CN104851765A - Method for improving field emission performance of carbon nano tube by microwave hydrogen plasma treatment - Google Patents
Method for improving field emission performance of carbon nano tube by microwave hydrogen plasma treatment Download PDFInfo
- Publication number
- CN104851765A CN104851765A CN201510153273.4A CN201510153273A CN104851765A CN 104851765 A CN104851765 A CN 104851765A CN 201510153273 A CN201510153273 A CN 201510153273A CN 104851765 A CN104851765 A CN 104851765A
- Authority
- CN
- China
- Prior art keywords
- carbon nano
- tube
- microwave
- field emission
- hydrogen plasma
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Abstract
The invention discloses a method for improving field emission performance of a carbon nano tube by microwave hydrogen plasma treatment. The method mainly includes the preparation technologies of: performing bombarding pretreatment on a protreated clean silicon wafer with energy-carrying iron ions; using a conventional thermochemical vapor deposition method to prepare a carbon nano tube array on the silicon single crystal wafer; using low-power microwave hydrogen plasma to treat the carbon nano tube array; and performing heat treatment on the obtained carbon nano tube array for 3 hours at a temperature of 1273K, thereby obtaining a carbon nano tube array with improved field emission performance. Surfaces of the carbon nano tubes treated through the method enrich a large number of defects, part of the carbon nano tubes are open at the top and have smaller diameters, and when serving as field emission cathodes, the carbon nano tubes have very low opening fields and threshold fields. Heat treatment of the carbon nano tubes improves bonding of the carbon nano tubes to a substrate, thereby enabling maximum field emission current density to be substantially improved, and the method provided by the invention shows relatively high practical value in the aspect of application of large field emission current density.
Description
Technical field
The invention belongs to the preparation and application technical field of nano material, relate to and utilize low power microwave hydrogen plasma process carbon nano-tube and high-temperature heat treatment is carried out to promote the method for its field-electron emission performance to it.
Background technology
Since 1991 are found, carbon nano-tube just because of electricity and the mechanical performance of its excellence, at photo-detector, can store up, all many-sides such as transistor have shown good application prospect.In addition, the great draw ratio of carbon nano-tube and good conductivity have also become a kind of desirable filed emission cathode material, have potential application foreground in fields such as New-generation vacuum pipe, X-ray tube, Electronic Speculum electron gun, field emission flat displays.Flied emission is that electronics overcomes material surface potential barrier and escapes into process in vacuum, and high performance field-electron emission often links together with indexs such as low unlatching and threshold field, large Flied emission current density, good field emission stabilities.Be that the field-transmitting cathode of base compares other field emmision materials many with carbon nano-tube, have and open the advantages such as field is low, Flied emission current density is large.But, the unlatching field of the carbon nanotube field emission cathode of current gained is generally all greater than 1.5 V/ μm, be equivalent to when cathode and anode spacing is 1 millimeter, need the high pressure of 1500 volts that cathode material just can be made to open field-electron emission, say nothing of and obtain large Flied emission current density, will need larger anode voltage, this high working voltage is very disadvantageous to practical application.Therefore, the operating voltage reducing carbon nanotube-based field-transmitting cathode by certain means is necessary.Comparatively typical method is by the work function processing carbon nano-tube or overflow to reduce electronics by carbon nano-tube and other low-work-function material compound, namely reduce the surface potential barrier that electronics effusion carbon nano-tube needs to overcome, but the effect that this method is brought is very limited often.Another kind method be then from carbon nano tube structure start with promote its field enhancement factor (
β), specifically can be divided into increasing carbon nano-tube draw ratio and increasing carbon nano-tube effective field and launch two kinds of methods of counting.The draw ratio of carbon nano-tube refers to the ratio of its length and diameter, directly relevant to field enhancement factor, can simply be expressed as:
β=
l/
d, wherein
lwith
drepresent length and the diameter of carbon nano-tube respectively, it plays the part of important role in carbon nano tube field-emission process.If do not consider the impact of the factors such as electric field shielding, external electric field (
e) certain when, determine electronics can transmitting on the scene point out effusion local electric field intensity (
e local) just only relevant with the draw ratio of carbon nano-tube:
e local=
β E, draw ratio is larger (namely
βlarger), accordingly
e locallarger, then electronics more easily overcomes the effusion of carbon nano tube surface potential barrier.As can be seen here, when length of carbon nanotube changes little, reduce carbon nanotube diameter by certain means and can promote its field-electron emission.Launch point aspect on the scene, carbon nano-tube is limited to the geometric shape of its one dimension, and field-electron emission mainly occurs in the little tip of its radius of curvature, is then difficult to launch electronics at flat sites such as tube walls, and this is totally unfavorable to acquisition high field emission current density undoubtedly.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, those rich defects effectively can be removed and the carbon nano-tube of contact instability 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, aging (high electric field continues field-electron emission) and high-temperature heat treatment also can reduce the quantity of rich defect carbon nano-tube to a certain extent, thus make to be that the field-transmitting cathode of base has better field emission stability with carbon nano-tube.
As can be seen here, by introducing technological means process carbon nano-tube, its geometric shape is changed, and obtain more effective field launch point, open field and threshold field to reduce it, promote its Flied emission current density, this technological means can also promote the field emission stability of carbon nano-tube to a certain extent simultaneously, is that the filed emission cathode material of base is launched application in high current density stationary field and given play to higher value by enabling prepared with carbon nano-tube.
Summary of the invention
The object of the invention is to overcome existing with carbon nano-tube be the field-transmitting cathode of base open field and threshold field relatively high, Flied emission current density is relatively low, the deficiency that under high field emission current density, field emission stability is bad, utilize a kind of simple low power microwave plasma and high-temperature heat treatment process process carbon nano-tube, its structure is changed, form blemish enrichment, opening, the carbon nano-tube attenuated, and carbon nano-tube is combined with substrate strengthen, final acquisition one open field and threshold field low, Flied emission current density is large, the filed emission cathode material of what under high current density, field emission stability was good with carbon nano-tube is base.
The object of the invention is to be reached by following measure:
A kind of microwave hydrogen plasma process promotes the method for Field Emission of Carbon Nanotubes, it is characterized in that: carrying and the silicon wafer that bombarded of iron ion can prepare carbon nano pipe array with thermal chemical vapor deposition method, and utilize microwave hydrogen plasma process carbon nano pipe array, by regulating microwave power to be 80-100W, base reservoir temperature is 1000K, chamber pressure is 1kPa, processing time is the 0.5-2 hour pattern controlling carbon nano-tube, then gained carbon nano-pipe array to be listed at 1273K temperature heat treatment 3 hours, the enrichment of final acquisition blemish, opening, attenuate, the carbon nano pipe array that field emission performance improves.
Microwave hydrogen plasma process of the present invention promotes the method for Field Emission of Carbon Nanotubes, and the method preparing carbon nano pipe array can be traditional thermal chemical vapor deposition method, also can be the method that can be used for preparing array carbon nano tube arbitrarily.
Microwave hydrogen plasma process of the present invention promotes the method for Field Emission of Carbon Nanotubes, and the device for generation of low-power hydrogen plasma can be that microwave source drives, and also can be that radio frequency source drives.
The present invention further discloses the method that microwave hydrogen plasma process promotes Field Emission of Carbon Nanotubes, 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 reative cell of microwave heating appts, pass into 10sccm high-purity hydrogen (5N), regulate reative cell air pressure to be about 1kPa, and 1000K is heated to substrate, wait for air pressure and temperature stabilization;
(7) on the basis of step (6), start microwave source, adjustment microwave power is 80-100W, starts to process carbon nano-tube, and the processing time is 0.5-2 hour;
(8) on the basis of step (7), close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, to the carbon nano pipe array heat treatment 3 hours of gained, its object is to promote the combination between carbon nano-tube and substrate;
(9) carbon nano-tube after microwave H plasma treatment and high-temperature heat treatment obtained with step (8) is that negative electrode assembles field-electron emission device according to a conventional method, specific as follows: with on conducting resinl growth to be had the silicon single crystal flake of carbon nano pipe array after process stick to copper metal electrode that thickness is about 2 millimeters as field-transmitting cathode, 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 the threshold electric field of the carbon nanotube field emission cathode material after microwave H plasma treatment and high-temperature heat treatment
2required electric field) only there is 0.75-1.07 V/ μm, (Flied emission current density is 10 mA/cm to threshold field
2required electric field) only there is 1.39-1.66 V/ μm, maximum field emission can reach 74.74 mA/cm
2, and aging after, be 22.86 mA/cm in mean field emission
2under the high field emission current density of (corresponding applying constant electrical field intensity is only 1.54 V/ μm), also there is good field emission stability.
The method that microwave hydrogen plasma process disclosed by the invention promotes Field Emission of Carbon Nanotubes compared with prior art its superiority is:
Carbon nanotube field emission cathode after microwave hydrogen plasma process prepared by this method, the effect of microwave hydrogen plasma makes carbon nanotube diameter diminish on the one hand, adds its draw ratio; On the other hand due to the etching of hydrogen plasma, having there is a large amount of defect in carbon nano tube surface, thus introduces Flied emission point new in a large number; In addition, that hydrogen plasma has etched away iron-containing catalyst in carbon nano-tube, relatively thick tip, defines the carbon nano-tube of opening, and the carbon nano-tube of this opening significantly promotes its field enhancement factor due to the minimum meeting of radius of curvature.Under the acting in conjunction of these structural changes, make the carbon nanotube field emission cathode after prepared process have low-down unlatching field (0.75-1.07 V/ μm) and threshold field (0.75-1.07 V/ μm), these indexs are all far superior to original undressed carbon nano pipe array.High-temperature heat treatment carbon nano-tube improves the adhesion between carbon nano-tube and substrate further, maximum field emission is significantly enhanced, reaches as high as 74.74 mA/cm
2, and when carbon nano-tube is after fully aging, can in mean field emission up to 22.86 mA/cm
2extraordinary field emission stability (in 50 hours, current density does not obviously decay) is still had when (corresponding applying constant electrical field intensity is only 1.54 V/ μm).Microwave hydrogen plasma used and high-temperature heat treatment method, technique is comparatively simple, and can not introduce other impurity in carbon nano-tube, has higher practical value.
Accompanying drawing illustrates:
Fig. 1 is the scanning electron microscopic picture of carbon nano-tube after process under original carbon nanotubes and different condition, comprising:
The ESEM end view of 11. original carbon nanotubes the first half, illustration is the high power ESEM end view on corresponding carbon nano-tube top;
The ESEM end view of 12.100W microwave hydrogen plasma process 0.5 hour, 1273K high-temperature heat treatment carbon nano-tube after 3 hours, illustration is the high power ESEM end view on corresponding carbon nano-tube top;
The ESEM end view of 13.100W microwave hydrogen plasma process 1 hour, 1273K high-temperature heat treatment carbon nano-tube after 3 hours, illustration is the high power ESEM end view on corresponding carbon nano-tube top;
The ESEM end view of 14.100W microwave hydrogen plasma process 2 hours, 1273K high-temperature heat treatment carbon nano-tube after 3 hours, illustration is the high power ESEM top view of corresponding carbon nano-tube, the carbon nano-tube that display top has part to attenuate;
Fig. 2 is the structural representation of microwave hydrogen plasma process used and high-temperature heat treatment device in the present invention; Hydrogen purity used is 5N, and heater is self-control graphite heater, vacuumizes with " molecular pump+mechanical pump " combination unit;
Fig. 3 is the low power transmission electron microscope picture of the single-root carbon nano-tube in embodiment 1 after hydrogen plasma process and high-temperature heat treatment, and the carbon nano-tube tip that display is coated with iron catalyst particle is etched away by hydrogen plasma;
Figure 4 shows that the structural representation of high vacuum Flied emission tester, for testing the field emission performance of carbon nano-tube 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, two-plate keeping parallelism and constant spacing is 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. 5 is the field emission performance figure of the carbon nano-tube after different condition process, specifically comprise comparing of the sample that obtains in embodiment 1, embodiment 2, embodiment 3 and original carbon nanotubes field emission performance, what it characterized is the variation relation that Flied emission current density increases with electric field strength;
Figure 6 shows that the transmission electron microscope picture of the single-root carbon nano-tube of embodiment 2 after 100W, hydrogen plasma process in 1 hour and 1273K, 3 hours high-temperature heat treatment, can find out that its surface exists a large amount of defect;
Figure 7 shows that original carbon nanotubes and the high power transmission electron microscope picture of carbon nano-tube after hydrogen plasma process and high-temperature heat treatment, comprising:
The high power transmission electron microscope picture of 71. original undressed carbon nano-tube, display carbon nanotube diameter is about 48 nanometers;
72.100W microwave hydrogen plasma process 2 hours, 1273K high-temperature heat treatment attenuate after 3 hours the high power transmission electron microscope picture of carbon nano-tube (corresponding embodiment 3), and display carbon nanotube diameter is about 26 nanometers;
Figure 8 shows that in embodiment 3 after 100W, hydrogen plasma process hydrogen plasma process in 2 hours and 1273K, 3 hours high-temperature heat treatment carbon nano-tube, the Analysis on Mechanism figure that its field emission performance significantly promotes;
To Figure 9 shows that in embodiment 3 the field emission stability figure of carbon nano-tube in test in 50 hours after 100W, hydrogen plasma process hydrogen plasma process in 2 hours and 1273K, 3 hours high-temperature heat treatment, what characterize is when extra electric field is constant, Flied emission current density relation over time.
ewith
j meanwhat represent respectively is constant electric field strength and average Flied emission current density in field emission stability test process.
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, Microwave Treatment, Flied emission tester all have commercially available.
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 ESEM end view of gained carbon nano pipe array the first half under this condition, can find out, carbon nano pipe array is better, carbon nano-tube then presents pattern bending, separated from one another by subapical part, and can obviously find out, carbon nano-tube tip diameter is relatively large, presents graininess, be then caused by interior iron-containing catalyst.
(4) Microwave plasma treatment and high-temperature heat treatment carbon nano-tube:
The microwave hydrogen plasma process of carbon nano-tube and high-temperature heat treatment all complete in microwave heating appts (having commercially available), are the structural representation of this device shown in Fig. 2.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 1.0 × 10
-3pa, then 10sccm hydrogen (purity is 5N) is passed into, adjustable pressure is about 1kPa, and 1000K is heated to graphite sample platform self-control graphite heater, after temperature and stable gas pressure, start microwave source, adjustment microwave power is 100W, namely start the hydrogen plasma process of carbon nano-tube, the processing time is 0.5 hour.Then close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, carries out high-temperature heat treatment to the carbon nano pipe array of gained, the time is 3 hours.The ESEM end view of the carbon nano pipe array after process is in the present embodiment shown in Fig. 1 12, compared with 11 original carbon nanotubes in Fig. 1, the change of carbon nano-tube pattern is on the whole less, be mainly reflected in following two aspects: the carbon nano-tube top that (1) bends is etched away, and new carbon nano-tube tip portion also demonstrates good array; (2) that be coated with iron catalyst, thicker carbon nano-tube tip is removed under the effect of hydrogen plasma, and the low power transmission electron microscope picture that (12 illustrations in Fig. 1) process rear single-root carbon nano-tube from the present embodiment shown in Fig. 3 also clearly can find out this structural change.
(5) field emission performance test:
The field emission performance test of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 4.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).The obtained carbon nanotube-sample conducting resinl after microwave hydrogen plasma process and high-temperature heat treatment 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 carbon nano-tube obtained under different disposal condition is shown in Fig. 5, sample prepared by specifically comprising in the present embodiment, embodiment 2, embodiment 3 compares with original carbon nanotubes field emission performance, and what it characterized is the variation relation that Flied emission current density increases with electric field strength.Can find out that unlatching field and the threshold field of carbon nano-tube prepared in the present embodiment and be respectively 1.05 and 1.65 V/ μm are better than 1.18 and 1.72 V/ μm of original carbon nanotubes.The enhancing of this field emission performance is mainly because the removal at thicker carbon nano-tube tip adds caused by its field enhancement factor.In addition, after the present embodiment process, the maximum field emission of carbon nano-tube reaches 45.17 mA/cm
2, be almost 2 times of (22.91 mA/cm of original carbon nanotubes
2).
(6) field electronic emitter assembling (conventional sectional method):
Having the silicon single crystal flake of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment to stick to thickness growth with conducting resinl 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) Microwave plasma treatment and high-temperature heat treatment carbon nano-tube:
The microwave hydrogen plasma process of carbon nano-tube and high-temperature heat treatment all complete in microwave heating appts (having commercially available), are the structural representation of this device shown in Fig. 2.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 1.0 × 10
-3pa, then 10sccm hydrogen (purity is 5N) is passed into, adjustable pressure is about 1kPa, and 1000K is heated to graphite sample platform self-control graphite heater, after temperature and stable gas pressure, start microwave source, adjustment microwave power is 100W, namely start the hydrogen plasma process of carbon nano-tube, the processing time is 1 hour.Then close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, carries out high-temperature heat treatment to the carbon nano pipe array of gained, the time is 3 hours.The ESEM end view of the carbon nano pipe array after process is in the present embodiment shown in Fig. 1 13, in Fig. 1,11 is shown compared with original carbon nanotubes, carbon nano pipe array is still better, and the carbon nano-tube tip being coated with iron catalyst is etched away by hydrogen plasma; There is a large amount of rough defect in carbon nano tube surface, the transmission electron microscope picture that (13 illustrations in Fig. 1) process rear single-root carbon nano-tube from the present embodiment shown in Fig. 6 also clearly can find out that carbon nano tube surface exists a large amount of defect, and these defects can become potential effective field launch point in emission process on the scene.
(5) field emission performance test:
The field emission performance test of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 4.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).The obtained carbon nanotube-sample conducting resinl after microwave hydrogen plasma process and high-temperature heat treatment 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.As can be seen from Figure 5, the unlatching field of prepared in the present embodiment carbon nano-tube, threshold field and maximum field emission are respectively 0.96 V/ μm, 1.57 V/ μm and 57.91 mA/cm
2, 1.18 V/ μm of original carbon nanotubes, 1.72 V/ μm and 22.91 mA/cm are far superior to
2.The increase of this field emission performance is mainly because the removal on thicker carbon nano-tube top and the introducing of a large amount of defect add caused by its field enhancement factor.
(6) field electronic emitter assembling (conventional sectional method):
Having the silicon single crystal flake of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment to stick to thickness growth with conducting resinl 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) Microwave plasma treatment and high-temperature heat treatment carbon nano-tube:
The microwave hydrogen plasma process of carbon nano-tube and high-temperature heat treatment all complete in microwave heating appts (having commercially available), are the structural representation of this device shown in Fig. 2.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 1.0 × 10
-3pa, then 10sccm hydrogen (purity is 5N) is passed into, adjustable pressure is about 1kPa, and 1000K is heated to graphite sample platform self-control graphite heater, after temperature and stable gas pressure, start microwave source, adjustment microwave power is 100W, namely start the hydrogen plasma process of carbon nano-tube, the processing time is 2 hours.Then close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, carries out high-temperature heat treatment to the carbon nano pipe array of gained, the time is 3 hours.The ESEM end view of the carbon nano pipe array after process is in the present embodiment shown in Fig. 1 14, compared with the original carbon nanotubes shown in 11 in Fig. 1, carbon nano pipe array is still better, and the carbon nano-tube tip being coated with iron catalyst is etched away by hydrogen plasma; And, there is the carbon nano-tube (14 illustrations in Fig. 1) that section diameter is very thin in carbon nano-tube top, this change diametrically of carbon nano-tube attenuate after also can processing from the original carbon nanotubes shown in Fig. 7 and the present embodiment carbon nano-tube high power transmission electron microscope picture in clearly to find out: after processing in original carbon nanotubes and the present embodiment, the diameter of carbon nano-tube is about 71 in 48(Fig. 7 respectively) and 26 nanometers (72 in Fig. 7), while carbon nano tube surface also enriched defect.This opening, defect enrichment, the carbon nano-tube that attenuates will have larger draw ratio and more Flied emission point undoubtedly than original carbon nanotubes, thus will have larger field enhancement factor.
(5) field emission performance test:
The field emission performance test of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 4.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).The obtained carbon nanotube-sample conducting resinl after microwave hydrogen plasma process and high-temperature heat treatment 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.As can be seen from Figure 5, the unlatching field of prepared in the present embodiment carbon nano-tube, threshold field and maximum field emission are respectively 0.75 V/ μm, 1.39 V/ μm and 74.74 mA/cm
2, 1.18 V/ μm of original carbon nanotubes, 1.72 V/ μm and 22.91 mA/cm are far superior to
2, also to be far superior to the field emission performance of the carbon nano-tube in embodiment 1 and embodiment 2 after microwave hydrogen plasma process and high-temperature heat treatment.The increase of this field emission performance is mainly because the removal on thicker carbon nano-tube top and the introducing of a large amount of defect add caused by its field enhancement factor.Figure 8 shows that in the present embodiment after hydrogen plasma process and high-temperature heat treatment carbon nano-tube, the Analysis on Mechanism figure that its field emission performance significantly promotes.Opening, defect enrichment, the pattern change such as to attenuate are the main causes that carbon nano-tube opens field, threshold field significantly reduces, change on these patterns improve carbon nano-tube draw ratio, introduce more effective field launch point, and then improve the field enhancement factor of carbon nano-tube, cause carbon nano tube field electron emissivity to promote.High-temperature heat treatment then makes the remainder fe of carbon nano-tube root (separating out from iron-silicon transition zone that bombardment preliminary treatment is formed when also some iron may be 1273K high-temperature process) occur polycondensation phenomenon (universal phenomenon in nano material high-temperature heat treatment), formed coated at carbon nano-tube root, this coated adhesion that will promote to a certain extent between carbon nano-tube and substrate, thus maximum field emission is increased.Figure 9 shows that the field emission stability figure of carbon nano-tube after hydrogen plasma process and high-temperature heat treatment in the present embodiment, sign be when extra electric field is constant, Flied emission current density relation over time.Because burin-in process (high electric field continues Flied emission) significantly can promote the field emission stability of carbon nano-tube, in the present embodiment, carbon nano tube field-emission stability is also formerly pass through
e=1.56 V/ μm, 1 hours aging process obtains afterwards.After aging, reducing constant electric field strength is 1.54 V/ μm, and the testing time is 50 hours.Can find out, in test in 50 hours, (mean field emission is up to 22.86 mA/cm
2), Flied emission current density does not obviously decay, and fluctuates less, and in testing, constant electric field strength is only 1.54 V/ μm, and this low operating voltage is very important to practical application.As can be seen here, carbon nano pipe array after microwave hydrogen plasma process and high-temperature heat treatment, there is low-down unlatching and threshold field, greatly Flied emission current density, and after fully aging, under high field emission current density, also show good field emission stability.
(6) field electronic emitter assembling (conventional sectional method):
Having the silicon single crystal flake of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment to stick to thickness growth with conducting resinl 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) Microwave plasma treatment and high-temperature heat treatment carbon nano-tube:
The microwave hydrogen plasma process of carbon nano-tube and high-temperature heat treatment all complete in microwave heating appts (having commercially available), are the structural representation of this device shown in Fig. 2.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 1.0 × 10
-3pa, then 10sccm hydrogen (purity is 5N) is passed into, adjustable pressure is about 1kPa, and 1000K is heated to graphite sample platform self-control graphite heater, after temperature and stable gas pressure, start microwave source, adjustment microwave power is 80W, namely start the hydrogen plasma process of carbon nano-tube, the processing time is 1 hour.Then close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, carries out high-temperature heat treatment to the carbon nano pipe array of gained, the time is 3 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 4.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).The obtained carbon nanotube-sample conducting resinl after microwave hydrogen plasma process and high-temperature heat treatment 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 unlatching field of carbon nano-tube prepared in the present embodiment, threshold field and maximum field emission are respectively 1.07 V/ μm, 1.66 V/ μm and 39.20 mA/cm
2, be better than 1.18 V/ μm of original carbon nanotubes, 1.72 V/ μm and 22.91 mA/cm
2.
(6) field electronic emitter assembling (conventional sectional method):
Having the silicon single crystal flake of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment to stick to thickness growth with conducting resinl 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) Microwave plasma treatment and high-temperature heat treatment carbon nano-tube:
The microwave hydrogen plasma process of carbon nano-tube and high-temperature heat treatment all complete in microwave heating appts (having commercially available), are the structural representation of this device shown in Fig. 2.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 1.0 × 10
-3pa, then 10sccm hydrogen (purity is 5N) is passed into, adjustable pressure is about 1kPa, and 1000K is heated to graphite sample platform self-control graphite heater, after temperature and stable gas pressure, start microwave source, adjustment microwave power is 80W, namely start the hydrogen plasma process of carbon nano-tube, the processing time is 2 hours.Then close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, carries out high-temperature heat treatment to the carbon nano pipe array of gained, the time is 3 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 4.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).The obtained carbon nanotube-sample conducting resinl after microwave hydrogen plasma process and high-temperature heat treatment 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 unlatching field of carbon nano-tube prepared in the present embodiment, threshold field and maximum field emission are respectively 0.84 V/ μm, 1.52 V/ μm and 61.75 mA/cm
2, 1.18 V/ μm of original carbon nanotubes, 1.72 V/ μm and 22.91 mA/cm are far superior to
2.
(6) field electronic emitter assembling (conventional sectional method):
Having the silicon single crystal flake of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment to stick to thickness growth with conducting resinl 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) Microwave plasma treatment and high-temperature heat treatment carbon nano-tube:
The microwave hydrogen plasma process of carbon nano-tube and high-temperature heat treatment all complete in microwave heating appts (having commercially available), are the structural representation of this device shown in Fig. 2.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 1.0 × 10
-3pa, then 10sccm hydrogen (purity is 5N) is passed into, adjustable pressure is about 1kPa, and 1000K is heated to graphite sample platform self-control graphite heater, after temperature and stable gas pressure, start microwave source, adjustment microwave power is 90W, namely start the hydrogen plasma process of carbon nano-tube, the processing time is 1 hour.Then close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, carries out high-temperature heat treatment to the carbon nano pipe array of gained, the time is 3 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 4.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).The obtained carbon nanotube-sample conducting resinl after microwave hydrogen plasma process and high-temperature heat treatment 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 unlatching field of carbon nano-tube prepared in the present embodiment, threshold field and maximum field emission are respectively 1.01 V/ μm, 1.60 V/ μm and 53.47 mA/cm
2, be better than 1.18 V/ μm of original carbon nanotubes, 1.72 V/ μm and 22.91 mA/cm
2.
(6) field electronic emitter assembling (conventional sectional method):
Having the silicon single crystal flake of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment to stick to thickness growth with conducting resinl 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) Microwave plasma treatment and high-temperature heat treatment carbon nano-tube:
The microwave hydrogen plasma process of carbon nano-tube and high-temperature heat treatment all complete in microwave heating appts (having commercially available), are the structural representation of this device shown in Fig. 2.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 1.0 × 10
-3pa, then 10sccm hydrogen (purity is 5N) is passed into, adjustable pressure is about 1kPa, and 1000K is heated to graphite sample platform self-control graphite heater, after temperature and stable gas pressure, start microwave source, adjustment microwave power is 90W, namely start the hydrogen plasma process of carbon nano-tube, the processing time is 2 hours.Then close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, carries out high-temperature heat treatment to the carbon nano pipe array of gained, the time is 3 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 4.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).The obtained carbon nanotube-sample conducting resinl after microwave hydrogen plasma process and high-temperature heat treatment 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 unlatching field of carbon nano-tube prepared in the present embodiment, threshold field and maximum field emission are respectively 0.81 V/ μm, 1.47 V/ μm and 66.02 mA/cm
2, 1.18 V/ μm of original carbon nanotubes, 1.72 V/ μm and 22.91 mA/cm are far superior to
2.
(6) field electronic emitter assembling (conventional sectional method):
Having the silicon single crystal flake of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment to stick to thickness growth with conducting resinl 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 8
(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) Microwave plasma treatment and high-temperature heat treatment carbon nano-tube:
The microwave hydrogen plasma process of carbon nano-tube and high-temperature heat treatment all complete in microwave heating appts (having commercially available), are the structural representation of this device shown in Fig. 2.First prepared carbon nano pipe array is placed on graphite sample platform, to process chamber forvacuum to about 1.0 × 10
-3pa, then 10sccm hydrogen (purity is 5N) is passed into, adjustable pressure is about 1kPa, and 1000K is heated to graphite sample platform self-control graphite heater, after temperature and stable gas pressure, start microwave source, adjustment microwave power is 85W, namely start the hydrogen plasma process of carbon nano-tube, the processing time is 2 hours.Then close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, carries out high-temperature heat treatment to the carbon nano pipe array of gained, the time is 3 hours.
(5) field emission performance test:
The field emission performance test of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment completes in high vacuum Flied emission tester (having commercially available), is the structural representation of this testing apparatus shown in Fig. 4.In test cabinet, vacuum degree maintains about 1 × 10
-7the Pa(titanium getter pump often opened vacuumizes).The obtained carbon nanotube-sample conducting resinl after microwave hydrogen plasma process and high-temperature heat treatment 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 unlatching field of carbon nano-tube prepared in the present embodiment, threshold field and maximum field emission are respectively 0.84 V/ μm, 1.49 V/ μm and 63.71 mA/cm
2, 1.18 V/ μm of original carbon nanotubes, 1.72 V/ μm and 22.91 mA/cm are far superior to
2.
(6) field electronic emitter assembling (conventional sectional method):
Having the silicon single crystal flake of the carbon nano-tube after microwave hydrogen plasma process and high-temperature heat treatment to stick to thickness growth with conducting resinl 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 relevant situation 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 method for a microwave hydrogen plasma process lifting Field Emission of Carbon Nanotubes, it is characterized in that: carrying and the silicon wafer that bombarded of iron ion can prepare carbon nano pipe array with thermal chemical vapor deposition method, and utilize microwave hydrogen plasma process carbon nano pipe array, by regulating microwave power to be 80-100W, base reservoir temperature is 1000K, chamber pressure is 1kPa, processing time is the 0.5-2 hour pattern controlling carbon nano-tube, then gained carbon nano-pipe array to be listed at 1273K temperature heat treatment 3 hours, the enrichment of final acquisition blemish, opening, attenuate, the carbon nano pipe array that field emission performance improves.
2. microwave hydrogen plasma process promotes a method for Field Emission of Carbon Nanotubes, and it is characterized in that: the method preparing carbon nano pipe array can be traditional thermal chemical vapor deposition method, also can be the method that can be used for preparing array carbon nano tube arbitrarily.
3. microwave hydrogen plasma process according to claim 1 promotes the method for Field Emission of Carbon Nanotubes, it is characterized in that: the device for generation of low-power hydrogen plasma can be that microwave source drives, and also can be that radio frequency source drives.
4. the microwave hydrogen plasma process described in claim 1 promotes the method for Field Emission of Carbon Nanotubes, 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;
(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 microwave device, pass into 10sccm high-purity hydrogen (5N), regulate reative cell air pressure to be about 1kPa, and 1000K is heated to substrate, wait for air pressure and temperature stabilization;
(7) on the basis of step (6), start microwave source, adjustment microwave power is 80-100W, starts to process carbon nano-tube, and the processing time is 0.5-2 hour;
(8) on the basis of step (7), close microwave system, stop passing into hydrogen, base reservoir temperature is risen to 1273K, to the carbon nano pipe array heat treatment 3 hours of gained, final that obtain different-shape, that field emission performance improves carbon nano pipe array.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510153273.4A CN104851765B (en) | 2015-04-02 | 2015-04-02 | Method for improving field emission performance of carbon nano tube by microwave hydrogen plasma treatment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510153273.4A CN104851765B (en) | 2015-04-02 | 2015-04-02 | Method for improving field emission performance of carbon nano tube by microwave hydrogen plasma treatment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN104851765A true CN104851765A (en) | 2015-08-19 |
| CN104851765B CN104851765B (en) | 2017-02-01 |
Family
ID=53851326
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510153273.4A Expired - Fee Related CN104851765B (en) | 2015-04-02 | 2015-04-02 | Method for improving field emission performance of carbon nano tube by microwave hydrogen plasma treatment |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN104851765B (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108987218A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting graphene film-silicon nanowire array composite material field emission performance |
| CN108987217A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting graphene sheet-carbon nanotube film flexible composite field emission performance |
| CN108987214A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting carbon nano pipe array field emission performance |
| CN108987215A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting graphene film-carbon nano-tube array composite material field emission performance |
| CN108987216A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting carbon nano pipe array-carbon nano-tube film flexible composite field emission performance |
| US11753303B2 (en) * | 2017-09-27 | 2023-09-12 | Sugita Densen Co., Ltd. | Carbon nanotube array and its production method, and spun carbon nanotube yarn and its production method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5709577A (en) * | 1994-12-22 | 1998-01-20 | Lucent Technologies Inc. | Method of making field emission devices employing ultra-fine diamond particle emitters |
| CN1398782A (en) * | 2002-08-28 | 2003-02-26 | 武汉理工大学 | One-dimensional hydrogen-storing carbon nano-material etched via microwave plasma and its prepn process |
| US20030122466A1 (en) * | 2001-12-28 | 2003-07-03 | Ahn Seong Deok | Field emission device and method of fabricating the same |
| CN101508421A (en) * | 2009-04-01 | 2009-08-19 | 北京师范大学 | Carbon nano-fibre/carbon nano-tube heterogeneous nano-array for field electronic emitter and manufacturing technology thereof |
| CN103482607A (en) * | 2013-10-08 | 2014-01-01 | 上海理工大学 | Enrichment method of semiconductor type carbon nanotubes |
| CN103515180A (en) * | 2013-05-16 | 2014-01-15 | 中山大学 | In-situ plasma glow processing method for improving field emission characteristics of tungsten oxide nanometer material thin film |
-
2015
- 2015-04-02 CN CN201510153273.4A patent/CN104851765B/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5709577A (en) * | 1994-12-22 | 1998-01-20 | Lucent Technologies Inc. | Method of making field emission devices employing ultra-fine diamond particle emitters |
| US20030122466A1 (en) * | 2001-12-28 | 2003-07-03 | Ahn Seong Deok | Field emission device and method of fabricating the same |
| CN1398782A (en) * | 2002-08-28 | 2003-02-26 | 武汉理工大学 | One-dimensional hydrogen-storing carbon nano-material etched via microwave plasma and its prepn process |
| CN101508421A (en) * | 2009-04-01 | 2009-08-19 | 北京师范大学 | Carbon nano-fibre/carbon nano-tube heterogeneous nano-array for field electronic emitter and manufacturing technology thereof |
| CN103515180A (en) * | 2013-05-16 | 2014-01-15 | 中山大学 | In-situ plasma glow processing method for improving field emission characteristics of tungsten oxide nanometer material thin film |
| CN103482607A (en) * | 2013-10-08 | 2014-01-01 | 上海理工大学 | Enrichment method of semiconductor type carbon nanotubes |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11753303B2 (en) * | 2017-09-27 | 2023-09-12 | Sugita Densen Co., Ltd. | Carbon nanotube array and its production method, and spun carbon nanotube yarn and its production method |
| CN108987218A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting graphene film-silicon nanowire array composite material field emission performance |
| CN108987217A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting graphene sheet-carbon nanotube film flexible composite field emission performance |
| CN108987214A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting carbon nano pipe array field emission performance |
| CN108987215A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting graphene film-carbon nano-tube array composite material field emission performance |
| CN108987216A (en) * | 2018-01-31 | 2018-12-11 | 天津师范大学 | A method of promoting carbon nano pipe array-carbon nano-tube film flexible composite field emission performance |
| CN108987215B (en) * | 2018-01-31 | 2019-12-31 | 天津师范大学 | Method for improving field emission performance of graphene sheet-carbon nanotube array composite material |
| CN108987217B (en) * | 2018-01-31 | 2019-12-31 | 天津师范大学 | Method for improving field emission performance of graphene sheet-carbon nanotube film flexible composite material |
| CN108987216B (en) * | 2018-01-31 | 2020-04-28 | 天津师范大学 | Method for improving field emission performance of carbon nanotube array-carbon nanotube film flexible composite material |
Also Published As
| Publication number | Publication date |
|---|---|
| CN104851765B (en) | 2017-02-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN104851765A (en) | Method for improving field emission performance of carbon nano tube by microwave hydrogen plasma treatment | |
| CN105070619B (en) | Preparation method for carbon nanotube array cathode on Fe-based metal alloy substrate | |
| CN103510048B (en) | A kind of preparation method of loose structure Arrays of Copper Nanowires and its method for testing of film conductivity | |
| Chouhan et al. | Field emission from optimized structure of carbon nanotube field emitter array | |
| CN104616944A (en) | Preparation method for ultrathin up-right graphene field emission cathode rich in wrinkle on surface | |
| CN104882346A (en) | Method for preparing field emission cathode of carbon nanotube array coated with carbon nanoparticles | |
| CN108987214B (en) | Method for improving field emission performance of carbon nanotube array | |
| Li et al. | Novel nanofabricated Mo field-emitter array for low-cost and large-area application | |
| CN105200390B (en) | A kind of method that Direct precipitation nano-graphene suppresses secondary | |
| CN104952674A (en) | Method for manufacturing nano carbon sheet-carbon nano tube composite-structure field-emission cathode | |
| CN108987215B (en) | Method for improving field emission performance of graphene sheet-carbon nanotube array composite material | |
| CN1135588C (en) | Method of raising the field electron emitting performance of carbon nanotube film | |
| Kim et al. | Field-emission performance and structural change mechanism of multiwalled carbon nanotubes by oxygen plasma treatment | |
| CN104934275B (en) | Field Electron Emission cathode array based on metal molybdenum substrate and preparation method thereof | |
| CN114134566B (en) | Method for improving heterogeneous epitaxial nucleation uniformity of diamond | |
| CN104882347A (en) | Method for preparing field emission cathode of nano carbon sheet-silicon nanowire composite structure | |
| CN108987218B (en) | Method for improving field emission performance of graphene sheet-silicon nanowire array composite material | |
| Kyung et al. | Improvement of electron field emission from carbon nanotubes by Ar neutral beam treatment | |
| Mann et al. | Direct growth of multi-walled carbon nanotubes on sharp tips for electron microscopy | |
| JP4707336B2 (en) | Manufacturing method of electron source using carbon nanofiber | |
| CN108987216B (en) | Method for improving field emission performance of carbon nanotube array-carbon nanotube film flexible composite material | |
| CN108987217B (en) | Method for improving field emission performance of graphene sheet-carbon nanotube film flexible composite material | |
| Zhang et al. | Efficient surface-conduction field emission electron sources from tin oxide film | |
| CN113943932B (en) | Preparation method of graphene field emission source | |
| Chumak et al. | Fabrication and complex investigation of LAFE based on CNT by PECVD with island catalyst |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| EXSB | Decision made by sipo to initiate substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20170201 Termination date: 20170402 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |