TW200407261A - A method for trimming an array of carbon nanotubes - Google Patents

Abstract

The invention provides a method for trimming an array of carbon nanotubes. The method includes the steps of: providing an aligned carbon nanotubes array, providing a pulsed laser source, orienting the incident pulsed laser in a given direction, exposing an upper portion of carbon nanotubes array to radiation of the pulsed laser. The carbon nanotubes of the upper portion of the carbon nanotubes array are thus evaporated and shaped into a plurality of sharpening tips. The resultant carbon nanotubes array has a lower threshold of emission field, and enhanced field emission performance.

Description

200407261 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a method for trimming nanomaterials, and particularly to a method for adjusting the shape and direction of one-dimensional nanomaterials. [Previous technology] Nanomaterials are a class of new materials with special electrical, magnetic, optical, thermal, mechanical, or chemical properties. They have extremely important application prospects in the field of mesoscopic and nanodevice development. The one-dimensional nanometer material has a nanometer scale in a two-dimensional direction and the length direction is much larger than the two-dimensional direction. In 1970, the Japanese scientist I i ima discovered carbon nanotubes, see "Helical microtubules of graphitic carbon", S Iijima,

Mature, vol. 354, p 56 (1991). The diameter of a typical carbon nanotube is generally several nanometers to tens of nanometers, and the length is generally in the order of micrometers. "Its potential applications have been widely concerned, especially in the field of electronics." ^ Carbon nanotubes have extremely high electrical conductivity Excellent, and it has a tip surface area that is close to the theoretical limit (the smaller the tip surface area, the more concentrated the local electric field). Therefore, the carbon nanotube system is known as the best field emission material. Emission voltage (less than 100 volts), which can transmit extremely large current density, and the current is extremely stable, so it is suitable for the field emission display. The method of growing the dazzling stone anti-nano tube, including the thunder method and chemical gas With phase deposition and the like, the obtained carbon flattening has certain defects. For example, the powder reminder is easy to be intertwined as a% emitting material, so it is evenly distributed, the emission point is small, and the emission current is dense due to prison. Page 5 200407261 V. Description of the invention (2) It is difficult to increase the degree and limit carbon nanometer Field emission efficiency of the tube; although the carbon nanotube array generated by the chemical vapor phase method is vertically ordered and highly uniform, the excessively high density of the gamma carbon nanotube will cause a strong electric field between the carbon nanotubes. In addition, metal particles that play a catalytic role may also remain on the tips of carbon nanotubes. If not removed, it will affect electron emission. Please refer to the tenth figure. The Chinese publication No. jCNl 2 92354A, which was published on April 25, 2001, discloses a method for opening the carbon nanotubes and purifying the carbon nanotubes. The carbon nanotubes 112 are first placed in Oriented vertically on the substrate 110, and then adjust the positions of the bracket 146 and the laser emitter 144 so that the laser gun 142 is aligned with the carbon nanotube at a predetermined height and parallel to the surface of the substrate 110 to emit the laser beam 140, thereby Truncate carbon nanotube] 12. However, this method requires precise adjustment. The position of the emission point of the beam 140 needs to be adjusted separately for the carbon nanotubes of different heights to be trimmed. # 1 increases the difficulty; and the truncated carbon nanotube distance is extremely small. The density is large, and there is a strong electric field shielding effect between carbon nanotubes. 'Improve the electric field threshold of the overall field emission. Other one-dimensional nanomaterials, such as nanowires and nanorods, are also used as field emission materials. They also face such problems. Therefore, a simple and easy method is provided to improve the carbon nanotubes, nanowires, and nanometers. Field emission performance of one-dimensional nanomaterials such as rods is really necessary. [Content] The object of the present invention is to provide a method for adjusting the shape and direction of a one-dimensional nanomaterial, thereby improving its field emission performance. Another object of the present invention is to provide a method for cleaning the surface of one-dimensional nanomaterials. 200407261 V. Description of the invention (3) ----- The present invention provides a method for adjusting the shape and direction of a one-dimensional nanometer material =: = providing a substrate having a-flat surface; one-dimensional growth is directly grown on the substrate surface Nano material array or a material array transplanted to the surface of the substrate, wherein the one-dimensional nano-two /, a surface with parallel substrate surface; providing a laser Turn on the laser emission source, and make the laser beam illuminate the surface of the one-dimensional nanometer material array. Compared with the prior art, the method provided by the present invention has simple steps and is easy to implement, which can improve the field emission performance of one-dimensional nanomaterials. [Embodiment] Please refer to the first figure, which is a flowchart of the method of the present invention for adjusting the shape and direction of carbon nanotubes, including the following steps: Step 1 is to provide a substrate, which can be glass, silicon Or a metal substrate to support the carbon nanotube; step 2 is to place the carbon nanotube on the substrate, wherein the carbon nanotube can be grown directly on a glass, silicon or metal substrate by chemical vapor deposition, or The prepared carbon nano tube array is transplanted to the plate; f Step 3 is to provide a laser beam emission source, which is prepared to emit laser beam to illuminate the nano tube array; Step 4 is to adjust the laser beam emission The emission angle of the source is to adjust the orientation angle of the laser beam emission source relative to the carbon nanotube array substrate. Step 5 is to turn on the laser beam emission source to launch the laser projectile carbon gain meter array. So far, in order to prevent excessive laser beam from damaging the stability of the connection between the broken nano tube and the substrate, the intensity and pulse time of the laser can be adjusted;

5. Description of the invention (4) Step 6 is to turn off the laser emission source. Please refer to the second figure, the third figure, and the fourth figure together, which are specific processes for adjusting the shape and direction of the carbon nanotube array according to the first embodiment of the method of the present invention. First, a substrate 10 is provided and a carbon nanotube array T 2 is directly grown on the substrate 10 or a carbon nanotube array i 2 is transplanted onto the substrate 10 by a transplantation method: The substrate material may be glass, stone or Metal and its oxides. The initial M nanotube array is shown in the second figure. The carbon nanotube array M includes a plurality of carbon nanotubes (not labeled) perpendicular to the substrate 10. The carbon nanotubes can be chemically The vapor deposition method directly grows on the substrate 10, or it can be prepared and then moved to the substrate 10. Generally, the prepared carbon nanotube array has a thin layer of carbon on the surface with disordered orientation, uneven diameter, and poor shape. The thickness of the thin tube is about 2 microns or less. The top of the carbon nanotube may also have catalytic metal particles. Then, the laser beam 14 is incident perpendicularly to the carbon nanotube array 12 The surface, that is, the incident direction of the laser beam 14 is perpendicular to the substrate surface. Among them, the laser beam 14 may be a pulsed laser. The irradiation process should be avoided in an atmosphere with too high oxygen content. Since carbon nanotubes are easily ablated even at room temperature in a pure oxygen atmosphere, It can be selected to be carried out at room temperature under nitrogen, hydrogen or some oxygen-containing gas or mixed gas environment. In addition, it is difficult to form a tip when the ambient gas pressure is less than 0.2 atmosphere, so the gas pressure should be greater than 0.2 The atmospheric pressure is preferably 0. 5, 1 .5 atm. In this embodiment, an air atmosphere is used, and the pressure of the air is 1 atmosphere of ink. At room temperature, a carbon dioxide tube array is irradiated with a pulsed laser beam emitted by a 308 nm excimer laser. Among them, the single pulse work of a pulsed laser beam 200407261 V. Description of the invention (5) The rate is 150 mJ, the irradiation area is 0.5 cm2, and 20 pulses are irradiated. The pulsed laser burns off the thin layer on the surface of the carbon nanotube array, which can remove the remaining metal particles and open the top of the carbon nanotube. At the same time, the surface of the carbon nanotube is tens of microns down due to the surface. The gas between them is heated and instantly expands, sowing the carbon nanotubes next to it, forming a needle-like structure of varying sizes. As shown in the fourth figure, after repeated repeated pulsed laser irradiation, the carbon nanotube array i 2 gradually forms a plurality of tapered tips 5 of various sizes, and the direction of the tip 15 is vertically upward. That is, the direction in which the laser beam 4 is incident. After the predetermined tip shape is formed, the laser irradiation is stopped. In order to avoid the excessive expansion of the gas between the carbon nanotubes from damaging the bonding strength between the carbon nanotube array 12 and the substrate 10, the intensity of the pulsed laser, the pulse time and the number of irradiations can be adjusted, and a weaker laser is used. 3. Multiple irradiations can achieve the same effect as strong lasers and fewer irradiations, but it can protect the combination of the carbon nanotube array 12 and the substrate 10 firmly from falling off. Please refer to the fourth figure again. The method of the present invention treats the carbon nanotube tube array laser tip 15 obtained by laser irradiation, which is composed of tens to thousands of carbon nanotubes of varying lengths. The height of 15 is relatively small compared with the height of the carbon nanotube array before processing. After laser irradiation, the top of the carbon nanotube with a tip 5 has an opening at the top, which is conducive to the formation of effective emission under a lower electric field. There is a large distance between the tips to avoid mutual electric field shielding effects, thereby improving the -field emission effect. The seventh and eighth figures are the scanning electron microscope (SEM) images of the broken nanometer tube array obtained before and after the first embodiment of the present invention, respectively.

200407261 V. Description of the invention (6) It was found that the treated carbon nano tube array was cylindrical at the lower end and tapered at the top, and the needle-shaped tip of the tube was: 乂, the diameter of the lower cylindrical was 〖〇 ^ ^ Typical depth is 30 micrometers and 10 test meters' with a cone-shaped gigameter at the top. There is a significantly larger distance between adjacent tips. For the laser image of the second embodiment of the method of the present invention, the following steps are used: f image 'its I prepared carbon nanometers are the same as' the difference is that the i pulse is adjusted; body :: ==-embodiment phase ο upper right Inclined shot II: The two-cornered angle pulse pulse is pre-tilted from the upper right of the substrate u ..., the angle of the surface of the shooting anti-nano tube array 12 and the density of the carbon nanotube array 12 =: The larger the tilt, the more n = The greater the body pressure, the greater the tilt angle X field angle is greater than taking a large tilt angle, it will be difficult to form + 嫂. -When the angle is less than 35 degrees, it is easy to form an effective emission: the tip, greater than 35 f% forms a wave-like undulating shape. In this embodiment, a new carbon nanotube array consisting of a tip t5 is turned off after 20 pulses are irradiated. The tip 15 is inclined = two-shaped, and the tip 15 faces the pulsed laser. The direction in which the beam 4 enters, that is, the nano tube array 12 is tilted by 3 °. Seen from the cross-sectional view of the needle center, == obliquely, the oblique direction is consistent with the laser incident direction. The other side is kept vertical. The ninth figure is a laser irradiation treatment of the second embodiment of the present invention; It can be seen in the figure that the carbon nanotube array formed a needle-shaped tip with a clear pitch after the rationale, and the tip has a tilt. Page 10 200407261 V. Description of the invention (Ό, the angle of the tilt and the shape of the laser incident, the top shows Conical, tip diameter of 10 microns' top cone straight through the method of the present invention can be used to process line, nano-rods and other one-dimensional nanomaterials such as shot intensity, pulse, number of shots, or the ring described in the present invention A patent application has been filed. However, the above examples, since those who cannot limit the skills of this case, rely on the essence of the present invention should be covered by the following patent scope of application. The depth of a pear is tens of nanometers. The author only applies to the inner god ’s work, the tip is 30 micron. The tube, but also different materials, can reach the bottom of the equivalent end of the patent of this invention, and the lower part can be used for processing and adjustment. The same effect elements, Ming preferred. Whether it cooked modified or variant has a cylindrical cylindrical lightning pulse fruit processing nm. Then note the case of the embodiment according to the law, are

Page 11 200407261 Brief description of the drawings [Simplified description of the drawings] The first diagram is a flow chart of the method of the present invention for adjusting a carbon nanotube. The second diagram of the gt shape and direction is the schematic diagram of the first solid shape and the initial direction of the carbon nanotube array in the method of the present invention. The carbon nanotube array is irradiated with the laser beam during the orientation and direction: the whole second nano tube shape is shown in the fourth diagram of the method of the present invention, which is used to adjust the shape and orientation of the carbon nanotubes obtained after irradiation. " Anti-s-shaped intent. Sectional view of the shape of the water-repellent s array. The fifth figure is a schematic view of a tube array used in the second embodiment of the method of the present invention. Laser beam irradiates carbon nanometers

Figure 6 is a schematic cross-sectional view of the shape of a rabbit nanotube array obtained after laser beam irradiation according to the second embodiment of the method of the present invention. The seventh figure is a SEM image of a carbon nanotube array without laser irradiation in the first embodiment of the method of the present invention. "The eighth figure is an SEM image of a carbon nanotube array after laser irradiation in the first embodiment of the method of the present invention.

The ninth figure is a SEM image of a carbon nanotube array after laser irradiation in the second embodiment of the method of the present invention. The tenth 5l is a schematic diagram of the prior art carbon nano tube load breaking method. [Description of main component symbols] Substrate 10 Laser beam 14 Carbon nanotube array 12 Tip 15

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Claims (1)

200407261 1. A method for trimming the direction and shape of a one-dimensional nanometer material, which includes the steps of: providing on the one-dimensional nanometer material array; providing an opening of the array; 3. As in the applied shape 4. As in the applied shape 5. As in the applied shape nano fiber 6. As in the applied shape array 7. As in the applied shape one of the substrates' has a flat surface; one-dimensional growth directly on the surface A nano material array or a row is transplanted to the surface of the substrate, wherein the one-dimensional nano material has a surface parallel to the surface of the substrate; a laser emission source; a source 'emits a laser beam to irradiate the above-mentioned one-dimensional nano material substrate surface material Bursts of laser radiation on the surface. Patent Fan Method, Patent Fan Method, Patent Fan Method, Patent Fan Method, Patent Material Fan Method, Surface. The patented method includes adjusting the direction of the one-dimensional nanomaterial and the array of one-dimensional nanomaterial described in item 1 perpendicular to the substrate, and adjusting the direction of the one-dimensional nanomaterial described in item 1 and the laser. Beam system pulsed laser. . Adjust the direction of the one-dimensional nanomaterial described in item 1 and wherein the one-dimensional nanomaterial is a carbon nanotube. The adjusted one-dimensional nanometer material described in item 1 of the mouth circle, wherein the one-dimensional nanometer material is nanowire, too; * ^^ rice rod or the adjusted one-dimensional nanometer material described in item 1 The laser beam was incident perpendicularly to the one-way and quasi-nano material. The adjustment described in item 1. Page 13 200407261 6. Scope of patent application The surface of the array. 8. The method for adjusting the direction and shape of a one-dimensional nanomaterial as described in item 7 of the scope of the patent application, wherein the laser beam and the one-dimensional nanomaterial array form an angle of 0 ° to 35 ° in the longitudinal direction. 9. The method for adjusting the direction and shape of a one-dimensional nanomaterial as described in item 1 of the scope of the patent application, wherein the method is performed in one or more mixed gases of air, nitrogen, hydrogen, and a gas containing a portion of oxygen. 10. The method for adjusting the direction and shape of a one-dimensional nanomaterial as described in item 9 of the scope of the patent application, wherein the pressure formed by the gas is (K 2 to 2 atm. 11. The method for adjusting the direction and shape of a one-dimensional nanomaterial as described above, wherein the pressure formed by the gas is in the range of 0.5 to 1.5 atm. 1 2. The direction of one-dimensional nanomaterial is adjusted as described in item 11 of the scope of patent application and A method of shape, wherein the air pressure is 1 atmosphere. 1 3. A method of adjusting the direction and shape of a one-dimensional nano material, comprising the steps of: providing a one-dimensional nano material array having a surface; providing a laser Adjust the emission angle of the laser emission source. Turn on the laser emission source and emit the laser beam to illuminate the surface of the one-dimensional nanometer material array. 1 4. Adjust as described in item 13 of the scope of patent application. A method for the direction and shape of a material of nanometer, wherein the laser beam is a pulsed laser. 1 5. Adjust the direction of a material of nanometer as described in item 13 of the scope of patent application. Page 14 200407261 6. Method of applying for patent scope and shape, wherein the one-dimensional nano material is carbon nano tube, nano wire, nano rod or nano fiber material. 16. The method for adjusting the direction and shape of a one-dimensional nano material as described in item 13 of the scope of the patent application, wherein the emission angle of the laser emission source is greater than 0 degrees and less than 35 degrees. 1 7. The method for adjusting the direction and shape of a one-dimensional nanomaterial as described in item 13 of the scope of the patent application, wherein the method is performed in one or more mixed gases of air, nitrogen, hydrogen, and a gas containing some oxygen . 1 8. The method for adjusting the direction and shape of a one-dimensional nanomaterial as described in item 17 of the scope of the patent application, wherein the gas pressure is 0.2 to 2 atmospheres. 19. The method for adjusting the direction and shape of a one-dimensional nano material as described in item 18 of the scope of the patent application, wherein the gas pressure is within the range of 0.5 to 1.5 atmospheric pressure. 20. The method for adjusting the direction and shape of a one-dimensional nanomaterial as described in item 19 of the scope of patent application, wherein the air pressure is 1 atmosphere. Page 15