Emitter, manufacturing method thereof, electron gun using the same, and electronic equipment using the 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 manufacturing method thereof, an electron gun using the emitter, and an electronic device using the emitter. [Background technology]

[0002] In order to obtain high-resolution and high-brightness observation images, various improvements have been made to the electron guns in electron microscopes. Emitters using such electron guns include field emission type, Schottky type, etc., 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, allowing more electrons to be emitted from the tip.

[0003] Metal borides and rare earth oxides are known as low work function materials, and it has been reported that they are used as emitters (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] JP 2008-16451 A [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 stably emits electrons with high efficiency, a manufacturing method thereof, an electron gun using the same, and electronic equipment using the same. [Means for solving the problem]

[0006] The emitter equipped with a nanoneedle of the present invention solves the above-mentioned problems by comprising the nanoneedle made of a compound represented by the general formula REOx (wherein 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. 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 length of the nanoneedle in the short direction may be 1 nm or more and 1 μm or less, and the length of the nanoneedle in the long direction may be 500 nm or more and 30 μm or less. The electron-emitting end of the nanoneedle may be tapered, the radius of curvature of the end being 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 a (001) or a (110) plane if the compound is in a cubic crystal phase, a (010) plane if the compound is in an injective crystal phase, or a (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 (wherein 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 performed 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 The method may include maintaining the material in an environment with a degree of vacuum of 0.1 Pa or less and a relative humidity of 10% to 70%. The processing may include cutting the thin film from a 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 above emitter, thereby achieving the above object. The emitter may further comprise a support needle and a filament, the nanoneedle being attached to the filament via a support needle comprised 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 field emission gun or a Schottky gun. An electronic device according to the present invention includes the above-mentioned electron gun, thereby solving the above-mentioned problems. The electronic instrument 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. Effect of the Invention

[0007] The emitter of the present invention includes a nanoneedle 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). Compounds represented by REOx have a low work function and excellent electron emission ability. By using such an emitter, it is possible to provide an electron gun that is stable over the long term and an electronic device using 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 made of a compound represented by the general formula REOx (wherein 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 a nanoneedle to provide an emitter. [Brief description of the drawings]

[0009] [Figure 1] Schematic diagram showing an emitter of the present invention. [Diagram 2] Flowchart showing the steps for manufacturing the emitter of the present invention [Diagram 3] Schematic diagram showing an electron gun of the present invention. [Figure 4] Electron density of states (DOS) diagram of REOx (RE=La, x=1) [Diagram 5] Diagram of the density of electronic states (DOS) of various crystal systems of REOx (RE=La, x=1.4165 or 1.4375). [Figure 6] Figure showing the results of molecular dynamics simulation [Figure 7] SEM (A) and TEM (B) images of LaOx nanoneedles. [Figure 8] Figure 1 shows 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 PREFERRED EMBODIMENTS

[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 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 the 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 becomes 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 the cubic system, the monoclinic system, and the hexagonal 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 (the space group No. 164 in International Tables for Crystallography). In this case, the lattice constants a and c (nm) respectively preferably satisfy 0.37 < a < 0.41 and 0.58 < c < 0.64. 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 (the space group No. 12 in International Tables for Crystallography). In this case, the lattice constants a, b, and c (nm) respectively preferably satisfy 1.40 < a < 1.50, 0.30 < b < 0.40, and 0.85 < c < 0.95. 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. If the length of the RE-O chemical bond (the distance between adjacent atoms) calculated from the lattice constant obtained by Rietveld analysis of the results of X-ray diffraction or neutron diffraction in the above-mentioned space group for the obtained REOx compound is within ±5% of the length of the chemical bond 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 are compared with the X-ray diffraction results of the obtained REOx compound, and the main phase and secondary phase can be identified from the agreement or deviation of the main peaks.

[0033] The REOx compound may further contain gallium (Ga). This allows the compound to stably emit electrons 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 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 efficient generation of electric field concentration at the end 120 of the nanoneedle 110 from which electrons should be emitted, and allows 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 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 short-side length d 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 should be emitted is in the range of 1% to 10% of the short-side length d of the nanoneedle 110. Furthermore, it is even more preferable that the radius of curvature r of the tip of the end 120 from which electrons should be emitted is 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 forming the end 120 into a tapered shape can be performed, for example, by ion beam, field evaporation, or the like. Using a focused ion beam is preferable because Ga can be added to the REOx compound. The radius of curvature r of the tip of the end 120 from which the electrons of the emitter 100 are to be emitted is calculated from an SEM image of the end 120. It can be confirmed from the SEM image of the end 120 that the end 120 has a tapered shape.

[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 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 process 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: Using a focused ion beam, 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 of the focused ion beam, the thin film obtained in step S210 may be cut out 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 placed thereon in a scanning manner 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 the first embodiment. 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 the handling of the nanoneedle 110. Note that, in FIG. 4, the filament 320 has a hairpin shape (U-shaped), but is not limited to this, and the shape of the filament 320 may be any shape, such as V-shaped.

[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 gun, or to a heating power supply if the electron gun 400 is a Schottky gun.

[0054] The electron gun 400 is 10 -8 Pa~10 -7 Pa(10 -8 Pa or more 10 -7 The emitter 410 may be placed under a vacuum of 100 Pa or less, in which 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] The 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 emitter 410 from which the nanoneedle 110 is to emit electrons, and the electrons are extracted. Furthermore, the 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 emitter 410 from which the nanoneedle 110 is to emit electrons, and they are emitted toward the sample. Note that a flash power supply connected to the electrode 440 may be used to perform flashing as appropriate to clean the surface of the nanoneedle 110. These operations are performed under the above-mentioned vacuum.

[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 should be emitted, and electrons are extracted. 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 should be emitted, and the electrons are emitted toward the sample. These operations are performed in the vacuum described above. Note that, since the heating power supply can cause thermoelectrons to be emitted from the nanoneedle 110 of the emitter 410, the electron gun 400 may further include a suppressor (not shown) for shielding the thermoelectrons.

[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 stably emit electrons for a long period of time. Such an electron gun 400 can be used in any electronic device having an electron focusing capability. For example, such an 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.

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

[0061] [Example 1] In Example 1, the electronic state and work function 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, and an ultrasoft pseudopotential was used with plane waves as basis functions. The density gradient approximation was adopted, and the cutoff energy of the plane waves was set to 80Ry. The work function was calculated from the difference between the vacuum level and the Fermi level. Quantum Espresso v7.0 (downloaded from https: / / www.quantum-espresso.org) was used for these calculations. The results are shown in Figure 4 and Table 6.

[0062] FIG. 4 shows the density of electronic 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) surface was calculated to be 2.3 eV from the difference between the calculated Fermi level and the vacuum level. Although not shown, the electronic state density of other materials CeO, PrO, NdO, and SmO is 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, in particular, when RE was La or Ce, a low work function comparable to that of LaB6 (2.3 eV) was obtained, suggesting that REOx (RE is a rare earth element, x = 1) is a material that functions 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 generation 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 stabilities of REOx (RE = La, x = 1, 1.4375) and LaB6 were estimated by first-principles molecular dynamics simulations. 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 into H and OH on the (001) plane of LaB6, but did not dissociate on the (001) plane of LaO. Although not shown, water molecules also did not dissociate on the (110) plane of hexagonal LaOx (x = 1.14375), similar to LaO. From this, it can be seen that REOx (1 ≤ x < 1.5) is chemically more stable than LaB6, suggesting that it is effective for an emitter.

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

[0075] The surface of a metal made of La (manufactured by High Purity Chemical Laboratory 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 at 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 FIG. 2). In detail, platinum (Pt) was evaporated on 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 cut out a LaOx thin film piece. A tungsten (W) tip was brought into contact with the surface of the cut LaOx thin film piece, and Pt was evaporated at the contact point to fix the LaOx thin film piece and the tungsten tip. This LaOx thin film piece was picked up using a tungsten tip and placed on a tungsten support needle. Then, Pt was evaporated, and the LaOx single crystal piece was fixed on the support needle and cut at an appropriate position. A tungsten W (310) needle with a radius of 100 nm was processed by FIB to have a flat shape at the end, and used as the support needle. In this manner, 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, the Ga ion beam was accelerated using the FIB system and scanned over 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 (JEM-3100F, manufactured by JEOL Ltd.). The observation results are shown in Figure 7.

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

[0081] Figure 7(A) shows that a tapered LaOx nanoneedle is located on a tungsten support needle with Pt interposed between them. 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 length of the LaOx nanoneedle in the short direction.

[0082] According to Figure 7(B), it was found that 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 elemental analysis was performed 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] Although shown in gray scale in Figure 8, the bright areas in Figure 8(B) and Figure 8(C) 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 Pt used to fix the tungsten support needle and the LaOx nanoneedle. Here again, the atomic ratio of La to O in the LaOx nanoneedle is 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, we investigated the field emission characteristics of the LaOx nanoneedles using a field emission microscope (FEM). -7The sample was kept at a high vacuum of 100 Pa and thermal flashing was performed to clean the tip of the LaOx nanoneedle (the end from which electrons should 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 observe the field emission pattern. The field emission pattern was projected onto a screen (microchannel plate, diameter 1 cm) placed 5 cm away from the LaOx nanoneedle. The results are shown in Figure 9.

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

[0090] The bright areas in Figure 9 are shown in gray scale, and it was found that the LaOx nanoneedles emitted electrons from the screen and functioned as emitters. In particular, the LaOx nanoneedles showed 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, and an applied voltage of 750 V, as well as at a current value of 100 nA and an applied voltage of 800 V. The results are shown in Figure 10.

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

[0093] According to Fig. 10, the current was stable under both conditions of a current value of 36 nA and an applied voltage of 750 V, and a current value of 100 nA and an applied voltage of 800 V. Fluctuations in the emission current (<ΔI 2 > 1 / 2 / I) were evaluated, and the values ​​were 2% / 15 min and 2% / 10 min, respectively, which were significantly lower. This shows that the LaOx nanoneedles of the present invention have excellent characteristics 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 having 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, 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 a rare earth element 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. 2. The emitter of claim 1, wherein the RE element is at least one element selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd) and samarium (Sm).

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

9. The emitter of claim 1 , wherein the nanoneedle has a short-side length of 1 nm to 1 μm, and a long-side length of 500 nm to 30 μm.

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

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

12. The crystal plane of the electron-emitting end of the nanoneedle is When the compound has a cubic crystal phase, the crystal phase is either a (001) 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 crystal phase.

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

14. A method for producing an emitter according to any one of claims 1 to 13, comprising the steps of: 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 a general formula REOx (wherein x is 1 or more and less than 1.5); forming the thin film into a needle shape using a focused ion beam; The method includes:

15. The formation of the thin film is performed 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 The method according to claim 14, further comprising maintaining the substrate in an environment with a vacuum degree of 0.1 Pa or less and a relative humidity of 10% to 70%.

16. The method of claim 14, wherein the processing comprises cutting the thin film from a surface of the RE-containing metal and placing the cut thin film on a support needle.

17. An electron gun having at least an emitter, An electron gun, wherein the emitter is an emitter according to any one of claims 1 to 13.

18. the emitter further comprises a support needle and a filament; 18. The electron gun of claim 17, wherein the nanoneedle is attached to the filament via a support needle comprised of an element selected from the group consisting of tungsten (W), tantalum (Ta), platinum (Pt), rhenium (Re) and carbon (C).

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

20. An electronic device having an electron gun, The electron gun is an electron gun according to claim 17, 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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