A method for preparing a nano-taper field emission cathode

Abstract

A preparation method of a nano-taper field emission cathode, comprising the following steps: (1) cleaning a silicon wafer substrate, and then performing metal ion implantation on the upper layer of the silicon substrate after drying; (2) depositing SiO2 on the substrate in step 1 as a mask layer; (3) self-assembling polystyrene microspheres on the surface of the substrate in step 2; (4) etching the SiO2 layer to form a nano-pillar mask structure through first plasma etching; (5) cleaning the sample piece through solvent ultrasonic cleaning, and then performing etching cleaning through a plasma adhesive remover; (6) performing dry etching on the Si substrate material by taking the SiO2 nano-pattern structure as a mask, i.e. second plasma etching, and finally performing ultrasonic cleaning to obtain the nano-taper field emission cathode. The method improves the conductive performance of the tip, is more conducive to electron emission, and the nano material is more stable and is not easy to fall off after multiple emissions.

Description

Technical Field

[0001] This application relates to a method for preparing a nanocone field emission cathode, which belongs to the field of materials. Background Technology

[0002] A field emission electrode (FEE) is an electron emission device that utilizes the electron emission characteristics of a material under a high electric field. A high-gradient electric field is formed on the electrode surface, causing free electrons on the surface to be subjected to a strong electric force, thus ejecting them from the electrode surface. The basic working principle of an FEE is that the high-gradient electric field generated on the surface of the emitting material produces a strong reactive force, perturbing surface electrons and ejecting them into space. FEEs possess many excellent properties, such as: high emission current (the emission current increases rapidly with increasing electric field strength), uniform distribution, low energy (electron energy can reach as low as a few electron volts), fast response speed, and high sensitivity. These properties also determine the importance of FEE in microelectronic devices; for example, they are widely used in electron microscopy, field emission display technology (FED), X-ray sources, miniaturized beam sources, and moving particle detection.

[0003] The main methods for fabricating field emission electrodes include: the cone array type represented by Spindt cathodes, cast all-metal, and all-silicon materials, which usually use electrochemical or deposition etching processes; and the carbon nanotube electrode method, which utilizes the special properties of carbon nanotubes to grow carbon nanotube arrays on the surface of a conductor substrate, and then selects carbon nanotubes with suitable morphology to prepare a cone shape for use as a field emission electrode.

[0004] Carbon nanotube electrodes are more expensive and have a more complex process than cone array electrodes, making them less suitable for mass production. Therefore, cone array electrodes have advantages in terms of cost and large-scale production. The emission point distribution density of field emission electrodes has always been a research focus. Conventional processes use photolithography to control the emission point density at the micro-nano level, but photolithography equipment is expensive, the photoresist used is expensive, and the storage environment is harsh. Without photolithography, it is difficult to achieve the emission point density at the micro-nano level. Summary of the Invention

[0005] This invention discloses a method for preparing a nanocone field emission cathode, comprising the following steps:

[0006] (1) Clean the silicon substrate, dry it, and then implant metal ions into the upper surface layer of the silicon substrate;

[0007] (2) A layer of SiO2 is deposited on the substrate in step 1 as a mask layer;

[0008] (3) Step 2: Self-assembly of polystyrene microspheres on the substrate surface;

[0009] (4) The SiO2 layer was etched into a nanopillar structure array by plasma etching under CHF3 and Ar conditions;

[0010] (5) Use solvent ultrasonic cleaning for sample cleaning, and then use plasma desizing machine to pass O2 through to etch and clean the sample surface. The ultimate goal is to remove PS microspheres from the surface.

[0011] (6) A mixture of fluorine-based gas and inert gas is used as the etching gas. The SiO2 nanopattern structure is used as a mask to dry etch the Si substrate material. The process parameters are controlled to etch out a silicon-based nanocone periodic structure array. Finally, the nanocone modified with nanoparticles is ultrasonically cleaned to obtain a nanocone field emission cathode.

[0012] The cleaning described in step (1) includes: first, ultrasonic cleaning using deionized water or a solvent; then, Ar plasma cleaning; the solvent is one of anhydrous ethanol solution, hydrogen peroxide solution or acetone solution.

[0013] The ions mentioned in step (1) can be any one of Au, Ag, and Cu, and the ion particles are used to enhance the electron emission intensity; the ion beam current is 10-15mA and the beam energy is 100-150keV.

[0014] In step (2), a PECVD device is used for deposition, and the thickness of the mask layer is 50-300 nm.

[0015] The polystyrene microspheres in step (3) have a particle size of 300 nm-1 μm; the self-assembly method includes, but is not limited to: water / air interface self-assembly method, spin coating method, dip coating method, physical self-confining method; the polystyrene microspheres form a periodic hexagonal array after self-assembly.

[0016] In step (4), CHF3 and Ar are used as working gases for etching, with CHF3 flow rate of 20-50 sccm, Ar flow rate of 10-20 sccm, etching time of 1-5 min, working pressure of 20-50 torr, and power of 300-800 W.

[0017] The solvent mentioned in step (5) is one or more of acetone and anhydrous ethanol solution, wherein the O2 flow rate is 10-50 sccm, the power is 100-500W, and the time is 1-10 min.

[0018] The fluorine-based gas mentioned in step (6) is SF6 or NF3; the inert gas is one of N2 or Ar; the flow rate of the fluorine-based gas is 20-100 sccm, the flow rate of the inert gas is 10-20 sccm, the etching time is 2-10 min, the pressure is 20-50 torr, and the power is 100-500 w.

[0019] The beneficial technical effects of this application are as follows: 1. The field emission electrode micro / nano structure manufactured in this patented solution uses plasma etching and PECVD, which are simpler than conventional manufacturing methods. When preparing nanoscale structure arrays, the high-precision photolithography process in conventional processes is eliminated; 2. The controllable size of PS microspheres makes the distribution density of field emission electrodes controllable, resulting in low production costs and great application prospects; 3. Ion implantation makes it easier for conductive nanomaterials to be concentrated at the nanocone tip, thereby improving the conductivity of the tip and making it more conducive to electron emission; moreover, compared with the method of depositing particles, nanomaterials are more stable and are not easy to fall off after multiple emission. Attached Figure Description

[0020] Figure 1 Silicon substrate that has undergone ion implantation treatment;

[0021] Figure 2 : Silicon substrate with SiO2 mask layer deposited;

[0022] Figure 3 : The substrate surface of self-assembled polystyrene microspheres;

[0023] Figure 4 : Sample substrate after the first plasma etching process;

[0024] Figure 5 : Sample substrate after removing PS microspheres;

[0025] Figure 6 : The surface of the nanocone field emission cathode after the second plasma etching treatment;

[0026] Figure 7 SEM characterization of the surface structure of the field emission cathode prepared in Example 1;

[0027] Figure 8 EDS energy dispersive spectroscopy detection of the field emission cathode prepared in Example 1. Detailed Implementation

[0028] Example 1:

[0029] The method for preparing a nanocone field emission cathode includes the following steps:

[0030] (1) First, clean the silicon sample. The cleaning methods include: first, use ultrapure water for ultrasonic cleaning; then use Ar plasma cleaning. The purpose of this is to make the substrate surface smooth and dust-free; after the substrate is cleaned and dried, Au ions are implanted into the upper surface layer of the silicon substrate.

[0031] (2) A SiO2 layer with a thickness of 60nm was deposited on the substrate in step 1 using PECVD. The PECVD program parameters were: N2O 480sccm, SiH4 12sccm, N2 240sccm, RF power 50W, Temperature 350℃, Time 39s.

[0032] (3) In step 2, polystyrene microspheres are self-assembled on the substrate surface. The microspheres have a particle size of 300 nm. The self-assembly is carried out by liquid / air interface transfer method. The PS microspheres are arranged closely together mainly due to van der Waals forces, forming a periodic hexagonal structure array.

[0033] (4) Perform the first plasma etching on the sample from step 3. The etching program parameters are: CHF3 35sccm, Ar 15sccm, Time 3min, Pressure 30torr, RF power 500w. Fluorine ions and argon ions etch the PS microspheres and the SiO2 under the gaps between the microspheres. On the one hand, the size of the PS microspheres is reduced, and on the other hand, the SiO2 layer is etched into a periodic nanopillar structure with the PS microspheres as a mask.

[0034] (5) The sample from step 4 was placed in acetone and ethanol solutions for ultrasonic cleaning, and then etched and cleaned using a plasma stripper. The program parameters were: O2 20sccm, RF power 200W, Time 5min. The PS microspheres on the sample surface were removed.

[0035] (6) Perform a second plasma etching on the sample from step 5. The etching program parameters are: NF3 20 sccm, Ar 20 sccm, Time 4 min, Pressure 30 torr, RF power 150 w. The Si substrate surface is etched with silicon cone structure under the mask of SiO2 nanopillars. Finally, the nanoparticle-modified nano silicon cone is ultrasonically cleaned to obtain nano cone field emission cathode, which can be used for a series of subsequent electrode connections.

[0036] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, and all such modifications and additions should fall within the protection scope of the present invention.

Claims

1. A method for preparing a nanocone field emission cathode, comprising the following steps: (1) Clean the silicon substrate, dry it, and then implant metal ions into the upper surface layer of the silicon substrate; (2) A layer of SiO2 is deposited on the substrate in step 1 as a mask layer; (3) Step 2: Self-assembly of polystyrene (PS) microspheres on the substrate surface; (4) The SiO2 layer was etched into a nanopillar mask structure by first plasma etching with CHF3 and Ar; (5) Use solvent ultrasonic cleaning for sample cleaning, and then use plasma desizing machine to pass O2 through to etch and clean the sample surface. The ultimate goal is to remove PS microspheres from the surface. (6) Using fluorine-based gas and inert gas as etching gas, and SiO2 nanopattern structure as mask, dry etching is performed on Si substrate material, i.e. second plasma etching. The process parameters are controlled to etch out silicon-based nanocone periodic structure array. Finally, the nanocone modified with nanoparticles is ultrasonically cleaned to obtain nanocone field emission cathode.

2. The method as described in claim 1, characterized in that... The cleaning described in step (1) includes: first, ultrasonic cleaning using deionized water or a solvent; then, Ar plasma cleaning; the solvent is one of anhydrous ethanol solution, hydrogen peroxide solution or acetone solution.

3. The method as described in claim 1, characterized in that... The metal ion mentioned in step (1) is any one of Au, Ag, and Cu. The metal ion is used to enhance the electron emission intensity. The metal ion beam current is 10-15 mA and the beam energy is 100-150 keV.

4. The method as described in claim 1, characterized in that... In step (2), deposition is performed using a PECVD device.

5. The method as described in claim 1, characterized in that... The polystyrene microspheres in step (3) have a particle size of 300 nm-1 μm; the self-assembly methods in step (3) include: water / air interface self-assembly, spin coating, dip coating, and physical self-confining; the polystyrene microspheres form a periodic hexagonal array after self-assembly.

6. The method as described in claim 1, characterized in that... In step (4), CHF3 and Ar are used as working gases for etching, with CHF3 flow rate of 20-50 sccm, Ar flow rate of 10-20 sccm, etching time of 1-5 min, working pressure of 20-50 torr, and power of 300-800 W.

7. The method as described in claim 1, characterized in that... The solvent mentioned in step (5) is one or more of acetone and anhydrous ethanol solution, wherein the O2 flow rate is 10-50 sccm, the power is 100-500W, and the time is 1-10 min.

8. The method as described in claim 1, characterized in that... The fluorine-based gas mentioned in step (6) is SF6 or NF3; the inert gas is one of N2 or Ar; the flow rate of the fluorine-based gas is 20-100 sccm, the flow rate of the inert gas is 10-20 sccm, the etching time is 2-10 min, the pressure is 20-50 torr, and the power is 100-500 w.

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