A kind of surface nano tip array and preparation method thereof
Technical field
The present invention relates to a kind of surface nano tip and preparation method thereof, particularly relate to a kind of surface nano tip array and preparation methods field, that on various solid materials, make such as feds, scanning probe system, biology sensor, nano impression and photoelectronics of being applied in.
Background technology
The technology of existing making surface nano tip roughly has three kinds: the direct growth method; Electrochemical erosion method; Template.Now the technology to three kinds of existing making surface nano tips specifically describes as follows:
1, the direct growth legal system is equipped with the amorphous carbon nanocone: referring to documents 1, " field emission characteristic of growth amorphous carbon nanocone on copper sheet " (Field emission from amorphous-carbon nanotips on copper), be stated from " Journal of Applied Physics. " 2003, Vol.15 is on the No.10:6796-6799.The amorphous carbon nano-cone array is seen accompanying drawing 1.This method is to adopt microwave plasma body technique direct growth amorphous carbon nanocone on copper sheet, this nano-cone array exists that uniformity (orientation, cone angle and distribution etc.) is relatively poor, draw ratio is less and shortcoming such as the top radius of curvature is bigger, and the application in its emission on the scene field is restricted.
2, make two-dimentional silicon awl array by photoetching technique and electrochemical etching method: referring to documents 2, " field emission characteristic of electrochemical production silicon tip array " (Electron field emission characteristicsof electrochemical etched Si tip array), be stated from " Solid State Communication " 2002, Vol.123: 205-207.This method at first utilizes traditional photoetching and magnetron sputtering technique to prepare patterned Si on silicon substrate
3N
4Mask, thus use reactive ion etching technology that the silicon etching that exposes is fallen to form two-dimentional silicon post array then, remove Si again
3N
4Mask corrodes into tapered structure with electrochemical method with the silicon post at last.Silicon awl array is seen accompanying drawing 2.The silicon awl draw ratio of this method preparation is too little, the top radius of curvature is too big, complicated process of preparation, and the launch stability when making it as field emission cold-cathode is relatively poor, sensitivity is low, and the prospect of practical application is little.
3, template: go out inverted pyramid shape template by anisotropic etch on substrate, fill diamond thick-film then, the method for template is fallen in final etching, produces pyramidal diamond point.Referring to documents 3, " making of diamond field emission array " (fabrication of a diamond field emitter array) is stated from " Applied Physics Letter " 1994, and Vol.64 is on the No.20:2742-2744.This method adopts earth silicon mask, with KOH solution or (CH
3) NOH solution carries out anisotropic etch to monocrystalline silicon piece, produces the template of inverted pyramid shape, adopts the diamond film of traditional CVD method growth to fill inverted pyramid shape hole then, at last template is removed and obtain pyramidal diamond point.The diamond cone array is seen accompanying drawing 3.The diamond point of this structure is owing to less draw ratio, bigger tip curvature radius, and complicated process of preparation can not obtain complete electrical information and pattern information when it is used as scan-probe.Defectives such as the method that existing making prepares surface nano tip exists complex process, be difficult to realize large-area manufacturing, can not be widely used in various solid materials (metal, semiconductor and insulator), tack difference and pattern (as orientation, cone angle, highly, top radius of curvature and density) uniformity and poor controllability, thereby the application potential in fields such as electronics emission on the scene, scanning probe system and photoelectron is subjected to very big restriction.
Summary of the invention
One of purpose of the present invention: the existing suitable material of nano-cone array that had both overcome the preparation of existing direct growth method is limited in scope, uniformity and poor controllability, success rate is low and defective such as tack difference, too little, the radius of curvature of the existing draw ratio of surface nano tip array that overcomes the preparation of existing electrochemical erosion method and template again is big, it is too little and can not obtain complete electrical information and pattern information as probe to make area, and in defectives such as the application potential of terms of mechanics are little; Thereby provide a kind of have controlled draw ratio, controlled density, little tip radius of curvature, and the suitable material scope is wide, and can be used for the surface nano tip array of feds, scanning probe system, biology sensor, nano impression and optoelectronic areas.
Two of purpose of the present invention: a kind of nanocone area preparation method big and controlled, the simple relatively surface nano tip array of preparation technology that has is provided.
The object of the present invention is achieved like this:
Surface nano tip array provided by the invention is the using plasma lithographic technique, on substrate, prepare nano-cone array, its nanocone has draw ratio between 50-8000, the tip radius of curvature is lower than 5 nanometers, base diameter is that 200 nanometers are to 2000 nanometers, cone angle is 16 °-72 °, and density is 10
9Cm
-2-10
5Cm
-2
In above-mentioned technical scheme, described substrate comprises high pressure CVD single-crystalline diamond or thin-film material; Metal sheet such as copper sheet or iron plate; Insulation films such as SiC, ZnO, AlN or BN; Semiconductor material thin film, for example: silicon (n type and p type), porous silicon, GaAs, GaN etc.
The method for preparing surface nano tip array provided by the invention, using plasma etching technics in biased chemical vapor deposition (CVD) equipment (with reference to the accompanying drawings 4) may further comprise the steps:
1) substrate processing: adopt conventional semiconductor cleaning, order is for cleaning substrate respectively in acetone, ethanol and deionized water solvent;
2) backing material after the step 1) cleaning is placed in the stainless steel circle holder 2, and be put in the CVD equipment, be evacuated to 10
-2Torr;
3) the pre-etching of surperficial hydrogen plasma: adopt hydrogen plasma that sample surfaces is carried out pre-etching processing earlier, adopt following etching condition: feed high-purity hydrogen, gas pressure is 2-10Torr, the sample heating-up temperature is in 800-900 ℃ of scope, bias voltage is 300-500V, bias current is 50-150mA, and the time is 15-30 minute;
4) bias voltage in the CVD equipment is turned off, heater current is turned off, and is evacuated to 10 again
-2Torr;
5) adopt following concrete etching condition again, carry out plasma etching and form surface nano tip array: plasma adopts methane/hydrogen, feeds methane/hydrogen gas mixture during etching, and the volume ratio of its mist is (0.5~20): 100; When adopting argon gas or nitrogen and hydrogen as the mist of plasma etching, the volume ratio that feeds argon gas (nitrogen)/hydrogen mixing is (1~100): (0~100).The sample heating-up temperature is in 700-1300 ℃ of scope, and pressure is 2-30Torr, and bias voltage is 300-500V, and bias current is 10-200mA, and the time is 15 minutes-30 hours, promptly prepares surface nano tip array of the present invention.
In above-mentioned technical scheme, in step 3) and 5) in, in order to strengthen etching effect to poorly conductive and the big material 1 of area, comprise that also employing-Pt metallic filaments grid mesh 3 cuts apart the method for discharge, promptly place Pt metallic filaments grid mesh 3 on the surface of substrate 1, the diameter of metallic filaments grid mesh 3 is 0.2 millimeter, guarantees that between metal grid mesh 3 and the stainless steel circle holder 2 be conducting, can induce local plasmon body 4 to form.For the uniformity that guarantees etching effect with realize the large tracts of land etching, also adopted the method for many bank lights silk to replace single filamentray structure commonly used (only otherwise the rated power that exceeds the constant pressure source of powering gets final product).
In above-mentioned technical scheme, described substrate comprises high pressure CVD single-crystalline diamond or thin-film material; Metal sheet; Insulation films such as SiC, ZnO, AlN or BN; Semiconductor material thin film, for example: silicon (n type and p type), porous silicon, GaAs, GaN etc.
In above-mentioned technical scheme, when in step 1), adopting ultrasonic cleaning body material substrate 1, carry out 15 minutes ultrasonic processing approximately; To thin-film material substrate 1, adopt 1~2 minute method of ultrasonic cleaning to handle, or after film growth finishes, do not take out vacuum chamber, directly carry out plasma 4 etchings (as the CVD diamond film).
In above-mentioned technical scheme, also be included in the relatively poor thin-film material of electric conductivity is done substrate 1, during as the CVD diamond film, should select it is grown on the good relatively substrate of electric conductivity, first-class as doped silicon, metal, and the film thickness of growth is generally less than 30 microns.
In above-mentioned technical scheme, the method of described growing diamond film comprises hot filament chemical vapour deposition (CVD) (HFCVD), DC plasma and chemical gas-phase deposition (DCPCVD) and microwave plasma CVD (MWPCVD) method, or other conventional diamond film growth method; Also be included in the growing diamond membrane process, adopt common process to carry out boron doping, nitrogen doping.This doped diamond film is easier generation glow discharge in etching process, and can prepare the better diamond cone of electric conductivity.
Above-mentioned hydrogen plasma 4 pre-etching processes are essential (especially for metal samples), this process both can be with waiting 3 bombardments of hydrogen ion body to fall the foreign atom of substrate 1 surface absorption, can make the thick good fortune in original level and smooth relatively surface again, can induce follow-up surface nano tip array 5 to form.
Surface nano tip array of the present invention not only is suitable for various solid materials, and have high length-diameter ratio (highly/top radius of curvature) and a little top radius of curvature, also have controlled draw ratio, cone angle and density, great application prospect is all arranged in feds, scanning probe system, biology sensor, nano impression and photoelectronics field.
The invention has the advantages that:
1. the invention provides a kind of surface nano tip array, surface nano tip 5 has high length-diameter ratio (200-8000), little tip radius of curvature (less than 5nm), but also have controlled draw ratio, controlled cone angle (16 °-72 °) and controlled array density (10
8Cm
-2-10
5Cm
-2).
2. the present invention also provides a kind of method for preparing surface nano tip array, this method can realize on multiple material (comprising metal, semiconductor and insulator) backing material that large tracts of land makes surface nano tip and array thereof (or controlled area), and this method technology is simple relatively, production cost is low, workable.
3. because the draw ratio of the surface nano tip Yin Qigao of the present invention preparation, little top radius of curvature, good attachment characteristic, can be widely used in fields such as nano impression, field emission display, photoelectronics, scanning probe system and biology sensor, its range of application is more extensive.
Description of drawings:
The schematic diagram of the amorphous carbon nano-cone array of on copper sheet, growing of Fig. 1 prior art
Fig. 2 prior art pass through the schematic diagram that two-dimentional silicon awl array is made in photoetching technique and electrochemical corrosion
The anisotropic etch that passes through of Fig. 3 prior art goes out the schematic diagram that inverted pyramid shape template is filled adamantine method making pyramid diamond point then
Fig. 4 surface nano tip array manufacture craft of the present invention schematic flow sheet
Fig. 4 (a) is depicted as the substrate 1 that is placed in the stainless steel circle holder 2;
Fig. 4 (b) is depicted as and places Pt fine metal mesh grid 3 on substrate 1;
Fig. 4 (c) is depicted as 4 pairs of substrates of plasma 1 and carries out etching;
Fig. 4 (d) is depicted as plasma 4 etchings finish after formed surface nano tip array 5;
The drawing explanation:
1-backing material 2-stainless steel circle holder 3-Pt metallic filaments grid mesh
4-plasma slab 5-nano-cone array
Fig. 5 a, Fig. 5 b, Fig. 5 c, Fig. 5 d are respectively four kinds of schematic diagrames with surface nano tip array of different-shape (highly, density and cone angle) of the present invention
Concrete embodiment
The present invention will be further described in detail below in conjunction with drawings and Examples
Embodiment 1
With reference to figure 5a, make a diamond surface nano-cone array.The about 8-10 micron of the cone height of this diamond surface nano-cone array, tip radius of curvature are 5 nanometers, and the about 1600-2000 of draw ratio, base diameter are the 1-2 micron, about 34 ° of cone angle, and awl density is 2 * 10
6Cm
-2
With reference to figure 4a-d, describe concrete grammar of the present invention in detail by its processing step.
1), selects for use heated filament CVD method on 3cm * 2cm n type silicon chip, to prepare thickness and be approximately 15 microns diamond thick-film as etched substrate 1, adopted the ultrasonic processing silicon chip of bortz powder abrasive method 1 hour before the growth, backing material 1 after cleaning is placed in the stainless steel circle holder 2, and be put in the CVD equipment, be evacuated to 10
-2The concrete parameter of its heated filament of Torr CVD method growth is as follows: air pressure: 15Torr, and n type silicon substrate temperature: 750 ℃, methane/hydrogen volume ratio: 1.5/100, the time: grew 20 hours, promptly obtaining by substrate is the substrate of silicon chip growing diamond thick film on it;
2), behind the diamond thick-film growth ending, place Pt woven wire grid 3 on the surface of diamond thick-film, and make between Pt woven wire grid 3 and the stainless steel circle holder 2 to be conducting, again cavity to be evacuated to 10
-2Torr fills hydrogen then again to 15Torr, and hydrogen flowing quantity is 100sccm;
3), add heater current, regulating filament temperature is 2100 ℃, making substrate 1 temperature is 800 ℃, add the 300V bias voltage between filament and substrate 1 (negative electrode), the adjusting glow current is 150mA, regulates stable gas pressure at 20Torr, etch period is 0.5 hour, carries out hydrogen plasma 4 pre-etchings;
4), turn off bias current, bias voltage, turn off heater current, close gas, be evacuated to 10 again
-2Torr;
5) re-fill methane/hydrogen gas mixture to 15Torr, then, methane/hydrogen volume ratio: 3/97;
6), add heater current, making filament temperature is 2100 ℃, making substrate 1 temperature is 900 ℃, adds the 300V bias voltage between filament and substrate 1 (negative electrode), the adjusting glow current is 150mA, regulates stable gas pressure at 15Torr, etch period is 5 hours;
7), turn off bias current, bias voltage, turn off heater current, close gas, take out sample, obtain as the diamond nano on Fig. 5 a silicon face is bored array 5.
Embodiment 2
Diamond surface nano-cone array 5 concrete structures of present embodiment are referring to Fig. 5 (b); This about 1 micron of cusp height of Buddha's warrior attendant awl, tip radius of curvature are 2 nanometers, and draw ratio is approximately 500, and base diameter is 0.3 micron, and awl density is 5 * 10
8Cm
-2
The preparation technology who presses embodiment 1 makes, and the difference of present embodiment and embodiment 1 is as follows: methane during plasma 4 etchings/hydrogen volume ratio: 1.5/98.5, air pressure are 20Torr, and the time is 1 hour.
Embodiment 3
Porous silicon surface nano-cone array 5 concrete structures of present embodiment are referring to accompanying drawing 5 (c), and about 2 microns of this awl cusp height, tip radius of curvature are 5 nanometers, and draw ratio is about 400, and base diameter is 0.3 micron, and awl density is 4 * 10
8Cm
-2
As follows with the difference of embodiment 1:
1, present embodiment has adopted the porous silicon substrate 1 of electrochemical etching method preparation, and its concrete preparation method is as follows: n type silicon (6-9 Ω .cm): 1cm * 1cm, electrochemical corrosive liquid: C
2H
5OH/HF (49%) is 1: 1 (volume ratio), etching time: 15 minutes, and corrosion current: 20mA.
2, methane during plasma 4 etchings/hydrogen volume ratio: 2/98, air pressure is 20Torr, the time is 2 hours; Because how empty silicon electric conductivity is better, present embodiment does not adopt thin Pt metallic filaments grid mesh 3 to cut apart the method for discharge.
Embodiment 4
Copper surface nano tip array 5 concrete structures of present embodiment are referring to Fig. 5 (d); About 0.3 micron of this awl cusp height, tip radius of curvature are 5 nanometers, and draw ratio is about 60, and base diameter is 0.3 micron, and awl density is 2 * 10
9Cm
-2
As follows with the difference of embodiment 1:
1, the red metal sheet of present embodiment employing ultrasonic cleaning is as substrate 1, and thickness is 200 microns.
2, nitrogen during plasma 4 etchings/hydrogen volume ratio: 50/50, air pressure is 20Torr, the time is 1 hour; Because copper is conductor, present embodiment does not adopt thin Pt metallic filaments grid mesh 3 to cut apart the method for discharge.
Embodiment 5
Present embodiment has obtained surface nano tip array 5 on magnetron sputtering AlN film 1; About 0.4 micron of this awl cusp height, tip radius of curvature are 5 nanometers, and draw ratio is about 80, and base diameter is 0.2 micron, and awl density is 3 * 10
9Cm
-2
Difference from Example 1 is as follows:
1, the growing AIN film is as etched substrate 1 on 2cm * 2cm n type silicon substrate to adopt magnetically controlled sputter method, and the concrete parameter of growth is as follows: target: Al, atmosphere: N
2/ Ar, flow-rate ratio: 60/40, growth air pressure: 0.75Pa, the D growth temperature: 750 ℃, growth time: 1h;
2, argon gas during plasma 4 etchings/hydrogen volume ratio: 50/50, air pressure is 15Torr, the time is 1 hour.