CN104882346A - Method for preparing field emission cathode of carbon nanotube array coated with carbon nanoparticles - Google Patents

Abstract

The invention discloses a preparation method of a carbon nanotube array field emission cathode coated with carbon nanoparticle, and belongs to the field of preparation and application of nanomaterials. It mainly includes the following preparation processes: preparing carbon nanotube arrays on silicon single wafers by thermal chemical vapor deposition; using radio frequency technology to generate hydrogen plasma to process carbon nanotube arrays at low power for a long time; Carbon nanotube arrays coated with carbon nanoparticles act as cathodes to assemble field electron emitters. The carbon nanotube array coated with carbon nanoparticle prepared by this method has a particle diameter of generally 15-30 nanometers, and it has a lower turn-on field and threshold field and a better field emission cathode material than a simple carbon nanotube array. The field emission stability has high application value.

Description

A preparation method of carbon nanotube array field emission cathode coated with carbon nanoparticles

This invention was funded by the National Natural Science Foundation of China-Youth Fund Project (Project No. 51302187). This work was supported by the Key Project of Tianjin Applied Basic and Frontier Technology Research Program (Project No. 14JCZDJC32100).

technical field

The invention belongs to the technical field of preparation and application of nanometer materials, and relates to a method for preparing a nanometer material with a unique structure by using low-power plasma technology and using it for field electron emission devices.

Background technique

The development of high-performance field emission cathode materials has been a research hotspot in recent years. These materials have good application prospects in many fields such as new generation vacuum tubes, X-ray tubes, electron guns for electron microscopy, and field emission flat panel displays. Carbon nanotubes are an ideal field emission cathode material. First, carbon nanotubes are mainly composed of ^SP2 hybridized carbon atoms, which have very good electrical conductivity. Secondly, carbon nanotubes also have a huge length-to-diameter ratio that is incomparable to many one-dimensional and two-dimensional nanomaterials, enabling electrons to obtain a large local electric field intensity (that is, a large field enhancement factor) at their field emission points, thereby It is easier to overcome the surface barrier of carbon nanotubes (that is, the work function) and escape into the vacuum, which is very beneficial to obtain low turn-on field and threshold field and large field emission current density. Compared with graphene-based field emission cathode materials that have received widespread attention in recent years, carbon nanotube-based field emission cathodes have a lower turn-on field, generally less than 2 V/μm, while the turn-on field of graphene is often Greater than 4 V/μm. This feature of low turn-on field is very important in practical applications, and can greatly reduce the operating voltage of the field emission cathode. It can be seen that further reducing the working electric field of the carbon nanotube field emission cathode material and obtaining a larger field emission current density will increase its practical value. However, due to the influence of its own geometric shape, the field electron emission of carbon nanotubes mainly occurs at the tip (sharper) with a smaller curvature radius, and there is almost no field electron emission on the flat tube wall, that is, the effect of the external electric field can only A sufficiently large local electric field is formed at the tip of the carbon nanotube. Under the action of this large local electric field, the electrons can overcome the surface potential barrier of the carbon nanotube and escape, but due to the insufficient strength of the local electric field on the tube wall, the field electrons and cannot escape. The characteristic of carbon nanotubes that only emit field electrons at the tip greatly reduces the number of effective field emission points, which is not conducive to field electron emission with large current density. Therefore, if some means can be used to make carbon nanotubes have more new effective field emission points besides the tip, the turn-on field and threshold field of carbon nanotubes can be reduced to a certain extent, and their field emission can be increased. current density.

Due to its one-dimensional characteristics, the field emission cathode based on carbon nanotubes has a smaller heat dissipation surface than graphene, a two-dimensional material, and is more susceptible to the influence of Joule heat during the field emission process, especially in the case of high current density field emission. Under certain circumstances, a part of the effective field emission points will be burned due to the large accumulation of Joule heat, which will reduce the field electron emission capability of the cathode material to a certain extent, that is, compared with the two-dimensional nanomaterials such as graphene, carbon nanotubes, Its field emission stability is poor, which will greatly shorten the service life of carbon nanotube-based field emission cathodes in practical applications. Studies have shown that carbon nanotubes with rich defects and unstable contacts can be effectively removed by plasma treatment of carbon nanotubes, and these carbon nanotubes are the main factors for the decrease of field emission current during the field emission process. The removal will undoubtedly improve the field emission stability of the field emission cathode material. In addition, long-time high-temperature annealing can also reduce the number of defect-rich carbon nanotubes to a certain extent, so that the field emission cathode based on carbon nanotubes has better field emission stability.

It can be seen that by introducing technical means to process carbon nanotubes to make them have more effective field emission points, in order to reduce their turn-on field and threshold field, increase their field emission current density, and this technical means can also improve to a certain extent The field emission stability will make the prepared carbon nanotube-based field emission cathode material have higher application value.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of existing field emission cathodes based on carbon nanotubes that the number of effective field emission points is small, the opening field and threshold field are relatively high, the field emission current density is relatively low, and the field emission stability is not good. A simple low-power plasma process is used to process carbon nanotube arrays, and a carbon nanotube-based field emission cathode material with low turn-on field and threshold field, high field emission current density, and good field emission stability is provided.

The object of the present invention is achieved through the following measures:

A method for preparing a carbon nanotube array field emission cathode coated with carbon nanoparticles, characterized in that the radio frequency technology is used to generate hydrogen plasma to treat the carbon nanotube array prepared by thermal chemical vapor deposition, and the radio frequency power is adjusted to 30-50W , the substrate temperature is 1000K, the pressure in the reaction chamber is 100Pa, and the treatment time is 10-30 hours, and finally obtain the carbon nanotube array field emission cathode material coated with carbon nanoparticles of different shapes; the carbon nanoparticles refer to Particles typically 15-30 nm in diameter.

The carbon nanotube array of the present invention can be prepared by the traditional thermal chemical vapor deposition method, and can also be prepared by any other method that can prepare the carbon nanotube array.

The preparation method of the carbon nanotube array field emission cathode coated with carbon nanoparticles according to the present invention, the device used to generate hydrogen plasma in the preparation can be a low-power radio frequency source, or any other low-power generation device. Device for dense hydrogen plasma.

The present invention further discloses a preparation method of a carbon nanotube array field emission cathode coated with carbon nanoparticles, which is characterized in that the steps are as follows:

(1) The silicon single wafer was ultrasonically cleaned in deionized water, acetone, and absolute ethanol for 10 minutes each, and the ultrasonic power was 50W. The purpose was to remove organic pollutants on the surface of the silicon wafer.

(2) Put the silicon wafer obtained in step (1) into hydrofluoric acid with a volume ratio of 4% and soak for 5 minutes. The purpose is to remove the silicon dioxide covering layer on the surface of the silicon wafer, and then dry it naturally.

(3) The silicon wafer obtained in step (2) is subjected to energy-carrying iron ion bombardment pretreatment in a metal vapor vacuum arc ion source (MEVVA source). The time is 15 minutes, and the purpose is to improve the binding force between the carbon nanotubes and the silicon substrate.

(4) Put the silicon wafer bombarded with energy-carrying iron ions obtained in step (3) into a magnetron sputtering device to deposit an iron catalyst with a thickness of 5 nanometers. The specific method is: put the silicon wafer into the magnetron sputtering device On the inner sample stage, the iron source is a high-purity (4N) iron target with a diameter of 75 mm. First, vacuumize to about 8×10 ^-5 Pa, and then pass high-purity (5N) argon to adjust the pressure of the deposition chamber. When depositing, the DC power supply current is 60 mA, and a negative bias voltage of 150 volts is applied to the sample stage at the same time, the deposition time is 125 seconds, and the thickness of the obtained iron film is 5 nanometers.

(5) Put the silicon wafer deposited with the 5nm iron catalyst obtained in step (4) into a high-temperature quartz tube furnace, first heat-treat the catalyst under the conditions of 400sccm hydrogen and 853K for 1 hour, and then heat-treat the catalyst under the conditions of 150sccm ammonia and 1023K. Down treatment for 10 minutes to improve the catalyst activity, and finally under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, the carbon nanotube array was grown under normal pressure, and the growth time was 30 minutes.

(6) Put the carbon nanotube array obtained in step (5) into the processing chamber of the radio frequency device, feed high-purity hydrogen (5N), adjust the pressure of the reaction chamber to 100Pa, and heat the substrate to 1000K, wait for the pressure and temperature Stablize;

(7) Start the radio frequency source on the basis of step (6), adjust the radio frequency power to 30-50W, and start processing the carbon nanotube array. The processing time is 10-30 hours, and the final result is carbon nanoparticle-coated carbon nanotubes. tube array.

(8) Use the silicon single wafer grown with carbon nanotube arrays coated with carbon nanoparticles obtained in step (7) as the substrate to assemble the field electron emitter according to the conventional method, as follows: use conductive glue to grow the carbon nanoparticle The silicon single wafer of the coated carbon nanotube array is adhered to a copper metal electrode with a thickness of about 2 mm as a field emission cathode, and the cathode is grounded, and a copper plate with a thickness of about 2 mm is used as an anode. It is a 200-micron ring-mounted polytetrafluoroethylene isolation, and the load is positively biased on the anode plate to obtain stable field electron emission. The size of the field emission current can be adjusted by changing the magnitude of the positive bias; The open electric field (the electric field required for the field emission current density of 10 μA/cm ² ) of the field emission cathode material based on the grown carbon nanoparticle-coated carbon nanotube array is only 0.90-1.10 V/μm, and the threshold electric field ( The electric field required for a field emission current density of 10 mA/cm ² ) is only 1.44-1.63 V/μm, the maximum field emission current density can reach 46.78 mA/cm ² , and it has good field emission stability.

Compared with the prior art, the preparation method of the carbon nanotube array field emission cathode coated with carbon nanoparticles disclosed by the present invention has the following advantages:

The carbon nanotube array field emission cathode coated with carbon nanoparticles prepared by this method has very low turn-on field (0.90-1.10 V/μm) and threshold field (1.44-1.63 V/μm), and the maximum field emission current density can reach 46.78 mA/cm ² , and the field emission stability is good (the current change range is very small within 10 hours), these indicators are greatly improved compared with the original untreated carbon nanotube array. The plasma treatment method used has a relatively simple process, does not require high equipment, and does not introduce other impurities into the carbon nanotubes, and has high practical value.

Description of drawings :

Fig. 1 is a schematic diagram of the process flow for preparing carbon nanoparticle-coated carbon nanotube arrays in the present invention, which is mainly divided into preparation of clean silicon wafer substrates, deposition of iron catalysts by magnetron sputtering, preparation of carbon nanotube arrays by thermal chemical vapor deposition, low Power radio frequency hydrogen plasma treatment of carbon nanotube array and other four parts;

Fig. 2 is the scanning electron microscope picture of the carbon nanotube array prepared by the experimental conditions shown in embodiment 1, and the shown carbon nanotube length is about 23 microns, and the upper right corner illustration shows the scanning electron microscope picture of the carbon nanotube array top, The inset in the lower right corner shows the scanning electron microscope image of the middle part of the carbon nanotube;

Fig. 3 is the structural representation of radio frequency device used in the present invention; Used hydrogen purity is 5N, and heater is self-made molybdenum wire heater, uses " molecular pump+mechanical pump " combination device to evacuate;

Figure 4 is a scanning electron microscope image of a carbon nanoparticle-coated carbon nanotube array prepared under different conditions. Most of the obtained carbon nanoparticles have a diameter of 15-30 nanometers, including:

41. The scanning electron microscope picture of the carbon nanotube array coated with carbon nanoparticles prepared according to the conditions of Example 1 (radio frequency power: 30W; treatment time: 10 hours). The upper right and lower right corner illustrations are the corresponding high-power scanning electron microscope pictures, Corresponding to the part marked by the box in the figure;

42. The scanning electron microscope picture of the carbon nanotube array coated with carbon nanoparticles prepared according to the conditions of Example 2 (radio frequency power: 30W; treatment time: 20 hours);

43. The scanning electron microscope picture of the carbon nanotube array coated with carbon nanoparticles prepared according to the conditions of Example 3 (radio frequency power: 30W; treatment time: 30 hours);

Fig. 5 shows the structural representation of high vacuum field emission tester, is used for testing the field emission performance of the carbon nanotube array that the prepared carbon nanoparticle wraps in each embodiment; This device is a conventional diode configuration Field emission test device: the prepared field emission material is used as the cathode, and a stainless steel plate with a diameter of about 10 cm is used as the anode. 0-10kV adjustable positive bias; test data is automatically recorded by computer;

Fig. 6 is the field emission performance diagram of the carbon nanotube array coated with carbon nanoparticles prepared under different conditions, specifically including the sample prepared in Example 1, Example 2, Example 3 and the original carbon nanotube array field emission The performance comparison, which characterizes the change relationship of the field emission current density with the increase of the applied electric field intensity, wherein J _th represents the threshold field emission current density, and its magnitude is 10 mA/cm ² ;

Fig. 7 is the field emission stability diagram of the carbon nanotube array coated with carbon nanoparticles prepared in Example 2 and the original carbon nanotube array, which characterizes the change of field emission current density over time under the constant external electric field alternative relation.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to these embodiments. The silicon single wafer, absolute ethanol, acetone, hydrofluoric acid, high-purity hydrogen, high-purity acetylene, high-purity ammonia, high-purity argon, and high-purity iron targets used are all commercially available. Ultrasonic cleaning, metal vapor vacuum arc ion source (MEVVA source), magnetron sputtering, high temperature tube furnace, radio frequency, field emission tester and other devices are commercially available.

Shown in Fig. 1 is exactly the technological flow schematic diagram of the carbon nanotube array that the present invention prepares carbon nanoparticle coating, is divided into preparation clean silicon wafer substrate, magnetron sputtering deposition iron catalyst, thermal chemical vapor deposition method preparation carbon nanotube Array, low-power radio-frequency hydrogen plasma treatment of carbon nanotube array and other four parts, the parts related to sample preparation in the following embodiments are all executed according to these four steps.

Example 1

(1) Preparation of clean silicon wafer substrate:

First, cut the silicon wafer into small pieces of 2cm×2cm, clean them with ultrasonic (50W) in deionized water, acetone and absolute ethanol for 10 minutes, and then put the silicon wafer into hydrofluoric acid with a volume ratio of 4% for 5 minutes. Minutes for clean, contamination-free substrates free of silica overlays.

(2) Deposition of iron catalyst by magnetron sputtering:

The deposition of the iron catalyst was carried out in a magnetron sputtering device (commercially available). Prior to this, the silicon single wafer was pretreated by bombardment with energetic iron ions in a metal vapor vacuum arc ion source (MEVVA source, commercially available). The iron ion energy was about 15keV, the beam current was 10 mA, and the processing time 15 minutes, this treatment can effectively improve the binding force between the carbon nanotubes and the silicon substrate; then place the silicon wafer bombarded by the energy-carrying iron ions on the sample stage, and first evacuate the vacuum chamber to about 8×10 ^-5 Pa, to eliminate impurity gas pollution, then pass high-purity (5N) argon gas, adjust the chamber pressure to 1.0Pa; during deposition, the DC power supply current is 60 mA, and a 150-volt negative bias is applied to the sample stage at the same time, The deposition time was 125 seconds, and the thickness of the obtained iron film was 5 nanometers.

(3) Preparation of carbon nanotube arrays by thermal chemical vapor deposition:

The growth of carbon nanotube arrays is completed in a high-temperature tube furnace (commercially available), the method used is the traditional thermal chemical vapor deposition method, and the whole process is completed under normal pressure. First, the silicon wafer deposited with 5 nanometer iron catalyst is placed on the sample stage in the quartz tube of the tube furnace, and after the quartz tube is sealed, the iron catalyst is heat-treated for 1 hour under 400 sccm hydrogen gas and 853K conditions; Down treatment for 10 minutes to improve catalyst activity; Finally, carbon nanotube arrays were grown under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, and the growth time was 30 minutes. Figure 2 is the scanning electron microscope picture of the carbon nanotube array obtained under this condition. It can be seen that the length of the carbon nanotube is about 23 microns (Figure 2), and the top is curved (the illustration in the upper right corner of Figure 2), but the middle array The properties are good (inset in the lower right corner of Figure 2), and the surface is smooth.

(4) Low-power RF hydrogen plasma treatment of carbon nanotube arrays:

Hydrogen plasma treatment of carbon nanotube arrays is completed in a radio frequency device (commercially available), and Fig. 3 is a schematic diagram of the structure of the device. First place the prepared carbon nanotube array on the graphite sample stage, pre-evacuate the processing chamber to about 8×10 ^-4 Pa, and then heat the substrate in a hydrogen (purity 5N) atmosphere with a heating rate of about 60K/min until the temperature stabilizes at 1000K, and adjust the air pressure to 100Pa. After the temperature and air pressure are stable, start the RF source, adjust the RF power to 30W, and the processing time is 10 hours. Figure 4-41 is the SEM picture of the carbon nanotube array coated with carbon nanoparticles obtained under this condition. Compared with the original carbon nanotubes shown in Figure 2, the overall shape of the carbon nanotubes has little change , but the surface is covered by carbon nanoparticles, the particles are small, and the diameter is mostly 15-20 nanometers. From the high-power scanning electron microscope pictures in the upper right and lower right corners of Figure 4-41, it can be clearly seen that the smooth surface of the original carbon nanotubes ( Fig. 2 inset) are completely different, and these carbon nanoprotrusions may become potential effective field emission sites.

(5) Field emission performance test:

The field emission performance test of the carbon nanotube array coated with carbon nanoparticles is completed in a high vacuum field emission tester (commercially available), and Fig. 5 is a schematic structural diagram of the test device. The vacuum degree in the test chamber is maintained at about 1×10 ^-7 Pa (with a normally open titanium ion pump for vacuuming). The prepared carbon nanoparticle-coated carbon nanotube array sample is adhered on the copper sample stage with conductive glue, which is used as the field emission cathode, and the cathode is grounded; the anode is a stainless steel disc with a diameter of about 10 cm , the anode and cathode are kept parallel with a distance of 2 mm; during the test, an adjustable positive bias voltage of 0-10kV is loaded on the anode, and the bias voltage growth rate is constant at 500 V/min. The test results are automatically recorded into the computer through the program. Figure 6 shows the field emission properties of carbon nanoparticle-coated carbon nanotube arrays prepared under different conditions, specifically including the samples prepared in this example, example 2, and example 3 and the original carbon nanotubes. The comparison of the field emission performance of the arrays is characterized by the change relationship of the field emission current density with the increase of the applied electric field intensity. It can be seen that the turn-on field, threshold field, and maximum field emission current density of carbon nanoparticle-coated carbon nanotube arrays obtained after hydrogen plasma treatment at 30 W for 10 hours are 1.10 V/μm, 1.63 V/μm, and 1.63 V/μm, respectively. 37.24 mA/cm ² , better than 1.24 V/μm, 1.76 V/μm and 21.90 mA/cm ² of pristine carbon nanotubes. The improvement of field emission performance can be attributed to the increase of effective field emission sites on the surface of carbon nanotubes after long-term low-power hydrogen plasma treatment. A large number of carbon nanoparticles can become effective field emission sites. Compared with the original carbon Nanotubes with only tips emitting electrons will undoubtedly be greatly improved.

(6) Field electron emitter assembly (conventional assembly method):

A silicon single wafer with a carbon nanotube array coated with carbon nanoparticles is adhered to a copper electrode with a thickness of 2 mm by conductive glue, and it is used as a field emission cathode, and the cathode is grounded, and the anode is a thickness of 2 mm. mm copper plate electrodes, the anode and cathode are kept parallel, separated by a 200-micron ring-packed polytetrafluoroethylene, and the load is positively biased on the anode plate to obtain stable field electron emission and control the field emission current density This can be achieved by adjusting the anode plate bias.

Example 2

(1) Preparation of clean silicon wafer substrate:

First, cut the silicon wafer into small pieces of 2cm×2cm, clean them with ultrasonic (50W) in deionized water, acetone and absolute ethanol for 10 minutes, and then put the silicon wafer into hydrofluoric acid with a volume ratio of 4% for 5 minutes. Minutes for clean, contamination-free substrates free of silica overlays.

(2) Deposition of iron catalyst by magnetron sputtering:

The deposition of the iron catalyst was carried out in a magnetron sputtering device (commercially available). Prior to this, the silicon single wafer was pretreated by bombardment with energetic iron ions in a metal vapor vacuum arc ion source (MEVVA source, commercially available). The iron ion energy was about 15keV, the beam current was 10 mA, and the processing time 15 minutes, this treatment can effectively improve the binding force between the carbon nanotubes and the silicon substrate; then place the silicon wafer bombarded by the energy-carrying iron ions on the sample stage, and first evacuate the vacuum chamber to about 8×10 ^-5 Pa, to eliminate impurity gas pollution, then pass high-purity (5N) argon gas, adjust the chamber pressure to 1.0Pa; during deposition, the DC power supply current is 60 mA, and a 150-volt negative bias is applied to the sample stage at the same time, The deposition time was 125 seconds, and the thickness of the obtained iron film was 5 nanometers.

(3) Preparation of carbon nanotube arrays by thermal chemical vapor deposition:

The growth of carbon nanotube arrays is completed in a high-temperature tube furnace (commercially available), the method used is the traditional thermal chemical vapor deposition method, and the whole process is completed under normal pressure. First, the silicon wafer deposited with 5 nanometer iron catalyst is placed on the sample stage in the quartz tube of the tube furnace, and after the quartz tube is sealed, the iron catalyst is heat-treated for 1 hour under 400 sccm hydrogen gas and 853K conditions; Down treatment for 10 minutes to improve catalyst activity; Finally, carbon nanotube arrays were grown under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, and the growth time was 30 minutes.

(4) Low-power RF hydrogen plasma treatment of carbon nanotube arrays:

Hydrogen plasma treatment of carbon nanotube arrays is completed in a radio frequency device (commercially available), and Fig. 3 is a schematic diagram of the structure of the device. First place the prepared carbon nanotube array on the graphite sample stage, pre-evacuate the processing chamber to about 8×10 ^-4 Pa, and then heat the substrate in a hydrogen (purity 5N) atmosphere with a heating rate of about 60K/min, until the temperature stabilizes at 1000K, and adjust the air pressure to 100Pa. After the temperature and air pressure are stable, start the RF source, adjust the RF power to 30W, and the processing time is 20 hours. Figure 4-42 is the scanning electron microscope picture of the carbon nanotube array coated with carbon nanoparticles obtained in this example. Compared with the original carbon nanotube shown in Figure 2, the overall shape of the carbon nanotube does not change. Large, but the surface is covered by carbon nanoparticles, and the particle diameter is slightly increased compared with the carbon nanotubes obtained after 30W and 10 hours of treatment (Fig. In contrast to a smooth surface (Fig. 2 inset), these carbon nanoprotrusions could be potential effective field emission sites.

(5) Field emission performance test:

The field emission performance test of the carbon nanotube array coated with carbon nanoparticles is completed in a high vacuum field emission tester (commercially available), and Fig. 5 is a schematic structural diagram of the test device. The vacuum degree in the test chamber is maintained at about 1×10 ^-7 Pa (with a normally open titanium ion pump for vacuuming). The prepared carbon nanoparticle-coated carbon nanotube array sample is adhered on the copper sample stage with conductive glue, which is used as the field emission cathode, and the cathode is grounded; the anode is a stainless steel disc with a diameter of about 10 cm , the anode and cathode are kept parallel with a distance of 2 mm; during the test, an adjustable positive bias voltage of 0-10kV is loaded on the anode, and the bias voltage growth rate is constant at 500V/min. The test results are automatically recorded into the computer through the program. It can be seen from Figure 6 that the turn-on field, threshold field and maximum field emission current density of carbon nanoparticle-coated carbon nanotube arrays obtained after hydrogen plasma treatment at 30 W for 20 hours are 0.90 V/μm and 1.44 V, respectively. /μm and 43.42 mA/cm ² , far better than 1.24 V/μm, 1.76 V/μm and 21.90 mA/cm ² of pristine carbon nanotubes, and better than 1.10 mA/cm 2 of carbon nanotube arrays after 30W and 10 hours treatment V/μm, 1.63 V/μm, and 37.24 mA/cm ² . The significant improvement of field emission performance can be attributed to the increase of effective field emission sites on the surface of carbon nanotubes after long-term low-power hydrogen plasma treatment. A large number of carbon nanoparticles can become effective field emission sites, and the field emission current density is higher than that of the original Carbon nanotubes with only tip-emitting electrons will undoubtedly be greatly improved. Fig. 7 shows the field emission stability graphs of the carbon nanotube arrays coated with carbon nanoparticles prepared in this example and the original untreated carbon nanotube arrays. Variation of current density with time. It can be seen that the carbon nanoparticle-coated carbon nanotube array prepared in this example has better field emission stability than the original carbon nanotube array, and in the 10-hour test (the average field emission current density is 12.25 mA /cm ² ), the field emission current density has no obvious attenuation, and the fluctuation is small, but the current density of the pristine carbon nanotube sample is attenuated by about 17% during the 10-hour test (the average field emission current density is 9.80 mA/cm ² ). Although the average field emission current densities of both are near the threshold field emission current density ( J _th , 10 mA/cm ² ), the constant applied electric field strength of the carbon nanoparticle-coated carbon nanotube sample in the test is only 1.50 V/ μm, much smaller than the 1.80 V/μm of pristine CNT samples, this reduction in operating voltage is very important for practical applications. It can be seen that the long-time high temperature and plasma treatment greatly improved the field emission stability of the carbon nanotube array.

(6) Field electron emitter assembly (conventional assembly method):

A silicon single wafer with a carbon nanotube array coated with carbon nanoparticles is adhered to a copper electrode with a thickness of 2 mm by conductive glue, and it is used as a field emission cathode, and the cathode is grounded, and the anode is a thickness of 2 mm. mm copper plate electrodes, the anode and cathode are kept parallel, separated by a 200-micron ring-packed polytetrafluoroethylene, and the load is positively biased on the anode plate to obtain stable field electron emission and control the field emission current density This can be achieved by adjusting the anode plate bias.

Example 3

(1) Preparation of clean silicon wafer substrate:

First, cut the silicon wafer into small pieces of 2cm×2cm, clean them with ultrasonic (50W) in deionized water, acetone and absolute ethanol for 10 minutes, and then put the silicon wafer into hydrofluoric acid with a volume ratio of 4% for 5 minutes. Minutes for clean, contamination-free substrates free of silica overlays.

(2) Deposition of iron catalyst by magnetron sputtering:

The deposition of the iron catalyst was carried out in a magnetron sputtering device (commercially available). Prior to this, the silicon single wafer was pretreated by bombardment with energetic iron ions in a metal vapor vacuum arc ion source (MEVVA source, commercially available). The iron ion energy was about 15keV, the beam current was 10 mA, and the processing time 15 minutes, this treatment can effectively improve the binding force between the carbon nanotubes and the silicon substrate; then place the silicon wafer bombarded by the energy-carrying iron ions on the sample stage, and first evacuate the vacuum chamber to about 8×10 ^-5 Pa, to eliminate impurity gas pollution, then pass high-purity (5N) argon gas, adjust the chamber pressure to 1.0Pa; during deposition, the DC power supply current is 60 mA, and a 150-volt negative bias is applied to the sample stage at the same time, The deposition time was 125 seconds, and the thickness of the obtained iron film was 5 nanometers.

(3) Preparation of carbon nanotube arrays by thermal chemical vapor deposition:

The growth of carbon nanotube arrays is completed in a high-temperature tube furnace (commercially available), the method used is the traditional thermal chemical vapor deposition method, and the whole process is completed under normal pressure. First, the silicon wafer deposited with 5 nanometer iron catalyst is placed on the sample stage in the quartz tube of the tube furnace, and after the quartz tube is sealed, the iron catalyst is heat-treated for 1 hour under 400 sccm hydrogen gas and 853K conditions; Down treatment for 10 minutes to improve catalyst activity; Finally, carbon nanotube arrays were grown under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, and the growth time was 30 minutes.

(4) Low-power RF hydrogen plasma treatment of carbon nanotube arrays:

Hydrogen plasma treatment of carbon nanotube arrays is completed in a radio frequency device (commercially available), and Fig. 3 is a schematic diagram of the structure of the device. First place the prepared carbon nanotube array on the graphite sample stage, pre-evacuate the processing chamber to about 8×10 ^-4 Pa, and then heat the substrate in a hydrogen (purity 5N) atmosphere with a heating rate of about 60K/min until the temperature stabilizes at 1000K, and adjust the air pressure to 100Pa. After the temperature and air pressure are stable, start the RF source, adjust the RF power to 30W, and the processing time is 30 hours. Figure 4-43 is the scanning electron microscope picture of the carbon nanotube array coated with carbon nanoparticles obtained in this example. Compared with the original carbon nanotube shown in Figure 2, the overall shape of the carbon nanotube has little change , but the surface is covered by carbon nanoparticles, and the particle diameter is smaller than that obtained after 30W, 10 hours (Fig. 4-41) and 30W, 20 hours (Fig. 4-42), mostly at 15 -20 nm, and the particle boundary is not clear, but it is quite different from the smooth surface of pristine carbon nanotubes (Fig. 2 inset), these carbon nanoprotrusions may become potential effective field emission sites.

(5) Field emission performance test:

The field emission performance test of the carbon nanotube array coated with carbon nanoparticles is completed in a high vacuum field emission tester (commercially available), and Fig. 5 is a schematic structural diagram of the test device. The vacuum degree in the test chamber is maintained at about 1×10 ^-7 Pa (with a normally open titanium ion pump for vacuuming). The prepared carbon nanoparticle-coated carbon nanotube array sample is adhered on the copper sample stage with conductive glue, which is used as the field emission cathode, and the cathode is grounded; the anode is a stainless steel disc with a diameter of about 10 cm , the anode and cathode are kept parallel with a distance of 2 mm; during the test, an adjustable positive bias voltage of 0-10kV is loaded on the anode, and the bias voltage growth rate is constant at 500V/min. The test results are automatically recorded into the computer through the program. It can be seen from Figure 6 that the turn-on field, threshold field and maximum field emission current density of carbon nanoparticle-coated carbon nanotube arrays obtained after hydrogen plasma treatment at 30 W for 30 hours are 1.02 V/μm and 1.59 V, respectively. /μm and 35.44 mA/cm ² , which are better than 1.24 V/μm, 1.76 V/μm and 21.90 mA/cm ² of pristine carbon nanotubes. The improvement of field emission performance can be attributed to the increase of effective field emission sites on the surface of carbon nanotubes after long-term low-power hydrogen plasma treatment. A large number of carbon nanoparticles can become effective field emission sites. Compared with the original carbon Nanotubes with only tips emitting electrons will undoubtedly be greatly improved.

(6) Field electron emitter assembly (conventional assembly method):

A silicon single wafer with a carbon nanotube array coated with carbon nanoparticles is adhered to a copper electrode with a thickness of 2 mm by conductive glue, and it is used as a field emission cathode, and the cathode is grounded, and the anode is a thickness of 2 mm. mm copper plate electrodes, the anode and cathode are kept parallel, separated by a 200-micron ring-packed polytetrafluoroethylene, and the load is positively biased on the anode plate to obtain stable field electron emission and control the field emission current density This can be achieved by adjusting the anode plate bias.

Example 4

(1) Preparation of clean silicon wafer substrate:

First, cut the silicon wafer into small pieces of 2cm×2cm, clean them with ultrasonic (50W) in deionized water, acetone and absolute ethanol for 10 minutes, and then put the silicon wafer into hydrofluoric acid with a volume ratio of 4% for 5 minutes. Minutes for clean, contamination-free substrates free of silica overlays.

(2) Deposition of iron catalyst by magnetron sputtering:

The deposition of the iron catalyst was carried out in a magnetron sputtering device (commercially available). Prior to this, the silicon single wafer was pretreated by bombardment with energetic iron ions in a metal vapor vacuum arc ion source (MEVVA source, commercially available). The iron ion energy was about 15keV, the beam current was 10 mA, and the processing time 15 minutes, this treatment can effectively improve the binding force between the carbon nanotubes and the silicon substrate; then place the silicon wafer bombarded by the energy-carrying iron ions on the sample stage, and first evacuate the vacuum chamber to about 8×10 ^-5 Pa, to eliminate impurity gas pollution, then pass high-purity (5N) argon gas, adjust the chamber pressure to 1.0Pa; during deposition, the DC power supply current is 60 mA, and a 150-volt negative bias is applied to the sample stage at the same time, The deposition time was 125 seconds, and the thickness of the obtained iron film was 5 nanometers.

(3) Preparation of carbon nanotube arrays by thermal chemical vapor deposition:

The growth of carbon nanotube arrays is completed in a high-temperature tube furnace (commercially available), the method used is the traditional thermal chemical vapor deposition method, and the whole process is completed under normal pressure. First, the silicon wafer deposited with 5 nanometer iron catalyst is placed on the sample stage in the quartz tube of the tube furnace, and after the quartz tube is sealed, the iron catalyst is heat-treated for 1 hour under 400 sccm hydrogen gas and 853K conditions; Down treatment for 10 minutes to improve catalyst activity; Finally, carbon nanotube arrays were grown under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, and the growth time was 30 minutes.

(4) Low-power RF hydrogen plasma treatment of carbon nanotube arrays:

Hydrogen plasma treatment of carbon nanotube arrays is completed in a radio frequency device (commercially available), and Fig. 3 is a schematic diagram of the structure of the device. First place the prepared carbon nanotube array on the graphite sample stage, pre-evacuate the processing chamber to about 8×10 ^-4 Pa, and then heat the substrate in a hydrogen (purity 5N) atmosphere with a heating rate of about 60K/min, until the temperature stabilizes at 1000K, and adjust the air pressure to 100Pa. After the temperature and air pressure are stable, start the RF source, adjust the RF power to 40W, and the processing time is 10 hours.

(5) Field emission performance test:

The field emission performance test of the carbon nanotube array coated with carbon nanoparticles is completed in a high vacuum field emission tester (commercially available), and Fig. 5 is a schematic structural diagram of the test device. The vacuum degree in the test chamber is maintained at about 1×10 ^-7 Pa (with a normally open titanium ion pump for vacuuming). The prepared carbon nanoparticle-coated carbon nanotube array sample is adhered on the copper sample stage with conductive glue, which is used as the field emission cathode, and the cathode is grounded; the anode is a stainless steel disc with a diameter of about 10 cm , the anode and cathode are kept parallel with a distance of 2 mm; during the test, an adjustable positive bias voltage of 0-10kV is loaded on the anode, and the bias voltage growth rate is constant at 500V/min. The test results are automatically recorded into the computer through the program. The turn-on field, threshold field, and maximum field emission current density of the carbon nanoparticle-coated carbon nanotube array obtained in this example are 1.04 V/μm, 1.60 V/μm, and 36.12 mA/cm ² , respectively, which are better than those of the pristine carbon 1.24 V/μm, 1.76 V/μm and 21.90 mA/cm ² for nanotubes. The improvement of field emission performance can be attributed to the increase of effective field emission sites on the surface of carbon nanotubes after long-term low-power hydrogen plasma treatment. A large number of carbon nanoparticles can become effective field emission sites. Compared with the original carbon Nanotubes with only tips emitting electrons will undoubtedly be greatly improved.

(6) Field electron emitter assembly (conventional assembly method):

A silicon single wafer with a carbon nanotube array coated with carbon nanoparticles is adhered to a copper electrode with a thickness of 2 mm by conductive glue, and it is used as a field emission cathode, and the cathode is grounded, and the anode is a thickness of 2 mm. mm copper plate electrodes, the anode and cathode are kept parallel, separated by a 200-micron ring-packed polytetrafluoroethylene, and the load is positively biased on the anode plate to obtain stable field electron emission and control the field emission current density This can be achieved by adjusting the anode plate bias.

Example 5

(1) Preparation of clean silicon wafer substrate:

First, cut the silicon wafer into small pieces of 2cm×2cm, clean them with ultrasonic (50W) in deionized water, acetone and absolute ethanol for 10 minutes, and then put the silicon wafer into hydrofluoric acid with a volume ratio of 4% for 5 minutes. Minutes for clean, contamination-free substrates free of silica overlays.

(2) Deposition of iron catalyst by magnetron sputtering:

The deposition of the iron catalyst was carried out in a magnetron sputtering device (commercially available). Prior to this, the silicon single wafer was pretreated by bombardment with energetic iron ions in a metal vapor vacuum arc ion source (MEVVA source, commercially available). The iron ion energy was about 15keV, the beam current was 10 mA, and the processing time 15 minutes, this treatment can effectively improve the binding force between the carbon nanotubes and the silicon substrate; then place the silicon wafer bombarded by the energy-carrying iron ions on the sample stage, and first evacuate the vacuum chamber to about 8×10 ^-5 Pa, to eliminate impurity gas pollution, then pass high-purity (5N) argon gas, adjust the chamber pressure to 1.0Pa; during deposition, the DC power supply current is 60 mA, and a 150-volt negative bias is applied to the sample stage at the same time, The deposition time was 125 seconds, and the thickness of the obtained iron film was 5 nanometers.

(3) Preparation of carbon nanotube arrays by thermal chemical vapor deposition:

The growth of carbon nanotube arrays is completed in a high-temperature tube furnace (commercially available), the method used is the traditional thermal chemical vapor deposition method, and the whole process is completed under normal pressure. First, the silicon wafer deposited with 5 nanometer iron catalyst is placed on the sample stage in the quartz tube of the tube furnace, and after the quartz tube is sealed, the iron catalyst is heat-treated for 1 hour under 400 sccm hydrogen gas and 853K conditions; Down treatment for 10 minutes to improve catalyst activity; Finally, carbon nanotube arrays were grown under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, and the growth time was 30 minutes.

(4) Low-power RF hydrogen plasma treatment of carbon nanotube arrays:

Hydrogen plasma treatment of carbon nanotube arrays is completed in a radio frequency device (commercially available), and Fig. 3 is a schematic diagram of the structure of the device. First place the prepared carbon nanotube array on the graphite sample stage, pre-evacuate the processing chamber to about 8×10 ^-4 Pa, and then heat the substrate in a hydrogen (purity 5N) atmosphere with a heating rate of about 60K/min until the temperature stabilizes at 1000K, and adjust the air pressure to 100Pa. After the temperature and air pressure are stable, start the RF source, adjust the RF power to 40W, and the processing time is 20 hours.

(5) Field emission performance test:

The field emission performance test of the carbon nanotube array coated with carbon nanoparticles is completed in a high vacuum field emission tester (commercially available), and Fig. 5 is a schematic structural diagram of the test device. The vacuum degree in the test chamber is maintained at about 1×10 ^-7 Pa (with a normally open titanium ion pump for vacuuming). The prepared carbon nanoparticle-coated carbon nanotube array sample is adhered on the copper sample stage with conductive glue, which is used as the field emission cathode, and the cathode is grounded; the anode is a stainless steel disc with a diameter of about 10 cm , the anode and cathode are kept parallel with a distance of 2 mm; during the test, an adjustable positive bias voltage of 0-10kV is loaded on the anode, and the bias voltage growth rate is constant at 500V/min. The test results are automatically recorded into the computer through the program. The turn-on field, threshold field and maximum field emission current density of the carbon nanoparticle-coated carbon nanotube array obtained in this example are 0.96 V/μm, 1.52 V/μm and 41.48 mA/cm ² , which are better than those of the original carbon 1.24 V/μm, 1.76 V/μm and 21.90 mA/cm ² for nanotubes. The improvement of field emission performance can be attributed to the increase of effective field emission sites on the surface of carbon nanotubes after long-term low-power hydrogen plasma treatment. A large number of carbon nanoparticles can become effective field emission sites. Compared with the original carbon Nanotubes with only tips emitting electrons will undoubtedly be greatly improved.

(6) Field electron emitter assembly (conventional assembly method):

A silicon single wafer with a carbon nanotube array coated with carbon nanoparticles is adhered to a copper electrode with a thickness of 2 mm by conductive glue, and it is used as a field emission cathode, and the cathode is grounded, and the anode is a thickness of 2 mm. mm copper plate electrodes, the anode and cathode are kept parallel, separated by a 200-micron ring-packed polytetrafluoroethylene, and the load is positively biased on the anode plate to obtain stable field electron emission and control the field emission current density This can be achieved by adjusting the anode plate bias.

Example 6

(1) Preparation of clean silicon wafer substrate:

First, cut the silicon wafer into small pieces of 2cm×2cm, clean them with ultrasonic (50W) in deionized water, acetone and absolute ethanol for 10 minutes, and then put the silicon wafer into hydrofluoric acid with a volume ratio of 4% for 5 minutes. Minutes for clean, contamination-free substrates free of silica overlays.

(2) Deposition of iron catalyst by magnetron sputtering:

The deposition of the iron catalyst was carried out in a magnetron sputtering device (commercially available). Prior to this, the silicon single wafer was pretreated by bombardment with energetic iron ions in a metal vapor vacuum arc ion source (MEVVA source, commercially available). The iron ion energy was about 15keV, the beam current was 10 mA, and the processing time 15 minutes, this treatment can effectively improve the binding force between the carbon nanotubes and the silicon substrate; then place the silicon wafer bombarded by the energy-carrying iron ions on the sample stage, and first evacuate the vacuum chamber to about 8×10 ^-5 Pa, to eliminate impurity gas pollution, then pass high-purity (5N) argon gas, adjust the chamber pressure to 1.0Pa; during deposition, the DC power supply current is 60 mA, and a 150-volt negative bias is applied to the sample stage at the same time, The deposition time was 125 seconds, and the thickness of the obtained iron film was 5 nanometers.

(3) Preparation of carbon nanotube arrays by thermal chemical vapor deposition:

The growth of carbon nanotube arrays is completed in a high-temperature tube furnace (commercially available), the method used is the traditional thermal chemical vapor deposition method, and the whole process is completed under normal pressure. First, the silicon wafer deposited with 5 nanometer iron catalyst is placed on the sample stage in the quartz tube of the tube furnace, and after the quartz tube is sealed, the iron catalyst is heat-treated for 1 hour under 400 sccm hydrogen gas and 853K conditions; Down treatment for 10 minutes to improve catalyst activity; Finally, carbon nanotube arrays were grown under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, and the growth time was 30 minutes.

(4) Low-power RF hydrogen plasma treatment of carbon nanotube arrays:

Hydrogen plasma treatment of carbon nanotube arrays is completed in a radio frequency device (commercially available), and Fig. 3 is a schematic diagram of the structure of the device. First place the prepared carbon nanotube array on the graphite sample stage, pre-evacuate the processing chamber to about 8×10 ^-4 Pa, and then heat the substrate in a hydrogen (purity 5N) atmosphere with a heating rate of about 60K/min until the temperature stabilizes at 1000K, and adjust the air pressure to 100Pa. After the temperature and air pressure are stable, start the RF source, adjust the RF power to 50W, and the processing time is 20 hours.

(5) Field emission performance test:

The field emission performance test of the carbon nanotube array coated with carbon nanoparticles is completed in a high vacuum field emission tester (commercially available), and Fig. 5 is a schematic structural diagram of the test device. The vacuum degree in the test chamber is maintained at about 1×10 ^-7 Pa (with a normally open titanium ion pump for vacuuming). The prepared carbon nanoparticle-coated carbon nanotube array sample is adhered on the copper sample stage with conductive glue, which is used as the field emission cathode, and the cathode is grounded; the anode is a stainless steel disc with a diameter of about 10 cm , the anode and cathode are kept parallel with a distance of 2 mm; during the test, an adjustable positive bias voltage of 0-10kV is loaded on the anode, and the bias voltage growth rate is constant at 500V/min. The test results are automatically recorded into the computer through the program. The turn-on field, threshold field and maximum field emission current density of the carbon nanoparticle-coated carbon nanotube array obtained in this example are 0.98 V/μm, 1.51 V/μm and 40.57 mA/cm ² , which are better than those of the original carbon 1.24 V/μm, 1.76 V/μm and 21.90 mA/cm ² for nanotubes. The improvement of field emission performance can be attributed to the increase of effective field emission sites on the surface of carbon nanotubes after long-term low-power hydrogen plasma treatment. A large number of carbon nanoparticles can become effective field emission sites. Compared with the original carbon Nanotubes with only tips emitting electrons will undoubtedly be greatly improved.

(6) Field electron emitter assembly (conventional assembly method):

A silicon single wafer with a carbon nanotube array coated with carbon nanoparticles is adhered to a copper electrode with a thickness of 2 mm by conductive glue, and it is used as a field emission cathode, and the cathode is grounded, and the anode is a thickness of 2 mm. mm copper plate electrodes, the anode and cathode are kept parallel, separated by a 200-micron ring-packed polytetrafluoroethylene, and the load is positively biased on the anode plate to obtain stable field electron emission and control the field emission current density This can be achieved by adjusting the anode plate bias.

Example 7

(1) Preparation of clean silicon wafer substrate:

First, cut the silicon wafer into small pieces of 2cm×2cm, clean them with ultrasonic (50W) in deionized water, acetone and absolute ethanol for 10 minutes, and then put the silicon wafer into hydrofluoric acid with a volume ratio of 4% for 5 minutes. Minutes for clean, contamination-free substrates free of silica overlays.

(2) Deposition of iron catalyst by magnetron sputtering:

The deposition of the iron catalyst was carried out in a magnetron sputtering device (commercially available). Prior to this, the silicon single wafer was pretreated by bombardment with energetic iron ions in a metal vapor vacuum arc ion source (MEVVA source, commercially available). The iron ion energy was about 15keV, the beam current was 10 mA, and the processing time 15 minutes, this treatment can effectively improve the binding force between the carbon nanotubes and the silicon substrate; then place the silicon wafer bombarded by the energy-carrying iron ions on the sample stage, and first evacuate the vacuum chamber to about 8×10 ^-5 Pa, to eliminate impurity gas pollution, then pass high-purity (5N) argon gas, adjust the chamber pressure to 1.0Pa; during deposition, the DC power supply current is 60 mA, and a 150-volt negative bias is applied to the sample stage at the same time, The deposition time was 125 seconds, and the thickness of the obtained iron film was 5 nanometers.

(3) Preparation of carbon nanotube arrays by thermal chemical vapor deposition:

The growth of carbon nanotube arrays is completed in a high-temperature tube furnace (commercially available), the method used is the traditional thermal chemical vapor deposition method, and the whole process is completed under normal pressure. First, the silicon wafer deposited with 5 nanometer iron catalyst is placed on the sample stage in the quartz tube of the tube furnace, and after the quartz tube is sealed, the iron catalyst is heat-treated for 1 hour under 400 sccm hydrogen gas and 853K conditions; Down treatment for 10 minutes to improve catalyst activity; Finally, carbon nanotube arrays were grown under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, and the growth time was 30 minutes.

(4) Low-power RF hydrogen plasma treatment of carbon nanotube arrays:

Hydrogen plasma treatment of carbon nanotube arrays is completed in a radio frequency device (commercially available), and Fig. 3 is a schematic diagram of the structure of the device. First place the prepared carbon nanotube array on the graphite sample stage, pre-evacuate the processing chamber to about 8×10 ^-4 Pa, and then heat the substrate in a hydrogen (purity 5N) atmosphere with a heating rate of about 60K/min, until the temperature stabilizes at 1000K, and adjust the air pressure to 100Pa. After the temperature and air pressure are stable, start the RF source, adjust the RF power to 35W, and the processing time is 15 hours.

(5) Field emission performance test:

The field emission performance test of the carbon nanotube array coated with carbon nanoparticles is completed in a high vacuum field emission tester (commercially available), and Fig. 5 is a schematic structural diagram of the test device. The vacuum degree in the test chamber is maintained at about 1×10 ^-7 Pa (with a normally open titanium ion pump for vacuuming). The prepared carbon nanoparticle-coated carbon nanotube array sample is adhered on the copper sample stage with conductive glue, which is used as the field emission cathode, and the cathode is grounded; the anode is a stainless steel disc with a diameter of about 10 cm , the anode and cathode are kept parallel with a distance of 2 mm; during the test, an adjustable positive bias voltage of 0-10kV is loaded on the anode, and the bias voltage growth rate is constant at 500V/min. The test results are automatically recorded into the computer through the program. The turn-on field, threshold field and maximum field emission current density of the carbon nanoparticle-coated carbon nanotube array obtained in this example are 0.93 V/μm, 1.46 V/μm and 46.78 mA/cm ² , which are better than those of the pristine carbon 1.24 V/μm, 1.76 V/μm and 21.90 mA/cm ² for nanotubes. The improvement of field emission performance can be attributed to the increase of effective field emission sites on the surface of carbon nanotubes after long-term low-power hydrogen plasma treatment. A large number of carbon nanoparticles can become effective field emission sites. Compared with the original carbon Nanotubes with only tips emitting electrons will undoubtedly be greatly improved.

(6) Field electron emitter assembly (conventional assembly method):

A silicon single wafer with a carbon nanotube array coated with carbon nanoparticles is adhered to a copper electrode with a thickness of 2 mm by conductive glue, and it is used as a field emission cathode, and the cathode is grounded, and the anode is a thickness of 2 mm. mm copper plate electrodes, the anode and cathode are kept parallel, separated by a 200-micron ring-packed polytetrafluoroethylene, and the load is positively biased on the anode plate to obtain stable field electron emission and control the field emission current density This can be achieved by adjusting the anode plate bias.

Finally, it should be noted that the above only exemplifies typical embodiments of the present invention. But obviously the present invention is not limited to above-mentioned embodiment, also has many other experimental parameter combination methods, all situations that those of ordinary skill in this research field can directly derive or associate from the content disclosed by the present invention, all should be considered as protection scope of the present invention.

Claims (4)

1. A preparation method of a carbon nanotube array field emission cathode coated with carbon nanoparticles, characterized in that the carbon nanotube array prepared by the thermal chemical vapor deposition method is processed by utilizing radio frequency technology to generate hydrogen plasma, and the radio frequency power is adjusted to be 30 -50W, substrate temperature of 1000K, reaction chamber pressure of 100Pa, and treatment time of 10-30 hours, and finally obtain carbon nanotube array field emission cathode materials coated with carbon nanoparticles of different shapes; the carbon nanoparticles refer to These are particles typically 15-30 nm in diameter. 2. The preparation method of the carbon nanotube array field emission cathode coated by carbon nanoparticles as claimed in claim 1 is characterized in that: the described carbon nanotube array can be prepared by traditional thermal chemical vapor deposition, and can also be prepared by other methods. It can be prepared by any method that can prepare arrayed carbon nanotubes. 3. The preparation method of the carbon nanotube array field emission cathode coated by carbon nanoparticles as claimed in claim 1 is characterized in that: the device for generating hydrogen plasma can be a low-power radio frequency source, or any other A device that can generate low power density hydrogen plasma. 4. the preparation method of the carbon nanotube array field emission cathode of carbon nanoparticle coating described in claim 1 is characterized in that carrying out as follows: (1) Ultrasonic clean the silicon single wafer in deionized water, acetone and absolute ethanol for 10 minutes respectively, and the ultrasonic power is 50W; (2) Put the silicon wafer obtained in step (1) into hydrofluoric acid with a volume ratio of 4% and soak for 5 minutes; (3) The silicon wafer obtained in step (2) is subjected to energy-carrying iron ion bombardment pretreatment in a metal vapor vacuum arc ion source (MEVVA source). The time is 15 minutes; (4) placing the silicon wafer bombarded with energy-carrying iron ions obtained in step (3) into a magnetron sputtering device to deposit an iron catalyst with a thickness of 5 nanometers; (5) Put the silicon wafer deposited with the 5nm iron catalyst obtained in step (4) into a high-temperature quartz tube furnace, first heat-treat the catalyst under the conditions of 400sccm hydrogen and 853K for 1 hour, and then heat-treat the catalyst under the conditions of 150sccm ammonia and 1023K. Under low temperature treatment for 10 minutes, and finally under the conditions of 87sccm acetylene, 600sccm hydrogen, and 1023K, the carbon nanotube array was grown under normal pressure, and the growth time was 30 minutes; (6) Put the carbon nanotube array obtained in step (5) into the processing chamber of the radio frequency device, feed high-purity hydrogen (5N), adjust the pressure of the reaction chamber to 100Pa, and heat the substrate to 1000K, wait for the pressure and temperature Stablize; (7) Start the radio frequency source on the basis of step (6), adjust the radio frequency power to 30-50W, and start processing the carbon nanotube array. The processing time is 10-30 hours, and the final result is carbon nanoparticle-coated carbon nanotubes. tube array, and use it as a field emission cathode material to assemble field electron emission devices by conventional methods.