CN111128634A - Graphene field emission cathode and preparation method thereof - Google Patents
Graphene field emission cathode and preparation method thereof Download PDFInfo
- Publication number
- CN111128634A CN111128634A CN201911259741.0A CN201911259741A CN111128634A CN 111128634 A CN111128634 A CN 111128634A CN 201911259741 A CN201911259741 A CN 201911259741A CN 111128634 A CN111128634 A CN 111128634A
- Authority
- CN
- China
- Prior art keywords
- graphene
- nanoparticles
- metal
- layer
- conductive substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- 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
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2201/00—Electrodes common to discharge tubes
- H01J2201/30—Cold cathodes
- H01J2201/304—Field emission cathodes
- H01J2201/30446—Field emission cathodes characterised by the emitter material
- H01J2201/30453—Carbon types
Abstract
The invention provides a graphene field emission cathode, which comprises a conductive substrate and a graphene/nano metal composite layer combined on one surface of the conductive substrate, wherein the graphene/nano metal composite layer comprises a graphene layer and a nano metal material layer combined on the graphene layer, the nano metal material layer is arranged on the surface of the graphene layer, which is far away from the conductive substrate, the metal nano material layer is composed of metal nano particles, and the work function of the metal nano particles is less than or equal to 4.5 eV. According to the invention, the low-work-function metal nanoparticles are arranged on the surface of the graphene, so that the open electric field of the graphene cathode is obviously reduced, the field emission current density is improved, and the current emission stability of the graphene field emission cathode is improved.
Description
Technical Field
The invention belongs to the technical field of field emission, and particularly relates to a graphene field emission cathode and a manufacturing method thereof.
Background
Graphene is composed of a single layer of carbon atoms stacked in a plane to form a periodic hexagonal lattice structure, and is a novel two-dimensional carbon nanomaterial. The graphene has excellent conductivity and heat conduction characteristics, stable chemical properties and very high mechanical strength, and has important application prospects in the aspects of materials science, micro-nano processing, energy, biomedicine, drug delivery and the like. Particularly, graphene has abundant nanoscale edge structures and can be used as an efficient electron emission address. Therefore, as an ideal field emission material, graphene is expected to be applied in the fields of vacuum microwave devices, field emission displays, X-ray sources and the like.
The preparation method of the graphene field emission cathode mainly comprises a Chemical Vapor Deposition (CVD) method and a solution processing method. The CVD method is to place the substrate deposited with the catalyst in a high temperature furnace, then introduce a mixed gas containing a carbon precursor, and generate graphene on the surface of the substrate under the action of the catalyst. The graphene grown by the CVD method is generally parallel to the substrate direction, so that the effective field emission tips are few, and the emission current is small. In addition, the process for growing the graphene by the CVD method is complex, high in cost and long in time period, and practical application of the graphene field emission cathode is limited. The solution processing method is a preparation method of a graphene field emission cathode with mild preparation conditions, and comprises an electrophoretic deposition method, a dropping coating method, a spin coating method and the like. The electrophoretic deposition method is to uniformly disperse graphene and metal inorganic salt (charge additive) capable of providing charges in water or an organic solvent, and under the action of a direct current or alternating current electric field, the charged graphene moves to an anode or a cathode and is deposited on a conductive substrate to form a graphene film. Compared with the CVD method, the solution processing method has the advantages of simple and easily controlled process, short preparation period, capability of uniformly preparing the graphene field emission cathode on a substrate with any shape and size in a large area, and wide practical application prospect. However, the graphene cathode prepared by the solution processing method still has the problems of large field emission starting electric field, small emission current density and poor emission stability.
Disclosure of Invention
The invention aims to provide a graphene field emission cathode and a manufacturing method thereof, and aims to solve the problems of large field emission starting electric field, small emission current density and poor emission stability of the existing graphene field emission cathode.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a graphene field emission cathode, which comprises a conductive substrate and a graphene/nano-metal composite layer combined on one surface of the conductive substrate, wherein the graphene/nano-metal composite layer comprises a graphene layer and a metal nano-material layer combined on the graphene layer, the metal nano-material layer is arranged on the surface of the graphene layer, which is far away from the conductive substrate, the metal nano-material layer is made of metal nano-particles, and the work function of the metal nano-particles is less than or equal to 4.5 eV.
Preferably, the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles, hafnium nanoparticles, zirconium nanoparticles, vanadium nanoparticles, tin nanoparticles, yttrium nanoparticles.
Preferably, the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, and niobium nanoparticles.
Preferably, the thickness of the metal nano material layer is 2 nm-10 nm.
Preferably, the interface between the graphene layer and the metal nano-material layer forms a mixed material layer of graphene and metal nano-particles.
The second aspect of the present invention provides a method for preparing a graphene field emission cathode, comprising the following steps:
providing a conductive substrate, and preparing a graphene layer on one surface of the conductive substrate;
and depositing metal nano particles on the surface of the graphene layer, which is far away from the conductive substrate, and preparing a graphene/nano metal composite layer through vacuum annealing treatment, wherein the work function of the metal nano particles is less than or equal to 4.5 eV.
Preferably, the annealing temperature of the vacuum annealing treatment is 500-600 ℃, and the annealing time is 10-30 min.
Preferably, the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles, hafnium nanoparticles, zirconium nanoparticles, vanadium nanoparticles, tin nanoparticles, yttrium nanoparticles.
Preferably, the thickness of the metal nano material layer is 2 nm-10 nm.
Preferably, in the step of vacuum annealing, the interface between the graphene layer and the metal nanoparticles forms a mixed material layer of graphene and metal nanoparticles.
According to the graphene field emission cathode provided by the invention, the nano metal material layer with low work function is arranged on the surface of the graphene layer. On the one hand, the electronic interaction can take place between the nanometer metal particle in the nanometer metal material layer and the graphite alkene in the graphite alkene layer, and this kind of electronic interaction can change the electron structure of graphite alkene (nevertheless do not change the emission structure of graphite alkene), increases the state density near graphite alkene fermi energy level, increases the electron tunneling probability of graphite alkene to show the required electric field that opens of reduction graphite alkene emission, improve field emission current density, improve current emission stability. On the other hand, the metal nanoparticles distributed on the surface of the graphene layer can block partial cations from bombarding the surface of the graphene in the field emission process of the graphene cathode, so that the damage of a graphene emission structure in the field emission process is reduced, and the emission stability of the graphene field emission cathode is further improved.
According to the preparation method of the graphene field emission cathode, the low-work-function metal nanoparticles are deposited on the surface of the graphene layer, and annealing treatment is further performed. In the annealing treatment process, electronic interaction occurs between graphene in the graphene layer and the nano metal particles on the surface of the graphene, and the electronic interaction can change the electronic structure of the graphene (but does not change the emission structure of the graphene), increase the state density near the Fermi level of the graphene, and increase the electron tunneling probability of the graphene, so that the starting electric field required by graphene emission is obviously reduced, the field emission current density is improved, and the current emission stability is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a field emission graph of graphene field emission cathodes prepared in examples 1 to 5 and comparative example 1;
fig. 2 is a field emission graph of the graphene field emission cathodes prepared in comparative examples 1 and 2.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The weight of the related components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present invention as long as it is in accordance with the description of the embodiments of the present invention. Specifically, the weight described in the description of the embodiment of the present invention may be a unit of mass known in the chemical industry field, such as μ g, mg, g, and kg.
In a first aspect, the embodiment of the present invention provides a graphene field emission cathode, including a conductive substrate and a graphene/nano-metal composite layer bonded to a surface of the conductive substrate, where the graphene/nano-metal composite layer includes a graphene layer and a metal nano-material layer bonded to the graphene layer, and the metal nano-material layer is disposed on a surface of the graphene layer away from the conductive substrate, where the metal nano-material layer includes metal nanoparticles, and a work function of the metal nanoparticles is less than or equal to 4.5 eV.
According to the graphene field emission cathode provided by the embodiment of the invention, the nano metal material layer with a low work function is arranged on the surface of the graphene layer. On the one hand, the electronic interaction can take place between the nanometer metal particle in the nanometer metal material layer and the graphite alkene in the graphite alkene layer, and this kind of electronic interaction can change the electron structure of graphite alkene (nevertheless do not change the emission structure of graphite alkene), increases the state density near graphite alkene fermi energy level, increases the electron tunneling probability of graphite alkene to show the required electric field that opens of reduction graphite alkene emission, improve field emission current density, improve current emission stability. On the other hand, the metal nanoparticles distributed on the surface of the graphene layer can block partial cations from bombarding the surface of the graphene in the field emission process of the graphene cathode, so that the damage of a graphene emission structure in the field emission process is reduced, and the emission stability of the graphene field emission cathode is further improved.
In the embodiment of the present application, the conductive substrate is used as a substrate for depositing a thin film material, and is required to have good conductivity (in field emission, a voltage is applied to a cathode, and the voltage is applied to the substrate and then conducted to the cathode). The conductive substrate is selected from substrates that are capable of generating electrons upon energization and capable of transporting the electrons to the field emission cathode. In some embodiments, the conductive substrate is selected from metal substrates formed with a base material of at least one of iron, titanium, copper, chromium, cobalt, nickel, tungsten, molybdenum, tantalum, and platinum. The iron, titanium, copper, chromium, cobalt, nickel, tungsten, molybdenum, tantalum and platinum can generate electrons after being electrified and can transmit the electrons to the substrate of the field emission cathode. In some embodiments, the conductive substrate is an insulating substrate with a metal thin film disposed on a surface thereof, wherein a base material of the metal thin film is selected from at least one of iron, titanium, copper, chromium, cobalt, nickel, tungsten, molybdenum, tantalum, and platinum. In some embodiments, the conductive substrate is an Indium Tin Oxide (ITO) conductive glass or silicon wafer. Wherein, the silicon wafer can be a p-type or n-type silicon wafer with low resistivity.
In the embodiment of the present application, a graphene/nano-metal composite layer is disposed on a surface of the conductive substrate. Specifically, the graphene/nano-metal composite layer comprises a graphene layer and a metal nano-material layer combined on the graphene layer, wherein the metal nano-material layer is arranged on the surface of the graphene layer departing from the conductive substrate. It is worth noting that the metal nanoparticles in the metal nanoparticle material layer disposed on the surface of the graphene layer are not strictly separated from the graphene in the graphene layer, and even the metal nanoparticles in the metal nanoparticle material layer and the graphene in the graphene layer are mutually permeated, so that the probability of electronic interaction between the metal nanoparticles and the graphene is further increased through the mutual permeation. In some embodiments, the interface of the graphene layer and the metal nanoparticle material layer forms a mixed material layer of graphene and metal nanoparticles.
On the basis of the above embodiment, the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles, hafnium nanoparticles, zirconium nanoparticles, vanadium nanoparticles, tin nanoparticles, and yttrium nanoparticles. At least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles, hafnium nanoparticles, zirconium nanoparticles, vanadium nanoparticles, tin nanoparticles and yttrium nanoparticles is used as a material of the metal nano material layer, and the metal nano material layer has the advantage of low work function, so that the work function of graphene adjacent to the metal nano material layer can be reduced essentially, the electron tunneling probability of the graphene is increased, the starting electric field required by graphene emission is reduced, and the field emission current is increased. In a preferred embodiment, the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles. The metal nano particles and the graphene have electronic interaction, the electronic structure of the graphene can be changed through the electronic interaction (but the emission structure of the graphene is not changed), the state density near the Fermi level of the graphene is further increased, and the electron tunneling probability of the graphene is increased, so that the starting electric field required by graphene emission is remarkably reduced, the field emission current density is improved, and the current emission stability is remarkably improved.
In some embodiments, the thickness of the metal nanomaterial layer is 2nm to 10 nm. When the thickness of the metal nano material layer is 2 nm-10 nm, the metal nano particles can effectively increase the state density near the Fermi level of the graphene and increase the electron tunneling probability of the graphene, so that the starting electric field required by graphene emission is obviously reduced, the field emission current density is improved, and the current emission stability is obviously improved; in addition, the method can also block partial cations from bombarding the surface of the graphene in the field emission process of the graphene cathode, thereby reducing the damage of the graphene emission structure in the field emission process and further improving the emission stability of the graphene field emission cathode. When the thickness of the metal nano material layer is too thin and is less than 2nm, the metal nano material layer has an insignificant effect of improving the graphene field emission current and the stability of the emission current. When the thickness of the metal nano material layer is too thick and is higher than 10nm, the too thick metal nano material layer can cover the tip (emission point) of partial graphene, so that the field enhancement effect is reduced; and the metal nanoparticles are used as field enhancement points, and the density is too high, so that electric field shielding is generated, and the field enhancement effect is inhibited. In some embodiments, the thickness of the metal nanomaterial layer is 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, or the like.
The graphene field emission cathode provided by the implementation of the invention can be prepared by the following method.
The second aspect of the embodiments of the present invention provides a method for preparing a graphene field emission cathode, including the following steps:
s01, providing a conductive substrate, and preparing a graphene layer on one surface of the conductive substrate;
s02, depositing metal nano particles on the surface of the graphene layer, which is far away from the conductive substrate, and preparing a graphene/nano metal composite layer through vacuum annealing treatment, wherein the work function of the metal nano particles is less than or equal to 4.5 eV.
According to the preparation method of the graphene field emission cathode provided by the embodiment of the invention, the low-work-function metal nano particles are deposited on the surface of the graphene layer, and annealing treatment is further carried out. In the annealing treatment process, electronic interaction occurs between graphene in the graphene layer and the nano metal particles on the surface of the graphene, and the electronic interaction can change the electronic structure of the graphene (but does not change the emission structure of the graphene), increase the state density near the Fermi level of the graphene, and increase the electron tunneling probability of the graphene, so that the starting electric field required by graphene emission is obviously reduced, the field emission current density is improved, and the current emission stability is improved.
Specifically, in step S01, a conductive substrate is provided, which is used as a substrate for depositing a thin film material and is required to have good conductivity (field emission requires applying a voltage to a cathode, which is applied to the substrate and then conducted to the cathode). The conductive substrate is selected from substrates that are capable of generating electrons upon energization and capable of transporting the electrons to the field emission cathode. In some embodiments, the conductive substrate is selected from metal substrates formed with a base material of at least one of iron, titanium, copper, chromium, cobalt, nickel, tungsten, molybdenum, tantalum, and platinum. The iron, titanium, copper, chromium, cobalt, nickel, tungsten, molybdenum, tantalum and platinum can generate electrons after being electrified and can transmit the electrons to the substrate of the field emission cathode. In some embodiments, the conductive substrate is an insulating substrate with a metal thin film disposed on a surface thereof, wherein a base material of the metal thin film is selected from at least one of iron, titanium, copper, chromium, cobalt, nickel, tungsten, molybdenum, tantalum, and platinum. In some embodiments, the conductive substrate is an Indium Tin Oxide (ITO) conductive glass or silicon wafer. Wherein, the silicon wafer can be a p-type or n-type silicon wafer with low resistivity.
The method for preparing the graphene layer on one surface of the conductive substrate is not strictly limited. Preferably, graphene is deposited on the surface of the conductive substrate by a solution processing method.
In a preferred embodiment, the step of depositing graphene on the surface of the conductive substrate includes: and preparing a graphene solution, depositing the graphene solution on the surface of the conductive substrate, and drying to form a film. The graphene solution may be a graphene dispersion liquid using graphene as a solute, or a graphene electrophoretic dispersion liquid containing graphene and a metal inorganic salt.
In the embodiment of the present application, the graphene used for preparing the graphene solution is a graphene nanosheet, the source of the graphene is not strictly limited, and the graphene can be prepared by a Hummer method, which is not limited to this. The graphene nanosheet in the graphene solution can be single-layer graphene or multi-layer graphene. Wherein the multi-layer graphene comprises an few-layer graphene. In some embodiments, the lateral dimension of the graphene in the graphene emission thin film is 1 μm to 10 μm. In some specific embodiments, the lateral dimensions of the graphene in the graphene emission thin film are 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm.
In some embodiments, the concentration of graphene in the graphene solution is 0.1-10mg/ml, and when the concentration of graphene in the graphene solution is within this range, the graphene has better dispersibility and is not easy to introduce graphene agglomerates. If the concentration of the graphene solution is too high, the graphene is aggregated and precipitated to form a bulk graphene agglomerate, and the bulk graphene agglomerate can reduce the field emission performance of the graphene. If the concentration of the graphene in the graphene solution is too low, a complete film layer is not formed; but also the emission address is lowered, thereby lowering the field emission performance of the graphene. In some embodiments, the graphene solution has a concentration of 0.1mg/mL, 0.5mg/mL, 1mg/mL, 1.5mg/mL, 2mg/mL, 2.5mg/mL, 3mg/mL, 3.5mg/mL, 4mg/mL, 4.5mg/mL, 5mg/mL, 5.5mg/mL, 6mg/mL, 6.5mg/mL, 7mg/mL, 7.5mg/mL, 8mg/mL, 8.5mg/mL, 9mg/mL, 9.5mg/mL, 10mg/mL, and the like. More preferably, in order to improve the dispersibility of the graphene in the solution, the concentration of the graphene solution is 0.1-1 mg/ml. In some embodiments, the graphene solution has a concentration of 0.1mg/mL, 0.2mg/mL, 0.3mg/mL, 0.4mg/mL, 0.5mg/mL, 0.6mg/mL, 0.7mg/mL, 0.8mg/mL, 0.9mg/mL, 1mg/mL, and the like.
The method for depositing the graphene solution on the surface of the conductive substrate is not limited, and a dispensing method or an electrophoretic deposition method may be used, but is not limited thereto. The deposition of the graphene solution may even be achieved by printing, where conditions allow.
In a specific embodiment, an electrophoretic deposition method is adopted to deposit a graphene electrophoretic dispersion liquid on the surface of the conductive substrate to prepare the graphene emission thin film.
In a preferred embodiment, the method for depositing the graphene electrophoretic dispersion liquid on the surface of the conductive substrate by using an electrophoretic deposition method comprises: dispersing graphene nanosheets and metal inorganic salt in an organic solvent to obtain a graphene electrophoretic dispersion liquid; and placing the conductive substrate serving as a cathode and the other conductive substrate serving as an anode into the graphene electrophoretic dispersion liquid, applying direct-current voltage, and depositing graphene on the surface of the conductive substrate.
Wherein the metal inorganic salt is selected from metal inorganic salts capable of providing positive charges, and the metal inorganic salt is combined on the graphene nano-sheet to make the graphene nano-sheet positively charged. The metal inorganic salt includes, but is not limited to, Mg (NO)3)2、MgCl2、Al(NO3)3、AlCl3、NiCl2Or Ni (NO)3)2. The organic solvent is selected from organic solvents with good dissolving and dispersing performances on graphene nanosheets and metal inorganic salts, is preferably organic alcohol, and specifically can be ethanol, acetone or isopropanol. In a preferred embodiment, after the graphene nanosheets and the metal inorganic salt are dispersed in the organic solvent, ultrasonic dispersion is performed for 1-3 hours, and a uniform and stable graphene electrophoretic dispersion liquid is obtained.
And taking the conductive substrate as a cathode and the other conductive substrate as an anode, putting the conductive substrate into the graphene electrophoresis dispersion liquid, and under the action of direct current voltage, moving the positively charged graphene nanosheets towards the direction of the cathode to deposit on the conductive substrate to obtain the graphene layer. In a preferred embodiment, the conditions of the deposition process are: and (3) carrying out electrophoresis for 1-10 min under the action of a direct current voltage of 100-200V, so that the graphene with proper quantity and thickness can be obtained.
In a specific embodiment, a graphene dispersion liquid is deposited on the surface of the conductive substrate by a dropping method to prepare the graphene emission thin film. In a preferred embodiment, the method for dispensing the graphene dispersion liquid on the conductive substrate comprises: placing the conductive substrate on a heating plate, setting the heating temperature to be not higher than 200 ℃ (so as to avoid introducing oxygen and other heteroatoms into a graphene structure by high-temperature treatment and destroy the crystal structure and the attribute of graphene), taking the graphene dispersion liquid, slowly dripping the graphene dispersion liquid on the substrate, and forming a graphene layer after a solvent is quickly volatilized. Preferably, in order to avoid the solvent from volatilizing rapidly at too high a temperature, which may cause the generated film to have pores or even rupture, the heating temperature is not higher than 100 ℃, specifically, 80 ℃, 85 ℃, 90 ℃ and 95 ℃.
In the step S02, metal nanoparticles with a work function less than or equal to 4.5eV are deposited on the surface of the graphene layer away from the conductive substrate, so as to reduce the work function of the graphene cathode, and further reduce the turn-on electric field required by graphene emission. Preferably, the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles, hafnium nanoparticles, zirconium nanoparticles, vanadium nanoparticles, tin nanoparticles, yttrium nanoparticles. At least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles, hafnium nanoparticles, zirconium nanoparticles, vanadium nanoparticles, tin nanoparticles and yttrium nanoparticles is used as a material of the metal nano material layer, and the metal nano material layer has the advantage of low work function, so that the work function of graphene adjacent to the metal nano material layer can be reduced essentially, the electron tunneling probability of the graphene is increased, the starting electric field required by graphene emission is reduced, and the field emission current is increased. In a preferred embodiment, the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles. The metal nano particles and the graphene have electronic interaction, the electronic structure of the graphene can be changed through the electronic interaction (but the emission structure of the graphene is not changed), the state density near the Fermi level of the graphene is further increased, and the electron tunneling probability of the graphene is increased, so that the starting electric field required by graphene emission is remarkably reduced, the field emission current density is improved, and the current emission stability is remarkably improved.
In the embodiment of the application, the deposition thickness of the metal nanoparticles is 2 nm-10 nm. When the deposition thickness of the metal nanoparticles is 2 nm-10 nm, the metal nanoparticles can effectively increase the state density near the Fermi level of the graphene and increase the electron tunneling probability of the graphene, so that the starting electric field required by graphene emission is obviously reduced, the field emission current density is improved, and the current emission stability is obviously improved; in addition, the method can also block partial cations from bombarding the surface of the graphene in the field emission process of the graphene cathode, thereby reducing the damage of the graphene emission structure in the field emission process and further improving the emission stability of the graphene field emission cathode. When the deposition thickness of the metal nanoparticles is too thin and is less than 2nm, the metal nanoparticle layer has no obvious effect of improving the graphene field emission current and the stability of the emission current. When the deposition thickness of the metal nanoparticles is too thick and is higher than 10nm, the too thick metal nanoparticle layer can cover the tip (emission point) of graphene, so that the field emission effect is reduced; meanwhile, the deposition thickness of the metal nanoparticles is too thick, the density of the metal nanoparticles is high, and when an electric field is applied, an electric field shielding effect is generated between the metal nanoparticles, but a field enhancement effect is inhibited, so that the field emission performance is reduced. In addition, in some embodiments, the thickness of the metal nanomaterial layer is 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, or the like.
And placing the substrate on which the metal nano particles are deposited in a vacuum environment for annealing treatment. The size of the metal nano-particles is improved through annealing treatment, so that the field enhancement effect is enhanced. In a preferred embodiment, the annealing temperature of the vacuum annealing treatment is 500-600 ℃, and the annealing time is 10-30 min. In some embodiments, the annealing temperature of the vacuum annealing treatment is 500 ℃, 510 ℃, 520 ℃, 530 ℃, 540 ℃, 550 ℃, 560 ℃, 570 ℃, 580 ℃, 590 ℃, 600 ℃ or the like, and the annealing time is 10min, 12min, 15min, 18min, 20min, 22min, 25min, 28min, 30min or the like. Of course, within the above annealing temperature and annealing time ranges, the higher the annealing temperature is, the shorter the annealing time is preferred; the lower the annealing temperature, the longer the annealing time is preferably increased.
The following description will be given with reference to specific examples.
Example 1
A graphene field emission cathode is prepared by the following steps:
providing an iron-based conductive substrate;
preparing 0.2mg/ml graphene solution, and performing ultrasonic treatment at 200W for 1 hour to form a stable dispersion liquid. Wherein the graphene in the graphene solution is multilayer graphene with the size of 1-3 microns. Dripping the graphene solution on the iron-based conductive substrate to deposit a graphene film, and drying at the temperature of 90 ℃ to form a graphene cathode;
and depositing titanium nano particles with the thickness of 3nm on the surface of the graphene film, which is far away from the iron-based conductive substrate, by adopting a magnetron sputtering method, and annealing for 30 minutes at the temperature of 500 ℃ to prepare the titanium metal nano particle doped graphene cathode.
Example 2
A graphene field emission cathode is prepared by the following steps:
providing an iron-based conductive substrate;
preparing 0.2mg/ml graphene solution, and performing ultrasonic treatment at 200W for 1 hour to form a stable dispersion liquid. Wherein the graphene in the graphene solution is multilayer graphene with the size of 1-3 microns. And dripping the graphene solution on the iron-based conductive substrate to deposit a graphene film, and drying at the temperature of 90 ℃ to form a graphene cathode.
Depositing bismuth nanoparticles with the thickness of 3nm on the surface of the graphene film, which is far away from the iron-based conductive substrate, by adopting a magnetron sputtering method, and annealing for 30 minutes at the temperature of 500 ℃ to prepare the bismuth metal nanoparticle-doped graphene cathode.
Example 3
A graphene field emission cathode is prepared by the following steps:
providing an iron-based conductive substrate;
preparing 0.2mg/ml graphene solution, and performing ultrasonic treatment at 200W for 1 hour to form a stable dispersion liquid. Wherein the graphene in the graphene solution is multilayer graphene with the size of 1-3 microns. And dripping the graphene solution on the iron-based conductive substrate to deposit a graphene film, and drying at the temperature of 90 ℃ to form a graphene cathode.
And depositing indium nanoparticles with the thickness of 3nm on the surface of the graphene film, which is far away from the iron-based conductive substrate, by adopting a magnetron sputtering method, and annealing for 30 minutes at the temperature of 500 ℃ to prepare the graphene cathode doped with the indium metal nanoparticles.
Example 4
A graphene field emission cathode is prepared by the following steps:
providing an iron-based conductive substrate;
preparing 0.2mg/ml graphene solution, and performing ultrasonic treatment at 200W for 1 hour to form a stable dispersion liquid. Wherein the graphene in the graphene solution is multilayer graphene with the size of 1-3 microns. And dripping the graphene solution on the iron-based conductive substrate to deposit a graphene film, and drying at the temperature of 90 ℃ to form a graphene cathode.
And depositing tantalum nanoparticles with the thickness of 3nm on the surface of the graphene film, which is far away from the iron-based conductive substrate, by adopting a magnetron sputtering method, and annealing for 30 minutes at the temperature of 500 ℃ to prepare the graphene cathode doped with the tantalum metal nanoparticles.
Example 5
A graphene field emission cathode is prepared by the following steps:
providing an iron-based conductive substrate;
preparing 0.2mg/ml graphene solution, and performing ultrasonic treatment at 200W for 1 hour to form a stable dispersion liquid. Wherein the graphene in the graphene solution is multilayer graphene with the size of 1-3 microns. And dripping the graphene solution on the iron-based conductive substrate to deposit a graphene film, and drying at the temperature of 90 ℃ to form a graphene cathode.
And depositing niobium nano-particles with the thickness of 3nm on the surface of the graphene film, which is far away from the iron-based conductive substrate, by adopting a magnetron sputtering method, and annealing for 30 minutes at the temperature of 500 ℃ to prepare the niobium metal nano-particle doped graphene cathode.
Comparative example 1
A graphene field emission cathode is prepared by the following steps:
providing an iron-based conductive substrate;
preparing 0.2mg/ml graphene solution, and performing ultrasonic treatment at 200W for 1 hour to form a stable dispersion liquid. Wherein the graphene in the graphene solution is multilayer graphene with the size of 1-3 microns. And dripping the graphene solution on the iron-based conductive substrate to deposit a graphene film, and drying at the temperature of 90 ℃ to form a graphene cathode.
Comparative example 2
A graphene field emission cathode is prepared by the following steps:
providing an iron-based conductive substrate;
preparing 0.2mg/ml graphene solution, and performing ultrasonic treatment at 200W for 1 hour to form a stable dispersion liquid. Wherein the graphene in the graphene solution is multilayer graphene with the size of 1-3 microns. Dripping the graphene solution on the iron-based conductive substrate to deposit a graphene film, and drying at the temperature of 90 ℃ to form a graphene cathode;
and depositing titanium nano particles with the thickness of 15nm on the surface of the graphene film, which is far away from the iron-based conductive substrate, by adopting a magnetron sputtering method, and annealing for 30 minutes at the temperature of 500 ℃ to prepare the titanium metal nano particle doped graphene cathode.
The field emission current and the electric field intensity of the graphene field emission cathodes prepared in examples 1 to 5, and comparative examples 1 and 2 were tested, and field emission curves of the cathodes were plotted, as shown in fig. 1 and 2. As can be seen from fig. 1, the graphene field emission cathodes prepared in examples 1 to 5 have higher electric field strength than that of comparative example 1 at the same field emission current. As can be seen from fig. 2, although comparative example 2 deposits titanium nanoparticles on the surface of the graphene thin film facing away from the iron-based conductive substrate, a titanium metal nanoparticle-doped graphene cathode was prepared. However, the deposition thickness of the titanium nanoparticles is too thick, and the electric field intensity of the graphene field emission cathode is reduced.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A graphene field emission cathode comprises a conductive substrate and a graphene/nano-metal composite layer bonded on one surface of the conductive substrate, wherein the graphene/nano-metal composite layer comprises a graphene layer and a metal nano-material layer bonded on the graphene layer, the metal nano-material layer is arranged on the surface of the graphene layer, which faces away from the conductive substrate, the metal nano-material layer is made of metal nanoparticles, and the work function of the metal nanoparticles is less than or equal to 4.5 eV.
2. The graphene field emission cathode of claim 1, wherein the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles, hafnium nanoparticles, zirconium nanoparticles, vanadium nanoparticles, tin nanoparticles, yttrium nanoparticles.
3. The graphene field emission cathode of claim 1, wherein the metal nanoparticles are selected from at least one of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, and niobium nanoparticles.
4. The graphene field emission cathode of any one of claims 1-3, wherein the thickness of the metal nanomaterial layer is 2nm to 10 nm.
5. The graphene field emission cathode of any one of claims 1 to 3, wherein the interface of the graphene layer and the metal nanoparticle material layer forms a mixed material layer of graphene and metal nanoparticles.
6. A preparation method of a graphene field emission cathode is characterized by comprising the following steps:
providing a conductive substrate, and preparing a graphene layer on one surface of the conductive substrate;
and depositing metal nano particles on the surface of the graphene layer, which is far away from the conductive substrate, and preparing a graphene/nano metal composite layer through vacuum annealing treatment, wherein the work function of the metal nano particles is less than or equal to 4.5 eV.
7. The method for preparing the graphene field emission cathode of claim 6, wherein the annealing temperature of the vacuum annealing treatment is 500-600 ℃, and the annealing time is 10-30 min.
8. The method of claim 6 or 7, wherein the metal nanoparticles are at least one selected from the group consisting of indium nanoparticles, titanium nanoparticles, bismuth nanoparticles, tantalum nanoparticles, niobium nanoparticles, hafnium nanoparticles, zirconium nanoparticles, vanadium nanoparticles, tin nanoparticles, and yttrium nanoparticles.
9. The method of claim 6 or 7, wherein the metal nanoparticles are deposited to a thickness of 2nm to 10 nm.
10. The method of claim 6 or 7, wherein the step of preparing the graphene layer on one surface of the conductive substrate comprises: and preparing a graphene solution, depositing the graphene solution on the surface of the conductive substrate, and drying to form a film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911259741.0A CN111128634A (en) | 2019-12-10 | 2019-12-10 | Graphene field emission cathode and preparation method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911259741.0A CN111128634A (en) | 2019-12-10 | 2019-12-10 | Graphene field emission cathode and preparation method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN111128634A true CN111128634A (en) | 2020-05-08 |
Family
ID=70498151
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201911259741.0A Pending CN111128634A (en) | 2019-12-10 | 2019-12-10 | Graphene field emission cathode and preparation method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111128634A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112086580A (en) * | 2020-09-15 | 2020-12-15 | 武汉华星光电半导体显示技术有限公司 | Display panel and preparation method thereof |
| CN114203930B (en) * | 2021-12-09 | 2023-05-30 | 深圳市华星光电半导体显示技术有限公司 | Cathode, organic light-emitting diode and preparation method thereof |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102660740A (en) * | 2012-05-29 | 2012-09-12 | 东南大学 | Graphene and metal nanoparticle composite film preparation method |
| CN203134742U (en) * | 2013-03-20 | 2013-08-14 | 郑州航空工业管理学院 | Novel metal-based carbon nanotube field emission cold cathode |
| CN105513921A (en) * | 2015-12-25 | 2016-04-20 | 深圳先进技术研究院 | Carbon nano field emission cathode, preparation method and application thereof |
| CN105551909A (en) * | 2015-12-23 | 2016-05-04 | 深圳先进技术研究院 | Field emission cathode and preparation method and application thereof |
| CN108172488A (en) * | 2017-12-26 | 2018-06-15 | 深圳先进技术研究院 | Carbon nanometer field-transmitting cathode and its manufacturing method and application |
-
2019
- 2019-12-10 CN CN201911259741.0A patent/CN111128634A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102660740A (en) * | 2012-05-29 | 2012-09-12 | 东南大学 | Graphene and metal nanoparticle composite film preparation method |
| CN203134742U (en) * | 2013-03-20 | 2013-08-14 | 郑州航空工业管理学院 | Novel metal-based carbon nanotube field emission cold cathode |
| CN105551909A (en) * | 2015-12-23 | 2016-05-04 | 深圳先进技术研究院 | Field emission cathode and preparation method and application thereof |
| CN105513921A (en) * | 2015-12-25 | 2016-04-20 | 深圳先进技术研究院 | Carbon nano field emission cathode, preparation method and application thereof |
| CN108172488A (en) * | 2017-12-26 | 2018-06-15 | 深圳先进技术研究院 | Carbon nanometer field-transmitting cathode and its manufacturing method and application |
Non-Patent Citations (2)
| Title |
|---|
| JIHUA ZHANG ET AL.: "Improvement of the field emission of carbon nanotubes by hafnium coating and annealing", 《NANOTECHNOLOGY》 * |
| VISHAKHA KAUSHIK ET AL.: "Improved electron field emission from metal grafted", 《CARBON》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112086580A (en) * | 2020-09-15 | 2020-12-15 | 武汉华星光电半导体显示技术有限公司 | Display panel and preparation method thereof |
| CN114203930B (en) * | 2021-12-09 | 2023-05-30 | 深圳市华星光电半导体显示技术有限公司 | Cathode, organic light-emitting diode and preparation method thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Coskun et al. | Optimization of silver nanowire networks for polymer light emitting diode electrodes | |
| Zhu et al. | Fast Li storage in MoS2‐graphene‐carbon nanotube nanocomposites: advantageous functional integration of 0D, 1D, and 2D nanostructures | |
| Zhai et al. | High Electrocatalytic and Wettable Nitrogen‐Doped Microwave‐Exfoliated Graphene Nanosheets as Counter Electrode for Dye‐Sensitized Solar Cells | |
| Hong et al. | A universal method for preparation of noble metal nanoparticle‐decorated transition metal dichalcogenide nanobelts | |
| US20130224452A1 (en) | Metal nanoparticle-graphene composites and methods for their preparation and use | |
| EP2402285B1 (en) | Method for fabricating composite material comprising nano carbon and metal or ceramic | |
| Koh et al. | Effective hybrid graphene/carbon nanotubes field emitters by electrophoretic deposition | |
| CN111128634A (en) | Graphene field emission cathode and preparation method thereof | |
| Koh et al. | Effective large-area free-standing graphene field emitters by electrophoretic deposition | |
| Song et al. | An ultra-long and low junction-resistance Ag transparent electrode by electrospun nanofibers | |
| KR101425376B1 (en) | Large-area carbon nanomesh from polymer and method of preparing the same | |
| Shen et al. | Highly conductive vertically aligned molybdenum nanowalls and their field emission property | |
| Baiju et al. | Hydrothermal synthesis, dielectric properties of barium titanate, cobalt doped barium titanate, and their graphene nanoplatelet composites | |
| Tian et al. | Bilayer and three dimensional conductive network composed by SnCl2 reduced rGO with CNTs and GO applied in transparent conductive films | |
| Elshahawy et al. | Surface-Engineered TiO2 for high-performance flexible supercapacitor applications | |
| CN105513921B (en) | Carbon nanometer field-transmitting cathode and its preparation method and application | |
| Yu et al. | Electronic properties and field emission of carbon nanotube films treated by hydrogen plasma | |
| Ogihara et al. | Fabrication of patterned carbon nanotube thin films using electrophoretic deposition and ultrasonic radiation | |
| CN111081504B (en) | Field emission cathode and preparation method thereof | |
| Yu et al. | Field emission characteristics study for ZnO/Ag and ZnO/CNTs composites produced by DC electrophoresis | |
| CN111128633B (en) | Graphene field emission cathode and preparation method thereof | |
| CN110265559B (en) | Luminous electrochemical cell and preparation method thereof | |
| Huang et al. | Control of electrostatic self-assembly seeding of diamond nanoparticles on carbon nanowalls | |
| CN109616334B (en) | Preparation method of carbon-coated metal oxide nanodot-loaded graphene composite material | |
| CN109192359B (en) | Graphene transparent conductive film with rivet structure and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20200508 |