CN104649278B - A kind of preparation method of TaSi2 nano wire - Google Patents
A kind of preparation method of TaSi2 nano wire Download PDFInfo
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- CN104649278B CN104649278B CN201510050855.XA CN201510050855A CN104649278B CN 104649278 B CN104649278 B CN 104649278B CN 201510050855 A CN201510050855 A CN 201510050855A CN 104649278 B CN104649278 B CN 104649278B
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Abstract
A kind of TaSi2The preparation method of nano wire, the present invention adopts high-temperature gradient realizing laser suspension zone-melting directional solidification original position to prepare equally distributed TaSi in Si matrix2Nanofiber. By accurately controlling laser power and directional solidification rates makes smelt surface tension and self gravitation keep balance, it is achieved stablizing of melting zone, and quick pull sample downwards simultaneously, it is thus achieved that in silicon substrate, Large-Area-Uniform distribution and diameter are the TaSi of nanoscale2Fiber. Utilize sense coupling technology, by controlling flow and the etching power supply of etch period, etching gas and passivation gas and being passivated power, it is achieved the accurate control to silicon substrate etching speed, and then realize TaSi2The control of nanowire length.
Description
Technical field
The present invention relates to a kind of TaSi2The preparation method of nano wire and application thereof, belong to technical field of nano material. Realizing laser suspension zone-melting directional solidification technology is specifically utilized to obtain TaSi regularly arranged in Si matrix2Fiber, adopts sense coupling technology silicon substrate original position to be etched, and preparation forms that the linearity is good, oriented growth and regularly arranged TaSi2Nano wire.
Background technology
TaSi2There is high-melting-point (Tm=2040 DEG C), high conductivity (ρ293K=20.20 Ω μ .cm), relatively low work function (φ=0.59eV), and have good bond strength with silicon. Therefore, TaSi2Being considered as a kind of filed emission cathode material with broad prospect of application, scene effect diode, flat faced display, the microelectronic component such as the device such as sensor utilizes has important using value. At present, the method generally preparing silicide nano wire is hydrothermal synthesis method, template, chemical vapour deposition (CVD), electro-deposition, pulse laser deposition etc. But, nano wire prepared by current above method is usually present the problem that length is shorter, disordered arrangements, regularity are bad, limits the further raising of emission current. Therefore, at microelectronic, for increasing current intensity, improve the emissivity of electronics, oriented growth, regularly arranged high length-diameter ratio TaSi can be formed in the urgent need to one2Nano wire technology of preparing.
Document (" B.M.Ditchek, B.G.Yacobi, M.Levinson, DepletionzonelimitedtransportinSi-TaSi2Eutecticcomposites, JournalofAppliedPhysics, 63 (1988) 1964-1970 ").Czochralski crystal technique (CZ) is utilized to be prepared in Si matrix the TaSi of distribution2Fiber; Then pass through NaOH/NaOCl etching liquid and dissolve Si matrix, so that TaSi2Reveal, form array. But the TaSi of distribution in the Si matrix prepared by CZ method2Fiber has numerous unfavorable factor: Si melt easily and crucible reaction, causes the pollution of Si raw material; Low thermograde (< 100k/cm) can cause TaSi2Regularity be deteriorated; The excursion of the rate of pulling is only small, the TaSi of preparation2Fibre diameter thicker (> 1 μm); Chemical attack can damage TaSi simultaneously2Fiber, and it is difficult to all to corrode matrix complete, thus field emission performance is had adverse effect on.
Northwestern Polytechnical University's preparation method of a kind of Spindt type cathode array disclosed in the innovation and creation that publication number is CN103205808A, the preparation method utilizing Spindt type cathode array, prepare Si-TaSi2Eutectic autogenous composite material ingot casting, and it is oriented solidification by Bridgman method, obtain TaSi2Equally distributed test rod on Si matrix. Adopt HNO3/ HF corrosive liquid, has prepared TaSi by the method etched on the surface of sample2Spindt type cathode array. The TaSi obtained2The draw ratio of Spindt type cathode array be 35:1, pointed cone radius of curvature is 18nm. But Bridgman method thermograde is relatively low, the TaSi of preparation2Fibre diameter thicker (3 μm) is only in micron level, and surface density has only reached 1.05 × 106rod/cm2, the further raising of limiting field emitting performance. Chemical attack obtains TaSi2Pointed cone array utilizes it to TaSi just2The faint harm use of invading of fiber, but be also difficult to all to corrode matrix complete, it is thus achieved that TaSi2Fiber Aspect Ratio is limited.
Northwestern Polytechnical University's one disclosed in the innovation and creation that publication number is CN103205809A prepares Si base TaSi2The method of Nano pointed cone array, is oriented solidification by realizing laser suspension zone-melting directional solidification method, and directional solidification rates is 200 μm/s, it is thus achieved that diameter 200nm, and surface density is 1.4 × 107rod/cm2, equally distributed TaSi on Si matrix2Fiber samples rod. Adopt HNO3/ HF corrosive liquid, prepares TaSi by the method etched on the surface of sample2Pointed cone array. The TaSi obtained2The height of Nano pointed cone array is 2.5-7.5 μm, and radius of curvature is 54-140nm, and the length of array has reached 35:1. Its field emission performance is greatly improved, and can be applicable to the devices such as field emission display and field-effect diode, flat faced display, sensor. But chemical attack obtains TaSi2Pointed cone array is difficult to all to corrode matrix complete, it is thus achieved that TaSi2Fiber Aspect Ratio is limited.
Authorization Notice No. is a kind of realizing laser suspension zone-melting directional solidification device and directional freeze method disclosed in the patent of invention of CN102051669B. The device (Fig. 2) of described realizing laser suspension zone-melting directional solidification is characterised by: spectroscope 2, plano lens 8, convex lens 6 and reflecting mirror are all in same level with melting zone 14; The focal length of selected convex lens 6 is 200mm. The method using described realizing laser suspension zone-melting directional solidification device to be oriented solidification, comprises the following steps: the first step, makes precast body; By batch mixing, grinding, compacting, sintering and shaping, it is thus achieved that precast body, or obtain coupon from mother metal, and after removing surface scale and impurity, it is thus achieved that precast body; Second step, is oriented solidification to precast body; By the two ends of precast body clamping respectively on the upper grip and lower chuck of pull system, making convex lens Jing Ti center is 270～310mm with two spacings restrainting laser crossing point, and making laser form diameter on precast body surface is the hot spot of 3～4mm;Set laser power from for 20W, or make laser power be stepped up to 200～1400W with the speed of 50W/min; Starting sample rotary system, rotating speed is 1～150Rpm; Start pull-out mechanism, make precast body move from top to bottom by 1～300 μm/s speed, it is achieved directional solidification.
Precast body is carried out district and melts by this invention employing quality laser beam such as two-way grade, rotate precast body simultaneously, reach to make the purpose of precast body solid liquid interface leading edge temperature field uniform flat, overcome the cost in traditional method high, complex structure and other problems, and well solve problem with relatively simple method, it is possible to apply to the research that the oriented freezing organization of fusing point height, electrically non-conductive material, glass etc. develops. In this directional freeze method, directional solidification rates is only 1～300 μm/s, can only obtain the tissue of micron level, but can not prepare TaSi2Nano wire. Preparation TaSi2Nano wire need higher directional solidification rates. Therefore, it is necessary to Si-TaSi2The oriented freezing organization characteristic of eutectic composites carries out systematic research, it is determined that be obtained in that Nano grade TaSi2Directional solidification rates. The selection of laser power is relevant to multiple factors such as the fusing point of material, the reflectance of material for laser light, directional solidification rates, melting zone stability, for Si-TaSi2The preparation of eutectic composites, it is necessary to system and comprehensively test and determine related property, mate laser power.
Summary of the invention
Being difficult to all to corrode matrix complete in the chemical attack existed in prior art for overcoming, and can only obtain the deficiency of the tissue of micron level, the present invention proposes a kind of TaSi2The preparation method of nano wire.
The detailed process of the present invention is:
Step one, prepares the Si-TaSi of eutectic composition2Coupon:
With Si and Ta for raw material, it is configured to mother metal raw material by eutectic composition 94wt.%Si-6wt.%Ta. Being loaded by the mother metal raw material of preparation is placed in smelting furnace in silica crucible, is evacuated to smelting furnace lower than 2 × 10-4Pa also keeps. Raw material is made to be completely melt the fusing point of smelting furnace heating to eutectic mother metal raw material; Water-cooled 2h after insulation 30min, obtains the Si-TaSi of eutectic composition2Alloy cast ingot. The Si-TaSi that will obtain2Alloy cast ingot cuts into coupon.
Step 2, directional solidification original position prepares Si-TaSi2Spontaneous composite nano fiber coupon:
The two ends of coupon are filled respectively on upper grip and the lower chuck of the pull system being sandwiched between in realizing laser suspension zone-melting directional solidification stove. Adjust the focusing system of convex lens, make the irradiation of laser beam symmetry on the surface of sample sustained height; Laser levitation furnace chamber is evacuated to vacuum lower than 2 × 10-2Pa, is filled with Ar gas; Open laser instrument, sample heating is completely melt to melting zone. When adding heat fusing, laser power increases to 900～1400W with the speed of 50～100W/min, and keeps constant. Starting pull-out mechanism, make coupon move from top to bottom with 800～1500 μm/s speed, it is achieved the directional solidification of material, original position obtains spontaneous composite nano fiber coupon, and the organizational structure of obtained spontaneous composite nano fiber coupon is by Si matrix and TaSi2Nanofiber is constituted, and this TaSi2Nanofiber is regular to be distributed in Si matrix.
In described directional solidification, thermograde is 7000K/cm.
Step 3, prepares TaSi2Nano wire: described preparation TaSi2Nano wire is to eliminate the Si matrix in this nanofiber coupon by the mode etched, thus obtaining TaSi2The process of nano wire.
Adopt conventional directional freeze method to determine the steady-state growth district of nanofiber coupon, and arbitrarily intercept a cross section in this steady-state growth district. After described cross section sample carries out conventional metallographic process, sense coupling method is adopted to prepare TaSi2Nanometer field emission array. Described preparation TaSi2The detailed process of nanometer field emission array is: is put into by sample in the vacuum shuttle of inductively coupled plasma etching, after vacuum shuttle is evacuated to 80mtorr, carries out the etching of Si matrix with sample is delivered to reaction chamber from vacuum shuttle; In etching, alternately it is filled with passivation gas and etching gas successively, until etching terminates, obtains average diameter to be 60～100nm, length be the TaSi of 2～40 μm2Nano wire. In etching, passivation power is 10～14W, and etching power is 400～700W; Etch period is 5～15min.
Described passivation gas is C4F8, it is filled with C4F8The flow of gas is 75～85sccm; Described etching gas is SF6And O2Mixing gas, be filled with SF6Flow be 110～130sccm, be filled with O2Flow be 10～13sccm.
The duration that is filled with of described passivation gas is 5s, and the duration that is filled with of described etching gas is 8s.
The present invention utilizes sense coupling technology to etch silicon substrate completely, prepares the TaSi of oriented growth, regularly arranged, high length-diameter ratio2Nano wire, it is achieved nano wire application on high emission electric current cold cathode.
The present invention adopts high-temperature gradient realizing laser suspension zone-melting directional solidification original position to prepare equally distributed TaSi in Si matrix2Nanofiber. By accurately controlling laser power and directional solidification rates makes smelt surface tension and self gravitation keep balance, it is achieved stablizing of melting zone, and quick pull sample downwards simultaneously, it is thus achieved that in silicon substrate, Large-Area-Uniform distribution and diameter are the TaSi of nanoscale2Fiber. Utilize sense coupling technology, by controlling flow and the etching power supply of etch period, etching gas and passivation gas and being passivated power, it is achieved the accurate control to silicon substrate etching speed, and then realize TaSi2The control of nanowire length.
The present invention, by improving directional solidification rates, the surface density of increased fiber, makes the diameter of fiber reach Nano grade, adopts sense coupling technology on this basis, removes Si matrix completely, makes TaSi2Reveal, thus forming the TaSi of regular arrangement2Nano wire.
Due to TaSi2There is high-melting-point (Tm=2040 DEG C), directly preparation comparatively difficulty, but have good bond strength, Si-TaSi with silicon2Eutectic temperature is only 1400 DEG C, reduces preparation temperature. Realizing laser suspension zone-melting directional solidification approach application is prepared Si-TaSi to original position2Eutectic, it is possible to obtain the TaSi of regular arrangement in Si matrix2Fiber. In order to obtain the TaSi of Nano grade2Fiber, adopts realizing laser suspension zone-melting directional solidification method to Si-TaSi2The oriented freezing organization characteristic of eutectic composites has carried out systematic research. Inquire into the mutual relation of oriented freezing organization and directional solidification rates, it is determined that directional solidification rates can obtain the TaSi of Nano grade under 800～1500 μm/s2Fiber.
Si-TaSi2The fusing point of eutectic is only 1400 DEG C, but the reflectance of laser is higher, and the selection of laser power to ensure that the melting zone part that floating zone is melted melts fully. By infrared radiation thermometer thermometric and W/Re thermocouple correction, it is determined that the radiance of laser is 0.235, it is determined that be differently directed the laser power under freezing rate.When freezing rate is when 800～1500 μm/s, freezing rate is quite fast, need the sufficiently large complete penetration in power assurance melting zone, but excessive power can affect melting zone stability, so that by the scope determining melting zone Stable Length of melting zone stability, it is determined that the laser power scope of coupling under each directional solidification rates.
Si-TaSi2In eutectic autogenous composite material, TaSi2The length range of fiber is wider. When directional solidification rates is 800～1500 μm/s, TaSi2The length of fiber be 2～100 μm not etc., but most TaSi2Fibre length is in 2～40 μ m. In sense coupling technology, etch period and TaSi2Fibre length is proportionate, and the flow controlling etching gas and passivation gas is accurately controlled silicon substrate etching speed, and then realizes TaSi2The control of nanowire length.
The present invention utilizes the thermograde (7000K/cm) that realizing laser suspension zone-melting directional solidification technology is high, and high directional solidification rates (800～1500 μm/s), without advantages such as crucible pollutions, original position prepares the TaSi of regular arrangement in Si matrix2Fiber, fibre diameter has reached Nano grade, as shown in Figure 3; Adopt sense coupling technology, it is thus achieved that the TaSi of rule oriented arrangement2Nano wire (Fig. 4), its uniformity, regularity are good, pollution-free, without compromising on TaSi2Fiber; And length and the diameter of nano wire can be effectively regulated and controled by controlling technological parameter. Thus obtain good field emission performance, and as shown in Figure 5, TaSi prepared by above-mentioned technique2Nano wire adopts transparent anode method to carry out field emission characteristic test, test condition: test vacuum is better than 5 × 10-5Pa, cathode and anode spacing is about: 250 μm, it is thus achieved that electric current density and the relation of electric field intensity as it is shown in figure 5, the threshold electric field obtained is only 4.8V/ μm, maximum current density has reached 500 μ A/cm2, can be applicable to field emission display, it is also possible in devices such as field-effect diode, flat faced display, sensors.
Accompanying drawing explanation
Fig. 1 is the flow chart of the present invention.
Fig. 2 is structural representation and the A direction view of realizing laser suspension zone-melting directional solidification device.
Fig. 3 is the A-A direction view of Fig. 2
Fig. 4 is when directional solidification rates is 800 μm/s, Si-TaSi prepared by realizing laser suspension zone-melting technology2Eutectic autogenous composite material coupon cross section tissue SEM schemes.
Fig. 5 is the TaSi adopting sense coupling technology to prepare2The low multiple SEM figure of nano wire.
Fig. 6 is the TaSi adopting sense coupling technology to prepare2Nano wire height multiple SEM schemes.
Fig. 7 is when directional solidification rates is 800 μm/s, the TaSi of preparation2The field emission performance figure of nano wire. In figure:
1. laser instrument; 2. spectroscope; 3. the first reflecting mirror; 4. the second reflecting mirror; 5. the 3rd reflecting mirror; 6. convex lens; 7. convex lens translating device; 8. plano lens; 9. vacuum chamber; Drawing-and-rotating system; 11. group of motors; 12. melting zone.
Detailed description of the invention
Embodiment one
The present embodiment is a kind of TaSi2The preparation method of nano wire. The present embodiment adopts without crucible realizing laser suspension zone-melting directional solidification technology, and original position prepares TaSi regularly arranged in Si matrix2Nanofiber; Utilize and adopt sense coupling technology to be etched completely by silicon substrate, prepare oriented growth, regularly arranged TaSi2Nano wire.
The detailed process of the present invention is:
Step one, prepares the Si-TaSi of eutectic composition2Coupon:
With Si and Ta for raw material, it is configured to mother metal raw material by eutectic composition 94wt.%Si-6wt.%Ta.Being loaded by the mother metal raw material of preparation is placed in smelting furnace in silica crucible, is evacuated to smelting furnace lower than 2 × 10-4Pa also keeps. Raw material is made to be completely melt the fusing point of smelting furnace heating to eutectic mother metal raw material; Water-cooled 2h after insulation 30min, obtains the Si-TaSi of eutectic composition2Alloy cast ingot. The Si-TaSi that will obtain2Alloy cast ingot cuts into coupon.
Step 2, directional solidification original position prepares Si-TaSi2Spontaneous composite nano fiber coupon:
The two ends of coupon are filled respectively on upper grip and the lower chuck of the pull system being sandwiched between in realizing laser suspension zone-melting directional solidification stove. Adjust the focusing system of convex lens, make the irradiation of laser beam symmetry on the surface of sample sustained height; Laser levitation furnace chamber is evacuated to vacuum lower than 2 × 10-2Pa, is filled with Ar gas; Open laser instrument, sample heating is completely melt to melting zone. When adding heat fusing, laser power increases to 900W with the speed of 50W/min, and keeps constant. Starting pull-out mechanism, make coupon move from top to bottom with 800 μm/s speed, it is achieved the directional solidification of material, original position obtains spontaneous composite nano fiber coupon, and the organizational structure of obtained spontaneous composite nano fiber coupon is by Si matrix and TaSi2Nanofiber is constituted, and this TaSi2Nanofiber is regular to be distributed in Si matrix.
In described directional solidification, thermograde is 7000K/cm.
Step 3, prepares TaSi2Nano wire: described preparation TaSi2Nano wire is to eliminate the Si matrix in this nanofiber coupon by the mode etched, thus obtaining TaSi2The process of nano wire.
Adopt conventional directional freeze method to determine the steady-state growth district of nanofiber coupon, and arbitrarily intercept a cross section in this steady-state growth district. After described cross section sample carries out conventional metallographic process, sense coupling method is adopted to prepare TaSi2Nanometer field emission array. Described preparation TaSi2The detailed process of nanometer field emission array is: is put into by sample in the vacuum shuttle of inductively coupled plasma etching, after vacuum shuttle is evacuated to 80mtorr, carries out the etching of Si matrix with sample is delivered to reaction chamber from vacuum shuttle; In etching, alternately it is filled with passivation gas and etching gas successively, until etching terminates, obtains average diameter to be 100nm, length be the TaSi of 2～15 μm2Nano wire. In etching, passivation power is 10W, and etching power is 400W; Etch period is 5min.
Described passivation gas is C4F8, it is filled with C4F8The flow of gas is 75sccm; Described etching gas is SF6And O2Mixing gas, be filled with SF6Flow be 110sccm, be filled with O2Flow be 10sccm.
The duration that is filled with of described passivation gas is 5s, and the duration that is filled with of described etching gas is 8s.
The present invention utilizes sense coupling technology to etch silicon substrate completely, prepares the TaSi of oriented growth, regularly arranged, high length-diameter ratio2Nano wire, it is achieved nano wire application on high emission electric current cold cathode.
Embodiment two
The present embodiment is a kind of TaSi2The preparation method of nano wire. The present embodiment adopts without crucible realizing laser suspension zone-melting directional solidification technology, and original position prepares TaSi regularly arranged in Si matrix2Nanofiber; Utilize and adopt sense coupling technology to be etched completely by silicon substrate, prepare oriented growth, regularly arranged TaSi2Nano wire.
The detailed process of the present invention is:
Step one, prepares the Si-TaSi of eutectic composition2Coupon:
With Si and Ta for raw material, it is configured to mother metal raw material by eutectic composition 94wt.%Si-6wt.%Ta.Being loaded by the mother metal raw material of preparation is placed in smelting furnace in silica crucible, is evacuated to smelting furnace lower than 2 × 10-4Pa also keeps. Raw material is made to be completely melt the fusing point of smelting furnace heating to eutectic mother metal raw material; Water-cooled 2h after insulation 30min, obtains the Si-TaSi of eutectic composition2Alloy cast ingot. The Si-TaSi that will obtain2Alloy cast ingot cuts into coupon.
Step 2, directional solidification original position prepares Si-TaSi2Spontaneous composite nano fiber coupon:
The two ends of coupon are filled respectively on upper grip and the lower chuck of the pull system being sandwiched between in realizing laser suspension zone-melting directional solidification stove. Adjust the focusing system of convex lens, make the irradiation of laser beam symmetry on the surface of sample sustained height; Laser levitation furnace chamber is evacuated to vacuum lower than 2 × 10-2Pa, is filled with Ar gas; Open laser instrument, sample heating is completely melt to melting zone. When adding heat fusing, laser power increases to 1000W with the speed of 70W/min, and keeps constant. Starting pull-out mechanism, make coupon move from top to bottom with 1000 μm/s speed, it is achieved the directional solidification of material, original position obtains spontaneous composite nano fiber coupon, and the organizational structure of obtained spontaneous composite nano fiber coupon is by Si matrix and TaSi2Nanofiber is constituted, and this TaSi2Nanofiber is regular to be distributed in Si matrix.
In described directional solidification, thermograde is 7000K/cm.
Step 3, prepares TaSi2Nano wire: described preparation TaSi2Nano wire is to eliminate the Si matrix in this nanofiber coupon by the mode etched, thus obtaining TaSi2The process of nano wire.
Adopt conventional directional freeze method to determine the steady-state growth district of nanofiber coupon, and arbitrarily intercept a cross section in this steady-state growth district. After described cross section sample carries out conventional metallographic process, sense coupling method is adopted to prepare TaSi2Nanometer field emission array. Described preparation TaSi2The detailed process of nanometer field emission array is: is put into by sample in the vacuum shuttle of inductively coupled plasma etching, after vacuum shuttle is evacuated to 80mtorr, carries out the etching of Si matrix with sample is delivered to reaction chamber from vacuum shuttle; In etching, alternately it is filled with passivation gas and etching gas successively, until etching terminates, obtains average diameter to be 80nm, length be the TaSi of 2～30 μm2Nano wire. In etching, passivation power is 12W, and etching power is 600W; Etch period is 10min.
Described passivation gas is C4F8, it is filled with C4F8The flow of gas is 80sccm; Described etching gas is SF6And O2Mixing gas, be filled with SF6Flow be 120sccm, be filled with O2Flow be 12sccm.
The duration that is filled with of described passivation gas is 5s, and the duration that is filled with of described etching gas is 8s.
The present invention utilizes sense coupling technology to etch silicon substrate completely, prepares the TaSi of oriented growth, regularly arranged, high length-diameter ratio2Nano wire, it is achieved nano wire application on high emission electric current cold cathode.
Embodiment three
The present embodiment is a kind of TaSi2The preparation method of nano wire. The present embodiment adopts without crucible realizing laser suspension zone-melting directional solidification technology, and original position prepares TaSi regularly arranged in Si matrix2Nanofiber; Utilize and adopt sense coupling technology to be etched completely by silicon substrate, prepare oriented growth, regularly arranged TaSi2Nano wire.
The detailed process of the present invention is:
Step one, prepares the Si-TaSi of eutectic composition2Coupon:
With Si and Ta for raw material, it is configured to mother metal raw material by eutectic composition 94wt.%Si-6wt.%Ta.Being loaded by the mother metal raw material of preparation is placed in smelting furnace in silica crucible, is evacuated to smelting furnace lower than 2 × 10-4Pa also keeps. Raw material is made to be completely melt the fusing point of smelting furnace heating to eutectic mother metal raw material; Water-cooled 2h after insulation 30min, obtains the Si-TaSi of eutectic composition2Alloy cast ingot. The Si-TaSi that will obtain2Alloy cast ingot cuts into coupon.
Step 2, directional solidification original position prepares Si-TaSi2Spontaneous composite nano fiber coupon:
The two ends of coupon are filled respectively on upper grip and the lower chuck of the pull system being sandwiched between in realizing laser suspension zone-melting directional solidification stove. Adjust the focusing system of convex lens, make the irradiation of laser beam symmetry on the surface of sample sustained height; Laser levitation furnace chamber is evacuated to vacuum lower than 2 × 10-2Pa, is filled with Ar gas; Open laser instrument, sample heating is completely melt to melting zone. When adding heat fusing, laser power increases to 1400W with the speed of 100W/min, and keeps constant. Starting pull-out mechanism, make coupon move from top to bottom with 1500 μm/s speed, it is achieved the directional solidification of material, original position obtains spontaneous composite nano fiber coupon, and the organizational structure of obtained spontaneous composite nano fiber coupon is by Si matrix and TaSi2Nanofiber is constituted, and this TaSi2Nanofiber is regular to be distributed in Si matrix.
In described directional solidification, thermograde is 7000K/cm.
Step 3, prepares TaSi2Nano wire: described preparation TaSi2Nano wire is to eliminate the Si matrix in this nanofiber coupon by the mode etched, thus obtaining TaSi2The process of nano wire.
Adopt conventional directional freeze method to determine the steady-state growth district of nanofiber coupon, and arbitrarily intercept a cross section in this steady-state growth district. After described cross section sample carries out conventional metallographic process, sense coupling method is adopted to prepare TaSi2Nanometer field emission array. Described preparation TaSi2The detailed process of nanometer field emission array is: is put into by sample in the vacuum shuttle of inductively coupled plasma etching, after vacuum shuttle is evacuated to 80mtorr, carries out the etching of Si matrix with sample is delivered to reaction chamber from vacuum shuttle; In etching, alternately it is filled with passivation gas and etching gas successively, until etching terminates, obtains average diameter to be 60nm, length be the TaSi of 2～40 μm2Nano wire. In etching, passivation power is 14W, and etching power is 700W; Etch period is 15min.
Described passivation gas is C4F8, it is filled with C4F8The flow of gas is 85sccm; Described etching gas is SF6And O2Mixing gas, be filled with SF6Flow be 130sccm, be filled with O2Flow be 13sccm.
The duration that is filled with of described passivation gas is 5s, and the duration that is filled with of described etching gas is 8s.
The present invention utilizes sense coupling technology to etch silicon substrate completely, prepares the TaSi of oriented growth, regularly arranged, high length-diameter ratio2Nano wire, it is achieved nano wire application on high emission electric current cold cathode.
The device for directionally solidifying that the various embodiments described above adopt adopts Authorization Notice No. to be the device for directionally solidifying disclosed in the patent of invention of CN102051669B. As in figure 2 it is shown, this device includes laser instrument 1, vacuum chamber 9, drawing-and-rotating system 10, group of motors 11 and reflecting mirror, laser instrument 1 is positioned at vacuum chamber 9 side; The two ends of drawing-and-rotating system 10 are connected with two group of motors 11 respectively; It is characterized in that,
A. the described device for realizing laser suspension zone-melting directional solidification also includes spectroscope 2, plano lens 8, convex lens 6 and convex lens translating device 7;Reflecting mirror includes the first reflecting mirror the 3, second reflecting mirror 4 and the 3rd reflecting mirror 5; Spectroscope the 2, first reflecting mirror the 3, second reflecting mirror 4 and the 3rd reflecting mirror 5 are sequentially distributed outside vacuum chamber 9; Plano lens 8 has two, is inlaid in respectively on 9 liang of side bodies of vacuum chamber, and corresponding with position, melting zone 14;
B. spectroscope 2 is positioned at the laser exit place of vacuum chamber 9 side, laser instrument 1, and the distance of this spectroscopical centre distance laser instrument light-emitting window is 1m, the minute surface of spectroscope 2 and laser beam angle at 45 °, make laser beam be divided into the laser of the quality such as mutually perpendicular two bundles after spectroscope; Two bundle laser are in same level, and wherein beam of laser is received by the first reflecting mirror 3, and another beam of laser is received by the 3rd reflecting mirror 5;
C. the laser beam that the first reflecting mirror 3 receives is reflected to the second reflecting mirror 4; After the laser beam reflection that second reflecting mirror 4 receives, launch to corresponding plano lens 8 by being positioned at the convex lens 6 of vacuum chamber 9 side, and enter vacuum chamber 9 by described plano lens 8 and launch to corresponding plano lens 8, and enter vacuum chamber 9 by this plano lens 8 and launch to melting zone 14; The angle that second reflecting mirror 4 and the 3rd reflecting mirror 5 reflex between the laser beam in melting zone 14 is 160 °;
D. the first reflecting mirror 3 is positioned at the distance at vacuum chamber 9 opposite side, the center of this first reflecting mirror 3 and spectroscope 2 center is 1m; The minute surface of the first reflecting mirror 3 and the minute surface of spectroscope 2 are parallel to each other; Second reflecting mirror 4 and the 3rd reflecting mirror 5 lay respectively at vacuum chamber 9 both sides, and corresponding with the plano lens 8 on two side bodies with vacuum chamber 9 respectively; The minute surface of the second reflecting mirror 4 is corresponding with the minute surface of the first reflecting mirror 3, and the second reflecting mirror 4 minute surface becomes 50 ° of angles with the laser beam received; 3rd reflecting mirror 5 minute surface becomes 50 ° of angles with the laser beam received;
E. two panels convex lens 6 mirror body central point is 270～310mm to the distance between the intersection point of the laser beam reflected by the second reflecting mirror 4 the 3rd reflecting mirror 5.
The device characteristic of described realizing laser suspension zone-melting directional solidification is in that: spectroscope 2, plano lens 8, convex lens 6 and reflecting mirror are all in same level with melting zone 14; The focal length of selected convex lens 6 is 200mm.
Claims (2)
1. a TaSi2The preparation method of nano wire, it is characterised in that detailed process is:
Step one, prepares the Si-TaSi of eutectic composition2Coupon:
With Si and Ta for raw material, it is configured to mother metal raw material by eutectic composition 94wt.%Si-6wt.%Ta; Being loaded by the mother metal raw material of preparation is placed in smelting furnace in silica crucible, is evacuated to smelting furnace lower than 2 × 10-4Pa also keeps; Raw material is made to be completely melt the fusing point of smelting furnace heating to eutectic mother metal raw material; Water-cooled 2h after insulation 30min, obtains the Si-TaSi of eutectic composition2Alloy cast ingot; The Si-TaSi that will obtain2Alloy cast ingot cuts into coupon;
Step 2, directional solidification original position prepares Si-TaSi2Spontaneous composite nano fiber coupon:
The two ends of coupon are filled respectively on upper grip and the lower chuck of the pull system being sandwiched between in realizing laser suspension zone-melting directional solidification stove; Adjust the focusing system of convex lens, make the irradiation of laser beam symmetry on the surface of sample sustained height; Laser levitation furnace chamber is evacuated to vacuum lower than 2 × 10-2Pa, is filled with Ar gas; Open laser instrument, sample heating is completely melt to melting zone; When adding heat fusing, laser power increases to 900～1400W with the speed of 50～100W/min, and keeps constant; Starting pull-out mechanism, make coupon move from top to bottom with 800～1500 μm/s speed, it is achieved the directional solidification of material, original position obtains spontaneous composite nano fiber coupon, and the organizational structure of obtained spontaneous composite nano fiber coupon is by Si matrix and TaSi2Nanofiber is constituted, and this TaSi2Nanofiber is regular to be distributed in Si matrix;
In described directional solidification, thermograde is 7000K/cm;
Step 3, prepares TaSi2Nano wire: described preparation TaSi2Nano wire is to eliminate the Si matrix in this nanofiber coupon by the mode etched, thus obtaining TaSi2The process of nano wire;
Adopt conventional directional freeze method to determine the steady-state growth district of nanofiber coupon, and arbitrarily intercept a cross section in this steady-state growth district; After described cross section sample carries out conventional metallographic process, sense coupling method is adopted to prepare TaSi2Nanometer field emission array; Described preparation TaSi2The detailed process of nanometer field emission array is: is put into by sample in the vacuum shuttle of inductively coupled plasma etching, after vacuum shuttle is evacuated to 80mtorr, carries out the etching of Si matrix with sample is delivered to reaction chamber from vacuum shuttle; In etching, alternately it is filled with passivation gas and etching gas successively, until etching terminates, obtains average diameter to be 60～100nm, length be the TaSi of 2～40 μm2Nano wire; In etching, passivation power is 10～14W, and etching power is 400～700W; Etch period is 5～15min;
Described passivation gas is C4F8, it is filled with C4F8The flow of gas is 75～85sccm; Described etching gas is SF6And O2Mixing gas, be filled with SF6Flow be 110～130sccm, be filled with O2Flow be 10～13sccm.
2. TaSi as claimed in claim 12The preparation method of nano wire, it is characterised in that the duration that is filled with of described passivation gas is 5s, the duration that is filled with of described etching gas is 8s.
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