CN104882346A - Method for preparing field emission cathode of carbon nanotube array coated with carbon nanoparticles - Google Patents
Method for preparing field emission cathode of carbon nanotube array coated with carbon nanoparticles Download PDFInfo
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Abstract
The invention discloses a method for preparing a field emission cathode of a carbon nanotube array coated with carbon nanoparticles, and belongs to the fields of nano material preparation and application. The method mainly comprises the following preparation process of preparing a carbon nanotube array on a silicon single crystal wafer by a thermal chemical vapor deposition method; producing hydrogen plasmas by using the radio frequency technology and processing the carbon nanotube array for a long time at low power; and finally, taking the carbon nanotube array coated on the surface with carbon nanoparticles as a cathode assembly field electron emitter. According to the invention, the prepared carbon nanotube array coated with the carbon nanoparticles by the method has a general particle diameter of 15-30 nm, and as the field emission cathode material, the carbon nanotube array has a lower open field and threshold field than a single carbon nanotube array, better field emission stability, and a higher application value.
Description
The present invention obtains state natural sciences fund-youth fund funded projects (bullets 51302187).Obtain Tianjin application foundation and cutting edge technology research plan key project is subsidized (bullets 14JCZDJC32100).
Technical field
The invention belongs to nano material preparation and application technical field, relate to and utilize low-power plasma technique to prepare a kind of nano material with unique texture, and it is used for the preparation method of field-electron emission device.
Background technology
Develop the focus that high performance filed emission cathode material is recent researches always, these materials all have a good application prospect at numerous areas such as New-generation vacuum pipe, X-ray tube, Electronic Speculum electron gun, field emission flat displays.Carbon nano-tube is exactly a kind of ideal filed emission cathode material.First, carbon nano-tube is primarily of SP
2hydbridized carbon atoms forms, and has extraordinary conductivity.Secondly, the huge draw ratio that carbon nano-tube also has many one dimensions, two-dimension nano materials hardly matches, make electronics can obtain great local electric field intensity (namely field enhancement factor is larger) at its Flied emission point place, thus making it more easily overcome carbon nano tube surface potential barrier (i.e. work function function) and escape in vacuum, this is all very favorable to obtaining low unlatching field and threshold field and large Flied emission current density.Compare the graphene-based filed emission cathode material obtaining extensive concern in recent years, be that the field-transmitting cathode of base has lower unlatching field with carbon nano-tube, be generally less than 2 V/ μm, the unlatching field of Graphene is then often greater than 4 V/ μm.The feature of this low unlatching field is very important in actual applications, can significantly reduce the operating voltage of field-transmitting cathode in pole.As can be seen here, further reduce the applied electric field of carbon nanotube field emission cathode material, obtain larger Flied emission current density, its practical value will be promoted.But, carbon nano-tube is due to the impact of himself geometric shape, field-electron emission mainly occurs in the less tip of radius of curvature (more sharp-pointed), smooth tube wall then almost do not have field-electron emission, namely the effect of external electric field is merely able to form enough large local electric field at carbon nano-tube tip, electronics can overcome carbon nano tube surface potential barrier and overflow under the effect of this large local electric field, but due to local electric field insufficient strength on tube wall, field electronics can not be overflowed.This number only decreasing its effective field launch point in the feature of most advanced and sophisticated launching site electronics to a great extent of carbon nano-tube, is unfavorable for the field-electron emission of high current density.Therefore, if can be made by certain means carbon nano-tube except tip, also have how new effective field launch point, just can reduce unlatching field and the threshold field of carbon nano-tube to a certain extent, and increase its Flied emission current density.
Take carbon nano-tube as the feature of field-transmitting cathode due to its one dimension of base, heat-delivery surface is little relative to this two-dimensional material of Graphene, the impact of Joule heat is more easily subject in emission process on the scene, particularly in high current density Flied emission situation, part effective field launch point can burn because of a large amount of accumulation of Joule heat, this will reduce the field-electron emission ability of cathode material to a certain extent, namely carbon nano-tube is compared to this two-dimension nano materials of Graphene, its field emission stability is poor, this will significantly shorten the useful life of carbon nanotube-based field-transmitting cathode in actual applications.Research shows, the carbon nano-tube of those rich defects, contact instability effectively can be removed by Surface Modification of Carbon Nanotube By Plasma, and these carbon nano-tube principal element of declining of Flied emission process midfield emission current just, under action of plasma, it removal will be promoted the field emission stability of filed emission cathode material undoubtedly.In addition, long-time the high temperature anneal also can reduce the quantity of rich defect carbon nano-tube to a certain extent, thus makes to be that the field-transmitting cathode of base has better field emission stability with carbon nano-tube.
As can be seen here, more effective field launch point is made it have by introducing technological means process carbon nano-tube, open field and threshold field to reduce it, promote its Flied emission current density, and this technological means can also promote its field emission stability to a certain extent, be that the filed emission cathode material of base has higher using value with carbon nano-tube by making prepared.
Summary of the invention
The object of the invention is to overcome existing with carbon nano-tube be the field-transmitting cathode effective field launch point number of base few, open that field is relatively high with threshold field, relative low, the deficiency that field emission stability is bad of Flied emission current density, utilize a kind of simple low-power plasma process process carbon nano pipe array, provide a kind of and open field and threshold field is low, Flied emission current density is large, field emission stability is good carbon nanotube-based filed emission cathode material.
The object of the invention is to be reached by following measure:
The preparation method of the carbon nano-tube array field emission cathode that a kind of carbon nano-particle is coated, it is characterized in that the carbon nano pipe array utilizing radio-frequency technique generation hydrogen plasma to prepare to process thermal chemical vapor deposition method, adjustment radio-frequency power is 30-50W, base reservoir temperature is 1000K, reative cell air pressure is 100Pa, the processing time is 10-30 hour, finally obtains the carbon nano-tube array field emission cathode material that the carbon nano-particle of different-shape is coated; Described carbon nano-particle refers to the particle that diameter is generally 15-30 nanometer.
Carbon nano pipe array of the present invention can be prepared with traditional thermal chemical vapor deposition method, also can prepare by the method that other can prepare array carbon nano tube arbitrarily.
The preparation method of the carbon nano-tube array field emission cathode that carbon nano-particle of the present invention is coated, can be lower powered radio frequency source for generation of the device of hydrogen plasma in preparation, also can be that other can produce the device of low power density hydrogen plasma arbitrarily.
The present invention further discloses the preparation method of the coated carbon nano-tube array field emission cathode of carbon nano-particle, it is characterized in that carrying out as follows:
(1) by silicon single crystal flake each ultrasonic cleaning 10 minutes in deionized water, acetone and absolute ethyl alcohol successively, ultrasonic power is 50W, its object is to the organic pollution removing silicon wafer surface.
(2) silicon wafer that step (1) obtains being placed to volume ratio is soak 5 minutes in the hydrofluoric acid of 4%, its object is to the silica overlayer removing silicon wafer surface, naturally dries afterwards.
(3) silicon wafer obtained step (2) carries out carrying and can bombard preliminary treatment by iron ion in metal vapor vacuum arc source (MEVVA source), during bombardment, iron ion energy is about 15keV, line is 10 milliamperes, processing time is 15 minutes, its object is to promote the adhesion between carbon nano-tube and silicon base.
(4) step (3) is obtained carry can the silicon wafer that bombarded of iron ion to insert deposit thickness in magnetic control sputtering device be the iron catalyst of 5 nanometers, concrete grammar is: put into by silicon wafer on magnetic control sputtering device sample stage, source of iron to be a diameter be high-purity (4N) iron target of 75 millimeters, is first evacuated to about 8 × 10
-5pa, then passes into high-purity (5N) argon gas, and regulate deposition chambers air pressure to be 1.0Pa, during deposition, DC power supply electric current is 60 milliamperes, and on sample stage, add 150 volts of back bias voltages, sedimentation time is 125 seconds, and the iron film thickness that obtains is 5 nanometers simultaneously.
(5) silicon chip depositing 5 Nanoscale Iron catalyst that step (4) obtains is put into high quartz tube furnace, first by catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition, after under 150sccm ammonia, 1023K condition process 10 minutes to promote catalyst activity, finally growth at atmosphere carbon nano pipe array under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes.
(6) carbon nano pipe array that step (5) obtains is put into the process chamber of radio-frequency unit, pass into high-purity hydrogen (5N), regulate reative cell air pressure to be 100Pa, and 1000K is heated to substrate, wait for air pressure and temperature stabilization;
(7) on the basis of step (6), start radio frequency source, adjustment radio-frequency power is 30-50W, starts to process carbon nano pipe array, and the processing time is 10-30 hour, and final gained is the coated carbon nano pipe array of carbon nano-particle.
(8) silicon single crystal flake of the carbon nano pipe array that the growth obtained with step (7) has carbon nano-particle coated is that substrate assembles field electronic emitter according to a conventional method, specific as follows: to stick to growing the silicon single crystal flake of carbon nano pipe array having carbon nano-particle coated on copper metal electrode that thickness is about 2 millimeters as field-transmitting cathode with conducting resinl, and by minus earth, the copper coin of 2 millimeters is about as anode with a thickness, two electrode thickness are the ring dress polytetrafluoroethylene isolation of 200 microns, load positive bias is on positive plate, just can obtain stable field-electron emission, the size of Flied emission electric current regulates by changing positive bias size, (Flied emission current density is 10 μ A/cm to arrange the threshold electric field of the filed emission cathode material for base with the carbon nano-pipe array that the carbon nano-particle that silicon single crystal flake grows is coated
2required electric field) only there is 0.90-1.10 V/ μm, (Flied emission current density is 10 mA/cm to threshold field
2required electric field) only there is 1.44-1.63 V/ μm, maximum field emission can reach 46.78 mA/cm
2, and there is good field emission stability.
The preparation method of the carbon nano-tube array field emission cathode that carbon nano-particle disclosed by the invention is coated compared with prior art its superiority is:
The coated carbon nano-tube array field emission cathode of the carbon nano-particle prepared of this method has very low unlatching field (0.90-1.10 V/ μm) and threshold field (1.44-1.63 V/ μm), and maximum field emission can reach 46.78 mA/cm
2, and field emission stability good (curent change amplitude is very little in 10 hours), these indexs compare original undressed carbon nano pipe array all to be had and significantly improves.Method of plasma processing used, technique is comparatively simple, not high to equipment requirement, and can not introduce other impurity in carbon nano-tube, has higher practical value.
accompanying drawing explanation:
Fig. 1 is the process flow diagram that the present invention prepares carbon nano-particle enveloped carbon nanometer tube array, is mainly divided into the substrate of preparation clean silicon wafer, magnetron sputtering method Precipitated iron catalyst, thermal chemical vapor deposition method to prepare four parts such as carbon nano pipe array, low-power radio frequency hydrogen plasma process carbon nano pipe array;
Fig. 2 is the scanning electron microscopic picture by the carbon nano pipe array prepared by experiment condition shown in embodiment 1, shown length of carbon nanotube is about 23 microns, upper right corner illustration is depicted as the scanning electron microscopic picture on carbon nano pipe array top, and lower right corner illustration is depicted as the scanning electron microscopic picture in the middle part of carbon nano-tube;
Fig. 3 is the structural representation of radio-frequency unit used in the present invention; Hydrogen purity used is 5N, and heater is self-control molybdenum filament heater, vacuumizes with " molecular pump+mechanical pump " combination unit;
Fig. 4 is the scanning electron microscopic picture of the coated carbon nano pipe array of the carbon nano-particle prepared under different condition, and gained carbon nano-particle diameter, mostly in 15-30 nanometer, comprising:
41. by embodiment 1 condition (radio-frequency power: 30W; Processing time: 10 hours) prepared by the scanning electron microscopic picture of the coated carbon nano pipe array of carbon nano-particle, upper right and lower right corner illustration are corresponding high power scanning electron microscopic picture, correspond to square frame identification division in figure;
42. by embodiment 2 condition (radio-frequency power: 30W; Processing time: 20 hours) prepared by the scanning electron microscopic picture of the coated carbon nano pipe array of carbon nano-particle;
43. by embodiment 3 condition (radio-frequency power: 30W; Processing time: 30 hours) prepared by the scanning electron microscopic picture of the coated carbon nano pipe array of carbon nano-particle;
Figure 5 shows that the structural representation of high vacuum Flied emission tester, for testing the field emission performance of the coated carbon nano pipe array of carbon nano-particle prepared in each embodiment; This device is the Flied emission testing apparatus of a conventional diode configuration: with prepared field emmision material for negative electrode, be about the corrosion resistant plate of 10 centimetres with diameter for anode, anode position is accurately adjustable, and two die openings remain 2 millimeters; In test, by minus earth, in the adjustable positive bias of plate-load 0-10kV; Test data is by the automatic record of computer;
Fig. 6 is the field emission performance figure of the coated carbon nano pipe array of the carbon nano-particle prepared at different conditions, sample prepared by specifically comprising in embodiment 1, embodiment 2, embodiment 3 compares with original carbon nanotubes array field emission performance, what it characterized is the variation relation that Flied emission current density increases with electric field strength, wherein
j thwhat represent is threshold field emission, and its size is 10 mA/cm
2;
Fig. 7 is the field emission stability figure of the coated carbon nano pipe array of the carbon nano-particle prepared by embodiment 2 and original carbon nanotubes array, sign be when extra electric field is constant, Flied emission current density relation over time.
Embodiment
Below in conjunction with drawings and Examples, the present invention is described in more detail, but the invention is not restricted to these embodiments.Wherein used silicon single crystal flake, absolute ethyl alcohol, acetone, hydrofluoric acid, high-purity hydrogen, high purity acetylene gas, high-purity ammonia, high-purity argon gas, high purity iron target etc. all have commercially available.The devices such as ultrasonic cleaning, metal vapor vacuum arc source (MEVVA source), magnetron sputtering, high temperature process furnances, radio frequency, Flied emission tester all have commercially available.
The process flow diagram that the present invention prepares the coated carbon nano pipe array of carbon nano-particle is shown in Fig. 1, be divided into the substrate of preparation clean silicon wafer, magnetron sputtering method Precipitated iron catalyst, thermal chemical vapor deposition method to prepare four parts such as carbon nano pipe array, low-power radio frequency hydrogen plasma process carbon nano pipe array, part prepared by following examples relevant sample all performs by this four step.
Embodiment 1
(1) clean silicon wafer substrate is prepared:
First silicon chip is cut into 2cm × 2cm small pieces, in deionized water, acetone and absolute ethyl alcohol, each ultrasonic (50W) cleans 10 minutes successively, again silicon wafer is put into volume ratio be 4% hydrofluoric acid soak 5 minutes, obtain totally pollution-free and without the substrate of silica overlayer.
(2) magnetron sputtering method Precipitated iron catalyst:
Being deposited in magnetic control sputtering device (having commercially available) of iron catalyst is carried out.Before this, first by silicon single crystal flake in metal vapor vacuum arc source (MEVVA source, have commercially available) in carry out carry can an iron ion bombardment preliminary treatment, iron ion energy is about 15keV, line is 10 milliamperes, processing time is 15 minutes, and this process effectively can promote the adhesion between carbon nano-tube and silicon base; Then can be placed on sample stage by the silicon wafer that bombard of iron ion by carrying, first to vacuum chamber extremely about 8 × 10
-5pa, with despumation gaseous contamination, then pass into high-purity (5N) argon gas, adjustment chamber pressure is 1.0Pa; During deposition, DC power supply electric current is 60 milliamperes, and on sample stage, add 150 volts of back bias voltages, sedimentation time is 125 seconds, and the iron film thickness that obtains is 5 nanometers simultaneously.
(3) thermal chemical vapor deposition method prepares carbon nano pipe array:
The growth of carbon nano pipe array completes in high temperature process furnances (having commercially available), and method therefor is traditional thermal chemical vapor deposition method, and whole process completes at ambient pressure.First the silicon wafer depositing 5 Nanoscale Iron catalyst is inserted in tube furnace quartz ampoule on sample stage, close after good quartz ampoule, by iron catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition; After under 150sccm ammonia, 1023K condition process 10 minutes to promote catalyst activity; Finally carbon nano tube array grows under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes.The scanning electron microscopic picture of gained carbon nano pipe array is under this condition shown in Fig. 2, can find out, length of carbon nanotube is about 23 microns (Fig. 2), tip flexion (Fig. 2 upper right corner illustration), but middle part array better (Fig. 2 lower right corner illustration), and smooth surface.
(4) low-power radio frequency hydrogen plasma process carbon nano pipe array:
Hydrogen plasma process carbon nano-pipe array is listed in radio-frequency unit (having commercially available) and completes, and is the structural representation of this device shown in Fig. 3.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 8 × 10
-4pa, then heat substrate in hydrogen (purity is 5N) atmosphere, heating rate is about 60K/min, until temperature stabilization is at 1000K, and adjustable pressure is 100Pa, after temperature and air pressure are all stablized, start radio frequency source, adjustment radio-frequency power is 30W, and the processing time is 10 hours.The scanning electron microscopic picture of the coated carbon nano pipe array of the carbon nano-particle of gained is under this condition shown in Fig. 4-41, compared with original carbon nanotubes shown in Fig. 2, the change of carbon nano-tube overall pattern is little, but surface is coated by carbon nano-particle institute, particle is less, diameter is many in 15-20 nanometer, can clearly find out from Fig. 4-41 upper right and lower right corner high power scanning electron microscopic picture, completely different with the smooth surface (Fig. 2 illustration) of original carbon nanotubes, these Carbon Nanohorns rise all may become potential effective field launch point.
(5) field emission performance test:
The field emission performance test of the carbon nano pipe array that carbon nano-particle is coated completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 5.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).Carbon nano pipe array sample conducting resinl coated for prepared carbon nano-particle is sticked on copper sample platform, in this, as field-transmitting cathode, and by minus earth; Anode is the stainless steel plectane that a diameter is about 10 centimetres, anode and cathode keeping parallelism, and spacing is 2 millimeters; During test, the adjustable positive bias of load 0-10kV on anode, bias voltage speedup is constant is 500 V/min, and test result is recorded in computer automatically by program.The field emission performance figure of the coated carbon nano pipe array of the carbon nano-particle prepared at different conditions is shown in Fig. 6, sample prepared by specifically comprising in the present embodiment, embodiment 2, embodiment 3 compares with original carbon nanotubes array field emission performance, and what it characterized is the variation relation that Flied emission current density increases with electric field strength.Can find out, under 30W, be respectively 1.10 V/ μm, 1.63 V/ μm and 37.24 mA/cm through the unlatching field of the coated carbon nano pipe array of the carbon nano-particle of hydrogen plasma process gained after 10 hours, threshold field and maximum field emission
2, be better than 1.24 V/ μm of original carbon nanotubes, 1.76 V/ μm and 21.90 mA/cm
2.After the lifting of field emission performance is attributable to the process of long-time low-power hydrogen plasma, carbon nano tube surface effective field launch point increases, a large amount of carbon nano-particles all can become effective field launch point, and Flied emission current density compares original carbon nanotubes only has most advanced and sophisticated electron emission will significantly promote undoubtedly.
(6) field electronic emitter assembling (conventional sectional method):
With conducting resinl, the silicon single crystal flake growing the carbon nano pipe array having carbon nano-particle coated being sticked to thickness is on the copper electrode of 2 millimeters, it can be used as field-transmitting cathode, and by minus earth, anode to be a thickness the be copper plate electrode of 2 millimeters, anode and cathode keeping parallelism, separate with the ring dress polytetrafluoroethylene that thickness is 200 microns, load positive bias is on positive plate, just can obtain stable field-electron emission, the control of Flied emission current density size realizes by regulating positive plate bias voltage.
Embodiment 2
(1) clean silicon wafer substrate is prepared:
First silicon chip is cut into 2cm × 2cm small pieces, in deionized water, acetone and absolute ethyl alcohol, each ultrasonic (50W) cleans 10 minutes successively, again silicon wafer is put into volume ratio be 4% hydrofluoric acid soak 5 minutes, obtain totally pollution-free and without the substrate of silica overlayer.
(2) magnetron sputtering method Precipitated iron catalyst:
Being deposited in magnetic control sputtering device (having commercially available) of iron catalyst is carried out.Before this, first by silicon single crystal flake in metal vapor vacuum arc source (MEVVA source, have commercially available) in carry out carry can an iron ion bombardment preliminary treatment, iron ion energy is about 15keV, line is 10 milliamperes, processing time is 15 minutes, and this process effectively can promote the adhesion between carbon nano-tube and silicon base; Then can be placed on sample stage by the silicon wafer that bombard of iron ion by carrying, first to vacuum chamber extremely about 8 × 10
-5pa, with despumation gaseous contamination, then pass into high-purity (5N) argon gas, adjustment chamber pressure is 1.0Pa; During deposition, DC power supply electric current is 60 milliamperes, and on sample stage, add 150 volts of back bias voltages, sedimentation time is 125 seconds, and the iron film thickness that obtains is 5 nanometers simultaneously.
(3) thermal chemical vapor deposition method prepares carbon nano pipe array:
The growth of carbon nano pipe array completes in high temperature process furnances (having commercially available), and method therefor is traditional thermal chemical vapor deposition method, and whole process completes at ambient pressure.First the silicon wafer depositing 5 Nanoscale Iron catalyst is inserted in tube furnace quartz ampoule on sample stage, close after good quartz ampoule, by iron catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition; After under 150sccm ammonia, 1023K condition process 10 minutes to promote catalyst activity; Finally carbon nano tube array grows under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes.
(4) low-power radio frequency hydrogen plasma process carbon nano pipe array:
Hydrogen plasma process carbon nano-pipe array is listed in radio-frequency unit (having commercially available) and completes, and is the structural representation of this device shown in Fig. 3.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 8 × 10
-4pa, then heat substrate in hydrogen (purity is 5N) atmosphere, heating rate is about 60K/min, until temperature stabilization is at 1000K, and adjustable pressure is 100Pa, after temperature and air pressure are all stablized, start radio frequency source, adjustment radio-frequency power is 30W, and the processing time is 20 hours.The scanning electron microscopic picture of the coated carbon nano pipe array of the carbon nano-particle of gained is in the present embodiment shown in Fig. 4-42, compared with original carbon nanotubes shown in Fig. 2, the change of carbon nano-tube overall pattern is little, but surface is coated by carbon nano-particle institute, after particle diameter compares 30W, process in 10 hours, the carbon nano-tube (Fig. 4-41) of gained has increased slightly, mostly in 20-30 nanometer, completely different with the smooth surface (Fig. 2 illustration) of original carbon nanotubes, these Carbon Nanohorns rise all may become potential effective field launch point.
(5) field emission performance test:
The field emission performance test of the carbon nano pipe array that carbon nano-particle is coated completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 5.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).Carbon nano pipe array sample conducting resinl coated for prepared carbon nano-particle is sticked on copper sample platform, in this, as field-transmitting cathode, and by minus earth; Anode is the stainless steel plectane that a diameter is about 10 centimetres, anode and cathode keeping parallelism, and spacing is 2 millimeters; During test, the adjustable positive bias of load 0-10kV on anode, bias voltage speedup is constant is 500V/min, and test result is recorded in computer automatically by program.As can be seen from Figure 6,0.90 V/ μm, 1.44 V/ μm and 43.42 mA/cm are respectively through the unlatching field of the coated carbon nano pipe array of the carbon nano-particle of hydrogen plasma process gained after 20 hours, threshold field and maximum field emission under 30W
2, 1.24 V/ μm of original carbon nanotubes, 1.76 V/ μm and 21.90 mA/cm are far superior to
2, 1.10 V/ μm of carbon nano pipe array, 1.63 V/ μm and 37.24 mA/cm after the 30W that also will be better than, process in 10 hours
2.The increasing of carbon nano tube surface effective field launch point after significantly the promoting of field emission performance is attributable to the process of long-time low-power hydrogen plasma, a large amount of carbon nano-particles all can become effective field launch point, and Flied emission current density compares original carbon nanotubes only has most advanced and sophisticated electron emission will significantly promote undoubtedly.To Figure 7 shows that in the present embodiment the field emission stability figure of the carbon nano pipe array that prepared carbon nano-particle is coated and original unprocessed carbon nano pipe array, sign be under constant External Electrical Field, Flied emission current density relation over time.Can find out, the carbon nano pipe array that carbon nano-particle prepared in the present embodiment is coated has field emission stability more better than original carbon nanotubes array, and in test in 10 hours, (mean field emission is 12.25 mA/cm
2), Flied emission current density does not obviously decay, and fluctuates also very little, but original carbon nanotubes sample is in test in 10 hours, and (mean field emission is 9.80 mA/cm
2), current density decay about 17%.Although the mean field emission of the two all threshold field emission (
j th, 10 mA/cm
2) near, but in test, the constant electric field strength of carbon nano-particle enveloped carbon nanometer tube sample is only 1.50 V/ μm, and much smaller than 1.80 V/ μm of original carbon nanotubes sample, the reduction of this operating voltage is very important to practical application.As can be seen here, long-time high temperature and plasma treatment significantly improve the field emission stability of carbon nano pipe array.
(6) field electronic emitter assembling (conventional sectional method):
With conducting resinl, the silicon single crystal flake growing the carbon nano pipe array having carbon nano-particle coated being sticked to thickness is on the copper electrode of 2 millimeters, it can be used as field-transmitting cathode, and by minus earth, anode to be a thickness the be copper plate electrode of 2 millimeters, anode and cathode keeping parallelism, separate with the ring dress polytetrafluoroethylene that thickness is 200 microns, load positive bias is on positive plate, just can obtain stable field-electron emission, the control of Flied emission current density size realizes by regulating positive plate bias voltage.
Embodiment 3
(1) clean silicon wafer substrate is prepared:
First silicon chip is cut into 2cm × 2cm small pieces, in deionized water, acetone and absolute ethyl alcohol, each ultrasonic (50W) cleans 10 minutes successively, again silicon wafer is put into volume ratio be 4% hydrofluoric acid soak 5 minutes, obtain totally pollution-free and without the substrate of silica overlayer.
(2) magnetron sputtering method Precipitated iron catalyst:
Being deposited in magnetic control sputtering device (having commercially available) of iron catalyst is carried out.Before this, first by silicon single crystal flake in metal vapor vacuum arc source (MEVVA source, have commercially available) in carry out carry can an iron ion bombardment preliminary treatment, iron ion energy is about 15keV, line is 10 milliamperes, processing time is 15 minutes, and this process effectively can promote the adhesion between carbon nano-tube and silicon base; Then can be placed on sample stage by the silicon wafer that bombard of iron ion by carrying, first to vacuum chamber extremely about 8 × 10
-5pa, with despumation gaseous contamination, then pass into high-purity (5N) argon gas, adjustment chamber pressure is 1.0Pa; During deposition, DC power supply electric current is 60 milliamperes, and on sample stage, add 150 volts of back bias voltages, sedimentation time is 125 seconds, and the iron film thickness that obtains is 5 nanometers simultaneously.
(3) thermal chemical vapor deposition method prepares carbon nano pipe array:
The growth of carbon nano pipe array completes in high temperature process furnances (having commercially available), and method therefor is traditional thermal chemical vapor deposition method, and whole process completes at ambient pressure.First the silicon wafer depositing 5 Nanoscale Iron catalyst is inserted in tube furnace quartz ampoule on sample stage, close after good quartz ampoule, by iron catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition; After under 150sccm ammonia, 1023K condition process 10 minutes to promote catalyst activity; Finally carbon nano tube array grows under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes.
(4) low-power radio frequency hydrogen plasma process carbon nano pipe array:
Hydrogen plasma process carbon nano-pipe array is listed in radio-frequency unit (having commercially available) and completes, and is the structural representation of this device shown in Fig. 3.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 8 × 10
-4pa, then heat substrate in hydrogen (purity is 5N) atmosphere, heating rate is about 60K/min, until temperature stabilization is at 1000K, and adjustable pressure is 100Pa, after temperature and air pressure are all stablized, start radio frequency source, adjustment radio-frequency power is 30W, and the processing time is 30 hours.The scanning electron microscopic picture at the coated carbon nano pipe array of the carbon nano-particle of the present embodiment gained is shown in Fig. 4-43, compared with original carbon nanotubes shown in Fig. 2, the change of carbon nano-tube overall pattern is little, but surface is coated by carbon nano-particle institute, particle diameter compares 30W, 10 hours (Fig. 4-41) and 30W, after 20 hours (Fig. 4-42) process, the carbon nano-tube of gained is all little, mostly in 15-20 nanometer, and grain boundary is unintelligible, but it is completely different with the smooth surface (Fig. 2 illustration) of original carbon nanotubes, these Carbon Nanohorns rise all may become potential effective field launch point.
(5) field emission performance test:
The field emission performance test of the carbon nano pipe array that carbon nano-particle is coated completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 5.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).Carbon nano pipe array sample conducting resinl coated for prepared carbon nano-particle is sticked on copper sample platform, in this, as field-transmitting cathode, and by minus earth; Anode is the stainless steel plectane that a diameter is about 10 centimetres, anode and cathode keeping parallelism, and spacing is 2 millimeters; During test, the adjustable positive bias of load 0-10kV on anode, bias voltage speedup is constant is 500V/min, and test result is recorded in computer automatically by program.As can be seen from Figure 6,1.02 V/ μm, 1.59 V/ μm and 35.44 mA/cm are respectively through the unlatching field of the coated carbon nano pipe array of the carbon nano-particle of hydrogen plasma process gained after 30 hours, threshold field and maximum field emission under 30W
2, be better than 1.24 V/ μm of original carbon nanotubes, 1.76 V/ μm and 21.90 mA/cm
2.After the lifting of field emission performance is attributable to the process of long-time low-power hydrogen plasma, carbon nano tube surface effective field launch point increases, a large amount of carbon nano-particles all can become effective field launch point, and Flied emission current density compares original carbon nanotubes only has most advanced and sophisticated electron emission will significantly promote undoubtedly.
(6) field electronic emitter assembling (conventional sectional method):
With conducting resinl, the silicon single crystal flake growing the carbon nano pipe array having carbon nano-particle coated being sticked to thickness is on the copper electrode of 2 millimeters, it can be used as field-transmitting cathode, and by minus earth, anode to be a thickness the be copper plate electrode of 2 millimeters, anode and cathode keeping parallelism, separate with the ring dress polytetrafluoroethylene that thickness is 200 microns, load positive bias is on positive plate, just can obtain stable field-electron emission, the control of Flied emission current density size realizes by regulating positive plate bias voltage.
Embodiment 4
(1) clean silicon wafer substrate is prepared:
First silicon chip is cut into 2cm × 2cm small pieces, in deionized water, acetone and absolute ethyl alcohol, each ultrasonic (50W) cleans 10 minutes successively, again silicon wafer is put into volume ratio be 4% hydrofluoric acid soak 5 minutes, obtain totally pollution-free and without the substrate of silica overlayer.
(2) magnetron sputtering method Precipitated iron catalyst:
Being deposited in magnetic control sputtering device (having commercially available) of iron catalyst is carried out.Before this, first by silicon single crystal flake in metal vapor vacuum arc source (MEVVA source, have commercially available) in carry out carry can an iron ion bombardment preliminary treatment, iron ion energy is about 15keV, line is 10 milliamperes, processing time is 15 minutes, and this process effectively can promote the adhesion between carbon nano-tube and silicon base; Then can be placed on sample stage by the silicon wafer that bombard of iron ion by carrying, first to vacuum chamber extremely about 8 × 10
-5pa, with despumation gaseous contamination, then pass into high-purity (5N) argon gas, adjustment chamber pressure is 1.0Pa; During deposition, DC power supply electric current is 60 milliamperes, and on sample stage, add 150 volts of back bias voltages, sedimentation time is 125 seconds, and the iron film thickness that obtains is 5 nanometers simultaneously.
(3) thermal chemical vapor deposition method prepares carbon nano pipe array:
The growth of carbon nano pipe array completes in high temperature process furnances (having commercially available), and method therefor is traditional thermal chemical vapor deposition method, and whole process completes at ambient pressure.First the silicon wafer depositing 5 Nanoscale Iron catalyst is inserted in tube furnace quartz ampoule on sample stage, close after good quartz ampoule, by iron catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition; After under 150sccm ammonia, 1023K condition process 10 minutes to promote catalyst activity; Finally carbon nano tube array grows under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes.
(4) low-power radio frequency hydrogen plasma process carbon nano pipe array:
Hydrogen plasma process carbon nano-pipe array is listed in radio-frequency unit (having commercially available) and completes, and is the structural representation of this device shown in Fig. 3.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 8 × 10
-4pa, then heat substrate in hydrogen (purity is 5N) atmosphere, heating rate is about 60K/min, until temperature stabilization is at 1000K, and adjustable pressure is 100Pa, after temperature and air pressure are all stablized, start radio frequency source, adjustment radio-frequency power is 40W, and the processing time is 10 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano pipe array that carbon nano-particle is coated completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 5.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).Carbon nano pipe array sample conducting resinl coated for prepared carbon nano-particle is sticked on copper sample platform, in this, as field-transmitting cathode, and by minus earth; Anode is the stainless steel plectane that a diameter is about 10 centimetres, anode and cathode keeping parallelism, and spacing is 2 millimeters; During test, the adjustable positive bias of load 0-10kV on anode, bias voltage speedup is constant is 500V/min, and test result is recorded in computer automatically by program.The unlatching field of the carbon nano pipe array that the carbon nano-particle of the present embodiment gained is coated, threshold field and maximum field emission are respectively 1.04 V/ μm, 1.60 V/ μm and 36.12 mA/cm
2, be better than 1.24 V/ μm of original carbon nanotubes, 1.76 V/ μm and 21.90 mA/cm
2.After the lifting of field emission performance is attributable to the process of long-time low-power hydrogen plasma, carbon nano tube surface effective field launch point increases, a large amount of carbon nano-particles all can become effective field launch point, and Flied emission current density compares original carbon nanotubes only has most advanced and sophisticated electron emission will significantly promote undoubtedly.
(6) field electronic emitter assembling (conventional sectional method):
With conducting resinl, the silicon single crystal flake growing the carbon nano pipe array having carbon nano-particle coated being sticked to thickness is on the copper electrode of 2 millimeters, it can be used as field-transmitting cathode, and by minus earth, anode to be a thickness the be copper plate electrode of 2 millimeters, anode and cathode keeping parallelism, separate with the ring dress polytetrafluoroethylene that thickness is 200 microns, load positive bias is on positive plate, just can obtain stable field-electron emission, the control of Flied emission current density size realizes by regulating positive plate bias voltage.
Embodiment 5
(1) clean silicon wafer substrate is prepared:
First silicon chip is cut into 2cm × 2cm small pieces, in deionized water, acetone and absolute ethyl alcohol, each ultrasonic (50W) cleans 10 minutes successively, again silicon wafer is put into volume ratio be 4% hydrofluoric acid soak 5 minutes, obtain totally pollution-free and without the substrate of silica overlayer.
(2) magnetron sputtering method Precipitated iron catalyst:
Being deposited in magnetic control sputtering device (having commercially available) of iron catalyst is carried out.Before this, first by silicon single crystal flake in metal vapor vacuum arc source (MEVVA source, have commercially available) in carry out carry can an iron ion bombardment preliminary treatment, iron ion energy is about 15keV, line is 10 milliamperes, processing time is 15 minutes, and this process effectively can promote the adhesion between carbon nano-tube and silicon base; Then can be placed on sample stage by the silicon wafer that bombard of iron ion by carrying, first to vacuum chamber extremely about 8 × 10
-5pa, with despumation gaseous contamination, then pass into high-purity (5N) argon gas, adjustment chamber pressure is 1.0Pa; During deposition, DC power supply electric current is 60 milliamperes, and on sample stage, add 150 volts of back bias voltages, sedimentation time is 125 seconds, and the iron film thickness that obtains is 5 nanometers simultaneously.
(3) thermal chemical vapor deposition method prepares carbon nano pipe array:
The growth of carbon nano pipe array completes in high temperature process furnances (having commercially available), and method therefor is traditional thermal chemical vapor deposition method, and whole process completes at ambient pressure.First the silicon wafer depositing 5 Nanoscale Iron catalyst is inserted in tube furnace quartz ampoule on sample stage, close after good quartz ampoule, by iron catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition; After under 150sccm ammonia, 1023K condition process 10 minutes to promote catalyst activity; Finally carbon nano tube array grows under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes.
(4) low-power radio frequency hydrogen plasma process carbon nano pipe array:
Hydrogen plasma process carbon nano-pipe array is listed in radio-frequency unit (having commercially available) and completes, and is the structural representation of this device shown in Fig. 3.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 8 × 10
-4pa, then heat substrate in hydrogen (purity is 5N) atmosphere, heating rate is about 60K/min, until temperature stabilization is at 1000K, and adjustable pressure is 100Pa, after temperature and air pressure are all stablized, start radio frequency source, adjustment radio-frequency power is 40W, and the processing time is 20 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano pipe array that carbon nano-particle is coated completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 5.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).Carbon nano pipe array sample conducting resinl coated for prepared carbon nano-particle is sticked on copper sample platform, in this, as field-transmitting cathode, and by minus earth; Anode is the stainless steel plectane that a diameter is about 10 centimetres, anode and cathode keeping parallelism, and spacing is 2 millimeters; During test, the adjustable positive bias of load 0-10kV on anode, bias voltage speedup is constant is 500V/min, and test result is recorded in computer automatically by program.The unlatching field of the carbon nano pipe array that the carbon nano-particle of the present embodiment gained is coated, threshold field and maximum field emission are respectively 0.96 V/ μm, 1.52 V/ μm and 41.48 mA/cm
2, be better than 1.24 V/ μm of original carbon nanotubes, 1.76 V/ μm and 21.90 mA/cm
2.After the lifting of field emission performance is attributable to the process of long-time low-power hydrogen plasma, carbon nano tube surface effective field launch point increases, a large amount of carbon nano-particles all can become effective field launch point, and Flied emission current density compares original carbon nanotubes only has most advanced and sophisticated electron emission will significantly promote undoubtedly.
(6) field electronic emitter assembling (conventional sectional method):
With conducting resinl, the silicon single crystal flake growing the carbon nano pipe array having carbon nano-particle coated being sticked to thickness is on the copper electrode of 2 millimeters, it can be used as field-transmitting cathode, and by minus earth, anode to be a thickness the be copper plate electrode of 2 millimeters, anode and cathode keeping parallelism, separate with the ring dress polytetrafluoroethylene that thickness is 200 microns, load positive bias is on positive plate, just can obtain stable field-electron emission, the control of Flied emission current density size realizes by regulating positive plate bias voltage.
Embodiment 6
(1) clean silicon wafer substrate is prepared:
First silicon chip is cut into 2cm × 2cm small pieces, in deionized water, acetone and absolute ethyl alcohol, each ultrasonic (50W) cleans 10 minutes successively, again silicon wafer is put into volume ratio be 4% hydrofluoric acid soak 5 minutes, obtain totally pollution-free and without the substrate of silica overlayer.
(2) magnetron sputtering method Precipitated iron catalyst:
Being deposited in magnetic control sputtering device (having commercially available) of iron catalyst is carried out.Before this, first by silicon single crystal flake in metal vapor vacuum arc source (MEVVA source, have commercially available) in carry out carry can an iron ion bombardment preliminary treatment, iron ion energy is about 15keV, line is 10 milliamperes, processing time is 15 minutes, and this process effectively can promote the adhesion between carbon nano-tube and silicon base; Then can be placed on sample stage by the silicon wafer that bombard of iron ion by carrying, first to vacuum chamber extremely about 8 × 10
-5pa, with despumation gaseous contamination, then pass into high-purity (5N) argon gas, adjustment chamber pressure is 1.0Pa; During deposition, DC power supply electric current is 60 milliamperes, and on sample stage, add 150 volts of back bias voltages, sedimentation time is 125 seconds, and the iron film thickness that obtains is 5 nanometers simultaneously.
(3) thermal chemical vapor deposition method prepares carbon nano pipe array:
The growth of carbon nano pipe array completes in high temperature process furnances (having commercially available), and method therefor is traditional thermal chemical vapor deposition method, and whole process completes at ambient pressure.First the silicon wafer depositing 5 Nanoscale Iron catalyst is inserted in tube furnace quartz ampoule on sample stage, close after good quartz ampoule, by iron catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition; After under 150sccm ammonia, 1023K condition process 10 minutes to promote catalyst activity; Finally carbon nano tube array grows under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes.
(4) low-power radio frequency hydrogen plasma process carbon nano pipe array:
Hydrogen plasma process carbon nano-pipe array is listed in radio-frequency unit (having commercially available) and completes, and is the structural representation of this device shown in Fig. 3.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 8 × 10
-4pa, then heat substrate in hydrogen (purity is 5N) atmosphere, heating rate is about 60K/min, until temperature stabilization is at 1000K, and adjustable pressure is 100Pa, after temperature and air pressure are all stablized, start radio frequency source, adjustment radio-frequency power is 50W, and the processing time is 20 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano pipe array that carbon nano-particle is coated completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 5.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).Carbon nano pipe array sample conducting resinl coated for prepared carbon nano-particle is sticked on copper sample platform, in this, as field-transmitting cathode, and by minus earth; Anode is the stainless steel plectane that a diameter is about 10 centimetres, anode and cathode keeping parallelism, and spacing is 2 millimeters; During test, the adjustable positive bias of load 0-10kV on anode, bias voltage speedup is constant is 500V/min, and test result is recorded in computer automatically by program.The unlatching field of the carbon nano pipe array that the carbon nano-particle of the present embodiment gained is coated, threshold field and maximum field emission are respectively 0.98 V/ μm, 1.51 V/ μm and 40.57 mA/cm
2, be better than 1.24 V/ μm of original carbon nanotubes, 1.76 V/ μm and 21.90 mA/cm
2.After the lifting of field emission performance is attributable to the process of long-time low-power hydrogen plasma, carbon nano tube surface effective field launch point increases, a large amount of carbon nano-particles all can become effective field launch point, and Flied emission current density compares original carbon nanotubes only has most advanced and sophisticated electron emission will significantly promote undoubtedly.
(6) field electronic emitter assembling (conventional sectional method):
With conducting resinl, the silicon single crystal flake growing the carbon nano pipe array having carbon nano-particle coated being sticked to thickness is on the copper electrode of 2 millimeters, it can be used as field-transmitting cathode, and by minus earth, anode to be a thickness the be copper plate electrode of 2 millimeters, anode and cathode keeping parallelism, separate with the ring dress polytetrafluoroethylene that thickness is 200 microns, load positive bias is on positive plate, just can obtain stable field-electron emission, the control of Flied emission current density size realizes by regulating positive plate bias voltage.
Embodiment 7
(1) clean silicon wafer substrate is prepared:
First silicon chip is cut into 2cm × 2cm small pieces, in deionized water, acetone and absolute ethyl alcohol, each ultrasonic (50W) cleans 10 minutes successively, again silicon wafer is put into volume ratio be 4% hydrofluoric acid soak 5 minutes, obtain totally pollution-free and without the substrate of silica overlayer.
(2) magnetron sputtering method Precipitated iron catalyst:
Being deposited in magnetic control sputtering device (having commercially available) of iron catalyst is carried out.Before this, first by silicon single crystal flake in metal vapor vacuum arc source (MEVVA source, have commercially available) in carry out carry can an iron ion bombardment preliminary treatment, iron ion energy is about 15keV, line is 10 milliamperes, processing time is 15 minutes, and this process effectively can promote the adhesion between carbon nano-tube and silicon base; Then can be placed on sample stage by the silicon wafer that bombard of iron ion by carrying, first to vacuum chamber extremely about 8 × 10
-5pa, with despumation gaseous contamination, then pass into high-purity (5N) argon gas, adjustment chamber pressure is 1.0Pa; During deposition, DC power supply electric current is 60 milliamperes, and on sample stage, add 150 volts of back bias voltages, sedimentation time is 125 seconds, and the iron film thickness that obtains is 5 nanometers simultaneously.
(3) thermal chemical vapor deposition method prepares carbon nano pipe array:
The growth of carbon nano pipe array completes in high temperature process furnances (having commercially available), and method therefor is traditional thermal chemical vapor deposition method, and whole process completes at ambient pressure.First the silicon wafer depositing 5 Nanoscale Iron catalyst is inserted in tube furnace quartz ampoule on sample stage, close after good quartz ampoule, by iron catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition; After under 150sccm ammonia, 1023K condition process 10 minutes to promote catalyst activity; Finally carbon nano tube array grows under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes.
(4) low-power radio frequency hydrogen plasma process carbon nano pipe array:
Hydrogen plasma process carbon nano-pipe array is listed in radio-frequency unit (having commercially available) and completes, and is the structural representation of this device shown in Fig. 3.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 8 × 10
-4pa, then heat substrate in hydrogen (purity is 5N) atmosphere, heating rate is about 60K/min, until temperature stabilization is at 1000K, and adjustable pressure is 100Pa, after temperature and air pressure are all stablized, start radio frequency source, adjustment radio-frequency power is 35W, and the processing time is 15 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano pipe array that carbon nano-particle is coated completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 5.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).Carbon nano pipe array sample conducting resinl coated for prepared carbon nano-particle is sticked on copper sample platform, in this, as field-transmitting cathode, and by minus earth; Anode is the stainless steel plectane that a diameter is about 10 centimetres, anode and cathode keeping parallelism, and spacing is 2 millimeters; During test, the adjustable positive bias of load 0-10kV on anode, bias voltage speedup is constant is 500V/min, and test result is recorded in computer automatically by program.The unlatching field of the carbon nano pipe array that the carbon nano-particle of the present embodiment gained is coated, threshold field and maximum field emission are respectively 0.93 V/ μm, 1.46 V/ μm and 46.78 mA/cm
2, be better than 1.24 V/ μm of original carbon nanotubes, 1.76 V/ μm and 21.90 mA/cm
2.After the lifting of field emission performance is attributable to the process of long-time low-power hydrogen plasma, carbon nano tube surface effective field launch point increases, a large amount of carbon nano-particles all can become effective field launch point, and Flied emission current density compares original carbon nanotubes only has most advanced and sophisticated electron emission will significantly promote undoubtedly.
(6) field electronic emitter assembling (conventional sectional method):
With conducting resinl, the silicon single crystal flake growing the carbon nano pipe array having carbon nano-particle coated being sticked to thickness is on the copper electrode of 2 millimeters, it can be used as field-transmitting cathode, and by minus earth, anode to be a thickness the be copper plate electrode of 2 millimeters, anode and cathode keeping parallelism, separate with the ring dress polytetrafluoroethylene that thickness is 200 microns, load positive bias is on positive plate, just can obtain stable field-electron emission, the control of Flied emission current density size realizes by regulating positive plate bias voltage.
Finally it should be noted that, only list exemplary embodiments of the present invention above.But obviously the present invention is not limited to above-described embodiment; also have other experiment parameter combined methods many; the all scenario that those of ordinary skill in this research field can directly derive or associate from content disclosed by the invention, is all considered to be protection scope of the present invention.
Claims (4)
1. the preparation method of the carbon nano-tube array field emission cathode that a carbon nano-particle is coated, it is characterized in that the carbon nano pipe array utilizing radio-frequency technique generation hydrogen plasma to prepare to process thermal chemical vapor deposition method, adjustment radio-frequency power is 30-50W, base reservoir temperature is 1000K, reative cell air pressure is 100Pa, the processing time is 10-30 hour, finally obtains the carbon nano-tube array field emission cathode material that the carbon nano-particle of different-shape is coated; Described carbon nano-particle refers to the particle that diameter is generally 15-30 nanometer.
2. the preparation method of the carbon nano-tube array field emission cathode that carbon nano-particle according to claim 1 is coated, it is characterized in that: described carbon nano pipe array can be prepared with traditional thermal chemical vapor deposition method, also can prepare by the method that other can prepare array carbon nano tube arbitrarily.
3. the preparation method of the carbon nano-tube array field emission cathode that carbon nano-particle according to claim 1 is coated, it is characterized in that: the device for generation of hydrogen plasma can be lower powered radio frequency source, also can be that other can produce the device of low power density hydrogen plasma arbitrarily.
4. the preparation method of the carbon nano-tube array field emission cathode that the carbon nano-particle described in claim 1 is coated, is characterized in that carrying out as follows:
(1) by silicon single crystal flake each ultrasonic cleaning 10 minutes in deionized water, acetone and absolute ethyl alcohol successively, ultrasonic power is 50W;
(2) silicon wafer that step (1) obtains being placed to volume ratio is soak 5 minutes in the hydrofluoric acid of 4%;
(3) silicon wafer obtained step (2) carries out carrying and can bombard preliminary treatment by iron ion in metal vapor vacuum arc source (MEVVA source), and during bombardment, iron ion energy is about 15keV, and line is 10 milliamperes, and the processing time is 15 minutes;
(4) step (3) is obtained carry can the silicon wafer that bombarded of iron ion to insert deposit thickness in magnetic control sputtering device be the iron catalyst of 5 nanometers;
(5) silicon chip depositing 5 Nanoscale Iron catalyst that step (4) obtains is put into high quartz tube furnace, first by catalyst heat treatment 1 hour under 400sccm hydrogen, 853K condition, after under 150sccm ammonia, 1023K condition process 10 minutes, finally growth at atmosphere carbon nano pipe array under 87sccm acetylene, 600sccm hydrogen, 1023K condition, growth time is 30 minutes;
(6) carbon nano pipe array that step (5) obtains is put into the process chamber of radio-frequency unit, pass into high-purity hydrogen (5N), regulate reative cell air pressure to be 100Pa, and 1000K is heated to substrate, wait for air pressure and temperature stabilization;
(7) on the basis of step (6), radio frequency source is started, adjustment radio-frequency power is 30-50W, start to process carbon nano pipe array, processing time is 10-30 hour, final gained is the coated carbon nano pipe array of carbon nano-particle, and it can be used as filed emission cathode material to assemble field-electron emission device according to a conventional method.
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