CN102592914B - Method for controlling field emission electronic divergence angle by using nano carbon tube - Google Patents
Method for controlling field emission electronic divergence angle by using nano carbon tube Download PDFInfo
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- CN102592914B CN102592914B CN201210046316.5A CN201210046316A CN102592914B CN 102592914 B CN102592914 B CN 102592914B CN 201210046316 A CN201210046316 A CN 201210046316A CN 102592914 B CN102592914 B CN 102592914B
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Abstract
The invention discloses a method for controlling a field emission electronic divergence angle by using a nano carbon tube. The method comprises the steps of: applying a voltage between the carbon tube and a positive pole to form electron field emission by using the multi-wall nano carbon tube as an electron source of field emission; and changing the electric-field distribution of a port of the nano carbon tube through regulating and selecting the length of the extracted outer wall of the nano carbon tube and the voltage applied to the nano carbon tube, controlling the field emission electronic divergence angle, collimation or convergence, and controlling the focusing distance of an electron beam. According to the invention, under the condition without any additional focusing device, the divergence, focusing or collimation of field-emitted electronics is controlled.
Description
Technical field
The present invention relates to CNT (carbon nano-tube) electronic field emission field, is a kind of method of utilizing the CNT (carbon nano-tube) controlling filed electron emission angle of divergence.
This patent can be used for needing high brightness electron source and the processing of high-resolution electronics or imaging device.As electric lithography, electron microscope and electron diffraction apparatus etc.During particularly near field is surveyed, without the focus method of additional electron lens, can eliminate electron source with the restriction of distance between detection sample, thereby reduce electron beam diffusion, greatly improve the resolution of electronic imaging device.
Background technology
Since CNT (carbon nano-tube) in 1991 is found, because required bias voltage is very low and have the very high features such as emission, the electronic field emission device of CNT (carbon nano-tube) is studied widely in global scope.After 2000, the high brightness electron source based on CNT (carbon nano-tube) or x-ray source have obtained preliminary commercialization, and typical application has flat panel display, cathode-ray lamp, X-ray tube etc.; The corresponding high-resolution electron source equipment based on CNT (carbon nano-tube) is as electron beam lithography, and electron microscopic and diffractive technology etc. are also among flourish.
In traditional feds, adopt the metal probe of nano-scale as emission source, for example nanometer tungsten pin.Due to CNT (carbon nano-tube) nonmetal structure, but the atom of CNT (carbon nano-tube) exists with the combination of covalent bond, thereby can bear higher electric field than metal probe, reaches the electronic field emission requirement of the every nanometer of several volts.CNT (carbon nano-tube) has very little diameter, at its end electric field because geometry enhancement effect can improve several magnitudes, thereby even if add that very low voltage (for example tens volts) just can produce electron emission.Add that CNT (carbon nano-tube) has great Young's modulus and tensile strength, and chemically stable, only under excessive temperature, just can there is oxidation or hydrogenation etc. a series of advantage, make CNT (carbon nano-tube) become ideal field emitting electronic source.
Different according to the structure of CNT (carbon nano-tube), the angular distribution of field emission electron is also different.The single tube that for example end is uncapped may produce the electron beam of ring-type, and the end of hemisphere or plane can produce the electron beam of the different angles of divergence.And the electron beam of the CNT (carbon nano-tube) of many walls transmitting generally has better cylinder symmetry and stability, at high temperature according to the arrangement difference of carbon atom, may present symmetry of five jiaos or hexagonal etc., detailed introduction can be with reference to the comment document of Niels in 2004 [referring to document 1.Niels de Jonge and Jean-Marc Bonard, Carbon nanotube electron sources and applications, Phil.Trans.R.Soc.Lond.A (2004) 362,2239-2266.].But in general because the diameter of carbon nano-tube is very little, the electronics of its transmitting quite comes from point source how much, thereby has the larger angle of departure, and representative value is at several measurement levels.For the high-resolution electric lithography of needs or electronic imaging technology, the so large angle of divergence cannot meet the demands, and need to electron beam be collimated or be focused on.
Although the magnetic lens that traditional electron-beam convergence method for example adopts in electron microscope or electrostatic lens technology development comparative maturity, but its structure and control relative complex, expensive, and the more important thing is cannot electron source with survey near field that sample press close to very much and use in surveying.
Summary of the invention
The technical problem to be solved in the present invention is to overcome the problem that above-mentioned prior art exists, a kind of method of utilizing the CNT (carbon nano-tube) controlling filed electron emission angle of divergence is provided, realize lensless electron beam collimation and focus on, can make the distance between electron source and detection sample unrestricted simultaneously.
Employing is extracted the outer wall of multiple-wall carbon nanotube out certain distance, adds the electric field layer negatron lens effect that outer wall end forms after voltage, and the electron beam of field transmitting is produced to focusing effect.Thereby the angle of departure of controlling filed divergent bundle easily.
Implementer's case of the present invention is as follows:
Utilize the control method of CNT (carbon nano-tube) to the field emission electron angle of divergence, its feature is that the method comprises the following steps:
1. adopt existing conventional method to prepare multiple-wall carbon nanotube, therefrom select a multiple-wall carbon nanotube, its one end is sticked in a fixing metal support with conductive silver glue, one end sticks on a piezoelectric ceramic displacement controller with nano-precision in addition, stiff end at multiple-wall carbon nanotube adds a pulse voltage, the end of this CNT (carbon nano-tube) outer wall is opened, and this end becomes the carbon pipe of opening;
2. regulate the displacement of described piezoelectric ceramic displacement controller, to the direction that connects piezoelectric ceramic, extract the outer wall of described CNT (carbon nano-tube) out the distance suitable with this CNT (carbon nano-tube) diameter;
3. the port at described CNT (carbon nano-tube) extraction outer wall adds a pulse voltage, and the outer wall of this port is also opened, and forms and has the CNT (carbon nano-tube) that opening outer wall surrounds;
4. set up CNT (carbon nano-tube) field emission apparatus: the described CNT (carbon nano-tube) with the encirclement of opening outer wall is sticked on a metal probe with conductive silver glue, and this probe is fixed on a metallic support, this metallic support device is placed in the environment of ultra high vacuum, and vacuum degree is 10
-7～10
-12mbar, described metallic support is connected with a negative supply, the negative voltage that applies tens volts on the support of fixing metal probe forms negative electrode, anode consists of the phosphor screen of the ground connection outside certain distance, when applied negative voltage is when the port of described CNT (carbon nano-tube) forms the highfield strengthening for how much, cause the field transmitting of electronics, free electron is accelerated to arrive described phosphor screen by added bias voltage;
5. by adjust and select the length that the outer wall of CNT (carbon nano-tube) extracts out and the voltage applying in CNT (carbon nano-tube), change the Electric Field Distribution of described CNT (carbon nano-tube) port, the controlling filed electron emission angle of divergence, collimation or convergence, control the focusing distance of electron beam.
The described multiple-wall carbon nanotube method of preparing is arc discharge method, laser ablation method or chemical vapour deposition technique.
Advantage of the present invention:
1, the present invention adopts the angle of divergence of the method controlling filed electron emission of extracting CNT (carbon nano-tube) outer wall out, without additional other electron focusing devices, whole electron source apparatus letter is gathered, cheap.
2, method of the present invention does not need additional electron lens can realize the electron beam of high brightness collimation, is conducive to improve the resolution of existing electronic diffraction equipment.
3, method of the present invention can realize the Electron Beam Focusing of hundred nanometer focal lengths, effectively suppresses electron beam dispersion, improves the resolution of electron microscopic and photoetching technique.
4, the present invention is by adjust and select the outer wall of the CNT (carbon nano-tube) length of extracting out and the voltage applying in CNT (carbon nano-tube), can change the Electric Field Distribution of described CNT (carbon nano-tube) port, the controlling filed electron emission angle of divergence, collimation or convergence, the focusing distance of control electron beam.
Accompanying drawing explanation
Fig. 1 is multiple-wall carbon nanotube field emission apparatus schematic diagram
Fig. 2 is near voltage distribution schematic diagram CNT (carbon nano-tube) end
Fig. 3 is near electric field absolute value distribution schematic diagram CNT (carbon nano-tube) end
Fig. 4 is that the outer wall of CNT (carbon nano-tube) is extracted electron-propagation path schematic diagram corresponding to different distance out
Fig. 5 is that field emission electron bundle focal length and focused spot diameter extract the variation relation figure of distance with carbon pipe outer wall
Embodiment
Below in conjunction with embodiment and accompanying drawing, the invention will be further described, but should not limit the scope of the invention with this.
The present invention utilizes the control method of CNT (carbon nano-tube) to the field emission electron angle of divergence, comprises the following steps:
1. prepare multiple-wall carbon nanotube and [refer to document [2] .John Cumings and A.Zettl, Low-friction nanoscale linear bearing realized from multiwall carbon nanotubes, Science (2000) 289, 602-604.]: by conventional method (as arc discharge method, laser ablation method, chemical vapour deposition technique etc.) the single taking-up of multiple-wall carbon nanotube of preparing, its one end is sticked in a fixing metal support with conductive silver glue, one end sticks on a piezoelectric ceramic displacement controller with nano-precision in addition.Stiff end at carbon pipe adds a pulse voltage, and the end of the outer wall of CNT (carbon nano-tube) is opened, and this end becomes the carbon pipe of opening; The displacement of the piezoelectric ceramic described in regulating and controlling, extracts the outer wall of described CNT (carbon nano-tube) out the distance suitable with carbon pipe diameter to the direction that connects piezoelectric ceramic; At the port of extracting outer wall out, add a pulse voltage, the outer wall of this port is also opened; After CNT (carbon nano-tube) is taken off, the port of this CNT (carbon nano-tube) forms the shape as shown in dotted ellipse shape subgraph in Fig. 1.The outer wall 1 of carbon pipe is extracted out the distance of carbon pipe diameter magnitude with respect to carbon inside pipe wall 2, described distance from the straight tube top of carbon inside pipe wall 2 as starting point.
2. CNT (carbon nano-tube) field emission apparatus: as shown in Figure 1, the multiple-wall carbon nanotube of above-mentioned preparation is sticked on a metal probe 3 with conductive silver glue, and this probe is fixed on a metallic support 4.The negative voltage that adds tens volts on the support 4 of connection metal probe 3 forms negative electrode, and anode is by phosphor screen 5 formations of the ground connection of certain distance outer (typical case at several microns to several centimetres), to observe the bundle shape of spot of field emission electron.Added voltage forms at the port of carbon pipe the highfield strengthening for how much, causes the field transmitting of electronics, and free electron is accelerated to arrive phosphor screen 5 by added bias voltage.Because being easily subject to the impact of molecule in air, whole device, electron motion need to be placed in the environment of ultra high vacuum (10
-7～10
-12mbar).
3. near voltage carbon pipe distributes and Electric Field Distribution: the applied voltage of usining on carbon pipe and anode passes through the Poisson's equation of finite element method electrostatic field as boundary condition
obtain carbon pipe neighbouring electromotive force and Electric Field Distribution,
it is electromotive force.Due to the axial symmetry feature of carbon pipe, above equation can solve under two axisymmetric cylindrical coordinatess.Simulated conditions are set to the bias voltage of the add-10V of carbon pipe that a diameter is 10 nanometers, and outer wall is extracted 10 nanometers out.As shown in Figure 2, the voltage that left figure has provided amended carbon pipe distributes the analog result of typical two-dimensional columns symmetrical coordinates, and the voltage that right figure provides general carbon pipe under similarity condition distributes.Obviously visible general carbon pipe Potential Distributing layer is semi-circular outwards disperses, and at extraction part annex, forms the voltage distribution that is similar to convergence after extracting outer wall out 10 nanometers.Fig. 3 provides electric field (absolute value) corresponding in two kinds of situations and distributes, and the end that left figure outer wall is extracted out (mark arrow place) exists a very strong electric field 4.6G V/m, and the electronics of the internal wall emission of this electric field has the effect of convergence.Although carbon pipe end also can electron emission in this highfield, its emission area is very little, and directional divergence, and arriving the electronics with respect to the carbon inner tube layer transmitting after assembling after anode is a very weak background noise, can ignore.Right figure is near Electric Field Distribution situation general carbon pipe end, there is no the electric field that can cause electronics to be assembled.
4. the converging action of carbon pipe outer wall electric field to field emission electron: as shown in Figure 4, wherein a figure takes out 10 nanometers by outer wall to trajectory of electron motion, is converged near field after electron emission by the highfield of outer wall in above-mentioned electric field, and focal length is between 10 to 20 nanometers; Figure b extracts outer wall out 8 nanometers, and most of electron emission, by the highfield collimation of outer wall, presents the propagation parallel with symmetry axis, can produce in far field very little beam spot, the result of simulation approximately 5 nanometers.The electronics of a small amount of carbon tube edges transmitting is converged onto near field, but because fringe field a little less than, electron emission probability is little a lot of compared with center, its intensity can be ignored.Scheme as a comparison c and provided the electron trajectory of the general carbon pipe transmitting that is emission type.Fig. 5 has provided the relation that electron beam focal length length and focused spot diameter and carbon pipe outer wall extract distance, usings the diameter of carbon pipe as unit.Visible along with extracting Distance Shortened, the focal length length of side, it is large that focused spot diameter becomes.Until the electron beam of figure shown in b be while being tending towards collimating, focal length becomes infinity, and focused spot diameter is about half of carbon pipe diameter.
In sum, utilize the outer wall of multiple-wall carbon nanotube is extracted to the method with the suitable distance of carbon pipe diameter, can in the transmitting of the field of electronics, effectively control the angle of divergence of electronics, form and assemble or the beam spot of collimation, high brightness electron source is provided.In far field, (beyond several centimetres) can keep the size of carbon pipe diameter magnitude to the beam spot of collimation, thereby have more much higher brightness than the electron beam that is divergence form of general carbon pipe transmitting, and this will greatly improve the resolution of electronic diffraction equipment.And its focal length of the focused beam obtaining by the method can shorten to below 100 nanometers, this cannot realize by traditional electron focusing method.Under so short distance, the electron beam dispersion in communication process being brought by the Coulomb repulsion effect of the electric charge of electronics and electronics initial velocity and energy uncertainty can be suppressed greatly, thereby strengthen to improve electronic imaging device as the image quality of electron microscope, and this is for just having the meaning of particular importance with time-resolved electronic imaging device among develop actively.
Claims (2)
1. utilize the control method of CNT (carbon nano-tube) to the field emission electron angle of divergence, it is characterized in that the method comprises the following steps:
1. adopt existing conventional method to prepare multiple-wall carbon nanotube, therefrom select a multiple-wall carbon nanotube, its one end is sticked in a fixing metal support with conductive silver glue, one end sticks on a piezoelectric ceramic displacement controller with nano-precision in addition, stiff end at multiple-wall carbon nanotube adds a pulse voltage, the end of this CNT (carbon nano-tube) outer wall is opened, and this end becomes the carbon pipe of opening;
2. regulate the displacement of described piezoelectric ceramic displacement controller, to the direction that connects piezoelectric ceramic, extract the outer wall of described CNT (carbon nano-tube) out the distance suitable with this carbon pipe diameter;
3. the port at described CNT (carbon nano-tube) extraction outer wall adds a pulse voltage, and the outer wall of this port is also opened, and forms one and has the CNT (carbon nano-tube) that opening outer wall surrounds;
4. set up CNT (carbon nano-tube) field emission apparatus: the described CNT (carbon nano-tube) with the encirclement of opening outer wall is sticked on a metal probe with conductive silver glue, and this probe is fixed on a metallic support, this metallic support device is placed in to the environment of ultra high vacuum, vacuum degree is 10
-7～10
-12mbar, described metallic support communicates with a negative supply, the negative voltage that applies tens volts on the support of fixing metal probe forms negative electrode, anode consists of the phosphor screen of the ground connection outside certain distance, when applied negative voltage is when the port of described CNT (carbon nano-tube) forms the highfield strengthening for how much, cause the field transmitting of electronics, free electron is accelerated to arrive described phosphor screen by added bias voltage;
5. by adjust and select the length that the outer wall of CNT (carbon nano-tube) extracts out and the voltage applying in CNT (carbon nano-tube), change the Electric Field Distribution of described CNT (carbon nano-tube) port, the controlling filed electron emission angle of divergence, collimation or convergence, control the focusing distance of electron beam.
2. the control method of CNT (carbon nano-tube) to the field emission electron angle of divergence of utilizing according to claim 1, is characterized in that the described multiple-wall carbon nanotube method of preparing is arc discharge method, laser ablation method or chemical vapour deposition technique.
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| CN101261916A (en) * | 2008-04-08 | 2008-09-10 | 北京大学 | A single carbon nano electronic field emission cathode and its making method |
| CN102024639A (en) * | 2010-11-29 | 2011-04-20 | 清华大学 | Method for manufacturing electron emitter |
| CN102290304A (en) * | 2011-08-07 | 2011-12-21 | 张研 | Carbon nanotube field emission array with focusing gate |
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| CN101261916A (en) * | 2008-04-08 | 2008-09-10 | 北京大学 | A single carbon nano electronic field emission cathode and its making method |
| CN102024639A (en) * | 2010-11-29 | 2011-04-20 | 清华大学 | Method for manufacturing electron emitter |
| CN102290304A (en) * | 2011-08-07 | 2011-12-21 | 张研 | Carbon nanotube field emission array with focusing gate |
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