Emitter, electron gun, electronic apparatus, and method for manufacturing emitter

Abstract

Provided are an emitter capable of efficiently and stably emitting electrons over a long period of time, an electron gun and an electronic apparatus using the emitter, and a method for manufacturing the emitter. The surface of a metal containing a rare earth element is oxidized to form a metal oxide represented by general formula REOx (wherein RE represents a rare earth element, 1 < = xlt; 1.5), and a step for producing a film comprising a rare earth oxide represented by formula (1); and a step in which a film comprising a rare earth oxide is processed into a needle shape using a focused ion beam, and a film comprising a rare earth oxide is produced which has a structure represented by general formula REOx (in the formula, RE represents a rare earth element, 1 < = xlt; 1.5), and an emitter for a nanoneedle (10) formed from a rare earth oxide represented by formula (1).

Description

Technical Field

[0001] The present invention relates to an emitter, an electron gun and electronic equipment using the emitter, and a method for manufacturing the emitter. Background Art

[0002] The electron guns installed in electron microscopes have been improved in various ways to obtain high-resolution and high-brightness observation images. Among the electron guns used in electron microscopes, field emission type and Schottky type electron guns utilize the tunneling effect and Schottky effect to generate electric field concentration at the tip of the emitter to efficiently emit electrons.

[0003] As the material for the emitter of these electron guns, for example, lanthanum hexaboride (LaB) which is a low work function material is used. 6 ) and / or lanthanum oxide (La 2 O 3 ), yttrium oxide (Y 2 O 3 ), gadolinium oxide (Gd 2 O 3 ), Tantalum Carbide (Dy 2 O 3 ) and other rare earth oxides (see Patent Document 1). In addition, the present inventors have also proposed an emitter using hafnium carbide (HfC) (see Patent Document 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-16451

[0007] Patent Document 2: International Publication No. 2021 / 002305 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] However, as electron microscopes become more precise and performant, emitters with higher brightness and longer life are required.

[0010] Therefore, an object of the present invention is to provide an emitter capable of emitting electrons stably and efficiently for a long period of time, an electron gun and an electronic device using the emitter, and a method for manufacturing the emitter.

[0011] Solutions for solving problems

[0012] The emitter of the present invention is an emitter having nanoneedles, wherein the nanoneedles are composed of a general formula REO x (wherein RE is a rare earth element, 1≤x<1.5) is formed as a rare earth oxide.

[0013] At least the front end of the aforementioned nanoneedle may be composed of a crystalline phase. In this case, the aforementioned crystalline phase may be, for example, at least one crystal system selected from the group consisting of a cubic system, a monoclinic system, and a hexagonal system. Alternatively, when the aforementioned crystalline phase is a cubic system, the crystal plane of the front end of the aforementioned nanoneedle is a (001) plane or a (110) plane, when the aforementioned crystalline phase is a monoclinic system, the crystal plane of the front end of the aforementioned nanoneedle is a (010) plane, and when the aforementioned crystalline phase is a hexagonal system, the crystal plane of the front end of the aforementioned nanoneedle is a (102￣) plane.

[0014] The rare earth oxide may contain at least one rare earth element selected from the group consisting of La, Ce, Pr, Nd, and Sm.

[0015] Furthermore, the rare earth oxide may contain Ga in an amount of 0.5 atomic % or less.

[0016] On the other hand, the nanoneedle can have a maximum diameter of 1 nm or more and 1 μm or less, and a length of 500 nm or more and 30 μm or less. In this case, the radius of curvature of the front end of the nanoneedle can be set to be less than 50% of the maximum diameter. In addition, the radius of curvature of the front end of the nanoneedle can be set to 5 to 30 nm.

[0017] The emitter of the present invention may further include a support needle and a filament, wherein the support needle is formed of at least one element selected from the group consisting of W, Ta, Pt, Re and C, and the nanoneedle is attached to the filament via the support needle.

[0018] The electron gun of the present invention includes the above-mentioned emitter, and is, for example, a cold cathode field emission electron gun or a Schottky electron gun.

[0019] The electronic device of the present invention includes an electron gun, and is, for example, a scanning electron microscope, a transmission electron microscope, a scanning transmission electron microscope, an Auger electron spectrometer, an electron energy loss spectrometer, an energy dispersive electron spectrometer, or the like.

[0020] The method for manufacturing an emitter of the present invention is a method for manufacturing an emitter having nanoneedles, the method comprising: oxidizing the surface of a metal containing a rare earth element to form a nanoneedle having a general formula of REO x (wherein RE is a rare earth element, 1≤x<1.5); and using a focused ion beam, the film composed of the rare earth oxide is processed into a needle shape to obtain the nanoneedle.

[0021] In the step of forming the film composed of the rare earth oxide, the metal containing the rare earth element can be kept at a temperature of 0 to 800° C. and a pressure of 10 1 ~105 Pa, and a relative humidity of 10 to 70%, thereby oxidizing the surface of the above-mentioned metal.

[0022] In the step of processing the film composed of the rare earth oxide into a needle shape, the film composed of the rare earth oxide may be cut out from the surface of the metal and the film composed of the rare earth oxide may be placed on a supporting needle.

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to obtain an emitter and an electron gun capable of emitting electrons stably and efficiently for a long period of time. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram showing a configuration example of a transmitter according to the first embodiment of the present invention.

[0026] Figure 2 Yes means Figure 1 A schematic diagram of the structure of the nanoneedle 10 is shown.

[0027] Figure 3 This is a flowchart showing an example of the manufacturing process of the emitter according to the first embodiment of the present invention.

[0028] Figure 4 It is a diagram schematically showing the structure of an electron gun according to a second embodiment of the present invention.

[0029] Figure 5 is a graph showing the electron density of states (DOS) of LaO.

[0030] Figure 6 A to D are LaO with different crystal systems. x Plot of the electronic density of states (DOS) for (x=1.4165 or x=1.4375).

[0031] Figure 7 A and B are diagrams showing the results of molecular dynamics simulation.

[0032] Figure 8 A is LaO x SEM image of nanoneedles. Figure 8 B is a TEM image.

[0033] Fig. 9 A~C represent LaO x Figure 2 STEM-EDS mapping of nanoneedles.

[0034] Fig.10 It means LaO x Diagram of the field emission pattern of the nanoneedles.

[0035] Fig.11 It represents LaO x A graph showing the current stability of the nanoneedles. Detailed implementation mode

[0036] Hereinafter, the modes for implementing the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to the implementation modes described below.

[0037] (First implementation mode)

[0038] First, the emitter of the first implementation mode of the present invention will be described. Figure 1 It is a schematic diagram showing a structural example of the emitter of this implementation mode, Figure 2 It represents Figure 1 A schematic diagram of the structure of the nanoneedle 10 shown. As Figure 1 shown, the emitter 1 of this implementation mode includes a nanoneedle 10. The nanoneedle 10 is formed of a rare earth oxide represented by the general formula REO x (RE is a rare earth element), where 1 ≤ x < 1.5.

[0039] [REO x (where 1 ≤ x < 1.5)]

[0040] The inventors of the present invention have conducted in-depth research on rare earth oxides and found that the compound represented by the general formula REO x shown (hereinafter also referred to as the REO x compound) has a low work function and excellent electron emission ability. In particular, it has been found that the conductivity of the oxide (1 < x < 1.5) obtained by introducing oxygen vacancies into the rare earth oxide (REO) where x = 1 and RE is a divalent rare earth element, and the rare earth oxide (RE 2 O 3 ) where x = 1.5 and RE is a trivalent rare earth element is improved and the work function becomes lower.

[0041] From the viewpoint of chemical stability, the REO x compound is preferably 1 < x < 1.5. In addition, from the aspect of having a low work function and excellent electron emission ability, the REO x compound where 1.2 ≤ x < 1.5 is more preferred. Even more preferably, the REO x compound where 1.4 ≤ x ≤ 1.49, which is particularly chemically stable, has a lower work function, and has excellent electron emission ability.

[0042] In addition, the rare earth element (RE) of the REO x compound is not particularly limited, and is preferably at least one selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), and samarium (Sm). If the REO xFor a compound, a work function of less than 2.7 eV can be achieved. It should be noted that for REO x In the REO compound of the rare earth element (RE), lanthanum (La) is particularly preferred. By forming the nanoneedles 10 with lanthanum oxide, an emitter with a work function of 1.8 to 2.3 eV and excellent electron emission ability can be obtained.

[0043] The REO compound forming the nanoneedles 10 x compound may further contain gallium (Ga). Thereby, electrons can be emitted stably for a long time. At this time, from the viewpoint of maintaining the crystal structure, the amount of Ga in the REO x compound is preferably greater than 0 atomic % and 5 atomic % or less.

[0044] The REO compound forming the nanoneedles 10 x compound may be entirely composed of a crystalline phase or an amorphous phase, or may be composed of both a crystalline phase and an amorphous phase. However, the tip portion 10a of the nanoneedles 10 that emit electrons is preferably composed of a crystalline phase. Thereby, an excellent emitter capable of stably emitting electrons can be obtained.

[0045] Here, the REO x compound constituting the nanoneedles 10 may be either a single crystal or a polycrystal. However, from the aspect of ease of manufacturing, a polycrystal is preferred. In addition, the crystalline phase of the REO x compound may be at least one crystal system selected from the group consisting of a cubic crystal system, a monoclinic crystal system, and a hexagonal crystal system.

[0046] Hereinafter, taking the case where the rare earth element (RE) is lanthanum (La) (LaO x ) as an example, the crystal system will be described. When x = 1 in LaO x , that is, LaO is a crystal having a crystal structure of a cubic crystal system and belonging to the space group Fm3￣m (space group No. 225 in International Tables for Crystallography), as shown in Table 1 below. It should be noted that "3￣" means a line is added to 3, and the same applies to the following description. In addition, in the case of LaO, since the crystal structure becomes stable, the lattice constant a (nm) is preferably 0.45 < a < 0.55.

[0047] [Table 1]

[0048]

[0049] On the other hand, when 1 < x < 1.5 in LaO x , any one of a cubic crystal system, a hexagonal crystal system, and a monoclinic crystal system is adopted. LaO xWhen the crystal structure is cubic, it becomes a crystal belonging to the Ia3￣ space group (space group No. 206 in International Tables for Crystallography) shown in Table 2 below, or the Im3￣ space group (space group No. 229 in International Tables for Crystallography) shown in Table 3 below.

[0050] [Table 2]

[0051]

[0052] [Table 3]

[0053]

[0054] In the case of a crystal belonging to the Ia3￣ space group, the lattice constant a (nm) is preferably 1.10 < a < 1.20, and in the case of a crystal belonging to the Im3￣m space group, the lattice constant a is preferably 0.43 nm < a < 0.47 nm. Thus, the crystal structure is stabilized.

[0055] In addition, as shown in Table 4 below, when using a crystal structure of hexagonal system, it can also be a crystal belonging to the P3￣m1 space group (space group No. 164 in International Tables for Crystallography). At this time, the lattice constant a (nm) is preferably 0.37 < a < 0.41, and the lattice constant c (nm) is preferably 0.58 < c < 0.64. Thus, in LaO with a crystal structure of hexagonal system x a smaller work function can be achieved. x

[0056] [Table 4]

[0057]

[0058] Furthermore, as shown in Table 5 below, when LaO x adopts a crystal structure of monoclinic system, it can also be a crystal belonging to the C2 / m space group (space group No. 12 in International Tables for Crystallography). At this time, it is preferably that the lattice constant a (nm) is 1.40 < a < 1.50, the lattice constant b is 0.30 < b < 0.40, and the lattice constant c (nm) is 0.85 < c < 0.95. Thus, the crystal structure is stabilized.

[0059] [Table 5]

[0060]

[0061] REO x In a compound, when the rare earth element (RE) is an element other than La or a part of the constituent elements is replaced by other elements, the lattice constant changes, but the crystal structure, the sites occupied by atoms, and the atomic positions provided by their coordinates do not change significantly to the extent that the chemical bonds between the framework atoms are broken. Therefore, regarding the REO x compound, when performing Rietveld analysis on the results of X-ray diffraction and neutron diffraction in the aforementioned space group to obtain the lattice constant, and the length of the RE-O chemical bond (distance between adjacent atoms) calculated from this lattice constant is within ±5% compared to the length of the chemical bond calculated from the lattice constants and atomic coordinates of the crystals shown in Tables 1 to 5 above, it can be regarded as the same crystal structure.

[0062] It should be noted that for the REO x compound when it is composed of a crystalline phase, the aforementioned crystalline phases can be compounded. In this case, by comparing the diffraction peak positions (2θ) calculated using the crystal structure parameters shown in Tables 1 to 5 above with the X-ray diffraction results of the REO x compound forming the emitter, the main phase and the second phase can be identified based on the coincidence, shift, etc. of the main peaks.

[0063] In addition, when the front end portion 10a of the nanoneedle 10 is in a cubic crystal system crystalline phase of the REO x compound, its crystal plane is preferably the (001) plane or the (110) plane. Specifically, when the front end portion 10a of the nanoneedle 10 is formed by REO x (x = 1), the crystal plane is preferably the (001) plane, and when it is REO x (1 < x < 1.5, space group Ia3￣), the crystal plane is preferably the (110) plane, and when it is REO x (1 < x < 1.5, space group Im3￣m), the crystal plane is preferably the (001) plane.

[0064] On the other hand, when the REO x compound of the front end portion 10a of the nanoneedle 10 is in a hexagonal crystal system crystalline phase, the crystal plane is preferably the (102￣) plane. It should be noted that "2￣" means an overline is added to 2, and the same applies in the following description. In addition, for example, when the REO x compound of the front end portion 10a of the nanoneedle 10 is in a monoclinic crystal system crystalline phase, the crystal plane is preferably the (010) plane. These crystal planes are chemically stable, so by forming the front end portion 10a with these crystal planes, electrons can be efficiently emitted.

[0065] It should be noted that the above crystal plane is an example, and the crystal plane of the front end portion 10a of the nanoneedle 10 is not limited thereto. In principle, all crystal planes represented by values ​​below Miller index 3 can be used. Here, "below Miller index 3" means that the absolute value of each value is 3 or less.

[0066] [Dimensions of the nanoneedle 10]

[0067] Nano needle 10 Figure 2 The maximum diameter d shown is preferably 1 nm to 1 μm, and the length L is preferably 500 nm to 30 μm. By setting the size of the nanoneedle 10 to this range, electric field concentration can be efficiently generated at the tip 10a where electrons should be emitted, and more electrons can be emitted from the tip 10a of the nanoneedle 10.

[0068] The maximum diameter d of the nanoneedle 10 is more preferably 400 to 800 nm, and the length L is more preferably 1 to 3 μm. The nanoneedle 10 in this size range is easy to process, and thus emitters can be manufactured with a high yield.

[0069] On the other hand, the nanoneedle 10 is a shape that tapers toward the front end (the diameter becomes smaller), and the curvature radius r of the front end portion 10a is preferably less than 50% of the maximum diameter d. Thus, electrons can be efficiently emitted from the front end portion 10a. From the viewpoint of improving the emission efficiency of electrons, the curvature radius d of the front end portion 10a of the nanoneedle 10 is more preferably 1 to 10% of the maximum diameter d, and further preferably 1 to 5%.

[0070] The value of the curvature radius r of the front end portion 10a of the nanoneedle 10 is not particularly limited and can be appropriately adjusted according to the purpose of the emitter, etc. From the viewpoint of electrolytic concentration, it is preferably 0.5 to 75 nm, more preferably 5 to 50 nm, further preferably 10 to 30 nm, and particularly preferably 15 to 25 nm. For example, when the emitter of this embodiment is used in an electron gun, from a practical point of view, the value of the curvature radius r of the front end portion 10a of the nanoneedle 10 is preferably set to 5 to 50 nm.

[0071] The shape and curvature radius r of the front end portion 10a of the nanoneedle 10 can be confirmed by observation under a scanning electron microscope (SEM). In addition, the method for processing / treating the front end portion 10a of the nanoneedle 10 into the above-mentioned shape is not particularly limited, and for example, an ion beam method, an electric field evaporation method, etc. can be applied. In particular, the method using a focused ion beam can be used in REO x Since Ga is added to the compound, it is preferred.

[0072] [Other structures]

[0073] The emitter 1 of this embodiment may include a support needle 11 and a filament 12 in addition to the aforementioned nanoneedle 10. In this case, the nanoneedle 10 is attached to the filament 12 via the support needle 11. This improves the operability of the nanoneedle 10.

[0074] It should be noted that the support needle 11 may be formed of at least one element selected from the group consisting of tungsten (W), tantalum (Ta), platinum (Pt), rhenium (Re) and carbon (C). Figure 1 The shape of the filament 12 shown is a hairpin shape (U-shape), but the present invention is not limited thereto, and any shape such as a V-shape may be adopted.

[0075] [Manufacturing method]

[0076] Next, a method for manufacturing the emitter of this embodiment will be described. Figure 3 FIG. 1 is a flow chart showing an example of a manufacturing process of a transmitter according to this embodiment. Figure 3 As shown, in the manufacturing method of the emitter of this embodiment, the REO is formed x The nanoneedles 10 are formed by the step of forming a rare earth oxide film composed of a compound (step S1 ) and the step of processing the rare earth oxide film into a needle shape (step S2 ).

[0077] [Step S1: Rare Earth Oxide Film Formation Process]

[0078] In step S1, the surface of the metal containing rare earth element (RE) is oxidized to form a x (RE is a rare earth element) and 1≤x<1.5. In consideration of the processability in step S2, the rare earth oxide film formed here preferably has a thickness of 2 μm or more.

[0079] The metal containing a rare earth element (RE) used herein may be a metal containing one rare earth element (RE) or an alloy containing two or more rare earth elements (RE). In addition, it is preferred that the surface of the metal forming the rare earth oxide film is ground, thereby forming a uniform rare earth oxide film.

[0080] The oxidation method and conditions of the metal surface can be appropriately selected according to the type of rare earth element (RE) contained in the metal. For example, the metal can be oxidized at a temperature of 0 to 800°C for 10 1 ~10 5 The holding time at this time varies depending on the thickness of the oxide film, but in order to obtain an oxide film with a thickness of more than 2 μm, it can be kept in a range of more than 1 hour and less than 30 days. For example, in the case of forming polycrystalline LaO with a thickness of 2 to 3 μm, xIn the case of (where 1 < x < 1.5), it suffices to maintain it for a period of 1 to 3 weeks in an environment at room temperature (a temperature environment of 10 to 30 °C), a degree of vacuum of 50 to 150 Pa, and a relative humidity of 30 to 55%.

[0081] [Step S2: Rare earth oxide film processing step]

[0082] In Step S2, the rare earth oxide film formed in Step S1 is processed into a needle shape using, for example, a focused ion beam. At this time, before irradiating the focused ion beam, the rare earth oxide film formed in Step S1 may also be cut out from the surface of the metal and placed on a support needle. Thereby, the processability can be improved. It should be noted that the support needle used here may also have the function of the support needle 11 shown in Figure 1 shown.

[0083] The irradiation conditions of the focused ion beam are not particularly limited. For example, in the case of using gallium (Ga) ions, the following conditions can be adopted.

[0084] Current: 5 to 1000 pA (preferably 500 to 900 pA)

[0085] Voltage: 1 to 100 kV (preferably 20 to 40 kV)

[0086] Irradiation time: 1 to 60 minutes (preferably 5 to 15 minutes)

[0087] It should be noted that when the nanoneedle 10 is processed into a shape that tapers (diameter decreases) towards the tip, it suffices to irradiate the focused ion beam in a manner that scans from the outside to the inside of the rare earth oxide film.

[0088] As described in detail above, the emitter of the present embodiment includes a nanoneedle formed of a rare earth oxide represented by the general formula REO x (RE is a rare earth element), 1 ≤ x < 1.5. Therefore, it has a low work function and excellent electron emission ability. By using the emitter of the present embodiment, an electron gun and an electronic device capable of stably emitting electrons for a long time can be realized.

[0089] In addition, in the manufacturing method of the emitter of the present embodiment, the surface of a metal containing a rare earth element (RE) is oxidized to form a rare earth oxide film represented by the general formula REO x and 1 ≤ x < 1.5, and the oxide film is processed into a needle shape using a focused ion beam. Therefore, it is possible to easily form a nanoneedle formed of a REO x compound.

[0090] The emitter of this embodiment can emit electrons efficiently and stably, and can therefore be applied to any device with electron focusing capability, such as a scanning electron microscope, a transmission electron microscope, a scanning transmission electron microscope, an Auger electron spectrometer, an electron energy loss spectrometer, and an energy dispersive electron spectrometer.

[0091] (Second embodiment)

[0092] Next, an electron gun according to an embodiment of the present invention will be described. Figure 4 FIG. 2 is a diagram schematically showing an example of the structure of an electron gun according to the present embodiment. Figure 4 As shown, the electron gun 20 of the present embodiment is, for example, a cold cathode field emission electron gun or a Schottky electron gun, and includes the emitter 1 of the above-mentioned first embodiment.

[0093] In the electron gun 20 of the present embodiment, an extraction power source 22 is connected between the electrode 21 and the extraction electrode 23, and an acceleration power source 24 is connected between the electrode 21 and the acceleration electrode 25. Thus, a voltage is applied between the emitter 1 and the extraction electrode 23 by the extraction power source 22, and a voltage is applied between the emitter 1 and the acceleration electrode 25 by the acceleration power source 24. In the case where the electron gun 20 is a cold cathode field emission electron gun, the electrode 21 may be further connected to a flushing power source (not shown), and in the case where the electron gun 20 is a Schottky electron gun, the electrode 21 may be further connected to a heating power source (not shown).

[0094] The electron gun 20 of this embodiment can also be arranged at a pressure of 10 -8 ~10 -7 Under the vacuum condition of 1.5 Pa, the tip 10 a of the nanoneedle 10 of the emitter 1 can be kept clean.

[0095] [operate]

[0096] Next, the operation of the electron gun 20 of this embodiment is described. In the case where the electron gun 20 is a cold cathode field emission electron gun, a voltage is applied between the emitter 1 and the extraction electrode 23 by the extraction power supply 22. As a result, an electric field concentration is generated at the tip 10a of the nanoneedle 10 of the emitter 1, and electrons are extracted. In addition, a voltage is applied between the emitter 1 and the acceleration electrode 25 by the acceleration power supply 24. As a result, the electrons extracted at the tip 10a of the nanoneedle 10 of the emitter 1 are accelerated and emitted toward the sample.

[0097] It should be noted that, when the electron gun 20 is a cold cathode field emission electron gun, the surface of the nanoneedle 10 can be cleaned by appropriately cleaning it with a flushing power source connected to the electrode 21. In addition, these operations are preferably performed under the aforementioned vacuum conditions.

[0098] On the other hand, when the electron gun 20 is a Schottky electron gun, the heating power supply connected to the electrode 21 heats the emitter 1, and a voltage is applied between the emitter 1 and the extraction electrode 23 by the extraction power supply 22. Thus, the tip 10a of the nanoneedle 10 of the emitter 1 generates Schottky emission, and electrons are extracted. In addition, a voltage is applied between the emitter 1 and the acceleration electrode 25 by the acceleration power supply 24. Thus, the electrons extracted at the tip 10a of the nanoneedle 10 of the emitter 1 are accelerated and emitted toward the sample.

[0099] It should be noted that, in the case of the above structure, sometimes due to the voltage application based on the heating power supply, the nanoneedle 10 of the emitter 1 emits thermal electrons, so a suppressor (not shown) for shielding thermal electrons may be further provided in the electron gun 20.

[0100] As described in detail above, the electron gun of this embodiment is equipped with the emitter of the first embodiment, so that the emission of electrons is easy and the electrons can be stably emitted for a long time. The electron gun of this embodiment can be used in any electronic device with electron focusing capability. Specifically, it can be applied to electronic devices such as scanning electron microscopes, transmission electron microscopes, scanning transmission electron microscopes, Auger electron spectrometers, electron energy loss spectrometers, and energy dispersive electron spectrometers.

[0101] Example

[0102] Hereinafter, the effects of the present invention will be specifically described by way of examples.

[0103] <First Embodiment>

[0104] First, as a first embodiment of the present invention, the REO of a rare earth element (RE) of La, Ce, Pr, Nd or Sm, x=1 is obtained by first principle calculation. x The electronic state and work function of the compound. The calculations are based on the density functional method, using plane waves as basis functions and ultrasoft pseudopotentials. The density gradient approximation is introduced, and the cutoff energy of the plane wave is 80Ry. The work function is calculated from the difference between the vacuum level and the Fermi level. In these calculations, Quantum Espresso v7.0 (downloaded from https: / / www.quantum-espresso.org) was used. The results are shown in Table 6 below. In addition, Figure 5 is a graph showing the electron density of states (DOS) of LaO.

[0105] [Table 6]

[0106]

[0107] like Figure 4As shown, the electronic state of LaO is metallic, and the work function of its (001) plane is calculated to be 2.3 eV based on the difference between the calculated Fermi level and the vacuum level. Similarly to LaO, the electronic state densities of CeO, PrO, NdO, and SmO are also metallic, and the calculated work function is 2.7 eV or less. In addition, as shown in Table 6 above, in the case where the rare earth element (RE) is La and Ce, a low work function comparable to that of LaB 6 was obtained. Thus, it was confirmed that the REO x compound with x = 1 is a material that functions as an emitter.

[0108] <Example 2>

[0109] Next, as the second example of the present invention, the electronic state and work function of LaO x (x = 1.4165 to 1.4375) were obtained by first-principles calculations in the same manner as in the aforementioned first example. The results are shown in Table 7 below. It should be noted that the work function values of LaO and LaB 6 shown in Table 6 above are also shown in Table 7 below. In addition, Figure 6 A to D are graphs of the electronic state density (DOS) of LaO x (x = 1.4165 or x = 1.4375) with different crystal systems.

[0110] [Table 7]

[0111]

[0112] As Figure 6 shown, in any crystal system, oxygen defect levels are generated near the bottom of the conductor, and thus the electronic state of LaO x is metallic. In addition, as shown in Table 7 above, when 1 < x < 1.5 in LaO x , that is, in the case of oxygen vacancies in La 2 O 3 , the work function is 1.8 to 2.1 eV, which is lower than that of LaB 6 . Thus, it was confirmed that the REO x compound with 1 ≤ x < 1.5 is a material that functions as an emitter, and in particular, the REO x compound that satisfies 1 < x < 1.5 with oxygen vacancies is suitable.

[0113] <Example 3>

[0114] Next, as the third example of the present invention, LaO x (x = 1, 1.4375) and LaB 6Chemical stability. At this time, in addition to the method of the first embodiment described above, the Car-Parrinello method was used for the molecular dynamics part. The temperature was set to 500 K, and water molecules were arranged at a distance of from the surface for simulation. In these calculations, Quantum Espresso v7.0 (downloaded from https: / / www.quantum-espresso.org) was used.

[0115] Figure 7 A and B of Figure 7 are graphs showing the results of molecular dynamics simulations. 6 A of Figure 7 shows the crystal of LaB Figure 7 and the water molecules on its (001) plane. 2 B of 6 shows the crystal of LaO and the water molecules on its (001) plane. As x shown in A and B of x , the water molecules (H 6 O) are dissociated and adsorbed as H and OH on the (001) plane of LaB

[0116] <Example 4>

[0117] Next, as the fourth embodiment of the present invention, a transmitter equipped with nanoneedles was manufactured by the method shown in Figure 3 . Specifically, the surface of a metal made of La (manufactured by High Purity Chemical Research Institute Co., Ltd., diameter 10 mm × thickness 2 mm) was oxidized to form a thin film of rare earth oxide of LaO x (1 < x < 1.5). At this time, the La metal with its surface ground and finished was kept in an environment of room temperature (20 °C), relative humidity 45%, and vacuum degree 100 Pa for 2 weeks. x X-ray diffraction was performed on the oxidized La metal, and as a result, a hexagonal polycrystalline LaO

[0118] was formed on the surface (space group P63 / mmc, a = 0.39 nm, b = 0.39 nm, c = 0.61 nm). In addition, the LaO x obtained by observing with a scanning electron microscope (SEM) xThe film thickness is 2.5 μm. Furthermore, the atomic ratio of O to La in the oxide film was investigated using energy dispersive X-ray spectroscopy (EDX) attached to SEM, and the result was O / La = 1.48. From the above, it can be confirmed that hexagonal LaO is formed on the surface of La metal by oxidation treatment. x (x=1.48) polycrystalline thin film (thickness 2.5 μm).

[0119] Next, the oxide film on the surface of La metal was processed into a needle shape using a focused ion beam (FIB). x After platinum (Pt) is deposited on a certain area (15μm×3μm) of the film, the surrounding area and the bottom are cut / cut off to cut out the LaO x Then, the cut LaO x The surface of the thin film is in contact with a tungsten (W) chip, and Pt is evaporated at the contact point, thereby converting LaO x The film is fixed to the tungsten chip.

[0120] Then, use the tungsten chip to pick up the LaO x The thin film was placed on a tungsten support needle. At this time, the support needle was a tungsten (W) needle with a radius of 100 nm processed by FIB into a flat end shape. Then, LaO was fixed on the support needle by evaporating Pt. x The film is cut at the appropriate position. x The thin film sheet (width 2 μm×depth 2 μm×height 2.5 μm) was fixed to a tungsten support pin.

[0121] Next, the FIB system was used to irradiate the LaO with a Ga ion beam under the following conditions. x Film sheet.

[0122] Current: 790pA

[0123] Voltage: 30kV

[0124] Irradiation time: 10 minutes

[0125] Irradiation position: From LaO x Scan from the outside to the inside of the film

[0126] Environment: 10 -5 ~10 -3 Pa

[0127] The LaO formed by the above method was observed using a scanning electron microscope (Helios 650 manufactured by FEI Company Japan Ltd.) and a transmission electron microscope (JEM-3100F manufactured by JEOL Ltd.). x Nano needles. Figure 8 A is LaO x SEM image of nanoneedles. Figure 8 B is a TEM image. Figure 8 As shown in A, a LaO2 thin film is formed on the tungsten support needle, which is tapered toward the tip by Pt. x Nanoneedles. The LaO x The maximum diameter d of the nanoneedle is 600 nm, and the curvature radius r of the front end is 20 nm, which is 3.3% of the maximum diameter d. Figure 8 As shown in B, LaO x The tip of the nanoneedle is composed of a single crystal, and its crystal plane is (102￣).

[0128] Next, LaO was observed by scanning transmission electron microscopy. x The nanoneedles were subjected to elemental analysis by EDS. The results are shown in Table 8 below. Fig. 9 A~C represent LaO x Figure 1. STEM-EDS mapping of nanoneedles. Fig. 9 A to C are represented in grayscale. Fig. 9 B and Fig. 9 The brightly indicated areas in C indicate the presence of lanthanum (La) and oxygen (O). Fig. 9 As shown in A to C, LaO x The nanoneedles are substantially formed of La and O.

[0129] [Table 8]

[0130] element Energy (keV) quality% atom% C 0.277 0.01 0.04 O 0.525 14.20 58.39 Ga 9.241 2.12 2.00 La 4.650 83.18 39.40 Pt 2.048 0.50 0.17

[0131] As shown in Table 8, Pt was detected in the elemental analysis by EDS, but this was due to the presence of tungsten support needles and LaO x Pt used to fix the nanoneedles. In addition, LaO x The atomic ratio of La to O in the nanoneedles is 1.48 (=58.39 / 39.4), which is LaO 1.48 Furthermore, by using Ga as the ion source, from LaO x Ga was detected in the nanoneedles.

[0132] Next, the LaO x Field emission characteristics of nanoneedles. The chamber is maintained at 3×10- 7 Pa high vacuum, thermal flushing, clean LaO x Then, LaO x A negative voltage (750 V) was applied to the tip of the nanoneedle to induce electron emission.x The polarity of the extraction voltage at the tip of the nanoneedle is reversed to cause field emission, and the field emission pattern is observed. It should be noted that the field emission pattern is projected onto the nanoneedle disposed at a distance of 1.5 km from LaO. x The nanoneedles were on a screen (microchannel plate, 1 cm in diameter) at a distance of 5 cm.

[0133] Fig.10 To represent LaO x Diagram of the field emission pattern of the nanoneedles. Fig.10 The brightly displayed area is the area where the electrons collide with the screen, confirming that LaO x The nanoneedles perform field emission and function as emitters. In particular, LaO x The nanoneedles showed a single field emission pattern, which was shown to be advantageous for high brightness.

[0134] Furthermore, for LaO x The tip of the nanoneedle was heat-washed, and the current stability was measured at room temperature under two conditions: (A) current value: 36 nA, applied voltage: 750 V and (B) current value: 100 nA, applied voltage: 800 V. Fig.11 A and B represent LaO x Figure 2 shows the current stability of the nanoneedle. Fig.11 The current value shown in A is 36nA, the applied voltage is 750V, and Fig.11 The current value shown in B is 100nA and the applied voltage is 800V. Therefore, the fluctuation of the emission current (<ΔI 2 > 1 / 2 / I), the results were 2% / 15 minutes and 2% / 10 minutes, respectively, which are significantly low values. This indicates that the LaO x Nanoneedles have excellent properties as emitters.

[0135] From the above results, it was confirmed that according to the present invention, an emitter capable of emitting electrons stably and efficiently for a long period of time can be realized.

[0136] Description of Reference Numerals

[0137] 1 Transmitter

[0138] 10 nano needles

[0139] 10a Front end

[0140] 11 Support needle

[0141] 12 Filament

[0142] 20 Electron Gun

[0143] 21 Electrode

[0144] 22 Lead out power supply

[0145] 23. Extraction electrode

[0146] 24 Acceleration Power

[0147] 25 Accelerating electrode

Claims

1. A transmitter comprising a nanoneedle, The nanoneedles are composed of the general formula REO x The rare earth oxide is formed by RE, where RE is the rare earth element and 1≤x<1.

5.

2. The transmitter according to claim 1, wherein: At least the tip portion of the nanoneedle is composed of a crystalline phase.

3. The transmitter according to claim 2, wherein: The crystal phase is at least one crystal system selected from the group consisting of a cubic system, a monoclinic system, and a hexagonal system.

4. The transmitter according to claim 3, wherein: When the crystal phase is a cubic system, the crystal plane of the tip of the nanoneedle is a (001) plane or a (110) plane. When the crystal phase is a monoclinic system, the crystal plane of the tip of the nanoneedle is a (010) plane. When the crystal phase is a hexagonal system, the crystal plane of the tip portion of the nanoneedle is a (102￣) plane.

5. The transmitter according to any one of claims 1 to 4, wherein: The rare earth oxide contains at least one rare earth element selected from the group consisting of La, Ce, Pr, Nd, and Sm.

6. The transmitter according to any one of claims 1 to 5, wherein: The rare earth oxide contains Ga in an amount of 0.5 atomic % or less.

7. The transmitter according to any one of claims 1 to 6, wherein: The nanoneedle has a maximum diameter of 1 nm to 1 μm, and a length of 500 nm to 30 μm.

8. The transmitter according to claim 7, wherein: The curvature radius of the front end of the nanoneedle is less than 50% of the maximum diameter.

9. The transmitter according to claim 8, wherein: The curvature radius of the front end of the nanoneedle is 5 to 30 nm.

10. The launcher according to any one of claims 1 to 9, further comprising a support needle and a filament, The support needle is formed of at least one element selected from the group consisting of W, Ta, Pt, Re and C, The nanoneedle is mounted on the filament via the supporting needle. 11 . An electron gun comprising the emitter according to claim 1 . 12 . The electron gun according to claim 11 , which is a cold cathode field emission electron gun or a Schottky electron gun. 13 . An electronic device comprising the electron gun according to claim 11 or 12 .

14. A method for manufacturing an emitter, which is a method for manufacturing an emitter having nanoneedles, the method comprising: The surface of the metal containing rare earth elements is oxidized to form a x A process for forming a film composed of a rare earth oxide represented by, wherein RE is a rare earth element, 1≤x<1.5; and The step of processing a film composed of the rare earth oxide into a needle shape using a focused ion beam to obtain the nanoneedle.

15. The method for manufacturing a transmitter according to claim 14, wherein: In the step of forming the film composed of the rare earth oxide, the metal containing the rare earth element is kept at a temperature of 0 to 800° C. and a pressure of 10 1 ~10 5 Pa, and a relative humidity of 10 to 70%, thereby oxidizing the surface of the metal.

16. The method for manufacturing a transmitter according to claim 14 or 15, wherein: In the step of processing the film composed of the rare earth oxide into a needle shape, the film composed of the rare earth oxide is cut out from the surface of the metal, and the film composed of the rare earth oxide is placed on a supporting needle.

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