KR102386758B1 - Field emission device - Google Patents

Abstract

A field emission device according to an embodiment of the present invention is a cathode electrode having a first surface and a second surface opposite to the first surface, wherein the cathode electrode is a groove recessed from the first surface toward the second surface. including; and emitter structures disposed in the grooves, the emitter structures including a core extending in a first direction and a conductive wire surrounding the core, wherein the grooves are arranged in a second direction crossing the first direction, The emitter structures may be located at different vertical levels.

Description

Field Emission Device {FIELD EMISSION DEVICE}

The present invention relates to a field emission device, and more particularly, to a field emission device including a cathode electrode and an emitter structure electrically connected to each other.

A nanomaterial used as an emitter can emit electrons to the outside of the nanomaterial through a quantum tunneling effect by an external electric field. In order for the electron emission process to occur effectively, the tip of the emitter must have a sharp shape. Accordingly, nanomaterials having an elongated shape are widely used as field emission device emitters. For example, nanomaterials such as carbon nanotubes (CNTs) may be used as field emission device emitters. When the tip of the emitter has a sharp shape, the electric field is concentrated at the tip of the emitter, so that electron emission efficiency can be improved.

Recently, as field emission devices requiring high current emitter characteristics, such as X-ray tubes, have been widely used throughout the industry, they have an advantageous structure for field emission, are easy to manufacture, and have excellent durability, and field emission including the same. Research on the device is being actively conducted.

An object of the present invention is to provide an emitter structure having an advantageous structure for field emission, easy fabrication, and excellent durability, and a field emission device including the same.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A field emission device according to embodiments of the present invention is a cathode electrode having a first surface and a second surface opposite to the first surface, wherein the cathode electrode is recessed from the first surface toward the second surface. including grooves; and emitter structures disposed in the grooves, the emitter structures including a core extending in a first direction and a conductive wire surrounding the core, wherein the grooves are arranged in a second direction crossing the first direction, The emitter structures may be located at different vertical levels.

In example embodiments, the first surface of the cathode may include a concave region recessed toward the second surface, and the grooves may be formed on the concave region.

In example embodiments, the concave region may have a constant height along the first direction.

In example embodiments, the grooves may include first and second grooves extending side by side in the first direction, and a bottom surface of the first groove may be inclined with respect to a bottom surface of the second groove. .

In some embodiments, a diameter of the emitter structure may be smaller than a depth of the groove.

According to embodiments, the target may further include a target facing the first surface and including a third surface inclined with respect to the first surface.

In some embodiments, the third surface may be parallel to the second direction.

In embodiments, the conductive wire may include a plurality of strings, and the strings may have ends protruding in a direction away from the second surface.

In some embodiments, the ends of the strings may extend in a direction perpendicular to the first direction.

In some embodiments, the conductive wire may include a plurality of strings coupled to each other.

In some embodiments, the conductive wire may include carbon nanotubes.

In some embodiments, the display may further include a target on the first surface and a gate structure between the cathode and the target, wherein the gate structure may include a plurality of conductive bars extending in the first direction.

A field emission device according to embodiments of the present invention is a cathode electrode having a first surface and a second surface opposite to the first surface, wherein the cathode electrode is recessed from the first surface toward the second surface. comprising a groove, the groove extending in a first direction; an emitter structure disposed within the groove; and

a target including a third surface facing the first surface, wherein the emitter structure includes a core extending in the first direction and a conductive wire surrounding the core, wherein the conductive wire connects the target may include strings having ends projecting toward them.

In some embodiments, the strings may include carbon nanotubes.

According to embodiments, the ends may be located at a level lower than the top of the inner wall of the groove.

In example embodiments, the ends of the strings may extend in a second direction perpendicular to the first direction.

In some embodiments, the display device may further include a gate structure disposed between the target and the cathode electrode and having an opening extending in the first direction.

According to embodiments of the present invention, it is possible to provide a field emission device that is easy to manufacture and has excellent durability.

1 is a perspective view schematically illustrating a field emission device according to embodiments of the present invention.
2 is a plan view of a field emission device according to embodiments of the present invention.
3 and 4 are cross-sectional views taken along lines II' and II-II' of FIG. 2, respectively.
5 is a perspective view illustrating an emitter structure according to embodiments of the present invention.
6 is an enlarged cross-sectional view illustrating a portion BB of FIG. 5 .
7 is an enlarged cross-sectional view of a portion BB of FIG.
8A and 8B are enlarged cross-sectional views illustrating an enlarged portion AA of FIG. 3 .
9 is a cross-sectional view of a field emission device according to embodiments of the present invention.
10 is a perspective view of a gate electrode in embodiments of the present invention.
11 to 14 are schematic perspective views for explaining a method of manufacturing an emitter structure according to embodiments of the present invention.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention pertains. It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, 'comprises' and/or 'comprising' refers to the presence of one or more other components, steps, operations and/or elements mentioned. or addition is not excluded.

Further, the embodiments described herein will be described with reference to cross-sectional and/or plan views, which are ideal illustrative views of the present invention. In the drawings, thicknesses of films and regions are exaggerated for effective description of technical content. Accordingly, the shape of the illustrative drawing may be modified due to manufacturing technology and/or tolerance. Accordingly, the embodiments of the present invention are not limited to the specific form shown, but also include changes in the form generated according to the manufacturing process. For example, the etched region shown at a right angle may be rounded or have a predetermined curvature. Accordingly, the regions illustrated in the drawings have schematic properties, and the shapes of the illustrated regions in the drawings are intended to illustrate specific shapes of regions of the device and not to limit the scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail below with reference to the drawings.

1 is a perspective view schematically illustrating a field emission device according to embodiments of the present invention.

Referring to FIG. 1 , a field emission device according to embodiments of the present invention may include a cathode electrode 100 , an emitter structure 200 , a gate structure 400 , and a target 300 . According to embodiments, the field emission device may be an X-ray source that emits X-rays using an electron beam.

The cathode electrode 100 and the emitter structure 200 may be electron sources electrically connected to each other. The cathode electrode 100 may include a first surface 100a and a second surface 100b opposite to the second surface 100b. The cathode electrode 100 may include grooves GR recessed from the first surface 100a toward the second surface 100b. The grooves GR may extend in the first direction D1 and may be arranged in the second direction D2 . The grooves GR may be located at different vertical levels from the second surface 100b of the cathode electrode 100 . The cathode electrode 100 may include a concave region CR recessed from the first surface 100a toward the second surface 100b. The grooves GR may be formed on the concave region CR.

The emitter structures 200 may be disposed in the grooves GR. The emitter structures 200 may be respectively disposed in the grooves GR arranged in the second direction D2 . The emitter structures 200 may come into contact with the inner surfaces of the grooves GR to be electrically connected to the cathode electrode 100 . The emitter structures 200 may include a core 210 extending in the first direction D1 and a conductive wire 220 surrounding the core 210 . The core 210 and the conductive wire 220 may include a conductive material. The conductive wire 220 may include, for example, carbon nanotubes.

The target 300 may be disposed on the first surface 100a of the cathode electrode 100 . The target 300 may receive the electron beam b1 from the cathode electrode 100 and the emitter structures 200 to output X-rays. According to an example, the target 300 may be a reflective target inclined with respect to the cathode electrode 100 . In other words, the field emission device according to embodiments of the present invention may be a reflective field emission device.

The gate structure 400 may be disposed between the cathode electrode 100 and the target 300 . An electric field may be formed between the gate structure 400 and the cathode electrode 100 , and an electron beam may be emitted from the emitter structure 200 . The gate structure 400 may focus the electron beam emitted from the emitter structure 200 on the surface of the target 300 .

2 is a plan view of a field emission device according to embodiments of the present invention. 3 and 4 are cross-sectional views taken along lines II' and II-II' of FIG. 2, respectively. 5 is a perspective view illustrating an emitter structure according to embodiments of the present invention. 6 is an enlarged cross-sectional view illustrating a portion BB of FIG. 5 .

2 to 4 , the cathode electrode 100 may have a first surface 100a and a second surface 100b that face each other in the third direction D3 . The first surface 100a of the cathode electrode 100 may include planar regions FR and a concave region CR between the planar regions FR. The flat regions FR may be located at an edge of the first surface 100a and may be parallel to the second surface 100b.

The concave region CR may have a shape recessed toward the second surface 100b. The concave region CR may have a predetermined curvature so that the emitter structures 200 arranged in the second direction D2 may be arranged in an arc shape. A vertical level of the concave region CR may decrease as it moves away from the flat regions FR.

The concave area CR may have a constant vertical level along the first direction D1 . For example, as shown in FIG. 4 , the concave region CR may have a constant vertical level when viewed in a cross-section of the cathode electrode 100 cut in the first direction D1 . The concave region CR may have different vertical levels along the second direction D2 . For example, as shown in FIG. 3 , the uppermost surface of the first surface 100a may be flat, and the concave region CR recessed from the uppermost surface toward the second surface 100b is in the second direction D2 . ) along which other vertical levels can vary. For example, the concave region CR may have the lowest vertical level in the central portion of the cathode electrode 100 in the second direction D2 . As the concave region CR is formed on the first surface 100a , the distance between the first surface 100a and the second surface 100b may vary in the second direction D2 . The cathode electrode 100 may include a metal, and may provide external power to the emitter structures 200 .

The grooves GR of the cathode electrode 100 may be formed in the concave region CR of the first surface 100a. The grooves GR may have a shape recessed from the first surface 100a toward the second surface 100b. In a plan view, the grooves GR may extend in a first direction D1 and may be arranged in a second direction D2 crossing the first direction D1 . The grooves GR may be located at different vertical levels. For example, the groove GR located at the center portion of the concave area CR in the second direction D2 may have a lower vertical level than the grooves GR located at the edge portion. The grooves GR may be located on a curved line having the center of curvature of the focus area FR located on the surface of the target 300 .

The emitter structures 200 may be disposed in each of the grooves GR. Each of the emitter structures 200 may extend in a first direction D1 and may be arranged in a second direction D2 crossing the first direction D1 . The emitter structures 200 may be parallel to each other. In addition, each of the emitter structures 200 may be parallel to the first surface 100a and the second surface 100b of the cathode electrode 100 . As the grooves GR are positioned at different vertical levels, the emitter structures 200 may be positioned at different vertical levels. The emitter structures 200 may be arranged in an arc shape. For example, the emitter structures 200 may be positioned on a curve with the focus area FR positioned on the surface of the target 300 as the center of curvature. Accordingly, the electron beam b1 generated from the emitter structures 200 may be focused in the second direction D2 and may not be focused in the first direction D1 .

The target 300 may be positioned on the first surface 100a of the cathode electrode 100 and may have a third surface 300a facing the first surface 100a. The third surface 300a of the target 300 may receive the electron beam b1 from the cathode electrode 100 to generate the electromagnetic wave b2 . The third surface 300a may be inclined with respect to the emitter structures 200 , and the electromagnetic wave b2 may travel in the first direction D1 . Specifically, the third surface 300a may be parallel to the second direction D2, which is the direction in which the emitter structures 200 are arranged, and the first direction ( D1) can intersect. Accordingly, the line width of the electromagnetic wave b2 traveling in the first direction D1 may be reduced. The electromagnetic wave b2 may be, for example, X-rays. A focus area FR in which the electron beam b1 is focused may be formed on the third surface 100a of the target 300 . As illustrated in FIG. 4 , the focus area FR may extend in the first direction D1 .

5 and 6 , the emitter structure 200 may include a core 210 extending in one direction and a conductive wire 220 surrounding the core. The core 210 may include a metal. The conductive wire 220 may include a plurality of strings 221 , 222 , and 223 . For example, the conductive wire 220 may include first to third strings 221 , 222 , and 223 coupled to each other. Each of the first to third strings 221 , 222 , and 223 may include a conductive material. The conductive material may be, for example, carbon nanotubes. The first to third strings 221 , 222 , and 223 may have first to third ends 231,232 and 233 protruding in a direction away from the core 210 , respectively. The first to third ends 231,232 and 233 may extend side by side. For example, the first to third ends 231,232 and 233 may extend in a direction perpendicular to the direction in which the core 210 extends.

7 is an enlarged cross-sectional view showing an enlarged portion BB of FIG.

Referring to FIG. 7 , the cathode electrode 100 may include a first groove 200a and a second groove GR2 arranged in the second direction D2 . The first groove GR1 and the second groove GR2 may be positioned at different vertical levels. For example, the first groove GR1 and the second groove GR2 have the same depth, but the bottom surface GRb of the first groove GR1 is at a lower level than the bottom surface GR2b of the second groove GR2. can be located in

The first emitter structure 200a may be disposed in the first groove GR1 , and the second emitter structure 200b may be disposed in the second groove GR2 . The first emitter structure 200a and the second emitter structure 200b may be positioned at different vertical levels.

Specifically, the first emitter structure 200a may include a first core 210a and a first conductive wire 220a surrounding the first core 210a. The first conductive wire 220a may include a plurality of strings, and first ends 230a of the plurality of strings may extend in a direction away from the first core 210a. The second emitter structure 200b may include a second core 210b and a second conductive wire 220b surrounding the second core 210b. The second conductive wire 220b may include a plurality of strings, and second ends 230b of the plurality of strings may extend in a direction away from the second core 210b. The first ends 230a may extend side by side in one direction. The second ends 230b may extend side by side in another direction crossing one direction.

8A and 8B are enlarged cross-sectional views illustrating an enlarged portion AA of FIG. 3 .

Referring to FIG. 8A , the depth of the groove GR may be the same as the thickness or diameter of the emitter structure 200 . The ends 230 of the conductive strings may protrude toward the target 300 , and may be positioned at the same or higher vertical level than the first surface 100a of the cathode electrode 100 .

Referring to FIG. 8B , the depth of the groove GR may be greater than the thickness or diameter of the emitter structure 200 . The ends 230 of the strings may be positioned at a lower vertical level than the first surface 100a of the cathode electrode 100 . That is, the ends 230 may be located at a level lower than the top of the inner wall of the groove GR. Accordingly, a portion of the electron beam emitted from the ends 230 of the strings may be blocked by the upper portion UP of the inner surface of the groove GR, and the electron beam focusing speed may be improved.

9 is a cross-sectional view of a field emission device according to embodiments of the present invention. 10 is a perspective view of a gate electrode in embodiments of the present invention.

9 and 10 , the gate structure 400 may have a plate shape. The gate structure 400 may include a depression BR curved toward the cathode electrode 100 . A plurality of openings OP passing through the gate structure 400 may be formed in the depression BR. The openings OP may overlap the emitter structures 200 , respectively. The electron beam b1 emitted from the emitter structures 200 may pass through the openings OP and be focused on the focus area FR of the target 300 .

11 to 14 are schematic perspective views for explaining a method of manufacturing an emitter structure according to embodiments of the present invention.

Referring to FIG. 11 , a conductive wire 220 according to embodiments of the present invention is manufactured. The conductive wire 220 may be formed using the plurality of strings 221 , 222 , 223 and the braiding unit 10 . The plurality of strings 221 , 222 , and 223 may be coupled to each other by the braiding unit 10 . Each of the plurality of strings 221 , 222 , and 223 may include carbon nanotubes. The conductive wire 220 formed by the braiding unit 10 may be wound around the bobbin 20 .

Referring to FIG. 12 , the conductive wire 220 wound around the bobbin 20 may be wound around the core 210 . The conductive wire 220 may be spirally wound along the outer circumferential surface of the core 210 .

Referring to FIG. 13 , after bonding the adhesive sheet 30 to the conductive wire 220 , the adhesive sheet 30 may be removed to protrude the ends 230 of the strings. Specifically, the plurality of strings constituting the conductive wire 220 may be cut by the adhesive force of the adhesive sheet 30 to have a plurality of ends 230 . The ends 230 may be formed on a portion of the surface of the conductive wire 220 to which the adhesive sheet 30 is attached. The end 230 may not be formed in another area of the surface of the conductive wire 220 to which the adhesive sheet 30 is not attached. The ends 230 may extend in a direction parallel to the direction in which the adhesive sheet 30 is peeled off.

According to embodiments, as shown in FIG. 14 , the adhesive sheet 30 may be provided attached to one surface of the support member 40 . The support member 40 may be attached to the adhesive sheet 30 to keep the adhesive sheet 30 from being bent while the adhesive sheet 30 is peeled off from the conductive wire 220 . The adhesive sheet 30 may be peeled off in a second direction D2 perpendicular to the first direction D1 in which the core 210 extends. Accordingly, the ends 230 of the strings may extend in a direction parallel to the second direction D2 .

As mentioned above, although embodiments of the present invention have been described with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can practice the present invention in other specific forms without changing its technical spirit or essential features. You will understand that there is Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (17)

a cathode electrode having a first face and a second face opposite the first face, the cathode electrode comprising grooves recessed from the first face toward the second face; and
and emitter structures disposed in the grooves, the emitter structures including a core extending in a first direction and a conductive wire surrounding the core,
the grooves are arranged in a second direction intersecting the first direction,
The emitter structures are positioned at different vertical levels. According to claim 1,
The first surface of the cathode electrode includes a concave region recessed toward the second surface, and the grooves are formed on the concave region. 3. The method of claim 2,
The concave region has a constant height along the first direction. According to claim 1,
The grooves include a first groove and a second groove extending side by side in the first direction,
A bottom surface of the first groove is inclined with respect to a bottom surface of the second groove. According to claim 1,
A field emission device in which a diameter of the emitter structure is small compared to a depth of the groove. According to claim 1,
The field emission device further comprising a target facing the first surface and including a third surface inclined with respect to the first surface. 7. The method of claim 6,
and the third surface is parallel to the second direction. According to claim 1,
The conductive wire includes a plurality of strings,
wherein the strings have ends protruding in a direction away from the second surface. 9. The method of claim 8,
The end portions of the strings extend in a direction perpendicular to the first direction. According to claim 1,
The conductive wire is a field emission device comprising a plurality of strings coupled to each other. According to claim 1,
The conductive wire is a field emission device comprising carbon nanotubes. According to claim 1,
Further comprising a target on the first surface and a gate structure between the cathode and the target,
The gate structure may include a plurality of conductive bars extending in the first direction. A cathode electrode having a first surface and a second surface opposite to the first surface, wherein the cathode electrode includes a groove recessed from the first surface toward the second surface, the groove being in a first direction extended to;
an emitter structure disposed within the groove; and
Including a target including a third surface facing the first surface,
The emitter structure includes a core extending in the first direction and a conductive wire surrounding the core,
wherein the conductive wire includes strings having ends projecting toward the target. 14. The method of claim 13,
The strings are field emission devices including carbon nanotubes. 14. The method of claim 13,
and the ends are located at a level lower than the top of the inner wall of the groove. 14. The method of claim 13,
The end portions of the strings extend in a second direction perpendicular to the first direction. 14. The method of claim 13
The field emission device further comprising a gate structure disposed between the target and the cathode electrode and having an opening extending in the first direction.

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