Double-layer field emission cold cathode electron source and manufacturing method thereof

Abstract

The invention provides a double-layer field emission cold cathode electron source and a manufacturing method thereof, and relates to the technical field of nano electronics, and the double-layer field emission cold cathode electron source comprises a first cathode, an insulating layer, a second cathode and a grid electrode which are sequentially connected from bottom to top; the first cathode comprises a conductive substrate and a first layer of field emitter, and the first layer of field emitter is arranged on the upper surface of the conductive substrate; the second cathode comprises a conductive grid and a second layer of field emitter, the second layer of field emitter is arranged on the upper surface of the conductive grid, and the field emission current and the current density are improved by increasing the effective emission area of the cold cathode emitter; the manufacturing method is simple, the universality is high, the repeatability is high, current increasing of the field emission electron source is facilitated, and a feasible scheme is provided for promoting application of a large-current electron source in a vacuum microelectronic device.

Description

Technical Field

[0001] The present invention relates to the field of nanoelectronics, and more specifically, to a double-layer field emission cold cathode electron source and a manufacturing method thereof. Background Art

[0002] Field emission cold cathode electron sources have shown important application potential in vacuum electronic devices, and common applications include microwave tubes, X-ray sources, etc. Compared with hot cathodes, cold cathodes have the advantages of working at room temperature, low power consumption, and high current density. However, the emission current of cold cathodes is relatively small at present, and further increasing the current is a key issue to meet the application requirements of devices.

[0003] Although increasing the area of ​​the cathode film can increase the current, due to the existence of the electric field shielding effect, the densely arranged field emitters shield each other, and the electric field strength at the edge of the cathode is much greater than the electric field strength in the middle. This situation causes poor emission uniformity and serious edge emission phenomenon, so that the increase in area does not achieve a proportional increase in current. In response to this problem, the conventional treatment method is to make the cold cathode film into an array form, such as a point array, a line array, etc., and avoid the shielding effect by dispersing the emitters, so as to obtain a uniform electric field distribution. For example, the prior art discloses a field emission electron source structure, including a supporting substrate, a photocathode layer formed on the substrate, a source formed on a part of the photocathode layer, an insulating layer covering the source and the photocathode layer, a gate formed on the insulating layer, and a vacuum channel that penetrates the gate and the insulating layer and exposes the photocathode layer. Although this scheme avoids the shielding effect by dispersing the emitters to obtain a uniform electric field distribution, reduces the operating voltage required for the electron source structure, and improves the emission current density and the ability to resist ion bombardment, there are no emitters in the blank areas between the dot arrays, which greatly reduces the total emission area. According to calculations, the effective emission area of ​​the array accounts for less than one-half of the overall area, so the effect of increasing the current by using dispersed emitters is limited. Summary of the invention

[0004] In order to solve the problem of limited emission area and current enhancement effect of current field emission shielding effect method, the present invention proposes a double-layer field emission cold cathode electron source and a manufacturing method thereof, which can solve the field emission shielding effect problem, increase the effective emission area of ​​the cold cathode emitter, and improve the field emission current and current density, and the structure and process are simple and universal.

[0005] In order to achieve the above technical effects, the technical solution of the present invention is as follows:

[0006] A double-layer field emission cold cathode electron source comprises: a first cathode, an insulating layer, a second cathode and a grid connected in sequence from bottom to top; the first cathode comprises a conductive substrate and a first layer of field emitters, the first layer of field emitters being arranged on the upper surface of the conductive substrate; the second cathode comprises a conductive grid and a second layer of field emitters, the second layer of field emitters being arranged on the upper surface of the conductive grid.

[0007] The technical solution increases the effective emission area of ​​the cold cathode by designing a double-layer field emission cold cathode electron source with an integrated structure, thereby improving the field emission performance of the cold cathode; the conductive substrate, conductive grid and gate include conductive materials such as silicon, stainless steel, tungsten, molybdenum, copper, etc., which can be the same material or different materials; the first layer of field emitters and the second layer of field emitters include field emission films, field emission one-dimensional nanomaterials and field emission two-dimensional nanomaterials, etc., and the two layers of field emitters can be the same material or different materials; the insulating layer can include materials such as aluminum oxide and silicon dioxide.

[0008] Preferably, the grid is a flat plate structure or an open hole structure.

[0009] Preferably, the first layer of field emitters are arrayed field emitters, which are spatially staggered and aligned with the conductive grid holes, thereby increasing the effective field emission area and further improving the field emission performance.

[0010] Here, the first layer of field emitters is arranged in a lattice form, which reduces the electric field shielding effect and improves the uniformity of field emission.

[0011] Preferably, the first layer of field emitters is in a circular, linear or polygonal shape.

[0012] Preferably, the shape of the conductive mesh holes is the same as that of the first layer of field emitters.

[0013] Preferably, the arraying period of the first layer of field emitters is the same as that of the conductive grid holes, and the size of the arraying units is smaller than or equal to that of the conductive grid holes.

[0014] Preferably, the second layer of field emitters are arranged on the grid bars in the conductive grid to form gridded emitters; the positions of the second layer of field emitters are spatially staggered and aligned with the first layer of field emitters, thereby increasing the effective field emission area and further improving the field emission performance.

[0015] Here, setting the second layer of field emitters to a mesh shape can also avoid the electric field shielding effect, which is beneficial to the uniformity of field emission.

[0016] Preferably, the potential applied by the second layer of field emitters is higher than the potential applied by the first layer of field emitters, so that the second layer of field emitters not only participates in field emission as an emitter, but also plays a role in providing an electric field for the first layer of field emitters.

[0017] Preferably, the gate applies a potential higher than that applied by the second layer field emitter, thereby driving the second layer and the first layer field emitter to jointly field emit.

[0018] Here, the gate can receive the field emission current from the two layers of emitters at the same time, achieving current superposition.

[0019] A method for preparing a double-layer field emission cold cathode electron source is used to manufacture the double-layer field emission cold cathode electron source, and the steps include:

[0020] S1. Preparing a first cathode: Preparing a first layer of field emitters on a conductive substrate;

[0021] S2. Preparing a second cathode: Preparing a second layer of field emitters on a conductive grid;

[0022] S3. placing the conductive grid of the second cathode on the conductive substrate containing the first cathode, and aligning the first layer of field emitters with the second layer of field emitters in an alternating manner, and separating and fixing the first cathode from the second cathode by an insulating layer;

[0023] S4. Place the gate above the second layer of field emitters to complete the preparation of the double-layer field emission cold cathode electron source.

[0024] Here, the manufacturing method splits a thin film field emitter into a high-low double-layer patterned emitter, avoiding the problem of shielding effect of field emission, increasing the effective emission area of ​​the cold cathode emitter, and improving the field emission current and current density.

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0026] The present invention proposes a double-layer field emission cold cathode electron source and a manufacturing method thereof. The double-layer field emission cold cathode electron source comprises a first cathode, an insulating layer, a second cathode and a gate connected in sequence from bottom to top; the first cathode comprises a conductive substrate and a first layer of field emitters, and the first layer of field emitters is arranged on the upper surface of the conductive substrate; the second cathode comprises a conductive grid and a second layer of field emitters, and the second layer of field emitters is arranged on the upper surface of the conductive grid. By increasing the effective emission area of ​​the cold cathode emitter, the field emission current and current density are improved; the manufacturing method thereof is simple, highly versatile and highly repeatable, which is conducive to the current improvement of the field emission electron source and provides a feasible solution for promoting the application of large current electron sources in vacuum microelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram showing the structure of a double-layer field emission cold cathode electron source proposed in Example 1 of the present invention;

[0028] Figure 2A front view showing the first cathode in Example 1 of the present invention;

[0029] Figure 3 A top view of the first cathode in Example 1 of the present invention is shown;

[0030] Figure 4 A front view showing the second cathode in Example 1 of the present invention;

[0031] Figure 5 A top view of the second cathode in Example 1 of the present invention is shown;

[0032] Figure 6 A front view showing a double-layer cathode in Example 1 of the present invention;

[0033] Figure 7 A top view of a double-layer cathode in Example 1 of the present invention is shown;

[0034] Figure 8 A schematic diagram showing step S1 of the method for manufacturing a double-layer field emission cold cathode electron source in embodiment 3 of the present invention;

[0035] Fig. 9 A schematic diagram showing step S2 of the method for manufacturing a double-layer field emission cold cathode electron source in Embodiment 3 of the present invention;

[0036] Fig.10 A schematic diagram showing step S3 of the method for manufacturing a double-layer field emission cold cathode electron source in Embodiment 3 of the present invention;

[0037] In the figure: 1, first cathode; 11, conductive substrate; 12, first layer of field emitter; 2, insulating layer; 3, second cathode; 31, conductive grid; 32, second layer of field emitter; 4, gate. DETAILED DESCRIPTION

[0038] The positional relationships described in the drawings are only for illustrative purposes and should not be construed as limiting the present patent;

[0039] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the actual size;

[0040] It is understandable to those skilled in the art that descriptions of certain well-known contents in the drawings may be omitted.

[0041] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0042] Example 1

[0043] like Figure 1As shown, this embodiment proposes a double-layer field emission cold cathode electron source, including a first cathode 1, an insulating layer 2, a second cathode 3 and a gate 4 connected in sequence from bottom to top; the first cathode 1 includes a conductive substrate 11 and a first layer of field emitter 12, and the first layer of field emitter 12 is arranged on the upper surface of the conductive substrate 11; the second cathode 3 includes a conductive grid 31 and a second layer of field emitter 32, and the second layer of field emitter 32 is arranged on the upper surface of the conductive grid 31.

[0044] The conductive substrate 11, the conductive grid 31 and the gate 4 may be made of conductive materials such as silicon, stainless steel, tungsten, molybdenum, copper, etc., and may be the same material or different materials. In the present embodiment, a stainless steel plate is selected as the conductive substrate 11, a stainless steel grid is selected as the conductive grid 31, and a stainless steel plate is selected as the gate 4.

[0045] The first layer of field emitters 12 and the second layer of field emitters 32 include field emission films, field emission one-dimensional nanomaterials, field emission two-dimensional nanomaterials, etc. The two layers of field emitters can be made of the same material or different materials. In the present embodiment, upright carbon nanotubes are selected as both the first layer of field emitters 12 and the second layer of field emitters 32.

[0046] The material of the insulating layer 2 may include aluminum oxide, silicon dioxide, etc. In this embodiment, aluminum oxide is selected as the insulating layer 2.

[0047] The gate 4 can be a flat plate structure or an open hole structure.

[0048] The first layer of field emitters 12 are arrayed field emitters, and the shapes include circular, linear and polygonal. They are prepared on the conductive substrate 11 and their positions are aligned with the holes of the conductive grid 31 in a staggered manner.

[0049] The hole shapes of the conductive grid 31 include circular, linear and polygonal shapes, and are the same as the shape of the first layer of field emitters 12 .

[0050] The arraying period of the first layer of field emitters 12 is the same as the holes of the conductive grid 31 , and the size of the arraying unit is smaller than or equal to the holes of the conductive grid 31 .

[0051] Furthermore, the first layer of field emitters 12 are arrayed field emitters, which are staggered and aligned with the holes of the conductive grid 31. In this embodiment, the first layer of upright carbon nanotubes is arranged as a dot array, such as Figure 2 and Figure 3 As shown, arraying reduces the electric field shielding effect and improves the uniformity of field emission.

[0052] The second layer of field emitters 32 is applied with a higher potential than the first layer of field emitters 12 , and it not only participates in field emission as an emitter, but also plays a role in providing an electric field for the first layer of field emitters 12 .

[0053] like Figure 4 and Figure 5 As shown, in this embodiment, the second layer of upright carbon nanotubes is disposed on a stainless steel grid. The grid-shaped second layer of upright carbon nanotubes also avoids the electric field shielding effect, which is beneficial to the uniformity of field emission.

[0054] like Figure 6 and Figure 7 As shown, in this embodiment, the first layer and the second layer of upright carbon nanotubes are spatially staggered and aligned, and the overlapping area is equal to the entire cathode surface, and both layers of upright carbon nanotubes have uniform field emission capabilities, thereby increasing the effective field emission area and further improving the field emission performance.

[0055] Example 2

[0056] In this embodiment, the specific implementation of the double-layer field emission cold cathode electron source proposed in Embodiment 1 is further explained. The double-layer field emission cold cathode electron source includes a first cathode 1, an insulating layer 2, a second cathode 3 and a gate 4 connected in sequence from bottom to top; the first cathode 1 includes a conductive substrate 11 and a first layer of field emitters 12, and the first layer of field emitters 12 is arranged on the upper surface of the conductive substrate 11; the second cathode 3 includes a conductive grid 31 and a second layer of field emitters 32, and the second layer of field emitters 32 is arranged on the upper surface of the conductive grid 31.

[0057] In this embodiment, the potential applied by the second layer of field emitters 32 is higher than the potential applied by the first layer of field emitters 12 , so that it not only participates in field emission as an emitter, but also plays a role in providing an electric field for the first layer of field emitters 12 .

[0058] The gate 4 applies a higher potential than that applied by the second layer field emitter 32, thereby driving the second layer and the first layer field emitter 32 to perform field emission together.

[0059] As a preferred implementation, in this embodiment, the first layer of field emitters 12 is grounded and has a potential of zero, the voltage applied to the second layer of field emitters 32 is 120V, and the potential applied to the gate 4 is 240V.

[0060] Furthermore, in this embodiment, the distance between the first cathode 1 and the second cathode 3 of the double-layer field emission cold cathode electron source is set to 100μm. Based on the typical turn-on electric field value of carbon nanotubes of 1.2V / μm, the second cathode 3 can drive the first layer of upright carbon nanotubes to field-emit; similarly, the distance between the second layer of upright carbon nanotubes and the gate 4 of the double-layer field emission cold cathode electron source is set to 100μm, and the gate 4 can drive the second layer of upright carbon nanotubes to field-emit by applying a voltage higher than that of the second layer of upright carbon nanotubes by about 120V. Here, the gate 4 can receive the field emission currents of the two layers of emitters at the same time, realizing the superposition of currents.

[0061] Example 3

[0062] like Figures 8 to 10 As shown, this embodiment provides a method for manufacturing a double-layer field emission cold cathode electron source, comprising the following steps:

[0063] S1. Preparing a first cathode 1: Preparing a first layer of field emitters 12 on a conductive substrate 11;

[0064] S2. Preparing a second cathode 3: Preparing a second layer of field emitters 32 on the conductive grid 31;

[0065] S3. The conductive grid 31 of the second cathode 3 is placed above the conductive substrate 11 containing the first cathode 1, and the first layer of field emitters 12 and the second layer of field emitters 32 are staggered and aligned, and the first cathode 1 and the second cathode 3 are separated and fixed by the insulating layer 2;

[0066] S4. Place the gate 4 above the second layer of field emitters 32 to complete the preparation of the double-layer field emission cold cathode electron source.

[0067] Specifically, in this embodiment, a first layer and a second layer of upright carbon nanotube field emitters are prepared respectively and assembled into a double-layer field emission cold cathode electron source.

[0068] In step S1, if Figure 5 As shown, a vertical carbon nanotube array is grown on a stainless steel plate by using a thermal chemical vapor deposition method as the first layer of field emitters 12 .

[0069] In step S2, if Figure 6 As shown, the thermal chemical vapor deposition method is also used to deposit gridded upright carbon nanotubes on the stainless steel grid as the second layer of field emitters 32.

[0070] In step S3, if Figure 7As shown, a ceramic gasket with a thickness of 100 μm is then used to separate and fix the two layers of emitters, and the first layer of upright carbon nanotube array is aligned with the stainless steel grid through an optical microscope so that the two layers of upright carbon nanotube emitters are spatially staggered and aligned. At this time, the two layers of emitters complement each other and fill the entire surface area.

[0071] In step S4, a stainless steel grid 4 is placed above the second layer field emitter 32 to receive the current emitted by the two layers of field emitters. Figure 1 The double-layer field emission cold cathode electron source shown is completed.

[0072] The manufacturing method of the double-layer field emission cold cathode electron source proposed in this embodiment splits a thin film field emitter into a high and low double-layer patterned emitter, circumvents the problem of shielding effect of field emission, increases the effective emission area of ​​the cold cathode emitter, and increases the field emission current and current density; the second cathode 3 is a gridded field emitter, which not only participates in increasing the field emission current as part of the field emission, but also can apply voltage to increase the electric field intensity on the surface of the first layer of field emitters 12, thereby increasing the emission current of the first layer of field emitters 12. The whole set of process manufacturing methods is simple, highly versatile, and highly repeatable, which is conducive to the current increase of the field emission electron source and provides a feasible solution for promoting the application of high-current electron sources in vacuum microelectronic devices.

[0073] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A double-layer field emission cold cathode electron source, characterized in that: The invention comprises a first cathode (1), an insulating layer (2), a second cathode (3) and a gate (4) which are connected in sequence from bottom to top; the first cathode (1) comprises a conductive substrate (11) and a first layer of field emitters (12), and the first layer of field emitters (12) is arranged on the upper surface of the conductive substrate (11); the second cathode (3) comprises a conductive grid (31) and a second layer of field emitters (32), and the second layer of field emitters (32) is arranged on the upper surface of the conductive grid (31).

2. The double-layer field emission cold cathode electron source according to claim 1, characterized in that: The grid (4) is a flat plate structure or an open hole structure.

3. The double-layer field emission cold cathode electron source according to claim 1, characterized in that: The first layer of field emitters (12) are arrayed field emitters, which are spatially staggered and aligned with the holes of the conductive grid (31).

4. The double-layer field emission cold cathode electron source according to claim 3, characterized in that: The first layer of field emitters (12) is in the shape of a circle, a line or a polygon.

5. The double-layer field emission cold cathode electron source according to claim 3, characterized in that: The shape of the holes of the conductive grid (31) is the same as that of the first layer of field emitters (12).

6. The double-layer field emission cold cathode electron source according to claim 3, characterized in that: The arraying period of the first layer of field emitters (12) is the same as the holes of the conductive grid (31), and the size of the arraying units is smaller than or equal to the holes of the conductive grid (31).

7. The double-layer field emission cold cathode electron source according to claim 1, characterized in that: The second layer of field emitters (32) are arranged on the grid bars in the conductive grid (31) to form a gridded emitter; the positions of the second layer of field emitters (32) are spatially staggered and aligned with the first layer of field emitters (12).

8. The double-layer field emission cold cathode electron source according to claim 1, characterized in that: The potential applied by the second layer of field emitters (32) is higher than the potential applied by the first layer of field emitters (12).

9. The double-layer field emission cold cathode electron source according to claim 1, characterized in that: The gate (4) applies a higher potential than that applied by the second layer of field emitters (32).

10. A method for preparing a double-layer field emission cold cathode electron source, used to manufacture the double-layer field emission cold cathode electron source as claimed in any one of claims 1 to 9, characterized in that: include: S1. Preparing a first cathode (1): Preparing a first layer of field emitters (12) on a conductive substrate (11); S2. Preparing a second cathode (3): Preparing a second layer of field emitters (32) on a conductive grid (31); S3. placing the conductive grid (31) of the second cathode (3) above the conductive substrate (11) containing the first cathode (1), and aligning the first layer of field emitters (12) and the second layer of field emitters (32) in an alternating manner, and separating and fixing the first cathode (1) and the second cathode (3) by an insulating layer (4); S4. Place the gate (4) above the second layer of field emitter (3) to complete the preparation of the double-layer field emission cold cathode electron source.

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