CN113628944B - Method for preparing field electron emission cathode - Google Patents
Method for preparing field electron emission cathode Download PDFInfo
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- CN113628944B CN113628944B CN202110686254.3A CN202110686254A CN113628944B CN 113628944 B CN113628944 B CN 113628944B CN 202110686254 A CN202110686254 A CN 202110686254A CN 113628944 B CN113628944 B CN 113628944B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
- H01J3/02—Electron guns
- H01J3/021—Electron guns using a field emission, photo emission, or secondary emission electron source
- H01J3/022—Electron guns using a field emission, photo emission, or secondary emission electron source with microengineered cathode, e.g. Spindt-type
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/30—Cold cathodes, e.g. field-emissive cathode
- H01J1/304—Field-emissive cathodes
- H01J1/3042—Field-emissive cathodes microengineered, e.g. Spindt-type
- H01J1/3044—Point emitters
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
- H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes
Abstract
The invention relates to a preparation method of a field electron emission cathode, which comprises the following steps: providing a substrate; forming a nanocrystalline diamond film on the substrate; annealing the substrate with the nanocrystalline diamond film in an oxygen-containing atmosphere to obtain a diamond nano burr structure; and processing the surface of the diamond nanopunch structure into a hydrogen termination. The method can prepare the nanocrystalline diamond film with a nano-scale close-packed structure, the film has high growth rate, and the diamond nano burr structure with large length-diameter ratio and high density can be easily obtained by utilizing the film through high selection ratio oxidation reaction, so that the field enhancement factor can be greatly improved. The high selectivity of the oxidation reaction in the method of the invention results in a low diamond consumption. In addition, the method does not need a graphical mask process, so that related equipment and processes are simple, and the processing cost can be greatly reduced.
Description
Technical Field
The invention relates to the field of field electron emission, in particular to a preparation method of a field electron emission cathode.
Background
Compared with thermionic emission which needs to heat metal to more than 1000 ℃, the field electron emission works at room temperature and can realize stable emission of current, has higher efficiency, lower power consumption, faster response rate and easy miniaturization, and has wide application scenes and huge potential in the current major technological trends of digitization, miniaturization and integration. In addition to traditional metallic materials, there have been a great deal of work reporting on the characteristics and mechanisms of field electron emission of semiconductor materials such as silicon, aluminum nitride, diamond, etc., as well as various novel nanomaterials.
The planar structure limits the field enhancement factor of the cathode material, and the improvement method is to utilize the local field enhancement effect of the tip. At present, the processing method for realizing such a diamond field electron emission tip generally adopts selective etching blocked by a patterned mask, i.e. Reactive Ion Etching (RIE) which is common in the micro-nano processing technology. On one hand, because the diamond removal rate in the RIE process is high, single crystal or polycrystalline diamond is mostly adopted as the base material. On the other hand, related process development focuses on different mask materials, such as photoresist, aluminum and nanoparticles like SiO 2 Nanospheres, and the like; and different etching auxiliary gases, e.g. CF 4 、SF 6 And inert gases such as argon and nitrogen, etc. The finally realized tip is mainly a conical and rod-shaped diamond array with micron and submicron large length-diameter ratio. Therefore, although the field emission performance of the RIE-prepared diamond field electron emission array structure is good, the quality of the substrate is importantThe process is harsh, the cost of the process is high, the controllability is not ideal, and the high cost is one of the main obstacles for the practicability of the diamond, so the process is not suitable for large-scale application and development.
Disclosure of Invention
It is an object of the present invention to overcome at least one of the above technical problems and to provide a method for manufacturing a field electron emission cathode.
In order to achieve the above object, the present invention provides the following technical solutions.
A method of making a field electron emission cathode comprising:
providing a substrate;
forming a nanocrystalline diamond film on the substrate;
annealing the substrate with the nanocrystalline diamond film in an oxygen-containing atmosphere to obtain a diamond nano burr structure; and
and processing the surface of the diamond nano burr structure into a hydrogen terminal.
Compared with the prior art, the invention achieves the following technical effects:
1. the method can prepare the nanocrystalline diamond film with a nano-scale close-packed structure, the film has high growth rate, and the diamond nano burr structure with large length-diameter ratio and high density can be easily obtained by utilizing the film through high-selectivity oxidation reaction, so that the field enhancement factor can be greatly improved.
2. The high selectivity of the oxidation reaction in the method of the invention results in a low diamond consumption.
3. The method of the invention does not need a graphical mask process, so that the related equipment and process are simple, and the processing cost can be greatly reduced.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
fig. 1 to fig. 3 are schematic diagrams of structures obtained in each step of the preparation method provided in example 1 of the present invention.
Fig. 4 and 5 are scanning electron microscope images of the structure obtained at each step in the manufacturing method provided in example 1 of the present invention.
FIG. 6 is a scanning electron microscope photograph of the structure obtained in comparative example 1 of the present invention.
Description of the reference numerals
100 is a substrate, 200 is a nanocrystalline diamond film, 300 is a diamond phase nano-skeleton, 400 is non-diamond phase carbon, 500 is a diamond nano-burr structure, and 600 is a hydrogen-terminated diamond nano-burr structure.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.
Various structural schematics according to embodiments of the present disclosure are shown in the figures. The figures are not drawn to scale, wherein certain details are exaggerated and some details may be omitted for clarity of presentation. The shapes of various regions, layers, and relative sizes and positional relationships therebetween shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, as actually required.
In the context of the present disclosure, when a layer/element is referred to as being "on" another layer/element, it can be directly on the other layer/element or intervening layers/elements may be present. In addition, if a layer/element is "on" another layer/element in one orientation, then that layer/element may be "under" the other layer/element when the orientation is reversed.
The invention will be further explained with reference to the drawings.
As described above, the present invention provides a method for preparing a field electron emission cathode, which comprises the following steps.
A substrate is provided.
The substrate may be diamond, silicon, gaN, siC, BN, iridium, stainless steel, or the like. The silicon substrate includes an N-type or P-type silicon substrate. The substrate of the present invention can be directly purchased from the market.
The substrate is first cleaned before it is used. The cleaning method of the present invention is not particularly limited, and a cleaning method commonly used in the art, such as wet cleaning, dry cleaning, cleaning using a chelating agent, ozone cleaning, or low-temperature spray cleaning, may be employed. The wet cleaning may be an RCA cleaning process, and the dry cleaning may be a plasma dry cleaning.
After cleaning, the surface of the substrate is preferably pretreated to increase the nucleation density of the diamond. The pretreatment method of the present invention may include seeding, mechanical scraping, ultrasonic scraping, pulsed laser irradiation, ion implantation, pre-deposition of graphite, and pre-deposition of amorphous carbon, among others. In a preferred embodiment of the invention, the pre-treatment step is carried out by seeding, in particular comprising: the substrate was placed in a suspension containing diamond nanoparticles and subjected to sonication. The suspension is a suspension of diamond nanoparticle powder with a diameter of 2nm or more in a solvent. The solvent may be water, absolute ethanol, toluene or other organic solvents. The ultrasound time is preferably 30min or more. After the implantation of the seed, the substrate is preferably cleaned and dried. For example, the substrate may be ultrasonically cleaned in absolute ethanol and blown dry with dry air or nitrogen.
A nanocrystalline diamond film is formed on a substrate.
The present invention forms a nanocrystalline diamond film on a substrate by Chemical Vapor Deposition (CVD). The chemical vapor deposition method includes Microwave Plasma Chemical Vapor Deposition (MPCVD), radio Frequency Chemical Vapor Deposition (RFCVD), direct current arc chemical vapor deposition (DCCVD), hot wire chemical vapor deposition (HFCVD), bias enhanced chemical vapor deposition, and the like. The nanocrystalline diamond film of the invention has a diamond phase nano skeleton structure which is densely and vertically arranged, and the skeleton is composed of non-diamond phase carbon. The nanocrystalline diamond film (with a special crystallographic structure) with the diamond phase nanometer skeleton structure which is densely and vertically arranged can be formed on the substrate by adjusting the process parameters of the chemical vapor deposition method, and the process parameters comprise working atmosphere, working air pressure, power, substrate temperature, hot wire temperature, bias voltage and the like. The growth process parameters of the nanocrystalline diamond film have an important influence on the formation of the nano burr structure.
In a preferred embodiment, the nanocrystalline diamond film is formed on a substrate by a microwave plasma chemical vapor deposition method. The growth process parameters of the nanocrystalline diamond film comprise: working atmosphere 20% CH 4 And 80% of H 2 The substrate temperature is 700 ℃, the microwave power is 1800W, and the working air pressure is 6kPa. CH in the case of preparing nanocrystalline diamond film by microwave plasma chemical vapor deposition 4 As a carbon source, carbon groups resulting from dissociation thereof are deposited on a substrate, and H 2 Are in equilibrium with each other. The invention prepares the nanocrystalline diamond film with a nano-scale close packing structure by controlling the technological parameters of the microwave plasma chemical vapor deposition method, including working atmosphere, substrate temperature, microwave power and working air pressure, and can prepare the nano-diamond burr structure with large length-diameter ratio, high density and nano-scale curvature radius based on the film.
And annealing the substrate with the nanocrystalline diamond film in an oxygen-containing atmosphere to obtain the diamond nano burr structure.
The oxygen-containing atmosphere of the present invention may be an air atmosphere or a mixed atmosphere of oxygen and an inert gas. The mixed atmosphere may include a mixed atmosphere of oxygen and nitrogen, a mixed atmosphere of oxygen and argon, and a mixed atmosphere of oxygen and helium. Oxygen in an oxygen-containing atmosphere acts as an oxidant and can undergo an oxidation reaction with the non-diamond phase carbon at high temperatures, thereby converting it to carbon dioxide or carbon monoxide for removal. The annealing temperature of the invention is above 400 ℃, the annealing time is determined according to the annealing temperature and the required burr height, and is preferably above 30 min. The annealing step can be performed in a variety of thermal processing equipment including, but not limited to, muffle furnaces, ovens, and the like.
The preparation of the diamond nano burr structure with large length-diameter ratio requires anisotropic etching with high selection ratio, so the preparation difficulty is very high. The invention adopts an oxidation annealing method to remove the non-diamond phase carbon part in the nanocrystalline diamond film, thereby forming the diamond nano burr structure with large length-diameter ratio. The method has the following advantages: the selection ratio is high, the consumption of the diamond is low, and a graphical mask process is not needed, so that related equipment and processes are simple, and the processing cost can be greatly reduced.
And processing the surface of the diamond nano burr structure into a hydrogen terminal.
The surface treatment method of the present invention is not particularly limited, and conventional methods in the art, such as hydrogenation treatment including plasma hydrogenation, high temperature hydrogenation, and the like, may be employed.
The hydrogen-terminated diamond nano burr structure has the characteristics of large length-diameter ratio, high density and nano curvature radius. Specifically, the aspect ratio of the hydrogen-terminated diamond nanoprobe is preferably more than 1, and the distribution density of the hydrogen-terminated diamond nanoprobe on the substrate is 1.0 × 10 9 cm -2 The above. The diamond is an ideal material for preparing the metal-semiconductor composite SERS substrate, has extremely strong chemical inertness and good biocompatibility, and shows remarkable negative electron affinity property after the surface of the diamond is combined with a hydrogen terminal, so that the difficulty of leaving electrons from the surface of the material is greatly reduced, and the field enhancement factor is remarkably improved.
The invention will be further illustrated with reference to specific embodiments and the accompanying drawings.
Example 1
In a single-throw N type<100>On a monocrystalline silicon wafer 100, a nanocrystalline diamond film 200 with diamond phase nano-frameworks 300 arranged densely and vertically is grown by MPCVD, which comprises the following steps: (1) Putting the diamond nano-particle powder with the diameter of 50nm into a proper amount of absolute ethyl alcohol, and carrying out ultrasonic treatment for 1h; (2) Putting the cleaned monocrystalline silicon wafer into the suspension, and carrying out ultrasonic treatment for more than 30 min; (3) Putting the silicon chip into two cups of absolute ethyl alcohol in sequence, and ultrasonically cleaning the silicon chip for 30s respectively; (4) Taking out the silicon wafer anddrying with dry air. (5) Putting a silicon wafer into MPCVD equipment, wherein the growth process parameters are as follows: working atmosphere 20% CH 4 And 80% of H 2 The substrate temperature is 700 ℃, the microwave power is 1800W, the working pressure is 6kPa, the growth time is 3h, the structure shown in figure 1 is obtained, and the scanning electron microscope picture is shown in figure 4.
Annealing to remove non-diamond phase carbon 400 between the diamond phase nano frameworks 300 to obtain the diamond nano burrs with large length-diameter ratio and high density, and the method specifically comprises the following steps: the single crystal silicon wafer 100 on which the nanocrystalline diamond film 200 has grown is placed in a quartz boat and pushed into a muffle furnace in an atmosphere of air at an annealing temperature of 550 ℃ for an annealing time of more than 30 minutes to obtain a structure as shown in fig. 2, and a scanning electron microscopy image is shown in fig. 5, wherein the surface of the diamond nano burr structure 500 is an oxygen termination. The average length of the diamond nano burr is about 180nm, the diameter is less than 10nm, namely the length-diameter ratio is more than 18, and the distribution density of the diamond nano burr on the substrate is 1.8 multiplied by 10 9 cm -2 This demonstrates their structural features of large aspect ratio and high density.
The structure shown in fig. 2 was placed in an MPCVD chamber for hydrogenation treatment with the process parameters: a structure as shown in fig. 3, in which the diamond nanoprobe structure 500 was hydrogenated into a hydrogen-terminated diamond nanoprobe structure 600, was obtained by 100sccm hydrogen, 1300W microwave power, 3kPa working gas pressure, 770 c substrate temperature and 20min hydrogenation time. The length-diameter ratio of the hydrogen terminal diamond nano burr is more than 18, and the distribution density of the hydrogen terminal diamond nano burr on the substrate is 1.8 multiplied by 10 9 cm -2 。
Comparative example 1
This comparative example was carried out as described in example 1, except that the working atmosphere was 20% CH 4 10% of H 2 And 70% argon gas at 800 deg.C and 2100W under 8kPa; the diamond nanopunch structure 500 was not subjected to a hydrogenation treatment. The resulting structure is shown in fig. 6, and it can be seen that nano-burrs are not formed.
As can be seen from example 1 and comparative example 1, the growth process parameters of the nanocrystalline diamond film have an important influence on the formation of the nanophase burr structure.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (7)
1. A method of making a field electron emission cathode, comprising:
providing a substrate;
forming a nanocrystalline diamond film on the substrate;
annealing the substrate with the nanocrystalline diamond film in an oxygen-containing atmosphere to obtain a diamond nano burr structure; and
processing the surface of the diamond nano burr structure into a hydrogen terminal;
forming a nanocrystalline diamond film on the substrate by a chemical vapor deposition method;
the chemical vapor deposition method is a microwave plasma chemical vapor deposition method;
forming a nanocrystalline diamond film with a diamond phase nano framework structure which is densely and vertically arranged on the substrate by adjusting the technological parameters of a chemical vapor deposition method, wherein the frameworks are composed of non-diamond phase carbon, and the technological parameters comprise working atmosphere, working pressure, power and substrate temperature;
the working atmosphere is CH 4 And H 2 ；
The distribution density of the hydrogen terminal diamond nano burr on the substrate is 1.0 multiplied by 10 9 cm -2 The above.
2. The production method according to claim 1, wherein the diamond nanoprotrusions have a large aspect ratio.
3. A production method according to claim 1 or 2, characterized in that the substrate is diamond, silicon, gaN, siC, BN, iridium, or stainless steel.
4. A production method according to claim 1 or 2, characterized in that, before the nanocrystalline diamond film is formed, the surface of the substrate is subjected to pretreatment, which is seeding, mechanical scraping, ultrasonic scraping, bias enhancement, pulsed laser irradiation, ion implantation, pre-deposited graphite, or pre-deposited amorphous carbon.
5. The production method according to claim 1 or 2, wherein the oxygen-containing atmosphere is an air atmosphere or a mixed atmosphere of oxygen and an inert gas; the annealing temperature is above 400 ℃.
6. The production method according to claim 1 or 2, characterized in that, in the step of producing the hydrogen termination, a treatment method is a hydrogenation treatment.
7. The production method according to claim 6, wherein the hydrogenation treatment is plasma hydrogenation or high-temperature hydrogenation.
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| CN100593842C (en) * | 2008-07-01 | 2010-03-10 | 上海大学 | Method for preparing nanocrystalline diamond film field-effect transistor |
| CN106835011B (en) * | 2016-12-20 | 2019-06-25 | 深圳先进技术研究院 | A kind of structural member and preparation method thereof with diamond-like array |
| CN112301423B (en) * | 2020-09-23 | 2021-11-05 | 中国科学院金属研究所 | Preparation method of one-dimensional diamond nanocone array material |
| CN112779517B (en) * | 2020-12-28 | 2022-07-01 | 吉林工程技术师范学院 | Preparation method of self-supporting nanocone diamond |
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