CN111293013A - Field emission cold cathode structure and manufacturing method thereof - Google Patents
Field emission cold cathode structure and manufacturing method thereof Download PDFInfo
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- CN111293013A CN111293013A CN202010227464.1A CN202010227464A CN111293013A CN 111293013 A CN111293013 A CN 111293013A CN 202010227464 A CN202010227464 A CN 202010227464A CN 111293013 A CN111293013 A CN 111293013A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/30—Cold cathodes, e.g. field-emissive cathode
- H01J1/304—Field-emissive cathodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/30—Cold cathodes, e.g. field-emissive cathode
- H01J1/304—Field-emissive cathodes
- H01J1/3042—Field-emissive cathodes microengineered, e.g. Spindt-type
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
- H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2201/00—Electrodes common to discharge tubes
- H01J2201/30—Cold cathodes
- H01J2201/304—Field emission cathodes
- H01J2201/30403—Field emission cathodes characterised by the emitter shape
- H01J2201/30434—Nanotubes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2201/00—Electrodes common to discharge tubes
- H01J2201/30—Cold cathodes
- H01J2201/304—Field emission cathodes
- H01J2201/30446—Field emission cathodes characterised by the emitter material
- H01J2201/30453—Carbon types
- H01J2201/30469—Carbon nanotubes (CNTs)
Abstract
The invention discloses a field emission cold cathode structure, which comprises a cold cathode and a cathode substrate, wherein the front surface of the cold cathode is arranged into a rectangular structure, and the cold cathode is vertically arranged on the cathode substrate; the ratio of the length to the width of the cold cathode is more than or equal to 100, the cold cathode is used as an emitter, and the emitting end face of the cold cathode is of a linear one-dimensional structure; the ratio of the height to the width of the cold cathode is greater than or equal to 50, so that the cold cathode is in a two-dimensional linear structure, the width of the cold cathode is less than 10 micrometers, and the cold cathode is made of carbon nanotube materials. The cold cathode structure described in this embodiment can have field emission capability of obtaining large current and high current density, is an optimal structure for realizing the application of a field emission cold cathode device, and can meet the performance requirements of an electron source of a specific device.
Description
Technical Field
The invention relates to the technical field of vacuum electronic devices, in particular to a field emission cold cathode structure and a manufacturing method thereof.
Background
Field emission is a method of generating electrons in a vacuum by lowering the height and width of the barrier of the emitter vacuum surface by applying an external electric field, thereby achieving electron emission. An electron emission structure based on the physical principle of field emission is called a cold cathode. Compared with the existing commercial hot cathode, the field emission cold cathode has the characteristics of normal-temperature work, quick start-up time, low power consumption, large current density and the like, and has application prospects in the field of electronic information, such as microwave and terahertz wave vacuum electronic devices, X-ray tubes, ion neutralizers, electron beam lithography and the like.
New generation vacuum electronic devices, X-ray tubes, etc. require miniaturized, integratable, high performance electron sources, and cold cathodes meet such requirements. Facing the requirements of a large-current high-current-density electron source, the carbon nano tube, the tungsten-molybdenum nano pointed cone and other nano materials show excellent large-current field emission characteristics. These nanomaterials are used as cold cathodes and have been nano-lattice structures or other structures as emitters. The nano lattice structure is characterized in that a vertical carbon nano tube is used as an emission point, each carbon nano tube is separated by a certain distance to form a row-column lattice, the electric field shielding effect can be reduced, and the problems of poor stability, easy breakdown and poor lattice emission uniformity exist.
Although the carbon nanotubes have excellent field emission characteristics, the excellent characteristics of the carbon nanotubes for cold cathode applications are limited by the structure of the emitter and cannot be fully utilized. The emitter structure is a key factor for restricting excellent field emission characteristics, and the search for a more excellent carbon nanotube emitter structure is an important problem for realizing the application of a cold cathode device.
Disclosure of Invention
The invention provides a field emission cold cathode structure and a manufacturing method thereof, aiming at solving the problem that the field emission characteristic of a carbon nano tube is limited by the structure of an emitter.
In order to achieve the purpose of the invention, the technical scheme is as follows: a field emission cold cathode structure comprises a cold cathode and a cathode substrate, wherein the front surface of the cold cathode is arranged into a cuboid structure, and the cold cathode is vertically arranged on the cathode substrate; the ratio of the length to the width of the cold cathode is more than or equal to 100, the cold cathode is used as an emitter, and the emitting end face of the cold cathode is of a linear one-dimensional structure; the ratio of the height to the width of the cold cathode is greater than or equal to 50, so that the cold cathode is in a two-dimensional linear structure, the width of the cold cathode is less than 10 micrometers, and the cold cathode is made of carbon nanotube materials.
Preferably, the carbon nanotubes are vertical carbon nanotubes, that is, the cold cathode is formed by densely arranging vertical carbon nanotubes, and each vertical carbon nanotube is perpendicular to the cathode substrate.
Further, the diameter of the vertical carbon nanotube is less than or equal to 5 nm.
Based on the field emission cold cathode structure, the invention also provides a manufacturing method of the field emission cold cathode structure, and the manufacturing method comprises the following steps:
s1: growing a vertical carbon nanotube film on a cathode substrate;
s2: vertically etching the vertical carbon nano tube outside the linear structure area on the cathode substrate by adopting high-power laser;
s3: the vertical carbon nanotubes which are not etched by the laser form a two-dimensional linear field emission cold cathode emission structure of the carbon nanotubes, and the cold cathode is vertical to the cathode substrate.
The invention has the following beneficial effects:
the carbon nano tube is adopted to construct the cold cathode with the cuboid structure, the length-width ratio of which is greater than or equal to 100, and the cold cathode is used as an emitter, the emitting end face of the cold cathode is of a linear one-dimensional structure, the influence of the electric field shielding effect among dense nano structures on the emitting characteristics of the emitter is reduced, the field emitting address is effectively increased, and the field emitting stability is improved. Therefore, the two-dimensional linear cold cathode structure can have the field emission capability of obtaining large current and high current density, is an optimal structure for realizing the application of a field emission cold cathode device, and can meet the performance requirements of an electron source of a specific device.
Drawings
Fig. 1 is a schematic diagram of a field emission cold cathode structure according to example 1, in which 1 represents a cold cathode structure and 2 represents a cathode substrate.
Fig. 2 is a topographical view of a cold cathode structure achieved in example 1, in which fig. (a) is a side view in the length-height direction of the structure, fig. (b) is a top view in the length-width direction of the structure, fig. (c) is a side view in the width-height direction of the structure, and fig. (d) is a partially enlarged view of fig. (a).
Fig. 3 is a field emission address image of the cold cathode structure described in example 1.
FIG. 4 is experimental data of example 1 using the two-pole structure test method, in which (a) is a field emission current-voltage relationship curve and (b) is an F-N curve.
Detailed Description
The invention is described in detail below with reference to the drawings and the detailed description.
Example 1
As shown in fig. 1, a field emission cold cathode structure includes a cold cathode, a cathode substrate, wherein the front surface of the cold cathode is configured as a rectangular structure, and the cold cathode is vertically disposed on the cathode substrate; the ratio of the length to the width of the cold cathode is more than or equal to 100, the cold cathode is used as an emitter, and the emitting end face of the cold cathode is of a linear one-dimensional structure; the ratio of the height to the width of the cold cathode is greater than or equal to 50, so that the cold cathode is in a two-dimensional linear structure, the width of the cold cathode is less than 10 micrometers, and the cold cathode is made of carbon nanotube materials.
In a specific embodiment, the actually fabricated field emission cold cathode structure, as shown in fig. 2(a) (b) (c), has a height of 500 μm, a length of 1mm, a width of 1 μm, a ratio of the length to the width of 1000, and a height to width ratio of 500, such that the cold cathode structure is in a two-dimensional line shape and is a high wall body with a microstructure as viewed from the side. A partial enlargement of the field emission cold cathode structure shows that the structure is composed of a close-packed array of vertical carbon nanotubes, each of which is perpendicular to the cathode substrate, and a single vertical carbon nanotube has a diameter of about 3nm, as shown in fig. 2 (d). The carbon nano tubes on the linear emission end surface are densely arranged in a single dimension, so that the problem of poor stability of a single vertical carbon nano tube is solved;
the field emission cathode structure described in this embodiment has the characteristics that the emission end face is a linear one-dimensional structure, so that the influence of the electric field shielding effect between the dense nanostructures on the emission characteristics of the emitter is reduced, and the field emission address is effectively increased, as shown in fig. 3. The cold cathode structure of the high wall body can improve the field emission enhancement factor; the two-dimensional linear cold cathode structure is composed of the dense vertical carbon nano tubes, and the integral failure of the emitter caused by the breakdown of a single vertical carbon nano tube can be avoided. Therefore, the structure can obtain high current capability by using low-voltage driving field emission and has higher field emission stability.
Based on the field emission cold cathode structure, the present embodiment further provides a manufacturing method of the field emission cold cathode structure, where the manufacturing method includes the following steps:
s1: and (3) growing a vertical carbon nanotube film with the height of about 500 mu m on the cathode substrate by adopting a thermal chemical vapor deposition method without limitation. Wherein the cathode substrate is made of silicon material.
S2: using continuous high-power laser with the power of 1.5W, the spot diameter of 0.1mm and the wavelength of 450nm to control the laser beam to be vertical to the surface of the vertical carbon nanotube array, and etching the vertical carbon nanotube outside the linear structure on the cathode substrate by a scanning method;
s3: the vertical carbon nanotubes left without being etched by the laser constitute a two-dimensional linear field emission cold cathode emission structure of the carbon nanotubes, and the cold cathode is perpendicular to the cathode substrate, so that the cold cathode of the two-dimensional linear structure of the vertical carbon nanotubes shown in fig. 2 is realized.
The method for etching the carbon nanotube by using the laser has the advantages that the microscopic morphology and the curvature radius of the top end of the carbon nanotube cold cathode can be modified to improve the field emission characteristic and the stability, which cannot be achieved by using a patterned direct growth method.
Based on the field emission cold cathode structure of this embodiment, this embodiment adopts a two-pole structure testing method to perform a field emission characteristic test on the cold cathode structure, and the vacuum degree of the vacuum chamber for the test<5×10-6Pa, the anode is a metal flat plate, the cathode is the field emission cold cathode structure described in this embodiment, and the distance between the anode and the cathode is 0.2 mm. The field emission current-voltage relation curve is obtained by testingAnd F-N curve as shown in FIG. 4, the field emission current is 1mA when the voltage of 450V is applied, and the F-N curve is linear, which shows that the two-dimensional linear cold cathode structure of the carbon nanotube conforms to the field emission rule.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. One of ordinary skill in the art will appreciate that other variations of the present invention are possible. The cathode takes other shapes, such as circular arc, sawtooth shape, irregular curved surface and the like. The material is made of other materials, such as graphene, zinc oxide nanowires, tungsten molybdenum nanowires and the like. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (4)
1. A field emission cold cathode structure comprises a cold cathode and a cathode substrate, and is characterized in that: the front surface of the cold cathode is arranged into a rectangular structure, and the cold cathode is vertically arranged on a cathode substrate; the ratio of the length to the width of the cold cathode is more than or equal to 100, the cold cathode is used as an emitter, and the emitting end face of the cold cathode is of a linear one-dimensional structure; the ratio of the height to the width of the cold cathode is greater than or equal to 50, so that the cold cathode is in a two-dimensional linear structure, the width of the cold cathode is less than 10 micrometers, and the cold cathode is made of carbon nanotube materials.
2. The field emission cold cathode structure of claim 1, wherein: the carbon nano-tubes are vertical carbon nano-tubes, namely the cold cathode is formed by densely arranging the vertical carbon nano-tubes, and each vertical carbon nano-tube is vertical to the cathode substrate.
3. The field emission cold cathode structure of claim 2, wherein: the diameter of the vertical carbon nanotube is less than or equal to 5 nm.
4. The method of manufacturing a field emission cold cathode structure according to any of claims 1 to 3, wherein: the steps of the manufacturing method include the following:
s1: growing a vertical carbon nanotube film on a cathode substrate;
s2: vertically etching the vertical carbon nano tube outside the linear structure area on the cathode substrate by adopting high-power laser;
s3: the vertical carbon nanotubes which are not etched by the laser form a two-dimensional linear field emission cold cathode emission structure of the carbon nanotubes, and the cold cathode is vertical to the cathode substrate.
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