CN204834554U - Field emission negative pole based on two dimension nanometer wall - Google Patents
Field emission negative pole based on two dimension nanometer wall Download PDFInfo
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- CN204834554U CN204834554U CN201520507686.3U CN201520507686U CN204834554U CN 204834554 U CN204834554 U CN 204834554U CN 201520507686 U CN201520507686 U CN 201520507686U CN 204834554 U CN204834554 U CN 204834554U
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Abstract
The utility model relates to a field emission negative pole based on two dimension nanometer wall includes: electron emission end, it includes welt layer and nanometer wall layer, the nanometer wall layer is latticedly, and buries and cover in the welt layer, the copper core, cooling device includes: first ceramic conducting strip, it is close to the aperture plate has been erect to the one end of nanometer wall layer, second pottery conducting strip, the outside of first ceramic conducting strip is located to its cover, semiconductor layer, its fill in between first ceramic conducting strip and the second pottery conducting strip, a power supply. Wherein, second pottery conducting strip passes through the sheetmetal and links to each other with the copper core. The present case adopts the nanometer wall of two -dimentional grid structure to make the negative pole obtain lower impedance, helps bigger emission current's production, can reduce the work function that the electron need be overcome, electron density and secondary electron emissivities that the increase can utilize at nanometer wall top bridged metal level, the grid of net trellis form can furthest improvement electronic percent of pass.
Description
Technical field
The utility model relates to the negative electrode in X-ray tube, particularly a kind of field-transmitting cathode based on two-dimensional nano wall.
Background technology
Electron emission device has important application in a lot of field, and such as X-ray tube needs cathode emission impact with energetic electrons target surface to produce X ray.Current electron emission part mainly adopts tungsten filament, and lanthanum hexaboride etc. all belong to thermal emission cathode.Electron emission is all that interior of articles electronics is excited after acquisition heat energy, and because self-energy is overflowed higher than surface potential barrier, response speed is slow, and directivity is poor, and needs good heat radiation.Field Electron Emission is the phenomenon of electron emission under highfield effect, carrys out oppressive surface potential barrier with outside highfield, and the peak of potential barrier is reduced, and make the narrowed width of potential barrier, cause the electronics of interior of articles not need to increase energy in addition, namely do not need to excite, just can overflow.The advantage of field-transmitting cathode clearly, being carried out because not needing target heating and dispelling the heat, being reached nanosecond to the response time of control signal, fast-pulse imaging can be realized, electron emission good directionality, and there is energy spread low (0.2 ~ 0.3eV), the advantage that the life-span is long.Flied emission needs an emission tip, and required external electrical field intensity is relevant with its tip radius, and radius is less, and the electric field strength of needs is less.Tradition field-transmitting cathode has some weak points, one, and material must be very hard, otherwise easily damaged by the Ions Bombardment in environment, most advanced and sophisticated once rust, just cannot realize Flied emission; Its two, hard inertia material is not easy to produce the tip that Flied emission needs, complex process.Therefore, nano material (as nanotube) becomes the hot topic selection of feds.If nanotube is lost top by Ions Bombardment, do not affect the field emission performance of remaining part, the diameter of nanotube can be controlled by the size of catalyst granules, easily its draw ratio of design.
Carbon nano-tube (Carbonnanotube, CNT) cut-in voltage is very low, beam intensity is high, the superior selection of Flied emission in the ideal case, people have utilized CNT filed emission cathode material to obtain a series of achievement in research, but how to manufacture reliable and stable, the CNT cold cathode meeting big current high voltage service condition remains a difficult point.In carbon nano-tube, the electronics of flowing is subject to the impact of quantum confinement, and can only move along nanotube axial direction on same layer tube wall, motion is radially restricted, and shows the character of One-dimensional Quantum line; And because the height of CNT can not be completely the same, because of electromagnetic shielding effect, easily cause some some local electric field excessively strong, cause nanotube transship and burn out, destroy adjacent Flied emission region, even damage whole negative electrode; CNT is independently each other, and be also incoherent between the electronics of outgoing, therefore its directivity is poor.These characteristics seriously hinder the large-scale application of CNT as field-transmitting cathode.
Utility model content
For the deficiencies in the prior art part, the purpose of this utility model is by the improvement to existing cathode construction, provides a kind of field-transmitting cathode based on two-dimensional nano wall.Two-dimensional nano wall has larger potentiality as field emmision material, its electronics is not flow along single line, but move along two dimensional surface, therefore this just determines it and possesses the characteristic that impedance is low, electron motion quality is little, the electronics of outgoing also has the characteristic of height correlation, is the superior selection of field-transmitting cathode.
The technical solution adopted in the utility model is as follows:
Based on a field-transmitting cathode for two-dimensional nano wall, comprising:
Electron transmitting terminal, it comprises liner plate layer and nanowall layer, and described nanowall layer is latticed, and buries and overlay in described liner plate layer;
Copper core, it is connected to the one side away from described nanowall layer in described liner plate layer;
Cooling device, it comprises:
First ceramic sheet, it is the column type of inner hollow, and the two ends of this cylinder are open design, it is outside that described first ceramic sheet is sheathed on described electron transmitting terminal, and near one end of described nanowall layer, erection has aperture plate at described first ceramic sheet; Described aperture plate is parallel with described nanowall layer, and described aperture plate is provided with two high-tension electricity terminals;
Second ceramic sheet, it is the column type of inner hollow, and the two ends of this cylinder are open design, the annular radii of described second ceramic sheet is greater than the annular radii of described first ceramic sheet, and described second ceramic sheet is sheathed on the outside of described first ceramic sheet;
Semiconductor layer, it is filled between described first ceramic sheet and the second ceramic sheet, and described semiconductor layer is also respectively equipped with two power interfaces;
Power supply, it is connected with two power interfaces of described semiconductor layer respectively;
Wherein, described second ceramic sheet is connected with described copper core by sheet metal.
Preferably, the described field-transmitting cathode based on two-dimensional nano wall, wherein, in described nanowall layer the four edges of each grid and the four edges of each grid in described aperture plate not overlapping on the axis along described nanowall layer place plane.
Preferably, the described field-transmitting cathode based on two-dimensional nano wall, wherein, the sizing grid of described nanowall layer is equal with the sizing grid of described aperture plate.
Preferably, the described field-transmitting cathode based on two-dimensional nano wall, wherein, the top of described nanowall layer is provided with metal level.
Preferably, the described field-transmitting cathode based on two-dimensional nano wall, wherein, described metal level is gold.
Preferably, the described field-transmitting cathode based on two-dimensional nano wall, wherein, described semiconductor layer is bismuth telluride.
The beneficial effects of the utility model are:
1) the nanometer wall of lattice structure makes negative electrode obtain lower impedance, contribute to the generation of larger emission current, and reduce the line that electromagnetic shielding causes and decline, simultaneously, electronics not only freely can trickle at two-dimensional nano wall, also can between the nanometer wall of different layers free exchange, and can also play and support nanometer wall, make it to keep better directivity and resistance to bombardment, avoid the effect of most advanced and sophisticated burr;
2) can reduce at the metal level of nanometer wall top bridge joint the work function that electronics needs to overcome, increase utilizable electron density and secondary ability; Meanwhile, the effect of piezo-resistance can also be played, the fluctuation of compacting emission current, thus make electric current more stable; And make nanometer wall firmer, particle hits to a certain degree can be stood, thus extend the useful life of cold cathode;
3) grid of mesh shape can improve the percent of pass of electronics to greatest extent, and the cooling device of annular can rapidly and efficiently cool aperture plate fast according to the principle of thermoelectric cooling, damages because of overheated to avoid aperture plate.
Accompanying drawing explanation
Fig. 1 is the structural representation of the field-transmitting cathode based on two-dimensional nano wall, wherein, for the ease of observing, omits the structure of high-tension electricity terminals, power supply and power interface in figure.
Fig. 2 is the stereogram of the electron transmitting terminal of field-transmitting cathode.
Fig. 3 is the vertical view of field-transmitting cathode; Wherein, for the ease of observing, the structure of aperture plate in figure, is omitted.
Fig. 4 is the grid of nanowall layer and the grid relative position relation figure spatially of aperture plate.
Fig. 5 is the structural representation of top after being modified with metal level of nanowall layer.
Fig. 6 is the structural representation be applied to by field-transmitting cathode in X-ray tube.
Embodiment
Below in conjunction with accompanying drawing, the utility model is described in further detail, can implements according to this with reference to specification word to make those skilled in the art.
This case proposes the field-transmitting cathode based on two-dimensional nano wall of an embodiment, comprising:
Electron transmitting terminal, it comprises liner plate layer 1 and nanowall layer 2, and nanometer wall stretches out along liner plate layer 1 plane, and overall in latticed, buries and overlays in liner plate layer 1; The selection of lining material should reduce contact resistance as far as possible, and can form firmly chemical bond with nanometer wall.Research shows, has the metal of good imbibition characteristic, and such as, the contact of Ti, Cr or Fe and carbon nanomaterial is almost ohm-type, there is not contact berrier.No matter be which kind of liner plate, what all should lengthen nanometer wall and liner plate layer contacts thickness, and it is longer to bury the length overlaying on liner plate, conductivity and mechanical strength better.
Copper core 3, it is connected to the one side away from nanowall layer 2 in liner plate layer 1;
Cooling device, it comprises:
First ceramic sheet 4, it is the column type of inner hollow, and the two ends of this cylinder are open design, and the first ceramic sheet 4 is sheathed on electron transmitting terminal outside, and near one end of nanowall layer 2, erection has aperture plate 5 at the first ceramic sheet 4; Aperture plate 5 is parallel with nanowall layer 2, and aperture plate 5 is provided with two high-tension electricity terminals, but their particular location is unrestricted; Aperture plate 5 mainly plays the effect that is drawn electronics and static focusing, himself needs the high pressure of some strength, and aperture plate 5, can the switch of control cathode electron stream after connection high-tension electricity.Electric field E=V/d, if do not have aperture plate 5, just must provide electric field by anode, and now d numerical value is comparatively large, and need higher voltage under identical electric field strength, switching manipulation is extremely inconvenient, can not produce high quality pulses electric current.If but had aperture plate 5, just at very short d, electronics can be drawn with very low V, play the effect of switching current, efficiently can not only perform pulse current operation, switching manipulation can also be carried out very easily at the lower voltage, be easy to realize pulse current, and reduce radiation dose.Meanwhile, the conducting strip of ceramic material is adopted can also to play the effect of isolated high pressure.
Second ceramic sheet 6, it is the column type of inner hollow, and the two ends of this cylinder are open design, the annular radii of the second ceramic sheet 6 is greater than the annular radii of the first ceramic sheet 4, and the second ceramic sheet 6 is sheathed on the outside of the first ceramic sheet 4;
Semiconductor layer 7, it is filled between the first ceramic sheet 4 and the second ceramic sheet 6, and semiconductor layer 7 is also respectively equipped with two power interfaces; The particular location not circumscribed of these two power interfaces;
Power supply, it is connected with two power interfaces of semiconductor layer 7 respectively; This power supply is conventional DC power supply, and its present position is unrestricted;
Wherein, the second ceramic sheet 6 is connected with copper core 3 by a sheet metal, and this sheet metal is used for heat conduction, its concrete material not circumscribed.
The material of nanometer wall also not circumscribed, can be carbon nanometer wall, also can be the nanometer wall of other composite materials.
As another embodiment of this case, wherein, in nanowall layer 2 four edges of each grid and the four edges of each grid in aperture plate 5 not overlapping on the axis along nanowall layer 2 place plane.Electronics is drawn in the effect of aperture plate 5, therefore in the grid in aperture plate 5 and nanowall layer 2, the relative position relation of grid will have influence on the efficiency of drawing electronics, in nanometer wall, electronics comes from nanometer wall wall body, and in aperture plate, electric field is positioned at the blank space of grid, but not on the body of aperture plate, therefore this just needs the four edges of each grid in nanowall layer 2 not overlapping on the axis along nanowall layer 2 place plane with the four edges of each grid in aperture plate 5, to ensure that the electric field formed in aperture plate can face nanometer wall thus can draw the electronics in nanometer wall.But the portions of electronics of drawing like this can strike aperture plate, thus produce amount of heat, this is also the reason needing to arrange cooling device.
As another embodiment of this case, wherein, the sizing grid of nanowall layer 2 is equal with the sizing grid of aperture plate 5.The efficiency of electronics is drawn in order to improve aperture plate further, can preferably the sizing grid of nanowall layer 2 be set to equal with the sizing grid of aperture plate 5, be convenient to like this find most highfield point, thus the electronics can drawn more efficiently in nanometer wall, contribute to the generation of larger emission current, and reduce the line that electromagnetic shielding causes and decline.
As another embodiment of this case, wherein, the top of nanowall layer 2 is provided with metal level 8.Metal level 8 can reduce the work function that when electronics is drawn, needs overcome, and increases density and the secondary ability that can utilize electronics; Meanwhile, the effect of piezo-resistance can also be played, the fluctuation of compacting emission current, thus make electric current more stable; And make nanometer wall firmer, particle hits to a certain degree can be stood, thus extend the useful life of cold cathode.The material preferably gold of metal level 8.
As another embodiment of this case, wherein, semiconductor layer 7 is bismuth tellurides.The cooling device of this case is the principle adopting thermoelectric cooling, based on peltier effect, also known as difference of temperature, in the closed circuit of two kinds of different metal compositions, if pass to direct current, a contact will be made to turn cold, a heating.And semi-conducting material is the most applicable material, as preferred, semiconductor layer 7 can be bismuth telluride.Adopt the good refrigeration effect of bismuth telluride, fast, power consumption is lower for refrigeration.
The radiation processes of cooling device is: after aperture plate is subject to impact with energetic electrons, and produce amount of heat, the first ceramic sheet 4 is connected with aperture plate 5, and the second ceramic sheet 6 is connected with copper core 3 by sheet metal.Heat can effectively be propagated into the second ceramic sheet 6 by semiconductor layer 7 from the first ceramic sheet 4, and conducts heat to copper core 3 by sheet metal, and heat conducts outside X-ray tube by copper core 3 fast.Because conducting strip is pottery, between the two without electric action, signal of telecommunication crosstalk between the two can be eliminated.
For carbon nanometer wall, the roughly preparation process of electron transmitting terminal is as follows:
1) liner plate is cleaned, to remove unwanted impurity.Liner plate is first by deionized water rinsing about 30 seconds.Subsequently, this liner plate is immersed in acetone and carries out 10 minutes ultrasonic agitation, removing organic impurities.In view of acetone washing has residual, isopropyl alcohol need be used other 10 minutes to soak.Finally, substrate dipping in deionized water, removes any chemical residual, dries up with drying nitrogen;
2) rotary coating double-tiered arch dam on substrate, 100 degrees Celsius of bakings after one minute, with laser (LW2002 as Microtech), the lattice designed in advance is etched on liner plate, toasts one minute to solidify photoresist at 100 degrees Celsius subsequently;
3) evaporation is about the thick catalyst metals of 100nm on liner plate, and the metal fallen on a photoresist by acetone cleaning removing, only leaves latticed catalyst metals together with photoresist.The growth of nanometer wall is carried out by the mode of MPECVD; In order to reach better resistance to bombardment performance, can at nanometer wall apical growth function metal level, as gold atom.MPECVD: reactant gas is the mixture of hydrogen and methane.Mass flowrate is set in 40 and 10SCCM respectively.The liner plate hydrogen plasma preheating of bias voltage 50 volts arrives 650-700 degree Celsius in 10-15 minute, is placed on bottom electrode.Time methane starts flowing, nanometer wall starts deposition, lower electrode bias-65 volt, and top electrode is grounded; Growth time is about 5 minutes, and the pressure of chamber remains on 1torr.Nanometer wall height is about 2 microns, and width is about 1-3 nanometer.
4) because the growth of part nanometer wall is in the region of catalyst-free, high-temperature baking can be carried out by target, solidify the nanometer wall be combined with catalyst, remove in conjunction with unstable nanometer wall; Clean further with deionized water subsequently, then carry out drying process, be i.e. obtained electron transmitting terminal.
Although embodiment of the present utility model is open as above, but it is not restricted to listed in specification and execution mode utilization, it can be applied to various applicable field of the present utility model completely, for those skilled in the art, can easily realize other amendment, therefore do not deviating under the universal that claim and equivalency range limit, the utility model is not limited to specific details and illustrates here and the legend described.
Claims (6)
1., based on a field-transmitting cathode for two-dimensional nano wall, comprising:
Electron transmitting terminal, it comprises liner plate layer and nanowall layer, and described nanowall layer is latticed, and buries and overlay in described liner plate layer;
Copper core, it is connected to the one side away from described nanowall layer in described liner plate layer;
Cooling device, it comprises:
First ceramic sheet, it is the column type of inner hollow, and the two ends of this cylinder are open design, it is outside that described first ceramic sheet is sheathed on described electron transmitting terminal, and near one end of described nanowall layer, erection has aperture plate at described first ceramic sheet; Described aperture plate is parallel with described nanowall layer, and described aperture plate is provided with two high-tension electricity terminals;
Second ceramic sheet, it is the column type of inner hollow, and the two ends of this cylinder are open design, the annular radii of described second ceramic sheet is greater than the annular radii of described first ceramic sheet, and described second ceramic sheet is sheathed on the outside of described first ceramic sheet;
Semiconductor layer, it is filled between described first ceramic sheet and the second ceramic sheet, and described semiconductor layer is also respectively equipped with two power interfaces;
Power supply, it is connected with two power interfaces of described semiconductor layer respectively;
Wherein, described second ceramic sheet is connected with described copper core by sheet metal.
2., as claimed in claim 1 based on the field-transmitting cathode of two-dimensional nano wall, it is characterized in that, in described nanowall layer the four edges of each grid and the four edges of each grid in described aperture plate not overlapping on the axis along described nanowall layer place plane.
3., as claimed in claim 2 based on the field-transmitting cathode of two-dimensional nano wall, it is characterized in that, the sizing grid of described nanowall layer is equal with the sizing grid of described aperture plate.
4., as claimed in claim 1 based on the field-transmitting cathode of two-dimensional nano wall, it is characterized in that, the top of described nanowall layer is provided with metal level.
5. as claimed in claim 4 based on the field-transmitting cathode of two-dimensional nano wall, it is characterized in that, described metal level is gold.
6., as claimed in claim 1 based on the field-transmitting cathode of two-dimensional nano wall, it is characterized in that, described semiconductor layer is bismuth telluride.
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| CN105047504A (en) * | 2015-07-14 | 2015-11-11 | 中国科学院苏州生物医学工程技术研究所 | Field emission cathode based on two-dimensional nanowall |
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| CN105047504A (en) * | 2015-07-14 | 2015-11-11 | 中国科学院苏州生物医学工程技术研究所 | Field emission cathode based on two-dimensional nanowall |
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| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20151202 Termination date: 20180714 |