Emitter, manufacturing method thereof, electron gun using same, and electronic device using same

Abstract

To provide an emitter that emits electrons stably with high efficiency, a manufacturing method thereof, an electron gun using the same, and electronic equipment using the same.SOLUTION: An emitter according to the present invention includes nanoneedles made of a compound represented by the general formula REOx (where RE is a rare earth element and x is 1 or more and less than 1.5). A method for manufacturing an emitter according to the present invention includes oxidizing the surface of a metal containing RE to form a thin film made of a compound represented by the general formula REOx (where x is 1 or more and less than 1.5), and processing the thin film into a needle shape using a focused ion beam.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In order to obtain high-resolution and high-brightness observation images, various improvements have been made to the electron guns used in electron microscopes. Emitters used in such electron guns include field emission types and Schottky types, and these are characterized by sharpening the tip of the emitter used in the electron gun to generate an electric field concentration effect at the tip, thereby emitting more electrons from the tip.

[0003] Metal borides and rare earth oxides are known as low work function materials, and their use as emitters has been reported (see, for example, Patent Document 1). In recent years, emitters using hafnium carbide (HfC) have also been developed (see, for example, Patent Document 2). In this field, there is a continuing demand for the development of emitter materials with high brightness and long life. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-16451 [Patent Document 2] International Publication No. 2021 / 002305 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an emitter that emits electrons stably with high efficiency, a method for manufacturing the same, an electron gun using the same, and electronic equipment using the same. [Means for solving the problem]

[0006] The emitter equipped with nanoneedles of the present invention solves the above-mentioned problems by comprising nanoneedles made of a compound represented by the general formula REOx (where RE is a rare earth element and x is 1 or more and less than 1.5). The x may be in the range of greater than 1 and less than 1.5. The x may be in the range of 1.4 or more and 1.49 or less. The compound may be in a crystalline and / or amorphous phase. The crystalline phase may belong to at least one crystalline system selected from the group consisting of cubic, monoclinic, and hexagonal systems. The crystalline phase may be polycrystalline. The RE may be at least one element selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd) and samarium (Sm). The RE element may be lanthanum (La). The nanoneedle may have a lateral length of 1 nm or more and 1 μm or less, and a longitudinal length of 500 nm or more and 30 μm or less. The electron-emitting end of the nanoneedle may be tapered, and the radius of curvature of the end may be 50% or less of the short length of the nanoneedle. The radius of curvature of the end portion may be in the range of 5 nm to 30 nm. The crystal plane of the electron-emitting end of the nanoneedle may be either the (001) plane or the (110) plane if the compound is in a cubic crystal phase, the (010) plane if the compound is in an injective crystal phase, or the (102) plane if the compound is in a hexagonal crystal phase. The compound may further contain gallium (Ga). The method for manufacturing the emitter according to the present invention includes oxidizing the surface of a metal containing RE (RE is a rare earth element) to form a thin film made of a compound represented by the general formula REOx (where x is 1 or more and less than 1.5), and processing the thin film into a needle shape using a focused ion beam, thereby solving the above-mentioned problem. The formation of the thin film is carried out by heating the RE-containing metal at a temperature in the range of 0°C to 800°C, for 10 1 Pa or more 10 5 This may include maintaining the material in an environment with a vacuum of 0.1 Pa or less and a relative humidity of 10% to 70%. The processing may include cutting the thin film from the surface of the RE-containing metal and placing the cut thin film on a support needle. The electron gun according to the present invention comprises at least the emitter described above, thereby solving the above problems. The emitter may further comprise a support needle and a filament, and the nanoneedle may be attached to the filament via a support needle made of an element selected from the group consisting of tungsten (W), tantalum (Ta), platinum (Pt), rhenium (Re), and carbon (C). The electron gun may be a cold cathode field emission electron gun or a Schottky electron gun. An electronic device according to the present invention includes the above electron gun, thereby solving the above problems. The electronic equipment may be selected from the group consisting of 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. [Effects of the Invention]

[0007] The emitter of the present invention includes nanoneedles made of a compound represented by the general formula REOx (where RE is a rare earth element and x is 1 or more but less than 1.5). Compounds represented by REOx have a low work function and excellent electron emission capability. Use of such an emitter can provide an electron gun that is stable over the long term and an electronic device that uses the same.

[0008] The method for producing an emitter of the present invention includes oxidizing the surface of a metal containing RE (RE is a rare earth element) to form a thin film of a compound represented by the general formula REOx (where x is 1 or more and less than 1.5), and processing the thin film into a needle shape using a focused ion beam. By using a focused ion beam, the compound represented by REOx can be easily processed into nanoneedles to provide an emitter. [Brief explanation of the drawings]

[0009] [Figure 1] Schematic diagram showing an emitter of the present invention. [Figure 2] Flowchart showing the steps for manufacturing the emitter of the present invention [Figure 3] Schematic diagram showing an electron gun of the present invention. [Figure 4] Electron density of states (DOS) of REOx (RE=La, x=1) [Figure 5] Diagram of the density of electronic states (DOS) of REOx (RE=La, x=1.4165 or 1.4375) in various crystal systems [Figure 6] Figure showing the results of molecular dynamics simulation [Figure 7] SEM (A) and TEM (B) images of LaOx nanoneedles. [Figure 8] Figure showing STEM-EDS mapping of LaOx nanoneedles [Figure 9] Figure showing the field emission pattern of LaOx nanoneedles [Figure 10] Current stability of LaOx nanoneedles DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that like elements are given like reference numerals and their description will be omitted.

[0011] (Embodiment 1) Embodiment 1 describes the emitter of the present invention and its manufacturing method.

[0012] FIG. 1 is a schematic diagram showing the emitter of the present invention.

[0013] The emitter 100 of the present invention includes a nanoneedle 110. The nanoneedle 110 is made of a compound represented by the general formula REOx (where RE is a rare earth element and x is a value greater than or equal to 1 and less than 1.5).

[0014] The inventors of the present application have intensively studied the oxides of RE, and have found that a compound having the general formula REOx (where x is a value greater than or equal to 1 and less than 1.5) has a low work function and excellent electron emission ability. Hereinafter, for simplicity, the compound represented by REOx will be simply referred to as an REOx compound.

[0015] In the REOx compound, when x = 1, it becomes REO, which is an oxide in which RE is divalent. On the other hand, when x = 1.5, it becomes RE2O3, which is an oxide in which RE is trivalent. The inventors of the present application have discovered that by using an oxide in which RE is divalent (x = 1) and an oxide in which oxygen is deficient in RE2O3 (1 < x < 1.5), the electrical conductivity is improved and the work function is lowered.

[0016] In the REOx compound, x is preferably greater than 1 and less than 1.5. Thereby, the REOx compound becomes chemically stable. x is more preferably 1.2 or more and less than 1.5. Thereby, the REOx compound has a lower work function and excellent electron emission ability. x is still preferably in the range of 1.4 or more and 1.49 or less. Thereby, the REOx compound is particularly chemically stable, has a lower work function, and has excellent electron emission ability.

[0017] The REOx compound may be in a crystalline phase and / or an amorphous phase. For example, the entire REOx compound may be in a crystalline phase or may be entirely in an amorphous phase, but the end portion 120 that emits electrons is preferably in a crystalline phase. Thereby, electrons can be stably emitted, and an excellent emitter can be provided. In such a case, the interior of the nanoneedle 110 composed of REOx may be in an amorphous phase, and the surface may be in a crystalline phase.

[0018] The crystalline phase may be a single crystal or a polycrystal. From the viewpoint of ease of manufacture, polycrystals are preferred.

[0019] The RE element is not particularly limited as long as it is a rare earth element, but is preferably an element selected from at least one of the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), and samarium (Sm). With these elements, a work function of 2.7 eV or less can be achieved. Among them, the RE element is more preferably La. In this case, by adjusting the composition, a work function of 1.8 eV to 2.3 eV is obtained, and the electron emission ability is excellent.

[0020] When the REOx compound is in a crystalline phase, it belongs to a crystal system selected from at least one of the group consisting of a cubic crystal system, a monoclinic crystal system, and a hexagonal crystal system. For the crystal system, for the sake of clarity, the case where RE is La will be described.

[0021] [LaOx, x = 1] As shown in Table 1, LaO has a cubic crystal structure and is a crystal belonging to the Fm3￣m space group (in this specification, "3￣" is the overbar display of 3 and is the 225th space group in the International Tables for Crystallography). The lattice constant a (nm) preferably satisfies 0.45 < a < 0.55. Thereby, the crystal structure becomes stable.

[0022] [LaOx, 1 < x < 1.5] LaOx has a crystal structure of either cubic, hexagonal, or monoclinic system. When LaOx has a cubic crystal structure, as shown in Table 2 and Table 3 respectively, it is a crystal belonging to Ia3￣ (in this specification, "￣" means overbar of 3, and it is the space group No. 206 in International Tables for Crystallography), or Im3￣m (in this specification, "￣" means overbar of 3, and it is the space group No. 229 in International Tables for Crystallography).

[0023] In the case of the space group of Ia3￣, the lattice constant a (nm) preferably satisfies 1.10 < a < 1.20. In the case of the space group of Im3￣m, the lattice constant a (nm) preferably satisfies 0.43 < a < 0.47. Thereby, the crystal structure becomes stable.

[0024] As shown in Table 4, LaOx may have a hexagonal crystal structure and be a crystal belonging to the P3￣m1 space group (space group No. 164 in International Tables for Crystallography). In this case, the lattice constants a and c (nm) preferably satisfy 0.37 < a < 0.4 and 0.58 < c < 0.64 respectively. When LaOx has a hexagonal crystal structure, it is preferable because a smaller work function can be achieved.

[0025] As shown in Table 5, LaOx may have a monoclinic crystal structure and be a crystal belonging to the C2 / m space group (space group No. 12 in International Tables for Crystallography). In this case, the lattice constants a, b, and c (nm) preferably satisfy 1.40 < a < 1.50, 0.30 < b < 0.40, and 0.85 < c < 0.95 respectively. Thereby, the crystal structure becomes stable.

[0026]

Table 1

[0027] [Table 2]

[0028] [Table 3]

[0029] [Table 4]

[0030] [Table 5]

[0031] In the case of REOx compounds, the lattice constant changes when RE is a rare earth element other than La or when some of the constituent elements are replaced with other elements, but the crystal structure, the sites occupied by the atoms, and the atomic positions given by their coordinates do not change so much that the chemical bonds between the skeletal atoms are broken. For the obtained REOx compounds, if the RE-O chemical bond length (nearest atom distance) calculated from the lattice constant obtained by Rietveld analysis of the results of X-ray diffraction and neutron diffraction using the space group described above is within ±5% of the chemical bond length calculated from the lattice constant and atomic coordinates of the crystals shown in Tables 1 to 5, it can be determined that the crystal structure is the same.

[0032] When the REOx compound is a crystalline phase, the above-mentioned crystalline phases may be combined. In this case, the diffraction peak positions (2θ) calculated using the crystal structure parameters in Tables 1 to 5 can be compared with the X-ray diffraction results of the obtained REOx compound, and the main phase and secondary phase can be identified based on the coincidence or deviation of the main peaks.

[0033] The REOx compound may further contain gallium (Ga). This allows electrons to be emitted stably for a long period of time. The Ga content may be greater than 0 atomic % and less than or equal to 5 atomic %. Within this range, the REOx crystal structure can be maintained.

[0034] The nanoneedle 110 made of the above-mentioned REOx compound preferably has a short-side length d (i.e., diameter) in the range of 1 nm to 1 μm, and a long-side length L in the range of 500 nm to 30 μm. Such sizes allow an electric field to be efficiently concentrated at the end 120 of the nanoneedle 110 from which electrons are to be emitted, allowing more electrons to be emitted from the end 120.

[0035] More preferably, the short-side length d of the nanoneedle 110 is in the range of 400 nm to 800 nm, and the long-side length L is in the range of 1 μm to 3 μm. Within these ranges, processing is easy, and emitters can be provided with a good yield.

[0036] The end 120 from which electrons are to be emitted has a tapered shape, and the radius of curvature r of the tip of the end 120 may be 50% or less of the length d in the short direction of the nanoneedle 110. This allows the emitter 100 of the present invention to efficiently emit electrons.

[0037] More preferably, the radius of curvature r of the tip of the end 120 from which electrons are to be emitted is in the range of 1% to 10% of the short-side length d of the nanoneedle 110. Furthermore, the radius of curvature r of the tip of the end 120 from which electrons are to be emitted is even more preferably in the range of 1% to 5% of the short-side length d of the nanoneedle 110. When the radius of curvature r of the tip of the end 120 and the short-side length d of the nanoneedle 110 satisfy the above conditions, an emitter having better effects of the present invention can be obtained.

[0038] The processing or treatment for tapering the end 120 can be performed by, for example, an ion beam, field evaporation, or the like. Focused ion beams are preferably used because they allow Ga to be added to the REOx compound. The radius of curvature r of the tip of the end 120 from which electrons of the emitter 100 are to be emitted is calculated from an SEM image of the end 120. The tapered shape of the end 120 can be confirmed from the SEM image of the end 120.

[0039] The value of the radius of curvature r of the tip of the end portion 120 from which electrons are to be emitted is not particularly limited, but in consideration of electric field concentration, it is preferably in the range of 0.5 nm or more and 75 nm or less, more preferably in the range of 5 nm or more and 50 nm or less, still more preferably in the range of 10 nm or more and 30 nm or less, and even still more preferably in the range of 15 nm or more and 25 nm or less.

[0040] Also, the value of the radius of curvature r of the tip of the end portion 120 from which electrons are to be emitted can be appropriately adjusted according to the use of the emitter and the like. Specifically, for example, when the emitter of the present invention is used in an electron gun, from a practical point of view, the radius of curvature r of the tip of the end portion 120 from which electrons are to be emitted may be in the range of 5 nm or more and 50 nm or less, or may be in the range of 10 nm or more and 30 nm or less, or in the range of 15 nm or more and 25 nm or less.

[0041] When the REOx compound is in a crystalline phase, the crystal plane of the end portion 120 from which electrons are to be emitted may be selected. For example, when the REOx compound is in a cubic crystal phase, it may be either the (001) plane or the (110) plane. Specifically, if it is REOx (x = 1), it is the (001) plane, if it is REOx (1 < x < 1.5, space group Ia3￣), it is the (110) plane, and if it is REOx (1 < x < 1.5, space group Im3￣m), it may be the (001) plane. For example, when the REOx compound is in a hexagonal crystal phase, it may be the (102￣) plane (the "2￣" is an overbar display of 0 in this specification). For example, when the REOx compound is in an orthorhombic crystal phase, it may be the (010) plane. These crystal planes are chemically stable and can efficiently emit electrons. The above is an example and is not limited thereto. In principle, all surfaces represented by numerical values with a Miller index of 3 or less can be adopted. Here, the Miller index of 3 or less means that the absolute value of each value is 3 or less.

[0042] Next, an exemplary manufacturing method of the emitter of the present invention will be described. FIG. 2 is a flowchart showing the steps of manufacturing the emitter of the present invention.

[0043] Step S210: Oxidize the surface of a metal containing RE (RE is a rare earth element) to form a thin film composed of a compound represented by the general formula REOx (where x is 1 or more and less than 1.5). Step S220: Use a focused ion beam to process the thin film obtained in Step S210 into a needle shape.

[0044] In Step S210, the thin film composed of the REOx compound preferably has a thickness of 2 μm or more in consideration of the processability in the subsequent Step S220.

[0045] In Step S210, the metal containing RE may be a metal composed of a single RE or an alloy containing two or more REs. It is preferable to grind the metal surface. Thereby, a uniform thin film can be formed.

[0046] In Step S210, the surface oxidation treatment varies depending on the selected RE element. Exemplarily, it may be maintained in an environment with a temperature range of 0°C or more and 800°C or less, a vacuum degree of 10 1 Pa or more and 10 5 Pa or less, and a relative humidity of 10% or more and 70% or less. The holding time varies depending on the thickness of the thin film. To obtain a thin film having a thickness of 2 μm or more, it may be held for 1 hour or more and 30 days or less. For example, when forming polycrystalline LaOx (1 < x < 1.5) with a thickness of 2 μm to 3 μm, it may be held for 1 week or more and 3 weeks or less in an environment with a room temperature (temperature range of 10°C or more and 30°C or less), a vacuum degree of 50 Pa or more and 150 Pa or less, and a relative humidity of 30% or more and 55% or less.

[0047] In step S220, prior to the irradiation with the focused ion beam, the thin film obtained in step S210 may be cut from the surface of the metal containing RE and placed on a support needle. This provides excellent processability. The support needle may also function as the support needle 330 shown in FIG. 3, which will be described later.

[0048] In step S220, the irradiation conditions of the focused ion beam are not particularly limited, but for example, the following conditions can be adopted using gallium (Ga) ions. Current: 5 to 1000 pA (preferably, 500 pA to 900 pA) Voltage: 1 to 100 kV (preferably, 20 kV to 40 kV) Irradiation time: 1 to 60 minutes (preferably, 5 to 15 minutes) In particular, when the end 120 from which electrons are to be emitted is tapered, it is advisable to irradiate the thin film so as to scan from the outside to the inside within the above range.

[0049] (Embodiment 2) In the second embodiment, an electron gun equipped with the emitter of the present invention will be described. FIG. 3 is a schematic diagram showing an electron gun of the present invention.

[0050] The electron gun 400 of the present invention includes an emitter 410 having at least the nanoneedle 110 described in Embodiment 1. In FIG. 3, the emitter 410 further includes a filament 320 and a support needle 330 in addition to the nanoneedle 110.

[0051] The nanoneedle 110 is attached to the filament 320 via a support needle 330 made of an element selected from the group consisting of tungsten (W), tantalum (Ta), platinum (Pt), rhenium (Re), and carbon (C). This is preferable because it simplifies handling of the nanoneedle 110. Note that, although the filament 320 in FIG. 4 has a hairpin shape (a U-shape), the shape of the filament 320 is not limited to this, and any shape such as a V-shape may be used.

[0052] In the electron gun 400, an extraction power supply 450 is connected between the electrode 440 and the extraction electrode 460, and the extraction power supply 450 applies a voltage between the emitter 410 and the extraction electrode 460. Furthermore, in the electron gun 400, an acceleration power supply 470 is connected between the electrode 440 and the acceleration electrode 480, and the acceleration power supply 470 applies a voltage between the emitter 410 and the acceleration electrode 480.

[0053] The electrode 440 may further be connected to a flash power supply if the electron gun 400 is a cold field emission electron gun, or to a heating power supply if the electron gun 400 is a Schottky electron gun.

[0054] The electron gun 400 is 10 -8 Pa~10 -7 Pa(10 -8 Pa or more 10 -7 In this case, the end of the emitter 410 from which electrons are to be emitted can be kept clean.

[0055] The operation of the electron gun 400 of the present invention when it is a cold cathode field emission electron gun will be briefly described.

[0056] An extraction power supply 450 applies a voltage between the emitter 410 and the extraction electrode 460. This generates an electric field concentration at the end of the nanoneedle 110 of the emitter 410 from which electrons are to be emitted, thereby extracting electrons. Furthermore, an acceleration power supply 470 applies a voltage between the emitter 410 and the acceleration electrode 480. This accelerates the electrons extracted at the end of the nanoneedle 110 of the emitter 410 from which electrons are to be emitted, and then the electrons are emitted toward the sample. Note that a flash power supply connected to the electrode 440 may be used to perform flashing as needed to clean the surface of the nanoneedle 110. These operations are performed in the vacuum described above.

[0057] The operation of the electron gun 400 of the present invention when it is a Schottky electron gun will be briefly described.

[0058] A heating power supply connected to the electrode 440 heats the emitter 410, and an extraction power supply 450 applies a voltage between the emitter 410 and the extraction electrode 460. This causes Schottky emission at the end of the nanoneedle 110 of the emitter 410 from which electrons are to be emitted, thereby extracting electrons. Furthermore, an acceleration power supply 470 applies a voltage between the emitter 410 and the acceleration electrode 480. This causes the electrons extracted at the end of the nanoneedle 110 of the emitter 410 from which electrons are to be emitted to be accelerated and emitted toward the sample. These operations are performed in the vacuum described above. Note that, because the heating power supply can cause thermions to be emitted from the nanoneedle 110 of the emitter 410, the electron gun 400 may further include a suppressor (not shown) for blocking thermions.

[0059] The electron gun 400 of the present invention includes an emitter 410 having the nanoneedle 110 described in detail in the first embodiment, and therefore can easily emit electrons and can emit electrons stably for a long period of time. Such an electron gun 400 can be used in any electronic device having electron focusing capabilities. For example, such an electronic device can be selected from the group consisting of 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.

[0060] The present invention will now be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples. [Example]

[0061] [Example 1] In Example 1, the electronic states and work functions of REOx (RE = La, Ce, Pr, Nd, Sm, x = 1) were calculated from first-principles calculations. Specifically, the calculations were based on density functional theory, using an ultrasoft pseudopotential with plane waves as the basis function. The density gradient approximation was incorporated, and the cutoff energy of the plane waves was set to 80 Ry. The work function was calculated from the difference between the vacuum level and the Fermi level. These calculations were performed using Quantum Espresso v7.0 (downloaded from https: / / www.quantum-espresso.org). The results are shown in Figure 4 and Table 6.

[0062] FIG. 4 is a diagram of the electron density of states (DOS) of REOx (RE=La, x=1).

[0063] According to Figure 4, the electronic state of LaO is metallic, and the work function of its (001) plane was calculated to be 2.3 eV from the difference between the calculated Fermi level and the vacuum level. Although not shown, the electronic densities of state of other materials, CeO, PrO, NdO, and SmO, are also metallic, similar to that of LaO. Their work functions were calculated to be 2.7 eV or less.

[0064] [Table 6]

[0065] According to Table 6, when RE is La or Ce, a low work function comparable to that of LaB6 (2.3 eV) is obtained, suggesting that REOx (RE is a rare earth element, x = 1) is a material that can function as an emitter.

[0066] [Example 2] In Example 2, the electronic state and work function of REOx (RE=La, x=1.4165 to 1.4375) were calculated from first principles calculations in the same manner as in Example 1. The results are shown in FIG.

[0067] FIG. 5 is a diagram of the electronic density of states (DOS) of REOx (RE=La, x=1.4165 or 1.4375) in various crystal systems.

[0068] According to FIG. 5, regardless of the crystal system, in all cases, due to the formation of oxygen defect levels near the bottom of the conductor, the electronic state of LaOx was metallic.

[0069] [Table 7]

[0070] Table 7 also shows the values of the work functions of LaO calculated in Table 6, as well as LaOx (1 < x < 1.5) and LaB6. As shown in Table 7, when LaOx is greater than 1 and less than 1.5, that is, in the case of oxygen deficiency in La2O3, it becomes 1.8 eV to 2.1 eV, which is lower than that of LaB6. From this, it is suggested that REOx (RE is a rare earth element, 1 ≤ x < 1.5) is a material that functions as an emitter, and in particular, REOx satisfying 1 < x < 1.5 with oxygen deficiency is preferable.

[0071] [Example 3] In Example 3, the chemical stability of REOx (RE = La, x = 1, 1.4375) and LaB6 was estimated by first-principles molecular dynamics simulation. Specifically, in addition to Example 1, the Car-Parrinello method was adopted for the molecular dynamics part. The simulation was carried out at a temperature of 500 K with water molecules placed at a distance of 4 Å from the surface. For these calculations, Quantum Espresso v7.0 (downloaded from https: / / www.quantum-espresso.org) was used. The results are shown in FIG. 6.

[0072] FIG. 6 is a diagram showing the results of the molecular dynamics simulation.

[0073] In FIG. 6, the left side shows the crystal of LaB6 and the state of water molecules on its (001) plane, and the right side shows the crystal of LaO and the state of water molecules on its (001) plane. According to FIG. 6, water molecules (H2O) were dissociatively adsorbed as H and OH on the (001) plane of LaB6, but did not dissociate on the (001) plane of LaO. Although not shown, on the (110) plane of hexagonal LaOx (x = 1.14375), similar to LaO, water molecules did not dissociate. From this, it can be seen that REOx (1 ≤ x < 1.5) is chemically more stable than LaB6 and is suggested to be effective for an emitter.

[0074] [Example 4] In Example 4, an emitter using LaOx (1 < x < 1.5) was fabricated.

[0075] 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 a compound represented by LaOx (1 < x < 1.5) (step S210 in FIG. 2). Specifically, the surface of the La metal was ground and polished, and then held for 2 weeks in an environment of room temperature (20°C), relative humidity 45%, and vacuum degree 100 Pa.

[0076] When X-ray diffraction was performed, it was confirmed that hexagonal polycrystalline LaOx (space group P63 / mmc, a = 0.39 nm, b = 0.39 nm, c = 0.61 nm) was formed on the surface. Also, from scanning electron microscope (SEM) observation, the film thickness of LaOx was 2.5 μm. Furthermore, when the atomic ratio of O and La was examined by energy dispersive X-ray spectroscopy (EDX) attached to the SEM, O / La was calculated to be 1.48. From the above, a polycrystalline thin film (thickness 2.5 μm) of hexagonal LaOx (x = 1.48) was obtained on the La metal by the oxidation treatment.

[0077] Next, the thin film was processed into a needle shape using a focused ion beam (FIB) (step S220 in Figure 2). Specifically, platinum (Pt) was deposited over a certain area (15 μm × 3 μm) of the LaOx thin film on the La metal, and then the periphery and bottom were cut and cut to obtain a LaOx thin film piece. A tungsten (W) tip was contacted with the surface of the cut LaOx thin film piece, and Pt was deposited at the contact point to fix the LaOx thin film piece to the tungsten tip. This LaOx thin film piece was picked up using the tungsten tip and placed on a tungsten support needle. Pt was then deposited, and the LaOx single crystal piece was fixed on the support needle and cut at the appropriate position. A tungsten W (310) needle with a radius of 100 nm was processed using FIB to have a flat shape at the end, which served as the support needle. In this way, a piece of LaOx thin film (2 μm wide × 2 μm deep × 2.5 μm high) was fixed to the tungsten support needle.

[0078] Next, a Ga ion beam was accelerated using the FIB system and scanned across the LaOx thin film under the following ion beam irradiation conditions: Current: 790pA Voltage: 30kV Irradiation time: 10 minutes Irradiation position: Scanning from the outside to the inside of the LaOx thin film Environment: 10 -5 Pa~10 -3 Pa

[0079] The LaOx nanoneedles thus obtained were observed using a scanning electron microscope (Helios 650, manufactured by Japan FI Co., Ltd.) and a transmission electron microscope (JEOL Ltd., JEM-3100F). The observation results are shown in Figure 7.

[0080] FIG. 7 shows an SEM image (A) and a TEM image (B) of LaOx nanoneedles.

[0081] Figure 7(A) shows that a tapered LaOx nanoneedle is positioned on a tungsten support needle via Pt. The width of the LaOx nanoneedle in the short direction (width d in Figure 1) was 600 nm. The radius of curvature of the tip of this end was 20 nm, which was 3.3% of the short length of the LaOx nanoneedle.

[0082] According to Figure 7(B), the tip of LaOx is a single crystal, and its crystal plane is (102).

[0083] The nanoneedles were observed by scanning transmission electron microscopy and subjected to elemental analysis by EDS, the results of which are shown in Figure 8 and Table 8.

[0084] FIG. 8 shows STEM-EDS mapping of LaOx nanoneedles.

[0085] The bright areas in Figures 8(B) and 8(C), which are shown in grayscale in Figure 8, indicate the presence of lanthanum (La) and oxygen (O), respectively. Figure 8 shows that the LaOx nanoneedles are essentially composed of La and O.

[0086] [Table 8]

[0087] In Table 8, Pt was detected, but this is due to the Pt used to fix the tungsten support needle and the LaOx nanoneedle. Here, too, the atomic ratio of La to O in the LaOx nanoneedle was 1.48 (=58.39 / 39.4), and LaO 1.48 Furthermore, Ga was detected in the LaOx nanoneedles by using Ga as the ion source.

[0088] Next, the field emission characteristics of the LaOx nanoneedles were investigated using a field emission microscope (FEM). -7The specimen was maintained at a high vacuum of 0.05 Pa and thermal flashing was performed to clean the tip of the LaOx nanoneedle (the end from which electrons were to be emitted). Next, a negative voltage (750 V) was applied to the tip of the LaOx nanoneedle to induce electron emission. The polarity of the extraction voltage at the tip of the LaOx nanoneedle was then reversed to perform field emission, and the field emission pattern was observed. The field emission pattern was projected onto a screen (microchannel plate, 1 cm diameter) placed 5 cm away from the LaOx nanoneedle. The results are shown in Figure 9.

[0089] FIG. 9 shows the field emission pattern of the LaOx nanoneedles.

[0090] The grayscale images in Figure 9 show the bright areas where electrons collided with the screen, revealing that the LaOx nanoneedles emitted electrons from the screen and functioned as emitters. In particular, the LaOx nanoneedles exhibited a single field emission pattern, which is advantageous for increasing brightness.

[0091] Furthermore, the tip of the LaOx nanoneedle was subjected to thermal flashing, and the current stability was measured at room temperature, a current value of 36 nA, an applied voltage of 750 V, and a current value of 100 nA, an applied voltage of 800 V. The results are shown in Figure 10.

[0092] FIG. 10 shows the current stability of LaOx nanoneedles.

[0093] As shown in Figure 10, the current was stable under both conditions: current value: 36 nA, applied voltage: 750 V, and current value: 100 nA, applied voltage: 800 V. The fluctuation of the emission current (<ΔI 2 > 1 / 2 / I) were evaluated and found to be 2% / 15 min and 2% / 10 min, respectively, which were significantly lower values. This indicates that the LaOx nanoneedles of the present invention have excellent properties as emitters. [Industrial Applicability]

[0094] The emitter of the present invention can emit electrons efficiently and stably, and can therefore be used in any instrument with electron focusing capabilities, such as a scanning electron microscope, a transmission electron microscope, a scanning transmission electron microscope, an Auger electron spectrometer, an electron energy loss spectrometer, or an energy dispersive electron spectrometer. [Explanation of symbols]

[0095] 100, 410 emitters 110 Nanoneedle 120 End to emit electrons 310 Support needle 320 filament 400 electron gun 440 electrode 450 Output power supply 460 Extraction electrode 470 Acceleration power supply 480 Accelerating electrode

Claims

1. An emitter comprising a nanoneedle, The nanoneedle is an emitter made of a compound represented by the general formula REOx (where RE is at least one element selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd), and x is 1 or more and less than 1.5).

2. The emitter of claim 1 , wherein x satisfies the range greater than 1 and less than 1.

5.

3. The emitter of claim 2 , wherein x satisfies the range of 1.4 to 1.

49.

4. The emitter of claim 1 , wherein the compound is in a crystalline and / or amorphous phase.

5. 5. The emitter of claim 4, wherein the crystalline phase belongs to at least one crystalline system selected from the group consisting of cubic, monoclinic, and hexagonal.

6. The emitter of claim 4 , wherein the crystalline phase is polycrystalline.

7. The emitter of claim 1 , wherein the RE is lanthanum (La).

8. The emitter of claim 1 , wherein the nanoneedle has a lateral length of 1 nm to 1 μm, and a longitudinal length of 500 nm to 30 μm.

9. the electron-emitting end of the nanoneedle is tapered; The emitter of claim 8 , wherein the radius of curvature of the end is less than or equal to 50% of the short length of the nanoneedle.

10. The emitter according to claim 9 , wherein the radius of curvature of the end portion satisfies the range of 5 nm to 30 nm.

11. The crystal plane of the electron-emitting end of the nanoneedle is When the compound has a cubic crystalline phase, the crystal plane is either a (001) plane or a (110) plane; When the compound is in a monomorphic crystalline phase, the (010) plane is 6. The emitter of claim 5, wherein the compound has a (102) plane when it is in a hexagonal crystalline phase.

12. The emitter of claim 1 , wherein the compound further comprises gallium (Ga).

13. A method for manufacturing an emitter according to any one of claims 1 to 12, comprising the steps of: oxidizing the surface of a metal containing RE (RE is at least one element selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr) and neodymium (Nd)) to form a thin film made of a compound represented by the general formula REOx (where x is 1 or more and less than 1.5); processing the thin film into a needle shape using a focused ion beam; The method includes:

14. The formation of the thin film is carried out by heating the RE-containing metal at a temperature in the range of 0° C. to 800° C. １ Pa or more 10 ５ The method according to claim 13, further comprising maintaining the substrate in an environment with a vacuum of 0.1 Pa or less and a relative humidity of 10% to 70%.

15. The method of claim 13, wherein the processing comprises cutting the thin film from the surface of the RE-containing metal and placing the cut thin film on a support needle.

16. An electron gun comprising at least an emitter, An electron gun, wherein the emitter is an emitter according to any one of claims 1 to 12.

17. the emitter further comprising a support needle and a filament; 17. The electron gun of claim 16, wherein the nanoneedles are attached to the filament via support needles made of an element selected from the group consisting of tungsten (W), tantalum (Ta), platinum (Pt), rhenium (Re), and carbon (C).

18. 17. The electron gun of claim 16, wherein the electron gun is a cold cathode field emission electron gun or a Schottky electron gun.

19. An electronic device having an electron gun, The electron gun is an electron gun according to claim 16, The electronic device is selected from the group consisting of 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.

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