TWI309428B - Emission source having carbon nanotube - Google Patents

Description

1309428 IX. Description of the Invention: [Technical Field] The present invention relates to a field emission electron source, and more particularly to a field source for capturing rice carbon nanotubes. [Prior Art] Carbon Nanotube (CNT) is a new type of carbon material discovered by Japanese researcher iijima in 1991. Please see "Helical Microtubules of Graphitic Carbon", S. Iijim

Nature, vol. 354, p56 (1991). The carbon nanotubes have excellent conductivity, electrical conductivity, good chemical stability and large aspect ratio, and they are connected to the top surface area (the smaller the top surface area, the carbon emission from the field emission vacuum electron source) The field has the potential to be researched, and the carbon nanotubes are known to have the best field emission (i, 1,), which can transmit a very large current density of two or two life's, so it is very suitable as an excellent point electron. Electron microscopy ((6) one - m1c job,) and other equipment electronic _ Electron body. At present, it is the second of the two! The non-naked official formed in the conductive mechanical method and the original method mainly includes micro-mirror manipulation synthesis Too:: '^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In the field source: the electrical contact of the carbon nanotube electric matrix in the field source = the base, the carbon nanotubes and the guiding performance, good, not easy to fully exert the field of the carbon nanotubes 1309428, First, a metal catalyst is bonded to the conductive substrate, and then deposited too Electric fox discharge and other methods directly on the conductive substrate it ίίί 'This method is simple, the operation is simple, the carbon tube and the conductive = good contact. However, the combination of the carbon nanotube and the conductive button is good. The tube is easy to fall off or is pulled out by the electric field force, so that the source & bad H cannot control the nano carbon method, and the production is ΐίίΐ low efficiency and poor controllability. In addition, the tube is applied to the field emission electron source. It is often necessary to pass the current to the current. According to Fowler_Nordheim, the magnitude of the emission current is determined by the magnitude of the local electric field and as the previous == (eV), only with the metal crane The work function is equivalent. [Inventive content] The stomach is closely connected to the conductive matrix to combine the large-volume current of the carbon nanotube field emission electron source. - 兮 ϊΐ ΐΐ ΐΐ ΐΐ ΐΐ 发射 发射 发射 发射 发射 ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ ΐΐ The conductive substrate has a top, and the nano-hetero-hybrid electrode is electrically connected at the top of the body, and the other end: the surface-modifying layer: the field-emitting electron source further includes a surface-to === =于_Carbon repair (Iv) lower than the power level of the carbon nanotube of Yi ^ _ ~ ~ power, the surface of the surface modification layer covers the surface of the base SOLUTIONS entire nanocarbon f. 1309428

Training

The surface modification layer material is tantalum carbide or titanium carbide. The work is 3=2 work 4 3·32 electron volts (4) The escape of titanium carbide The thickness of the watch and the veneer is 1~1〇. The surface modification layer has a thickness of 5 nm. Ϊίίί: The ί2 part is a cone, a truncated cone or a column. The electrical matrix material can be selected from the group consisting of tungsten, gold, molybdenum or platinum. The carbon nanotube is a multi-walled carbon nanotube. x 米 A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A Cm2. In the nano-ejecting electron source, the nano carbon tube conductive matrix, 纟σ is tight, and the electrical connection is good. The surface modification layer can effectively reduce the carbon nanotube field emission original; Under the action of the same size of the emission electric field of the carbon nanotubes, the solar half has a higher electron emission density and emission i stream. [Embodiment] The present invention will be further described in conjunction with the accompanying drawings. Description.

Referring to FIG. 1 and FIG. 2, an embodiment of the present invention provides an electron source 1〇, the carbon nanotube field emission electron source f J an electric substrate 12, a carbon nanotube 14 and a surface modification layer 16. The ΐn electric material is made of, for example, crane, gold, molybdenum, platinum, or the like. For the convenience of measurement, a conductive substrate 丨2 is probed by an atomic force microscope 18 (AFM) with a gold layer on its surface. The conductive substrate 12 has a top portion 122 that is tapered. The first end 142 of the carbon nanotube 14 is electrically connected to the top portion 122 of the conductive substrate 12 and is attached to the conductive substrate 12 via a Van der Waals force. The second end 144 of the carbon nanotube 14 is away from the conductive base 8 along the top 122 of the conductive substrate 12.

Extending in the direction of 12, as the electron emission end of the field emission electron source ίο. In the present embodiment, the carbon nanotube 14 is a multi-walled carbon nanotube having a diameter ranging from 1 to 50 nm, preferably 15 nm, and a length ranging from 10 to 100 μm, preferably 50 μm. The surface modification layer 16 is infiltrated on the surface of the carbon nanotube 14 and covers at least the surface of the carbon nanotube 14 as the second end 144 of the electron-emitting end. The work function of the surface modification layer π material is lower than the work function of the carbon nanotubes 14. I. The electrons of the surface modification layer 16 are selected from the group consisting of titanium carbide or zirconium carbide, and the work function is 3.82 electron volts and 3.32 electron volts, respectively. The thickness of the surface modification layer 16 is 1 to 10 nm, preferably 5 nm. In this embodiment, the surface modification layer 16 may also cover the entire surface of the carbon nanotube 14 and the electrical substrate 12. Since the carbon nanotube 14 is infiltrated as the surface of the second end 144 of the electron-emitting end and covered with the surface modification layer 16 having a lower work function than the carbon nanotube 14, the carbon nanotube field is under the action of an electric field of the same magnitude. The emission current of the source 10 is significantly increased compared to the emission current of the previous nanotube field emission electron source. In this embodiment, the field emission electron current of the carbon nanotube field emission electron source using titanium carbide or carbonized hammer as the surface modification layer 16 can reach 100 microamperes, preferably 45 to 65 microamperes, and the current emission density can reach 5 7xl〇7A/cm2. Further, after measuring that the field emission current of the carbon nanotube field emission electron source of the present embodiment is 45 to 65 microamperes, the electron emission can be continuously emitted for 50,000 seconds, and thus the surface modification is performed. The nano-stone anti-tube emission electron source has a good service life. In addition, in the embodiment of the present invention, the conductive substrate 12 can also be implemented in other shapes according to actual needs. The top of the conductive substrate 12 may also have other shapes, two circles, a shape or a small column shape, and is not limited to a taper. The carbon nanotube field emission electron source 10 of the embodiment can be applied to field emission flat panel display, electric field, wave amplifier, X-ray source or electron beam lithography, etc. Please refer to FIG. 3 and FIG. 4, the present invention The embodiment provides a method for emitting electron source from a carbon nanotube field, which is mainly composed of the following steps. 'τ〃, (1) provides two conductive substrates 32 and 42' which respectively have tapered tops 9 1309428 portions 322 and 422. The two tops 322 and 422 are disposed opposite each other and spaced apart by a certain distance. A small amount of carbon nanotube-containing solution 5{) was pipetted between the two tops 322 and 422, and the two were co-impregnated into the solution. (1) An alternating voltage is applied to the two conductive substrates 32 and 42 until a carbon nanotube is assembled between the top portions 322 and 422. (iii) cutting off the current between the two conductive substrates 32 and 42 and removing the solution 5 上 between the two conductive substrates opposite the tops 322 and 422. (d) separating the two opposite conductive substrates 32 and 42 such that the carbon tube is attached to at least the top of the conductive substrate to form a nanocarbon emission electron source. (5) Modifying the surface of the carbon nanotube to make the field emission electron source have a lower work function. In the embodiment, the conductive substrates 32 and 42 are both surface-gold-plated atomic force microscope probes. The conductive substrates 32 and 42 can also be made of other conductive materials, such as tungsten, gold, molybdenum, platinum, etc. Actual design is required. The tops 322 and 422 can also be shaped as ^; for example, a truncated cone shape or a small column shape, not limited to a taper. In addition, when the top portion 322 and the end surface are plane, the nano carbon is assembled. The most part of the process is set opposite to the end face of 422, such as the edge of the two end faces. The distance between the two tops 322 and 422 should be set according to the length of the carbon nanotube used. It is best to use a carbon nanotube containing a solution of the carbon nanotubes in the vicinity of the solution of the carbon nanotubes with isopropyl alcohol as the six doses of 'the carbon nanotubes by means of ultrasonic vibration. To make the solution 5G Huan, a small amount of carbon nanotubes can also be added to the tube synthesized by low pressure chemical vapor deposition (L: pr: _ Chemical Vapor D-S0Siti0n, LP-CVD). Of course, solution 50 can also be prepared by other methods. , stabilizer or increase the point _ filter, etc.; to 1309428., stable nai The carbon nanotube solution is suitable, and it is not necessary to be limited to the specific examples. In addition, the concentration of the solution 50 may affect the number of the carbon nanotubes assembled in the later stage. Generally, the concentration of the solution 50 is larger, and it is easier to assemble multiple roots in the later stage. Nano carbon tube. Therefore, according to the actual needs of the concentration of 5 溶液 solution, such as g to assemble a carbon nanotube, you should try to reduce the concentration of the solution 5 。. Otherwise 1 can also adjust the concentration of the solution 50, To some extent, the number of carbon nanotubes controlled by the carbon nanotubes is controlled. In order to avoid the mutual interference between the carbon nanotubes when emitting electrons, this embodiment only assembles a carbon nanotube on the conductive substrate. The solution 50 can be made by a straw. A pipette, syringe or other suitable device is removed and applied between the tops 322 and 422 of the conductive substrate. The applied solution 50 should not be so excessive that the two top portions 322 and 422 can be immersed together in the same solution 50. Alternatively, the two tops 322 and 422 can be directly immersed in a solution of less than 1 in a container such as a beaker. The solution 5 needs to be removed only by a pipette, a pipette, a syringe or the like. Device By shifting T, when the two tops 322 and 422 are directly immersed in a small amount of the solution 50 contained in a container such as a beaker, it is only necessary to remove the two tops 322 and 422 from the solution 50. In addition, in step (2) The peak value of the alternating voltage is preferably within 10 volts and the frequency is between 1 and 1 megahertz. This embodiment is mainly based on the principle of two-dimensional electrophoresis: in the alternating electric field, the nanometer in the solution 50 Moving toward the direction of the electric field strength, and finally moving to the area where the top of the two fields 322 and 422 are the largest, and is adsorbed to the two tops 322 and 422. Thereafter, the carbon nanotubes rely on the two tops 322 and 422. The van der Waals force is firmly adsorbed on the surfaces of the tops 322 and 422. 'Generally, the power-on time is only a few seconds to tens of seconds, so the assembly method is short and efficient. In the step (5), the modification method of the surface of the carbon nanotube further comprises the following steps: First, forming a metal layer on the surface of the carbon nanotube, the metal layer is selected to have a lower work function. Point and surface with carbon nanotubes 11 1309428

A material with good wettability. In this embodiment, the metal layer is selected from titanium metal or metal. The method of forming the metal layer comprises forming a metal layer having a thickness of 1 to 10 nm on the surface of the carbon nanotube by magnetron sputtering or electron beam evaporation. Preferably, in this embodiment, a metal junction layer or a metal titanium layer having a thickness of 5 nm is formed by magnetron sputtering on the surface of the carbon nanotube and the conductive substrate to which the carbon nanotube is attached. Then, in a vacuum environment, a higher current is emitted on the conductive substrate to which the carbon nanotube is attached to emit electrons for a predetermined time, so that the metal layer on the surface of the carbon nanotube is chemically reacted with the carbon nanotube to be carbonized. The surface modification layer is formed: the modification of the surface of the carbon nanotube is completed. In this embodiment, the power-on time is from 30 minutes to 2 hours, preferably 30 minutes. If the time is too = the metal ^ can not be completely carbonized, the time is too long will affect the service life of the carbon nanotubes. Preferably, the surface modifying layer formed is titanium oxide or a oxidized stagger layer, and the process of tempering the surface metal layer of the carbon nanotube can also be achieved by annealing. Those skilled in the art should understand that since the carbon nanotubes mainly emit electrons through their ends, it is actually only necessary to control the shaft-metal layer to cover the electricity: the end, and then further carbonization to modify the carbon nanotubes. The monitoring system is used for real-time monitoring and immediate adjustment of the entire carbon nanotube assembly process to improve the yield. For example, the two tops 322 and 422 of the carbon tube are in an open circuit, and the entire assembly process can be automated. Monitoring, avoiding deviations from 1309428 ίίϊ or semi-manual operation, and nanocarbon in chemical vapor deposition. Uncontrollable, improve production efficiency, enhance controllability, and at the same time, the production equipment that is hoisted has low production cost and is suitable for mass production. The embodiment of the present invention can further manufacture a plurality of carbon nanotubes, if f, a nano-carbon f field array, as shown in the flat field emission display ^ as an electron emission source. The cathode electrode layer on which one of the plurality of conductive substrates is formed may be directly immersed in a solution towel containing a carbon nanotube. By applying a voltage to

Ϊΐ 极 极 极 另 另 另 另 另 可 可 可 可 可 可 可 可 可 可 可 可 可 可 可 可卩 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = ...See Figure 5. As can be seen from the scanning electron micrograph, the nanocarbon officer is assembled at the tip of the force microscope and has been straightened. It is caused by the assembly of the carbon nanotubes in the two carbons. The electric field is polarized to produce galvanic couples. The distance between the two ends is charged. The electric field has its force—the component along its axial direction. The carbon tube is stretched and straightened. The remaining enthalpy is measured. 'This example passes through titanium carbide or tantalum carbide.

The electric field source of the official field emission electron source is about 1丄2 v/p (volts/micron) and 105 v//zm, respectively. The low-carbon carbon field emission electron source (5 V/M) field emission electron source field emission The current is also increased by four (A). In addition, after the =^ stone reversal or carbonization error modification, the carbon nanotube field emission electron source has a pull-out force of 35 2 nN for the deer opening electric field strength, respectively (Nano 1 and 26· 2nN, lower than the nano-carbon nanotube field emission before modification (54·4nN). Therefore, the modified carbon nanotube is too flat, the carbon tube is tightly combined with the conductive matrix, and the electrical connection is good. The assembly method of the electron source of the carbon nanotube field emission in the present invention is several tens of seconds, which is short in time and high in efficiency. Moreover, the entire production equipment required at the same time is simple, and the production cost is: Yang appropriate mold 13 1309428 i; ίThe effect of lowering the nanometer, the emission field of the electron field is emitted by the tube field. It will be understood by those skilled in the art that the present invention can be passed through other existing methods such as the longitudinal reduction method. Nai #carbon tube formed at the electron emission end of the carbon nanotubes has a low ^

The revision also increases the carbon nanotube field and sends Weizi (4) the launching power. 2. The hairpin has been in compliance with the requirements of the invention patent, and the patent application is only in accordance with the law. However, the above is only a preferred embodiment of the present invention. I can't use this _ this patent application scope. Any person skilled in the art will be able to use the equivalent modifications of the spirit of the present invention or the following patent application. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a field emission electron source of a carbon nanotube according to an embodiment of the present invention;

FIG. 3 is a longitudinal cross-sectional view of the π portion of FIG. 1; FIG. 3 is a schematic diagram showing the steps of a method for emitting electron source of a carbon nanotube field according to an embodiment of the present invention; FIG. 4 is a view of assembling a carbon nanotube of the embodiment of the present invention. A schematic diagram of a field emission electron source; ', FIG. 5 is a micrograph of a scanning electron microscope of a carbon nanotube field emission electron source according to an embodiment of the present invention. Figure 6 is a schematic diagram showing the comparison of current-voltage curves before and after modification of the carbon nanotube field emission electron source according to an embodiment of the present invention. [Main component symbol description] Nano carbon tube field emission electron source 1〇

Conductive substrate 12 H 14

1309428 Top 122, 322, 422 Carbon nanotubes 14 First end 142 Second end 144 Surface finish 16 Atomic force microscope 18 Solution 50 AC voltage 60 15

Claims (1)

: 1309428 , the patent application scope of the nano-tube field emission electron source, comprising: a conductive substrate, the conductive substrate has a top; and a carbon nanotube, one end of the carbon nanotube and the top of the conductive substrate Constructed, the other end extending outward along the top direction of the conductive substrate; the improvement is that the carbon nanotube field emission electron source further comprises a surface modification layer, the surface modification layer is uniformly distributed and infiltrated into the nano carbon two The surface, and covering at least one end of the carbon nanotube extending outward, the work function of the 2 decorative layer is lower than the work function of the carbon nanotube. Fu: Please use the carbon nanotube field emission electron source described in item 1 of the patent scope, ^. The surface modification layer covers the entire surface of the carbon nanotube and the conductive substrate. • The carbon nanotube field emission electron source described in claim 1 is 4, and the surface modification layer material is tantalum carbide or titanium carbide. In the carbon nanotube field emission electron source described in Item 3 of the patent scope, the work function of the carbonization junction is 3.32 eV, and the work function of the broken titanium is 3.82 eV. The nano carbon tube field emission electron source described in Fan Cai, 6: L The thickness of the surface modification layer is 1 to nanometer. The carbon nanotube field emission electron source described in item 5 of the track, 7 1 a, has a surface modification layer thickness of 5 nm. Applying the carbon nanotube field emission electron source described in item _i, 8/, if the top of the electric substrate is tapered, truncated or cylindrical. Among them, the electron source of the carbon nanotube field emitted by the <1,7 item, wherein the nanocarbon field emission electron source described in the first item is not multi-walled carbon nanotube. ^ Source, its 9th position, the carbon nanotube field emission electron Uo nanometer, the length of the carbon tube is 10~100 microns, and the diameter is 16 1309428 ψ * 11. As described in claim 10 The carbon nanotube field emits an electron source, wherein the carbon nanotube has a length of 50 microns and a diameter of 15 nm. The field emission current density is 5. 7xl07A/, the field emission current of the field of the carbon nanotube field emission electron source is 100 microamperes, and the field emission current density is 5. 7xl07A/ Cm2. 17