A dual layer field emission cold cathode electron source and a method of manufacturing the same

Abstract

The application provides a double-layer field emission cold cathode electron source and a manufacturing method thereof, relates to the field of nano-electronic technology, and the double-layer field emission cold cathode electron source comprises, from bottom to top, a first cathode, an insulating layer, a second cathode and a gate electrode; the first cathode comprises a conductive substrate and a first layer of field emission body, and the first layer of field emission body is arranged on the upper surface of the conductive substrate; the second cathode comprises a conductive grid and a second layer of field emission body, and the second layer of field emission body is arranged on the upper surface of the conductive grid; by increasing the effective emission area of the cold cathode emission body, the field emission current and the current density are improved; the manufacturing method is simple, has high universality and high repeatability, is beneficial to the current improvement of the field emission electron source, and provides a feasible scheme for promoting the application of the large-current electron source in vacuum microelectronic devices.

Description

Technical Field

[0001] This invention relates to the field of nanoelectronics, and more specifically, to a double-layer field emission cold cathode electron source and its manufacturing method. Background Technology

[0002] Field emission cold cathode electron sources have shown significant application potential in vacuum electronic devices, with common applications including microwave tubes and X-ray sources. Compared to hot cathodes, cold cathodes offer advantages such as room temperature operation, low power consumption, and high current density. However, the emission current of cold cathodes is currently relatively low, and further increasing the current is a key issue to meet the application requirements of these devices.

[0003] While increasing the area of ​​the cathode film can increase the current, the electric field shielding effect causes the densely packed field emitters to shield each other, resulting in a much stronger electric field at the cathode edge than in the center. This leads to poor emission uniformity and severe edge emission, meaning that increasing the area does not proportionally increase the current. To address this problem, a conventional approach is to fabricate the cold cathode film in an array, such as a dot array or a line array, to disperse the emitters and circumvent the shielding effect, thereby achieving a uniform electric field distribution. For example, existing technology discloses a field emission electron source structure including a supporting substrate, a photocathode layer formed on the substrate, a source electrode formed on a portion of the photocathode layer, an insulating layer covering the source electrode and the photocathode layer, a gate electrode formed on the insulating layer, and a vacuum channel penetrating the gate electrode and the insulating layer and exposing the photocathode layer. Although this approach circumvents the shielding effect by dispersing the emitters, thereby achieving a uniform electric field distribution, reducing the operating voltage required for the electron source structure, and increasing the emission current density and resistance to ion bombardment, the blank areas between the dots lack emitters, resulting in a drastically reduced total emission area. According to calculations, the effective emission area of ​​the array accounts for less than half of the total area, so the method of using dispersed emitters has limited effect on improving the current. Summary of the Invention

[0004] To address the limited improvement in emission area and current achieved by current field emission shielding methods, this invention proposes a double-layer field emission cold cathode electron source and its manufacturing method. This method 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. Furthermore, the structure and process are simple and versatile.

[0005] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows:

[0006] A dual-layer field emission cold cathode electron source includes: a first cathode, an insulating layer, a second cathode, and a gate connected sequentially from bottom to top; the first cathode includes a conductive substrate and a first field emitter, the first field emitter being disposed on the upper surface of the conductive substrate; the second cathode includes a conductive grid and a second field emitter, the second field emitter being disposed on the upper surface of the conductive grid.

[0007] This technical solution improves the effective emission area of ​​the cold cathode by designing an integrated double-layer field emission cold cathode electron source, thereby enhancing 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, and copper, which can be the same material or different materials. The first and second field emitters include field emission thin films, one-dimensional field emission nanomaterials, and two-dimensional field emission nanomaterials, which can be the same material or different materials. The insulating layer can include materials such as alumina and silicon dioxide.

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

[0009] Preferably, the first layer of field emitters is an array of field emitters, which are spatially aligned with the conductive mesh holes to increase the effective field emission area and thus improve the field emission performance.

[0010] Here, the first-layer field emitter is set in a lattice shape, which reduces the electric field shielding effect and improves the uniformity of field emission.

[0011] Preferably, the first layer of field emitter has a circular, linear, or polygonal shape.

[0012] Preferably, the shape of the conductive mesh hole is the same as the shape of the first layer field emitter.

[0013] Preferably, the arraying period of the first layer field emitter is the same as that of the conductive mesh aperture, and the size of the arraying unit is less than or equal to that of the conductive mesh aperture.

[0014] Preferably, the second field emitter is disposed on the grid strips in the conductive grid to form a gridded emitter; the position of the second field emitter is spatially staggered with that of the first field emitter, thereby increasing the effective field emission area and thus improving the field emission performance.

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

[0016] Preferably, the potential applied by the second-layer field emitter is higher than that applied by the first-layer field emitter, so that it not only participates in field emission as an emitter, but also provides an electric field for the first-layer field emitter.

[0017] Preferably, the gate is applied with a potential higher than that applied by the second-layer field emitter, thereby driving the second-layer and first-layer field emitters to emit together.

[0018] Here, the gate can simultaneously receive field emission currents from both emitters, achieving current superposition.

[0019] A method for fabricating a double-layer field emission cold cathode electron source, comprising the following steps:

[0020] S1. Fabrication of the first cathode: Fabrication of the first field emitter layer on a conductive substrate;

[0021] S2. Fabrication of the second cathode: Fabrication of a second field emitter on a conductive mesh;

[0022] S3. Place the conductive grid of the second cathode on the conductive substrate containing the first cathode, and align the first field emitter and the second field emitter alternately, and separate and fix the first cathode and the second cathode through the insulating layer;

[0023] S4. Place the gate above the second field emitter to complete the fabrication 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, which avoids the shielding effect problem of field emission, increases the effective emission area of ​​the cold cathode emitter, and improves the field emission current and current density.

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

[0026] This invention proposes a dual-layer field emission cold cathode electron source and its manufacturing method. The dual-layer field emission cold cathode electron source includes a first cathode, an insulating layer, a second cathode, and a gate connected sequentially from bottom to top. The first cathode includes a conductive substrate and a first field emitter layer, with the first field emitter layer disposed on the upper surface of the conductive substrate. The second cathode includes a conductive grid and a second field emitter layer, with the second field emitter layer disposed 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 is simple, highly versatile, and highly repeatable, which is beneficial for increasing the current of the field emission electron source and provides a feasible solution for promoting the application of high-current electron sources in vacuum microelectronic devices. Attached Figure Description

[0027] Figure 1 This diagram illustrates the structure of the double-layer field emission cold cathode electron source proposed in Embodiment 1 of the present invention.

[0028] Figure 2This is a front view of the first cathode in Embodiment 1 of the present invention;

[0029] Figure 3 This is a top view of the first cathode in Embodiment 1 of the present invention;

[0030] Figure 4 This is a front view of the second cathode in Embodiment 1 of the present invention;

[0031] Figure 5 This is a top view of the second cathode in Embodiment 1 of the present invention;

[0032] Figure 6 This is a front view of the double-layer cathode in Embodiment 1 of the present invention;

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

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

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

[0036] Figure 10 A schematic diagram illustrating 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 field emitter layer; 2. Insulating layer; 3. Second cathode; 31. Conductive mesh; 32. Second field emitter layer; 4. Gate. Detailed Implementation

[0038] The positional relationships depicted in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0039] To better illustrate this embodiment, some parts of the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions;

[0040] It is understandable to those skilled in the art that some well-known details may be omitted from the accompanying drawings.

[0041] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] Example 1

[0043] like Figure 1As shown, this embodiment proposes a dual-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 sequentially from bottom to top; the first cathode 1 includes a conductive substrate 11 and a first field emitter 12, the first field emitter 12 being disposed on the upper surface of the conductive substrate 11; the second cathode 3 includes a conductive grid 31 and a second field emitter 32, the second field emitter 32 being disposed on the upper surface of the conductive grid 31.

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

[0045] The first field emitter 12 and the second field emitter 32 include field emission thin films, one-dimensional field emission nanomaterials, and two-dimensional field emission nanomaterials, etc. The two field emitters can be made of the same material or different materials. In this embodiment, upright carbon nanotubes are selected as both the first field emitter 12 and the second field emitter 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 field emitter 12 is an array of field emitters, with shapes including circular, linear and polygonal, and is fabricated on a conductive substrate 11, with its position interleaved with the holes of the conductive grid 31.

[0049] The conductive mesh 31 has holes with shapes including circular, linear, and polygonal, and has the same shape as the first layer field emitter 12.

[0050] The first layer field emitter 12 has the same arraying period as the conductive mesh 31 holes, and the arraying unit size is less than or equal to the conductive mesh 31 holes.

[0051] Furthermore, the first layer of field emitters 12 is an array of field emitters, spatially staggered with the pores of the conductive mesh 31. In this embodiment, the first layer of upright carbon nanotubes is configured as a lattice 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 field emitter 32 is given a potential higher than that of the first-layer field emitter 12. It both participates in field emission as an emitter and provides an electric field for the first-layer field emitter 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 mesh. The mesh-like 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 and second layers of upright carbon nanotubes are spatially staggered and aligned, and the area of ​​their superposition is equal to the entire cathode surface. Both layers of upright carbon nanotubes have uniform field emission capabilities, thereby increasing the effective field emission area and thus improving the field emission performance.

[0055] Example 2

[0056] This embodiment further illustrates the specific implementation of the dual-layer field emission cold cathode electron source proposed in Embodiment 1. The dual-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 sequentially from bottom to top. The first cathode 1 includes a conductive substrate 11 and a first field emitter 12, with the first field emitter 12 disposed on the upper surface of the conductive substrate 11. The second cathode 3 includes a conductive grid 31 and a second field emitter 32, with the second field emitter 32 disposed on the upper surface of the conductive grid 31.

[0057] In this embodiment, the potential applied by the second-layer field emitter 32 is higher than the potential applied by the first-layer field emitter 12, so that it can both participate in field emission as an emitter and provide an electric field for the first-layer field emitter 12.

[0058] The gate 4 is applied with a potential higher than that applied by the second-layer field emitter 32, thereby driving the second-layer and first-layer field emitters 32 to emit together.

[0059] In a preferred embodiment, the first field emitter 12 is grounded and has a potential of zero, the voltage applied to the second field emitter 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 dual-layer field emission cold cathode electron source is set to 100 μm. Based on the typical turn-on electric field value of 1.2 V / μm for carbon nanotubes, applying a voltage of approximately 120 V to the second cathode 3 is sufficient to drive the field emission of the first layer of upright carbon nanotubes. Similarly, the distance between the second layer of upright carbon nanotubes and the gate 4 of the dual-layer field emission cold cathode electron source is set to 100 μm. Applying a voltage approximately 120 V higher than that to the gate 4 is sufficient to drive the field emission of the second layer of upright carbon nanotubes. Here, the gate 4 can simultaneously receive the field emission currents from both layers of emitters, achieving current superposition.

[0061] Example 3

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

[0063] S1. Fabrication of the first cathode 1: Fabrication of a first field emitter 12 on a conductive substrate 11;

[0064] S2. Fabrication of the second cathode 3: Fabrication of a second field emitter 32 on the conductive mesh 31;

[0065] S3. Place the conductive grid 31 of the second cathode 3 on the conductive substrate 11 containing the first cathode 1, and align the first field emitter 12 and the second field emitter 32 alternately, and separate and fix the first cathode 1 and the second cathode 3 through the insulating layer 2;

[0066] S4. Place the gate 4 above the second field emitter 32 to complete the fabrication 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 they are assembled into a double-layer field emission cold cathode electron source.

[0068] In step S1, as Figure 5 As shown, an array of upright carbon nanotubes is grown on a stainless steel plate using thermochemical vapor deposition as the first layer field emitter 12.

[0069] In step S2, as Figure 6 As shown, the same thermochemical vapor deposition method was used to deposit gridded upright carbon nanotubes on a stainless steel mesh as the second field emitter 32.

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

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

[0072] The method for manufacturing a dual-layer field emission cold cathode electron source proposed in this embodiment splits a thin-film field emitter into a high-low double-layer patterned emitter, avoiding the shielding effect problem of field emission, increasing the effective emission area of ​​the cold cathode emitter, and improving 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 applies voltage to increase the electric field strength on the surface of the first-layer field emitter 12, thereby increasing the emission current of the first-layer field emitter 12. The entire manufacturing process is simple, highly versatile, and highly repeatable, which is beneficial for increasing the current 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 merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a double-layer field emission cold cathode electron source, characterized in that, The dual-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 sequentially from bottom to top; the first cathode (1) includes a conductive substrate (11) and a first-layer field emitter (12), the first-layer field emitter (12) being disposed on the upper surface of the conductive substrate (11); the second cathode (3) includes a conductive grid (31) and a second-layer field emitter (32), the second-layer field emitter (32) being disposed on the upper surface of the conductive grid (31); The specific method for preparing the double-layer field emission cold cathode electron source is as follows: S1. Fabrication of the first cathode (1): Fabrication of the first field emitter (12) on a conductive substrate (11). S2. Fabrication of the second cathode (3): Fabrication of a second field emitter (32) on a conductive grid (31); S3. Place the conductive grid (31) of the second cathode (3) above the conductive substrate (11) containing the first cathode (1), and make the first field emitter (12) and the second field emitter (32) alternately aligned, and separate and fix the first cathode (1) and the second cathode (3) through the insulating layer (2); S4. Place the gate (4) above the second field emitter (32) to complete the preparation of the double-layer field emission cold cathode electron source.

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

3. The method for preparing a double-layer field emission cold cathode electron source according to claim 1, characterized in that, The first layer field emitter (12) is an arrayed field emitter, which is spatially aligned with the holes of the conductive mesh (31).

4. The method for preparing a double-layer field emission cold cathode electron source according to claim 3, characterized in that, The first layer field emitter (12) is circular, linear or polygonal in shape.

5. The method for preparing a double-layer field emission cold cathode electron source according to claim 3, characterized in that, The shape of the holes in the conductive mesh (31) is the same as that of the first layer field emitter (12).

6. The method for preparing a double-layer field emission cold cathode electron source according to claim 3, characterized in that, The first layer field emitter (12) has the same arraying period as the conductive mesh (31) holes, and the arraying unit size is less than or equal to the conductive mesh (31) holes.

7. The method for preparing a double-layer field emission cold cathode electron source according to claim 1, characterized in that, The second-layer field emitter (32) is disposed on the grid strip in the conductive grid (31) to form a gridded emitter; the position of the second-layer field emitter (32) is spatially staggered with that of the first-layer field emitter (12).

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

9. The method for preparing a double-layer field emission cold cathode electron source according to claim 1, characterized in that, The gate (4) is applied with a potential higher than that applied by the second-layer field emitter (32).

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