Field emission cathode device and method for forming a field emission cathode device - Patents.com

Abstract

The field emission cathode device and method of forming the same includes a rotating field emission cathode having a field emission material deposited on its surface, the field emission cathode rotating about an axis and electrically grounded, and a planar gate electrode extending parallel to the surface of the rotating field emission cathode and defining a gap therebetween. A gate voltage source is electrically connected to the gate electrode and positioned to interact with the gate electrode to generate an electric field that induces a portion of the surface of the rotating field emission cathode adjacent the gate electrode to emit electrons from the field emission material toward and through the gate electrode.

Description

[Technical Field]

[0001] The present application relates to field emission cathode devices, and more particularly, to a field emission cathode device and a method of forming a field emission cathode device. [Background Art]

[0002] A typical field emission cathode assembly includes a field emission cathode and an extraction gate structure, with a certain gap distance therebetween, and an example of the field emission cathode assembly is shown in FIG. 1. The cathode is generally a conductive substrate having a deposited layer of field emission material on the cathode surface adjacent the extraction gate structure. In such prior art examples, to extract field emission electrons (e.g., field emission current) from the cathode surface, an external voltage (V G ) is applied to the gate electrode, and the cathode is electrically grounded.

[0003] The emission area of the cathode is defined by the total area of the deposited layer of field emission material. To generate a stable field emission current, the field emission cathode can only operate continuously below a certain threshold of maximum current density, as shown in FIG. 2. In many cases, in high power / high current situations, the cathode can only operate stably, particularly in pulse modes with short pulse widths or durations (e.g., to achieve stable operation, current is generated intermittently at a specific duty cycle over a selected period of time). As shown in FIG. 3A, higher peak currents can be achieved while operating in pulse mode compared to the DC (continuous) mode of FIG. 2. The pulse width (duration) is even shorter than that shown in FIG. 3A, and as shown in FIG. 3B, the peak current can be further increased without causing cathode degradation.

[0004] However, operating the cathode in this manner can lead to damage to the gate electrode due to, for example, cathode hot spots (e.g., non-uniformity in the field emission layer on the cathode surface can cause higher peak currents in some areas of the cathode than in others) and / or cathode damage due to electron shock (e.g., reflection of electrons returning from the gate electrode to the cathode). Higher peak currents can also put stress on the cathode, potentially shortening its lifespan. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, there is a need for a field emission cathode and a method for forming such a field emission cathode that improves uniformity, increases the maximum current output (electron emission), and minimizes cathode stress to extend the service life of the cathode. Such a cathode and its formation method should preferably avoid potential gate electrode damage caused by cathode hot spots and mitigate potential cathode degradation due to ion bombardment. [Means for solving the problem]

[0006] The above and other needs are satisfied by embodiments of the present disclosure, including but not limited to the following exemplary embodiments, one particular embodiment providing a field emission cathode apparatus comprising a rotating field emission cathode comprising a field emission material deposited on the surface of the apparatus, the field emission cathode rotating about an axis and electrically grounded; a planar gate electrode extending parallel to the surface of the rotating field emission cathode with a gap between them; a gate voltage source electrically connected to the gate electrode and arranged to interact with the gate electrode to generate an electric field; the electric field induces a portion of the surface of the rotating field emission cathode adjacent to the gate electrode to emit electrons from the field emission material toward and through the gate electrode.

[0007] Another exemplary embodiment provides a method for forming a field emission cathode apparatus, comprising the step of defining a gap between the plane gate electrode and the surface of a rotating field emission cathode by positioning a plane gate electrode adjacent to and parallel to the surface of a rotating field emission cathode, the rotating field emission cathode comprising a field emission material deposited on its surface, being electrically grounded, and rotating about an axis extending through the rotating field emission cathode. A gate voltage source interacts with a gate electrode electrically connected to the gate voltage source to generate an electric field, the electric field being arranged to induce a portion of the surface of the rotating field emission cathode adjacent to the gate electrode to emit electrons from the field emission material toward and through the gate electrode.

[0008] Therefore, this disclosure includes, but is not limited to, the following exemplary embodiments.

[0009] Exemplary Embodiment 1: A field emission cathode apparatus comprising: a rotating field emission cathode that includes a field emission material deposited on its surface, rotates about an axis, and is electrically grounded; a planar gate electrode extending parallel to the surface of the rotating field emission cathode and defining a gap between them; and a gate voltage source electrically connected to the gate electrode and arranged to interact with the gate electrode to generate an electric field, wherein the electric field induces a portion of the surface of the rotating field emission cathode adjacent to the gate electrode to emit electrons from the field emission material toward and through the gate electrode.

[0010] Exemplary Embodiment 2: An apparatus of any of the above-described exemplary embodiments or a combination thereof, wherein the surface of the field emission cathode is the cylindrical surface of a cylindrical substrate, and the axis is a longitudinal axis extending along the cylindrical substrate.

[0011] Exemplary Embodiment 3: The gate electrode extends parallel to the cylindrical surface of the cylindrical substrate, in any of the above-described exemplary embodiments or a combination thereof.

[0012] Exemplary Embodiment 4: The electric field generated by the gate voltage source is located on the cylindrical surface of the rotating cylindrical substrate adjacent to the gate electrode. Extending in the direction of rotational angleAn apparatus or combination thereof of any of the above exemplary embodiments, wherein a portion is arranged to induce the emission of electrons from a field emission material toward and through the gate electrode.

[0013] Exemplary Embodiment 5: Cylindrical surface Extending in the direction of rotational angle The size of the portion is proportional to the dimension of the gap between the gate electrode and the cylindrical surface, in any of the devices or combinations thereof of the exemplary embodiments described above.

[0014] Exemplary Embodiment 6: The apparatus of any of the above-described exemplary embodiments or a combination thereof, wherein the gate voltage source is arranged to apply a constant (DC) voltage or a pulsed voltage to the gate electrode.

[0015] Exemplary Embodiment 7: A gate voltage source configured to apply a pulsed voltage to a gate electrode, wherein the magnitude of the pulsed voltage is inversely proportional to the pulse duration of the pulsed voltage, in any of the above-described exemplary embodiments or a combination thereof.

[0016] Exemplary Embodiment 8: The surface of the field emission cathode is a circular surface extending laterally to the disc-shaped substrate, and the axis extends perpendicularly to the circular surface and through the disc-shaped substrate, in any of the above-described exemplary embodiments or a combination thereof.

[0017] Exemplary Embodiment 9: An apparatus or combination thereof of any of the above-described exemplary embodiments, wherein the gate electrode extends parallel to and adjacent to a portion of the circular surface of the disc-shaped substrate, at least between the axis and the outer circumference of the circular surface.

[0018] Exemplary Embodiment 10: Any apparatus or combination thereof of the above-described exemplary embodiments, wherein the electric field generated by the gate voltage source is arranged to induce electron emission from the field emission material toward and through the gate electrode in a portion of the circular surface of a rotating disk-shaped substrate adjacent to the gate electrode.

[0019] Exemplary Embodiment 11: An apparatus of any of the above-described exemplary embodiments or a combination thereof, wherein the size of that portion of the circular surface is proportional to the angular dimension of the gate electrode.

[0020] Exemplary Embodiment 12: A method for forming a field emission cathode apparatus, comprising: an arrangement step of arranging a planar gate electrode adjacent to and parallel to the surface of a rotating field emission cathode, defining a gap between them, wherein the rotating field emission cathode includes a field emission material deposited on its surface, is electrically grounded, and rotates about an axis extending through the rotating field emission cathode; and an interaction step of generating an electric field by interacting a gate voltage source with a gate electrode electrically connected to the gate voltage source, wherein the electric field is arranged to induce a portion of the surface of the rotating field emission cathode adjacent to the gate electrode to emit electrons from the field emission material toward and through the gate electrode.

[0021] Exemplary Embodiment 13: The step of arranging a planar gate electrode includes arranging the planar gate electrode adjacent to and parallel to the cylindrical surface of the cylindrical substrate of the rotating field emission cathode, wherein the axis is a longitudinal axis extending along the cylindrical substrate, in any of the methods or combinations thereof of the above-described exemplary embodiments.

[0022] Exemplary Embodiment 14: The step of arranging a planar gate electrode includes the step of arranging the planar gate electrode adjacent to and parallel to the cylindrical surface of a cylindrical substrate, in any method or combination thereof of the above-described exemplary embodiments.

[0023] Exemplary Embodiment 15: The step of interacting the gate voltage source with the gate electrode involves the electric field generated by the gate voltage source on the cylindrical surface of the rotating cylindrical substrate adjacent to the gate electrode. Extending in the direction of rotational angle Any method or combination of the above exemplary embodiments, comprising the step of interacting a gate voltage source with a gate electrode to induce a portion to emit electrons from a field emission material.

[0024] Exemplary Embodiment 16: The step of arranging the planar gate electrode comprises: on the cylindrical surface Extending in the direction of rotational angle The method according to any one of the foregoing exemplary embodiments or a combination thereof, comprising the step of arranging the planar gate electrode adjacent to and parallel to the surface of the rotating field emission cathode such that the size of the portion is proportional to the dimension of the gap between the gate electrode and the cylindrical surface.

[0025] Exemplary Embodiment 17: The method according to any one of the foregoing exemplary embodiments or a combination thereof, wherein the step of causing a gate voltage source to interact with a gate electrode comprises the step of causing the gate voltage source to interact with the gate electrode to apply a constant (DC) voltage or a pulsed voltage to the gate electrode.

[0026] Exemplary Embodiment 18: The method according to any one of the foregoing exemplary embodiments or a combination thereof, wherein the step of causing a gate voltage source to interact with a gate electrode comprises the step of causing the gate voltage source to interact with the gate electrode to apply a pulsed voltage to the gate electrode, and the magnitude of the pulsed voltage is inversely proportional to the pulse duration of the pulsed voltage.

[0027] Exemplary Embodiment 19: The method according to any one of the foregoing exemplary embodiments or a combination thereof, wherein the step of arranging the planar gate electrode comprises the step of arranging the planar gate electrode adjacent to and parallel to a circular surface extending laterally of a disk-shaped substrate, and an axis extends through the disk-shaped substrate perpendicularly to the circular surface.

[0028] Exemplary Embodiment 20: The method according to any one of the foregoing exemplary embodiments or a combination thereof, wherein the step of arranging the planar gate electrode comprises the step of arranging the planar gate electrode parallel to and adjacent to a part of the circular surface of the disk-shaped substrate at least between the axis and the outer periphery of the circular surface.

[0029] Exemplary Embodiment 21: Any method or combination of the above exemplary embodiments, wherein the step of interacting a gate voltage source with a gate electrode includes arranging the gate voltage source to interact with the gate electrode such that the electric field generated by the gate voltage source induces a portion of the circular surface of the rotating disk substrate adjacent to the gate electrode to emit electrons from the field emission material.

[0030] Exemplary Embodiment 22: The step of arranging a planar gate electrode includes arranging the planar gate electrode adjacent to and parallel to the surface of a rotating field emission cathode such that the size of that portion of the circular surface is proportional to the angular dimension of the gate electrode, in any method or combination thereof of the above-described exemplary embodiments.

[0031] These and other features, aspects and advantages of the Disclosure will become apparent upon reading the following detailed description in conjunction with the accompanying drawings, which are briefly described below. The Disclosure includes any combination of two, three, four, or more features or elements described herein, whether they are expressly combined or otherwise enumerated in the description of specific embodiments herein. The Disclosure is intended to be interpreted comprehensively, and any separable feature or element of the Disclosure should be considered as intended, i.e., combined, in any aspect and embodiment, unless the context of the Disclosure expressly indicates otherwise.

[0032] It will be understood that the summary in this specification is provided solely for the purpose of summarizing some exemplary embodiments in order to provide a basic understanding of the disclosure. Therefore, it will be understood that the exemplary embodiments described above are merely examples and should not be construed as narrowing the scope or intent of the disclosure. It will be understood that the scope of the disclosure encompasses many potential embodiments, some of which will be described in more detail below, in addition to the embodiments summarized herein. Furthermore, other embodiments and advantages of such embodiments disclosed herein will become apparent from the following detailed description, considered in conjunction with the accompanying drawings illustrating the principles of the embodiments described.

[0033] Having given a general overview of this disclosure, I will now explain the attached drawings. The drawings are not necessarily drawn to an accurate scale. [Brief explanation of the drawing]

[0034] [Figure 1A] This is a schematic side view of a conventional example of a field emission cathode device. [Figure 1B] Figure 1A is a schematic plan view of a prior art example of a field emission cathode device. [Figure 2] This diagram schematically shows the field emission current from a field emission cathode operating in DC (continuous) voltage mode. [Figure 3A] This diagram schematically shows the peak field emission current from a field emission cathode operating in pulse voltage mode. [Figure 3B] This figure schematically shows the peak field emission current from a field emission cathode operating in a pulse voltage mode with a pulse duration shorter than that of Figure 3A. [Figure 4] This is a schematic cross-sectional view of a field emission cathode device having a planar gate electrode and a rotating cathode according to one aspect of the present disclosure. [Figure 5A] This figure schematically shows the field emission current from a field emission cathode having a planar gate electrode and a rotating cathode according to an embodiment of the present disclosure shown in Figure 4, operating in DC (continuous) voltage mode. [Figure 5B] This figure schematically shows the peak field emission current from a field emission cathode having a planar gate electrode and a rotating cathode according to an embodiment of the present disclosure shown in Figure 4, operating in a pulse voltage mode with a relatively long pulse duration. [Figure 6] This is a schematic cross-sectional view of a field emission cathode apparatus having a planar gate electrode and a rotating cathode according to one aspect of the present disclosure, showing a cathode having a rough surface and a field emission layer with uneven deposition. [Figure 7] This is a schematic plan view of a field emission cathode device according to another embodiment of the present disclosure, which has a rotating disc-shaped cathode having a gate electrode adjacent to the circular surface of the disc-shaped cathode. [Modes for carrying out the invention]

[0035] The Disclosure will be described in more detail below with reference to the attached drawings. The drawings illustrate several, though not all, aspects of the Disclosure. In fact, the Disclosure may be embodied in many different forms and should not be construed as being limited to the aspects described herein, but rather these aspects are provided to satisfy the applicable legal requirements of the Disclosure. Throughout, similar numbers refer to similar elements.

[0036] As described herein, a field emission cathode device is desirable that exhibits increased maximum current output (electron emission) of a field emission cathode while minimizing cathode stress and improving the uniformity of electron emission. However, operating a conventional field emission cathode device in this manner can result in damage to the gate electrode due to cathode hot spots (e.g., non-uniformity in the field emission layer on the cathode surface can cause higher peak currents in some areas of the cathode than in others) and / or damage to the cathode due to electron shock (e.g., reflection of electrons returning from the gate electrode to the cathode). Higher peak currents can also stress the cathode and, in some cases, shorten its service life.

[0037] Figures 4, 6, and 7 illustrate various embodiments of the field emission cathode apparatus 100 according to the present disclosure. In some embodiments, the field emission cathode apparatus 100 includes a rotating field emission cathode 200 (see, for example, Figure 4), the cathode 200 having a field emission material 225 deposited on its surface 250 (see, for example, Figure 1A). The field emission cathode 200 is further arranged to rotate about an axis and is electrically grounded. A planar gate electrode 300 extends parallel to the surface 250 of the rotating field emission cathode 200, with a gap 350 defined between them. A gate voltage source 400 is electrically connected to the gate electrode 300 and is arranged to interact with the gate electrode 300 to generate an electric field between the gate electrode 300 and the cathode 200. The generated electric field interacts with the surface 250 of the cathode 200, inducing a portion of the surface 250 of the rotating field-emission cathode 200 adjacent to the gate electrode 300 (which has a field-emission material 225 deposited thereon) to emit electrons 500 from the field-emission material 225 toward and through the gate electrode 300.

[0038] Therefore, the portion of the cathode surface 250 adjacent to and facing the gate electrode 300, and exposed to the electric field, is the only portion of the cathode 200 that emits electrons 500 at any given time during the rotation of the cathode 200. Thus, harmful factors such as hot spots, localized non-uniformity, and surface roughness of the field emission material 225 are minimized or eliminated, taking into account the rotation of the cathode 200 during the operation of the field emission cathode device 100. Furthermore, the possibility of cathode degradation due to ion bombardment is also minimized or eliminated. Thus, the improved uniformity and elimination / minimization of harmful factors improve the maximum current output (electron emission) of the field emission cathode while minimizing cathode stress (for example, only a portion of the cathode is energized for a given time, and that portion is not energized again until the cathode has fully rotated). Therefore, it is expected that the service life of the cathode will be extended.

[0039] In certain embodiments, the substrate 210 defining the cathode 200 (see, for example, Figure 1A) is made of a metal or other conductive material such as stainless steel, tungsten, molybdenum, or doped silicon. In such embodiments, the field emission material 225 deposited on the surface of the substrate 210 includes layers of nanotubes, nanowires, graphene, amorphous carbon, or combinations thereof. The gate electrode 300 is generally made of a conductive material with a high melting temperature, such as tungsten, molybdenum, stainless steel, or doped silicon. Furthermore, in some embodiments, the gap 350 defined between the gate electrode 300 and the surface 250 of the substrate 200 (the gap 350 is actually defined between the surface of the field emission material 225 deposited on the surface 250 of the substrate 210 / cathode 200 and the gate electrode 300, and references to the surface 250 of the substrate 210 or cathode 200 in this specification are explicitly intended to mean the surface of the field emission material 225 where appropriate) is, for example, about 100 μm to about 1 mm.

[0040] Accordingly, aspects of the present disclosure improve the uniformity of electron field emission from a rotating field emission cathode 200, even if the rotating field emission cathode 200 may have a relatively rough surface morphology and non-uniform emitter deposition (see, for example, Figure 6). For example, harmful factors that cause non-uniform field emission currents, including potential hot spots (which cause gate electrode damage), are minimized or eliminated while the cathode 200 is rotating during operation, resulting in improved overall field emission uniformity. Accordingly, aspects of the present disclosure reduce, minimize or eliminate potential hot spots that are concentrated in small localized areas of the cathode 200 or generate excessive amounts of (electron) current emitted from there, which could cause gate electrode damage due to ion bombardment. Rotation of the cathode 200 distributes or otherwise minimizes hot spot currents over a wider area (due to the rotation of the cathode) to reduce the risk of gate electrode damage, but also mitigates cathode degradation due to ion bombardment. In other words, while cathode 200 is rotating, only a small / localized portion of the cathode is exposed to the gate mesh opening (and consequently, to ion bombardment due to reflection of electrons from the gate electrode), which extends the cathode's lifespan by minimizing its exposure to ion bombardment.

[0041] In one particular embodiment, as shown in Figures 4 and 6, the surface 250 of the field emission cathode 200 is the cylindrical surface of a cylindrical substrate. In such an embodiment, the axis is a longitudinal axis extending along and through the cylindrical substrate (for example, the cylindrical cathode 200 rotates about the longitudinal axis of the cylinder). Thus, the field emission material 225 is deposited on the outer cylindrical surface of the cylinder (see, for example, Figure 6). In such an embodiment, the planar gate electrode 300 extends parallel to the cylindrical surface of the cylindrical substrate. Although the gate electrode is disclosed as planar in this embodiment, those skilled in the art will understand that other configurations of the gate electrode are also concave. For example, the cross-section of the gate electrode may be arcuate, whether concave or convex with respect to the cylindrical substrate, within the scope of this disclosure.

[0042] In an embodiment including a rotating cylindrical cathode 200, the electric field generated by the gate voltage source 400 and the gate electrode 300 is located on the cylindrical surface of the rotating cylindrical substrate adjacent to the gate electrode 300. Extending in the direction of rotational angle A portion (for example, a sector of a cylinder that extends along the length of the cylinder when viewed in cross-section) rotation angle A portion of the field emission material 225 is induced to emit electrons 500 from the field emission material 225 toward the gate electrode 300 and through the gate electrode 300. In a particular example, the cylindrical surface induced by the electric field Extending in the direction of rotational angle The size of the portion is proportional to the dimensions of the gap 350 between the gate electrode 300 and the cylindrical surface, or to the dimensions (length and / or width) of the gate electrode 300. In such a configuration, any given region of the cylindrical surface is induced to emit electrons in a shorter time compared to, for example, conventional field emission cathode devices as shown in Figures 1A and 1B.

[0043] In some embodiments, the gate voltage source 400 is configured to apply a constant (DC) voltage (see, for example, Figure 5A) or a pulsed voltage (see, for example, Figure 5B) to the gate electrode 300. When the gate voltage source 400 is configured to apply a pulsed voltage to the gate electrode 300, the magnitude of the pulsed voltage is inversely proportional to the pulse duration of the pulsed voltage. That is, a sufficiently large field emission current can be obtained by applying a relatively low gate voltage to the gate electrode 300 for a relatively long period of time without causing breakdown of the cathode 200 (or gate electrode 300) due to cathode hot spots, non-uniform emission current, electron shocks, etc., or without shortening its service life (see, for example, Figure 5B). Furthermore, as the cathode 200 rotates continuously while emitting electrons 500, any given emission region on the rotating surface emits electrons for a much shorter period of time compared to conventional field emission cathode devices (e.g., the cathode devices shown in Figures 1A and 1B). Therefore, compared to conventional field emission cathode devices, it is possible to generate a higher emission current for a longer period of time in either DC mode (Figure 5A) or a longer pulse mode (Figure 5B).

[0044] Those skilled in the art will understand that different variations of the field emission cathode apparatus 100 for mounting the rotating cathode 200 are also expected in this disclosure. For example, as shown in Figure 7, some alternative embodiments of this disclosure include a field emission cathode apparatus 100 that mounts a field emission cathode 200, which is arranged as a rotating disk that rotates about an axis perpendicular to the laterally extending circular surface, and has a field emission material 225 deposited on a circular surface extending laterally of the rotating disk. In such embodiments, gate electrodes 300 are positioned adjacent to and parallel to the laterally extending circular surface of the disk so as to define a specific gap between them. Thus, while the disk rotates about the axis, only regions of the cathode directly adjacent to the gate structure emit electrons in response to an electric field.

[0045] In other words, in an alternative embodiment, the surface of the field emission cathode 200 is a circular surface extending laterally from the disc-shaped substrate, and the axis of rotation extends perpendicularly to the circular surface and through the disc-shaped substrate. As the disc-shaped substrate rotates about the axis of rotation, the gate electrode 300 extends parallel to and adjacent to a portion of the circular surface of the disc-shaped substrate, at least between the axis and the outer circumference of the circular surface. Thus, the electric field generated by the gate voltage source 400 is induced in the portion of the circular surface of the rotating disc-shaped substrate adjacent to the gate electrode 300, so as to emit electrons from the field emission material toward and through the gate electrode 300 at any point during the rotation of the disc-shaped cathode. In a particular embodiment, the size of that portion of the circular surface is proportional to the angular dimension or area of ​​the gate electrode 300 adjacent to the disc-shaped cathode.

[0046] Many modifications and other embodiments of the invention described herein will come to mind to those skilled in the art who benefit from the teachings presented in the above description and the accompanying drawings and who relate to embodiments in this disclosure. Therefore, it should be understood that embodiments of the invention are not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the invention. Furthermore, while the above description and the accompanying drawings illustrate exemplary embodiments in particular exemplary combinations of elements and / or functions, it should be understood that different combinations of elements and / or functions may be provided by alternative embodiments without departing from the scope of this disclosure. In this regard, for example, different combinations of elements and / or functions than those expressly described above are also contemplated within the scope of this disclosure. Certain terms are used herein, but these terms are used in a general and descriptive sense and are not intended to be limiting.

[0047] The terms “first” and “second” may be used herein to describe various steps or predictions, and it will be understood that these steps or predictions should not be limited by these terms. These terms are used solely to distinguish one action or prediction from another. For example, without departing from the scope of this disclosure, the first prediction may be called the second prediction, and similarly, the second step may be called the first step. Where used herein, the terms “and / or” and the symbol “ / ” include any and all combinations of one or more items from the related enumerated items.

[0048] Where used herein, singular nouns ("a," "an," "the") refer to multiple objects unless the context clearly indicates otherwise. Where used herein, the terms "comprises," "comrising," "includes," and / or "including" indicate the presence of a given feature, integer, step, action, element, and / or component, but do not preclude the presence or addition of one or more other features, integers, steps, actions, elements, components, and / or groups thereof. Therefore, the terms used herein are intended solely to describe and not limit a particular embodiment.

Claims

1. A rotating field emission cathode comprising a field emission material deposited on its surface, which rotates about an axis and is electrically grounded, A planar gate electrode extending parallel to the aforementioned axis and defining a gap between it and the surface of the rotating field emission cathode, A gate voltage source electrically connected to the gate electrode and arranged to interact with the gate electrode to generate an electric field, wherein the electric field induces a portion of the surface of the rotating field emission cathode adjacent to the gate electrode, causing electrons to be emitted from the field emission material toward and through the gate electrode. Equipped with, The surface of the rotating field emission cathode is the cylindrical surface of a cylindrical substrate. The aforementioned axis is the central axis of the cylindrical surface, The field emission material comprises at least a layer of nanotubes, nanowires, graphene, amorphous carbon, or a combination thereof. The gate voltage source is configured to apply a pulse voltage to the gate electrode, in a field emission cathode device.

2. The apparatus according to claim 1, wherein the gate electrode extends parallel to the axis of the cylindrical substrate.

3. The apparatus according to claim 2, wherein the electric field generated by the gate voltage source is arranged to induce electrons in a portion of the cylindrical surface of the cylindrical substrate adjacent to the gate electrode that extends in the direction of rotational angle, causing electrons to be emitted from the field emission material toward the gate electrode and through the gate electrode.

4. The apparatus according to claim 3, wherein the size of the portion of the cylindrical surface extending in the direction of rotation is proportional to the dimension of the gap between the gate electrode and the cylindrical surface.

5. A method for forming a field emission cathode device, A step of positioning a planar gate electrode adjacent to the cylindrical surface of a cylindrical substrate of a rotating field emission cathode and parallel to an axis which is the central axis of the cylindrical surface of the cylindrical substrate, thereby defining a gap between the surface of the planar gate electrode and the rotating field emission cathode, wherein the rotating field emission cathode includes a field emission material deposited on its surface, is electrically grounded, rotates about the axis which extends through the rotating field emission cathode, and the field emission material includes layers of at least nanotubes, nanowires, graphene, amorphous carbon, or a combination thereof; A step of generating an electric field by interacting a gate voltage source with a gate electrode electrically connected to the gate voltage source, wherein the electric field is arranged to induce a portion of the surface of the rotating field emission cathode adjacent to the gate electrode, causing electrons to be emitted from the field emission material toward and through the gate electrode; Includes, The step of arranging the planar gate electrode includes arranging the planar gate electrode adjacent to the cylindrical surface of the cylindrical substrate of the rotating field emission cathode and parallel to the axis, The step of interacting the gate voltage source with the gate electrode includes the step of interacting the gate voltage source with the gate electrode and applying a pulse voltage to the gate electrode. method.

6. The method according to claim 5, wherein the step of interacting the gate voltage source with the gate electrode includes the step of interacting the gate voltage source with the gate electrode such that the electric field generated by the gate voltage source is arranged to induce electrons from the field emission material by inducing electrons from a portion of the cylindrical surface of the cylindrical substrate adjacent to the gate electrode that extends in the rotational angular direction.

7. The method according to claim 6, wherein the step of arranging the planar gate electrode includes arranging the planar gate electrode adjacent to the cylindrical surface of the cylindrical substrate of the rotating field emission cathode and parallel to the axis such that the size of the portion of the cylindrical surface extending in the rotational angle direction is proportional to the dimension of the gap between the gate electrode and the cylindrical surface.

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