845287A - Surface Conduction Field Emission Electron Source Device with Converging Characteristics - Google Patents

Abstract

The disclosed surface-conductive field-emission electron source device with convergence feature comprises a substrate with an inverted-T shaped or I-shaped grid, a cathode and an insulating layer, and an opposite anode fixed in a vacuum cavity. Wherein, arranging the grid between the insulating layer and the substrate, showing the grid through a hole to circle by the cathode; arranging an electron emission layer between the cathode and the insulating layer, and adding a layer of cathode between the emission layer and the insulating layer to form a sandwich cathode, as well as an electron scattering layer between the cathode and shown grid. This invention needs simple technique and low drive voltage, and has well electron convergence performance.

Description

Surface Conduction Field Emission Electron Source Device with Converging Characteristics

technical field

The invention relates to a device for obtaining electron beams in a vacuum environment by using the field electron emission (referred to as field emission) phenomenon---a surface conduction field emission electron source device with convergence characteristics

Background technique

The usual field emission electron source device uses electrons (field emission phenomenon) that escape from the surface of solid materials under the action of a strong external electric field, and uses the electric field applied by the gate and anode to realize the emission, modulation and acceleration of electrons to obtain luminescence, high Electronic devices with functions such as frequency oscillation and X-rays. At present, there are many kinds of field emission electron source device structures, such as metal or semiconductor microtip + circular hole gate (referred to as microtip type), surface conduction type (SED type), metal-insulator layer-metal (referred to as MIM type), Metal-insulating layer-semiconductor (MOS type), etc. In the microtip type structure, the cathode that emits electrons is located in the center of the circular hole grid; in the surface conduction type, the cathode is opposite to the anode; in the MIM or MOS structure, the grid completely covers the cathode. All electron source device structures have their own advantages and disadvantages. For example, the microtip type has high electron emission efficiency and relatively low driving voltage, but has the disadvantages of electron beam divergence and complicated preparation process; surface conduction type (SED type) has low driving voltage. , The advantages of simple preparation process, but also the disadvantages of electron beam divergence and low efficiency; the electron source of MIM or MOS structure has the disadvantages of low driving voltage, small electron beam divergence, low efficiency, and relatively high process requirements.

Contents of the invention

The purpose of the present invention is to provide a surface conduction field emission electron source device with converging characteristics, so as to make up for the deficiencies of the prior art.

The basic concept of the present invention is to change the electrode structure of the conventional field emission electron source so that the electron-emitting cathode surrounds the grid, so that the electrons emitted from the cathode converge to the grid, so as to solve the problem of the conventional surface conduction type (SED type) and micro The electron beam divergence problem of the pointed field emission electron source. That is, the self-convergence of electron beams can be realized by using a reasonable electrode structure.

The present invention is an improvement to the existing SED type and micro-tip type field emission devices, which includes a substrate having two or more than two electrodes of the cathode and the grid, and the parallel or opposite electrodes with a certain distance between the substrate and the substrate. The conductive substrate or metal wire, rod, etc. (as the anode) is contained and fixed in the vacuum container and the corresponding power supplies V ₁ and V ₂ , which are characterized in that on the substrate with the cathode and the control grid, the cathode surrounds the The exposed or exposed grid (in vacuum) allows the electrons emitted from the cathode to be focused by the cathode electrode itself during its movement towards the grid electrode, thereby reducing the divergence of the electron beam. The basic working principle of the present invention: under the action of the forward voltage of the grid 2, the electrons emitted from the electron emission layer 4 connected to the cathode 3 are accelerating towards the grid; at the same time, some electrons move towards the high voltage anode 1 . The electrons moving to the high-voltage anode 1 are simultaneously affected by the grid. Since the grid exposed to vacuum is surrounded by the cathode, the electrons moving to the high-voltage anode 1 are not only affected by the grid 2, but also restricted by the cathode 1 itself, so that the electrons converge to the center of the grid, which solves the problem The problem of electron beam divergence.

Therefore, the present invention includes a gate, a cathode and an insulating layer on the substrate, and an anode with a certain distance therebetween, and is contained and fixed in a vacuum cavity, and is characterized in that the gate is located between the insulating layer and the substrate, and through The grid with holes exposed from the insulating layer is surrounded by a cathode, and an electron emission layer is arranged between the cathode and the insulating layer.

To reduce the operating voltage applied to the gate, the gate can be extended to the surface of the insulating layer to form an inverted T-shaped gate structure, or an "I"-shaped gate structure higher than the upper surface of the insulating layer or flatter than , "I"-shaped gate structure lower than the insulating layer. Therefore, the above-mentioned gate may be a strip-shaped, inverted T-shaped or "I"-shaped gate structure.

Further, another layer of cathode is added between the insulating layer and the electron emission layer, so that the electron emission layer is between the two layers of cathodes to form an interlayer cathode, so as to improve the contact between the electron emission layer and the cathode.

In order to improve the emission current density and the uniformity of electron emission, an electron scattering layer can be provided on the surface of the insulating layer between the cathode and the exposed grid. The electron emission layer can be replaced by an electron scattering layer to simplify the process.

In summary, the present invention effectively solves the problem of electron beam divergence of microtip type and surface conduction type field emission electron source devices, and has simple process, low driving voltage and high efficiency.

Description of drawings

Fig. 1 is a schematic diagram of the basic structure of the present invention.

FIG. 2 is a schematic structural diagram of an inverted T-shaped gate of the present invention.

FIG. 3 is a schematic structural view of the "I" shaped gate of the present invention.

FIG. 4 is a schematic structural diagram of another "I"-shaped gate of the present invention.

Fig. 5 is a schematic diagram of the basic structure of the electron emission layer between two layers of cathodes of the present invention.

FIG. 6 is a schematic structural view of another electron emission layer between two layers of cathodes according to the present invention.

Fig. 7 is a schematic diagram of the basic structure of an electron scattering layer on the surface of the insulating layer of the present invention.

FIG. 8 is a schematic diagram of another structure of the present invention with an electron scattering layer on the surface of the insulating layer.

Fig. 9 is a schematic diagram of the array structure of the present invention.

Among them: 1, anode; 2, gate; 3, cathode; 4, electron emission layer; 5, insulating layer; 6, substrate;

7. Vacuum cavity; 8. Electron scattering layer. V ₁ and V ₂ are external power supplies.

Detailed ways

As shown in Fig. 1, the present invention comprises the grid 2 on the substrate 6, the cathode 3 and the insulating layer 5, and the anode 1 with a certain distance opposite to it, and is contained and fixed in the vacuum cavity 7 and a suitable power supply, which The feature is that the grid 2 is located between the insulating layer 5 and the substrate 6 , and the grid 2 exposed from the insulating layer 5 through the hole is surrounded by the cathode 3 , and an electron emission layer 4 is arranged between the cathode 3 and the insulating layer 5 .

Electron emission layer 4 can be the particle material such as metal, metal oxide, semiconductor, particle size is less than 50 microns, or by the mixture of above materials; Low-dimensional materials mainly include one-dimensional, quasi-one-dimensional, two-dimensional, quasi-two-dimensional nano-metals, metal oxides, elements or compound semiconductor materials. The function of the electron emission layer 4 is to emit electrons, similar to a traditional hot cathode; the cathode 2 is mainly an electrode for transporting electrons.

In order to reduce the operating voltage applied to the gate, the gate 2 exposed or exposed from the insulating layer hole can extend to the surface of the insulating layer 5 to form an inverted T-shaped gate structure, as shown in Figure 2; or form a high The "I"-shaped gate structure on the insulating layer 5 is shown in FIG. 3 . Therefore, the above-mentioned gate can be a strip-shaped, inverted T-shaped or "I"-shaped gate structure.

In order to reduce the probability that the electrons emitted from the electron emission layer 4 are captured by the grid 2 and improve the emission efficiency of the electrons, the grid in FIG. The layers are on the same plane, as shown in Figure 4, the gate and the insulating layer are on the same plane. Therefore, the height of the "I"-shaped gate structure exposed or exposed from the round hole can be adjusted according to the specific needs of the device, such as the magnitude of the gate operating voltage.

Considering that the contact resistance between the electron emission layer 4 and the cathode 3 is relatively large, in order to reduce the contact resistance, another layer of cathode (referred to as the lower cathode) can be added between the insulating layer 5 and the electron emission layer 4 in the structure shown in FIG. , the cathode 3 on the opposite electron emission layer 4 is the upper cathode), so that the electron emission layer is between the two layers of cathodes to form a sandwich cathode of "sandwich" structure, therefore, the electron emission layer below the cathode 3 There is another cathode between the insulating layer, as shown in Figure 5. The structure of the gate 2 may also have the structures shown in FIG. 1 , FIG. 2 , and FIG. 3 .

Similarly, in order to improve the efficiency of electron emission, reduce the operating voltage applied to the grid, and simplify the preparation process, the electron emission layer 4 in Fig. 5 can cover the cathode of the lower layer (i.e. the cathode between the insulating layer and the electron emission layer) ,As shown in Figure 6. Similarly, the gate 2 may also have the structures shown in FIG. 1 , FIG. 2 , and FIG. 3 .

In order to improve the uniformity of electron emission and increase the emission current density, an electron scattering layer 8 can be provided on the surface of the insulating layer between the cathode 3 and the exposed grid 2, as shown in FIG. 7 . The electron scattering layer 8 mainly scatters electrons, and can also emit electrons, so the emissive layer 4 can be replaced by the electron scattering layer 8, and the electron scattering layer 8 can be connected with the cathode 3, the grid 2, and the electron emission layer 4, or not. . The grid can also have the structures shown in FIG. 1 , FIG. 2 , and FIG. 4 ; the cathode can also have the structures shown in FIG. 5 and FIG. 6 . FIG. 8 is another form of the basic structure shown in FIG. 7 with the grid and cathode structure shown in FIG. 4, which can improve the efficiency of electron emission.

The above various structures can be regularly arranged repeatedly to form an array structure, that is, an array structure of any of the above structures is regularly arranged in the insulating layer 5 on the surface of the glass substrate 6 , as shown in FIG. 9 . The cathode and the grid on the surface of the substrate can realize X-Y matrix addressing similar to liquid crystal display.

The anode is a fluorescent screen, and it can also be a metal plate, column, wire, etc. The materials for preparing the cathode and the grid are metals such as aluminum, copper, nickel-chromium alloy, etc., or carbon conductive materials, or transparent conductive materials such as indium-doped tin oxide (ITO).

Electron emission layer 4 is the particle material such as common metal especially high-temperature metal, metal oxide, semiconductor, particle size is less than 50 microns, or by the mixing of above materials; , carbon nanotubes and other low-dimensional materials, low-dimensional materials mainly include one-dimensional, quasi-one-dimensional, two-dimensional, quasi-two-dimensional nano-metals, metal oxides, elements or compound semiconductor materials.

The above-mentioned insulating layer 5 can be a common oxide material such as silicon dioxide, aluminum oxide, or a composite material mixed in a certain proportion, or an organic-inorganic composite material. The thickness of the insulating layer depends on the properties of the selected material and ranges from 0.01 microns to 500 microns.

The electron scattering layer 8 is composed of particles with a resistivity lower than 10 ⁷ Ω.cm and a size smaller than 50 microns, or a thin film with a resistivity lower than 10 ⁷ Ω.cm and a thickness of less than 30 microns; It is an oriented magnetic particle material (such as rare earth magnetic material, oxide magnetic material, etc.), or it can be metal (such as gold, molybdenum, tungsten, etc.), metal oxide (such as magnesium oxide, titanium oxide, zinc oxide, etc.), Granular materials such as semiconductors (such as silicon, gallium arsenide, etc.).

Basic preparation technique of the present invention:

1. On the surface of the glass substrate 6, a gate 2 with a thickness of less than 50 microns is prepared by using a common microelectronics process (evaporation, deposition, photolithography, etching, etc.);

2. Prepare the insulating layer 5 on the above-mentioned glass substrate with the grid 2 by screen printing, spin coating, sputtering and other common methods; at the same time, use photolithography or directly use the method of screen printing to form a layer less than 5 in the insulating layer. 1mm hole through which part of grid 2 emerges;

3. After the insulating layer is prepared, the electron emission layer 4 is prepared around the exposed gate hole by using the usual evaporation, printing, sputtering and other processes, or in combination with microelectronic processes such as photolithography, and its thickness is preferably less than 1 mm. ;

4. On the above-mentioned electron emission layer 4, the cathode 3 can be covered with the electron emission layer and insulating layer except the exposed grid and its vicinity by using the microelectronic process method in step 1; the thickness of the cathode is less than 100 microns, Finally, the structure shown in Figure 1 is formed.

5. The method of step 4 can also be used to make the gate 2 extend to the surface of the insulating layer (it is easy to realize by photolithography process) while preparing the cathode 3, and be surrounded by the cathode to form an inverted T shape as shown in Figure 2 The structure of the gate, or the "I"-shaped gate shown in Figure 3.

6. Before step 2, the microelectronics process (mainly wet or dry etching method) can be used to selectively etch the insulating layer area that exposes the gate, and then the "I" shape prepared by the method of step 5 Gate, forming the gate structure shown in FIG. 4 .

7. After step 2, use step 6 and utilize the process of step 4 to prepare a layer of cathode (i.e. lower cathode) and "I" shaped grid, then repeat step 3 to prepare the electron emission layer, and step 4 to prepare another layer of cathode ( Upper cathode), forming the electron source of cathode and grid structure shown in Figure 5; Utilize microelectronics technology when preparing electron emission layer, can make it cover lower cathode, form the cathode structure shown in Figure 6;

8. Utilize step 5, step 3, step 4, and in combination with common microelectronic technology, respectively prepare any cathode structure shown in Fig. 1, Fig. 5, Fig. 6 and Fig. 1, Fig. 2, Fig. 3, Fig. 4 The electron source of any grid structure is shown;

9. After preparing the electron source with any cathode structure shown in Fig. 1, Fig. 5, and Fig. 6 and any of the gate structures shown in Fig. 1, Fig. 2, Fig. 3, and Fig. 4 by using the above steps, use the usual micro The electronic process can prepare an electron scattering layer in a designated area (such as the surface of the insulating layer, between the cathode and the exposed grid). The electron scattering layer may or may not be connected to the cathode, the grid, and the electron emission layer. For example, an electron scattering layer 4 is prepared in a corresponding device having the cathode structure shown in FIG. 1 and the gate structure shown in FIG. 3 to form the structure shown in FIG. 7; An electron scattering layer 4 is prepared in the corresponding device with the gate structure shown, forming the structure shown in FIG. 8 .

10. Prepare any of the cathode structures shown in Figure 1, Figure 5, and Figure 6 above and the gates on the surface of the substrate shown in Figure 1, Figure 2, Figure 3, and Figure 4 into strips using the usual microelectronics process shape, forming a strip-shaped cathode 3 and a strip-shaped grid 2. The strip cathode 3 can be perpendicular to the strip grid 2 or form an angle greater than 45 degrees with the strip grid; there is the above-mentioned field emission electron source structure at the intersection of the strip cathode 3 and the strip grid 2, so that Form an array structure, as shown in Figure 9. The width of the strip-shaped cathode and grid can be less than 10 mm, and the thickness can be less than 50 microns.

Claims (5)

1, a kind of surface conductive field emission electronic source device with the characteristic of converging, comprise grid (2), negative electrode (3) and insulating barrier (5) on the substrate (6), and anode at regular intervals on the other side (1), and the quilt containing is fixed in the vacuum cavity (7), it is middle with substrate (6) to it is characterized in that grid (2) is positioned at insulating barrier (5), and the grid (2) that from insulating barrier (5), reveals by the hole by negative electrode (3) around, be provided with an electron emission layer (4) between negative electrode (3) and the insulating barrier () 5.

2, the surface conductive field emission electronic source device with the characteristic of converging as claimed in claim 1 is characterized in that adding between above-mentioned insulating barrier (5) and the electron emission layer (4) one deck negative electrode (3) again and forms the interlayer negative electrode.

3, the surface conductive field emission electronic source device with the characteristic of converging as claimed in claim 1 is characterized in that there is electron scattering layer (8) on insulating barrier (5) surface between above-mentioned control grid (2) and the negative electrode (3).

4, the surface conductive field emission electronic source device with the characteristic of converging as claimed in claim 1 is characterized in that the described array structure of arranging above-mentioned a plurality of arbitrary structures in the lip-deep insulating barrier of glass substrate (6) (5) regularly.

5, the surface conductive field emission electronic source device with the characteristic of converging as claimed in claim 1 is characterized in that above-mentioned grid (2) can be inverted T-shaped or " worker " shape grid structure.

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