Scintillator, measuring device, mass analyzer, and electron microscope

Abstract

A scintillator and the like are provided for enhancing luminous intensity. The scintillator (S) comprises: a sapphire substrate (6); a GaN layer (4) provided on the incident side relative to the sapphire substrate (6) and containing GaN; a quantum well structure (3) provided on the incident side relative to the GaN layer (4); and a conductive layer (2) provided on the incident side relative to the quantum well structure (3). In the quantum well structure (3), a plurality of luminescent layers (21) containing InGaN and a plurality of barrier layers (22) containing GaN are alternately stacked, and an oxygen-containing layer (23) containing oxygen is provided between the quantum well structure (3) and the conductive layer (2).

Description

Technical Field

[0001] The present invention relates to a scintillator, a measuring device, a mass analyzer, and an electron microscope, and particularly to a solution having a quantum well structure. Background Art

[0002] Measurement devices that measure charged particles such as ions and electrons from a sample and obtain information about the sample are equipped with a detector for detecting charged particles. The following description primarily uses a mass spectrometer as an example. In a mass spectrometer, an ionized sample is used, and a mass spectrometer selects ions of a specific mass. These selected ions are introduced into a detector to measure the ion quantity. A detector utilizing a scintillator can be used to detect ion quantity.

[0003] In this detector, mass-selected ions are irradiated onto the conversion dynode in the detection section, generating electrons. A positive voltage of approximately 5 to 15 kV is applied to the detection section, causing the generated electrons to enter the detector's scintillator.

[0004] A scintillator emits light when a charged particle beam is incident on it. The light emitted by the scintillator, caused by the incident electrons, is converted into an electrical signal by a light-receiving element such as a phototube via a light guide, providing measurement information. The intensity of the detected light is used to determine the ion concentration. Detectors utilizing scintillators enable highly sensitive and durable detection.

[0005] In recent years, there has been a significant demand for increased dynamic range, reduced noise, and higher throughput in measurement. To meet these demands, it is necessary to shorten detection time and increase detection signals. Therefore, it is essential to increase the response speed of scintillators and enhance detection sensitivity.

[0006] As a conventional example, technologies for scintillators with fast response speeds are disclosed in the literature. Patent Document 1 discloses a scintillator having a light-emitting element comprising an InGaN / GaN quantum well layer formed on a substrate. Furthermore, the following is described: a cap layer having a larger bandgap energy than the constituent material of the nitride semiconductor layer comprising the InGaN / GaN quantum well layer is provided on the InGaN / GaN quantum well layer, and a metal back layer composed of Al is further provided on the cap layer.

[0007] Patent Document 2 describes providing a cap layer for growing a GaN layer on a multilayer structure of alternately stacked InGaN and GaN, and further vapor-depositing an Al thin film thereon for preventing static charge during incident electrons.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-298603 (corresponding to U.S. Patent No. 7,910,895)

[0011] Patent Document 2: Japanese Patent Application Publication No. 2017-135039 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] However, the existing technology has a problem of low luminous intensity.

[0014] Mass spectrometers and other measurement devices require a wide dynamic range capable of evaluating signals from weak to strong. Scintillators used for this purpose require a luminescence intensity that is as far removed from noise as possible, even with a small number of incident electrons.

[0015] Furthermore, it is more preferable if the saturation of the emission intensity is small even when a large number of incident electrons is present, thereby enabling measurement of changes in the number of electrons.

[0016] As a characteristic of the scintillator, it is necessary to generate sufficiently strong light emission when electrons are incident. Moreover, it is more preferable if the light emission almost disappears before the next incidence.

[0017] Existing light-emitting devices containing InGaN / GaN quantum well layers have a limited efficiency in converting incident electrons into light, resulting in low luminous intensity. Furthermore, electrons incident on the scintillator have a negative charge. If these electrons remain within the scintillator, they repel subsequent incident electrons, reducing the amount of electrons entering. Furthermore, some of these residual electrons may emit light after a short delay after entering the scintillator, reducing response speed.

[0018] In the scintillators described in Patent Documents 1 and 2, the inventors' research has revealed that the crystalline structure of the quantum well layer cannot efficiently convert incident electrons into light within the quantum well layer. Furthermore, conventional structures are known to be unable to control electrons remaining within the scintillator. Consequently, using conventional technology results in weak light output and inability to achieve adequate characteristics.

[0019] Therefore, the present invention has been made to solve such a problem, and provides a scintillator or the like that improves the light emission intensity.

[0020] In addition, some embodiments of the present invention can respond at a higher speed or have a wider dynamic range.

[0021] Means for solving problems

[0022] An example of a scintillator according to the present invention comprises: a substrate; a GaN layer, which is arranged on the incident side relative to the substrate and contains GaN; a quantum well structure, which is arranged on the incident side relative to the GaN layer; and a conductive layer, which is arranged on the incident side relative to the quantum well structure, wherein a plurality of light-emitting layers containing InGaN and a plurality of barrier layers containing GaN are alternately stacked in the quantum well structure, and an oxygen-containing layer containing oxygen is provided between the quantum well structure and the conductive layer.

[0023] One example of the measurement device according to the present invention is characterized in that, in a charged particle beam apparatus including a detector for detecting charged particles obtained by irradiation with a charged particle beam emitted from a charged particle source, the detector is the above-mentioned scintillator.

[0024] An example of a mass spectrometer according to the present invention is a mass spectrometer including a detector for detecting mass-separated ions, wherein the detector is the above-mentioned scintillator.

[0025] An example of the electron microscope according to the present invention is an electron microscope including a detector for detecting electron beams emitted from an evaluation object, wherein the detector is the above-mentioned scintillator.

[0026] This description incorporates the disclosure of Japanese Patent Application No. 2019-233378, which serves as the basis for the priority of this application.

[0027] Effects of the Invention

[0028] According to the scintillator and the like according to the present invention, incident charged particles can be efficiently emitted, thereby improving the emission intensity of the scintillator. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a diagram showing the structure of a scintillator according to Example 1 of the present invention.

[0030] Figure 2 Yes means having Figure 1 Diagram of the basic structure of a scintillator mass analyzer.

[0031] Figure 3 Yes Figure 1 An example of the emission spectrum of a scintillator.

[0032] Figure 4 Yes Figure 1 Graph showing oxygen composition distribution in a cross section of a scintillator.

[0033] Figure 5 Yes Figure 1 A graph showing the relationship between the resistance between the conductive layer and the quantum well structure in the scintillator and the luminous intensity.

[0034] Figure 6 This is a schematic diagram of a method for measuring the resistance value of a thin film.

[0035] Figure 7 This is a graph showing changes in emission intensity with time in a quantum well layer.

[0036] Figure 8 This is a graph comparing differences in area density of concave holes in the scintillator surface.

[0037] Figure 9 This is a graph showing the difference in luminous intensity depending on the area density of the concave holes in the scintillator.

[0038] Figure 10 This is a graph showing the relationship between the ratio of the thickness of the blocking layer and the light-emitting layer and the light-emitting intensity.

[0039] Figure 11 This is a graph showing changes in emission intensity relative to the overall thickness of the quantum well structure.

[0040] Figure 12 This is a diagram showing the basic structure of an electron microscope according to a modification of Example 1. DETAILED DESCRIPTION

[0041] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0042] Example 1.

[0043] Example 1 relates to a mass spectrometer equipped with a detector using a scintillator as a detection element. However, the application of the present invention is not limited to Example 1. A mass spectrometer is one example of a measuring device, and the scintillator of Example 1 can also be used in other measuring devices. As examples of other measuring devices, the scintillator of Example 1 can be used in electron microscopes using electron beams, in semiconductor pattern measurement devices using scanning electron microscopes, in inspection devices, and in observation devices.

[0044] The scintillator in this specification refers to an element that emits light in response to incident charged particle beams. The scintillator in this specification is not limited to the one shown in Example 1, and can be of various shapes and structures.

[0045] The specific structure of the scintillator according to Example 1 will be described below. Figure 1 1 and 2 show the structure of the scintillator S of Example 1, and particularly include a schematic diagram showing the structure of the light emitting section 1. The light emitting section 1 uses a light emitting element including a quantum well structure 3 containing GaN.

[0046] The scintillator S includes a substrate. The substrate can be, for example, a sapphire substrate 6. In addition, the scintillator S includes a GaN layer 4. The GaN layer 4 is a layer containing GaN and functions as a blocking layer.

[0047] The GaN layer 4 is provided on the incident side with respect to the sapphire substrate 6. In this specification, the so-called "incident side" refers to the side of the surface where charged particles to be detected enter in the scintillator S or in a specific layer contained in the scintillator S. The surface on the incident side is sometimes also referred to as the "upper surface". In Example 1, the GaN layer 4 can also be laminated on the upper surface of the sapphire substrate 6.

[0048] The scintillator S includes a quantum well structure 3. The quantum well structure 3 is provided on the incident side with respect to the GaN layer 4. In the quantum well structure 3, a plurality of light-emitting layers 21 and a plurality of blocking layers 22 are alternately laminated. The light-emitting layer 21 contains InGaN, and the blocking layer 22 contains GaN. The light-emitting layer 21 also functions as a quantum well layer.

[0049] The scintillator S includes a conductive layer 2. The conductive layer 2 is provided on the incident side with respect to the quantum well structure 3. In addition, the scintillator S includes an oxygen-containing layer 23. The oxygen-containing layer 23 is provided between the quantum well structure 3 and the conductive layer 2 (for example, at their interface).

[0050] An example of a more specific structure, composition, and manufacturing method of such a scintillator S will be described. However, the structure, composition, and manufacturing method are not limited to the following, and any method can be arbitrarily adopted as long as the above structure can be achieved.

[0051] First, the GaN layer 4 is grown on the sapphire substrate 6, and on it, for a light-emitting layer 21 containing a large amount of Ga 1-x In x N (where 0 < x < 1), while changing the composition respectively, it is grown to form the quantum well structure 3. The conductive layer 2 is directly formed on it. The conductive layer 2 is the layer formed on the most incident side in the scintillator S.

[0052] The conductive layer 2 is, for example, entirely composed of Al, but is not limited to this. For example, the conductive layer 2 is composed of at least one type or more of Al, Au, Ag, Ti, Pd, W, Nb. If these materials are used, a scintillator S with good characteristics can be formed.

[0053] The sapphire substrate 6 is in the shape of a disk with a diameter of 2 inches (about 5.1 cm), and the GaN layer 4 is grown so that the thickness c is within the range of 3 to 10 μm.

[0054] The quantum well structure 3 has Ga 1-x In xThe light-emitting layer 21 composed of N and the barrier layer 22 composed of GaN are alternately overlapped in multiple cycles, with the number of cycles ranging from 2 to 40. The thickness of the quantum well structure 3 is within the range of 20 nm to 2000 nm. On the incident side of the quantum well structure 3, an Al layer is formed by vapor deposition to a thickness ranging from 40 to 1000 nm as the conductive layer 2. This conductive layer 2 has a function of preventing electrostatic charge when electrons are incident.

[0055] An oxygen-containing layer 23 containing oxygen is provided between the conductive layer 2 and the quantum well structure 3. Furthermore, in the scintillator S according to Example 1, a concave hole 24 is formed from the quantum well structure 3 to the conductive layer 2, which widens as it approaches the incident side. These holes 24 are formed, for example, as a result of crystal strain or defects. Furthermore, since the scintillator S includes multiple light-emitting layers 21, the holes 24 do not necessarily need to extend across all of the light-emitting layers 21; however, multiple holes 24 are formed in at least the light-emitting layer 21 located closest to the incident side.

[0056] The plurality of light-emitting layers 21 may all have the same thickness and composition, or may have different thicknesses or compositions. Similarly, the plurality of barrier layers 22 may all have the same thickness and composition, or may have different thicknesses or compositions.

[0057] Furthermore, the interface 5 between the light-emitting portion 1 and the sapphire substrate 6 may be flat or have a concave-convex structure. For example, a structure having a continuous protrusion structure with a structure pitch within a range of 10 to 10,000 nm and a structure height within a range of 10 to 10,000 nm is effective in increasing the light output by extracting the light.

[0058] A product cut out into a given size from such a configuration is used as a scintillator S.

[0059] Figure 2 This diagram illustrates the basic structure of a mass spectrometer 30 according to Example 1. The mass spectrometer 30 separates ions by mass using electromagnetic forces and measures the mass-to-charge ratio of the ions being measured. The mass spectrometer 30 includes an ion source 31, a mass separation unit 32, a conversion dynode 33 (conversion electrode), an amplifier 34, and a signal output device 35.

[0060] The ion source 31 can adopt ESI, APCI, MALDI, APPI, etc. The mass separation unit 32 can be of QMS type, iontrap type, time-of-flight (TOF) type, FT-ICR type, Orbitrap type, or a combination thereof.

[0061] The mass spectrometer 30 converts ions mass-selected in the mass separation unit 32 into charged particles by colliding them with the conversion dynode 33 , detects the generated charged particles with the scintillator S, and converts the emitted light into a signal through the amplifier 34 and the signal output unit 35 for output.

[0062] exist Figure 3 An example of the emission spectrum of the scintillator S is shown.

[0063] In the scintillator S of Example 1, an oxygen-containing layer 23 is provided between the conductive layer 2 and the quantum well structure 3. Figure 4 1 shows an oxygen composition distribution diagram in a cross section of the scintillator S. In this figure, an oxygen-containing layer 23 is shown between the conductive layer 2 and the quantum well structure 3 .

[0064] The oxygen-containing layer 23 may contain an oxide of Ga. Including an oxide of Ga may facilitate control of the characteristics of the scintillator S. Alternatively, the oxygen-containing layer 23 may contain an oxide of the component (Al in this embodiment) constituting the conductive layer 2 .

[0065] This oxygen-containing layer 23 can be formed by exposing the layer to an oxygen-containing gas after growing the quantum well structure 3. Alternatively, it can be formed by further heating the layer in an oxygen-containing gas. The thickness of the oxygen-containing layer 23 is arbitrary, but if it is within the range of 1 nm to 100 nm, the resistance between the conductive layer 2 and the quantum well structure 3 can be appropriately controlled.

[0066] The scintillator S emits light by introducing energy into the quantum well structure 3, exciting carriers. If the incident electrons remain within the quantum well structure 3, excitation continues, increasing the intensity of the luminescence. If the incident electrons are immediately removed from the quantum well structure 3, the duration of excitation is reduced, resulting in a lower luminescence intensity. However, in this case, luminescence ends quickly, resulting in a shorter response time.

[0067] exist Figure 5 The relationship between the resistance between the conductive layer 2 and the quantum well structure 3 of the scintillator S and the luminous intensity is shown. Figure 5 This graph compares the luminous intensity under various conditions, with no specific unit assigned to the luminous intensity (vertical axis). This also applies to the other graphs below.

[0068] In the scintillator S, the above-mentioned luminous intensity and response time can be adjusted by controlling the resistance between the conductive layer 2 and the quantum well structure 3. For example, it is known that by setting the resistance between the conductive layer 2 and the quantum well structure 3 to an interface resistance of 10 -1 ~10 -5 Ωcm 2Within the range, good luminous intensity can be obtained. In addition, when the interface resistance is within this range, the response time has the possibility of being within a range where it can be fully utilized.

[0069] Here, in the evaluation of the resistance between the conductive layer 2 and the quantum well structure 3, generally used means for measuring the resistance value of a thin film are employed. As an example, in Figure 6 a method example of resistance value measurement (a method based on the formation of circular electrodes) is shown. It is possible to use such circular electrodes to implement means for evaluation using a galvanometer capable of measuring a minute current, etc. In Figure 6 the shape of the electrodes formed on the surface of the measurement sample is shown, and by measuring the resistance between the circular electrode and the outer peripheral electrode, the resistance value can be evaluated.

[0070] In addition, as a method for controlling the luminous intensity and the response time, the following method is also implemented. As one of the structures of this embodiment, the light-emitting layer 21 can be placed directly below the conductive layer 2 (Al layer). Here, the expression "directly below" refers to the positional relationship without sandwiching the blocking layer 22, disregarding the presence or absence of the oxygen-containing layer 23.

[0071] In this case, the light-emitting layer 21 in contact with the conductive layer 2 has a composition of Ga 1-y In y N (where 0 < y < 1), and it is a light-emitting layer 21 with a smaller bandgap energy than GaN. This layer has a higher conductivity than the GaN layer 4 by including In, and furthermore, has a smaller bandgap, so electrons are more likely to flow in. Therefore, the electrons incident on the quantum well structure 3 can immediately move to the conductive layer 2. The conductive layer 2 is composed of a conductor (e.g., Al) and excludes electrons without leaving them in the light-emitting part 1. This is effective in shortening the response time.

[0072] Here, when the electrons incident on the quantum well structure 3 are not immediately excluded, the remaining electrons become negative charges and act as a repulsive force on the electrons incident later, so the amount of incident electrons decreases, resulting in a reduction in the light emission output. In addition, among the remaining electrons, there are electrons that cause delayed luminescence that emits light after a slight time delay after incidence, which becomes a cause of impairing the high speed of luminescence. To address such problems, according to Embodiment 1, by immediately excluding the electrons after incidence, an increase in the light emission output and high speed of luminescence can be achieved.

[0073] In addition, as one of the modified examples of this embodiment, instead of the light-emitting layer 21, the blocking layer 22 can be placed directly below the conductive layer 2.

[0074] In Figure 7The graph shows the change in the light emitting intensity of the light emitting layer 21 with respect to time. This is the result of extremely high-speed evaluation of the change in light emitting output after electrons enter the light emitting layer 21 in nanoseconds. Figure 7 (a) is a graph showing changes in luminous intensity with time when a structure is used in which the conductive layer 2 (Al in this example) is in direct contact with the luminous layer 21. On the other hand, Figure 7 Graph (b) shows the change in luminescence intensity when a large-bandgap layer (e.g., a layer containing GaN, such as barrier layer 22) is formed on luminescent layer 21, and conductive layer 2 is formed thereon. The term "direct contact" here also disregards the presence or absence of oxygen-containing layer 23.

[0075] exist Figure 7 In (b), it can be seen that after the luminescence is started, there is residual luminescence for tens of nanoseconds. This is because the residual electrons cause delayed luminescence for tens of nanoseconds. Such luminescence impairs the high-speed response and degrades the characteristics of the device. On the other hand, Figure 7 In (a), it can be seen that the luminescence disappears within 10 ns after the start of luminescence. One of the factors for this is that the remaining electrons are immediately removed.

[0076] The scintillator S of Example 1 is as follows Figure 1 As shown in FIG. 1 , there are concave holes 24 extending from the quantum well structure 3 to the conductive layer 2. By controlling the area density of the holes 24 on the surface of the light emitting portion 1 to 10 4 pieces / cm 2 above 10 10 pieces / cm 2 Good light emitting characteristics can be obtained within the following ranges.

[0077] Controlling the area density of holes 24 can be achieved by adjusting the temperature, growth rate, composition, and raw materials during crystal growth. Regarding the luminescence in the quantum well structure 3, the carriers generated by excitation, namely electrons and holes, are confined in the light-emitting layer 21, making it easier for the electrons and holes to couple efficiently, thereby emitting light with high efficiency. This is the result of the inventors' research, which suggests that introducing a certain degree of crystal strain into the crystal is beneficial in order to further increase this luminescence. This differs from the conventional thinking that improving crystallization to reduce strain will improve efficiency. This result was first discovered through actual experiments using crystals in various states.

[0078] The reason why the luminescence intensity increases due to crystal strain is not strictly determined, but the following explanation is given as an example. The concave hole 24 generated by the strain becomes a void in a part of the interior of the quantum well structure 3. A wall based on the crystal with a lot of strain is formed around it. The quantum well structure 3 is a structure that confines carriers in a two-dimensional structure, and by confinement, the efficiency of luminescence is improved. It can be considered that by adding a crystal wall there, the local existence or bending of the energy band is generated around it, and the local existence of carriers around it is also generated. Therefore, it can be considered that the carrier confinement in the one-dimensional structure is further generated, and the efficiency of luminescence is increased. In addition, there is also the following situation: if the concave hole increases to a certain extent, the amount of crystal that should emit light decreases, and the amount of light emitted decreases instead.

[0079] Figure 8 This is a diagram comparing differences in the area density of the concave holes 24 on the surface of the scintillator. Figure 8 (a) is a diagram of the scintillator S of Example 1, Figure 8 (b) is a diagram of a conventional scintillator.

[0080] In addition, Figure 9 The difference in luminous intensity when the area density of the concave holes 24 is different is shown. 4 pieces / cm 2 above 10 10 pieces / cm 2 The luminous intensity increases within the following range: By using a crystal having concave holes with an appropriate area density in this manner, a scintillator with good characteristics can be produced.

[0081] The following describes the thickness of the quantum well structure 3. The scintillator S of Example 1 is preferably made under the following conditions to obtain the thickness of each layer. In order to find the more suitable conditions, a large number of scintillators are made, and in each scintillator, Figure 1 The ratio b / a of the thickness b of the barrier layer 22 and the thickness a of the light-emitting layer 21 is shown to be different. The production range is b / a in the range of 1.5 to 20, and the thickness a of the light-emitting layer 21 is in the range of 1 to 5 nm.

[0082] The quantum effect of the light-emitting layer 21 is generally greater when the thickness is less than 4 nm, which can lead to a shift in the emission wavelength and an increase in luminous efficiency. However, if the barrier layer 22 is too thin, the crystallinity may be reduced, resulting in a decrease in luminous intensity. Furthermore, if the quantum well structure 3 is too thin compared to the penetration distance of the electron beam, the electron beam may not be fully utilized, resulting in a decrease in luminous intensity. Taking these effects into consideration, the inventors of the present invention have newly identified the range in which luminous intensity is maximized.

[0083] Figure 10The relationship between the ratio b / a of the thickness b of the barrier layer 22 and the thickness a of the light-emitting layer 21 and the luminescence intensity is shown. As can be seen from this figure, the luminescence intensity increases until the ratio b / a reaches approximately 5, but the luminescence intensity is approximately maximized when the ratio b / a is 6 or greater. In other words, by setting the ratio b / a to 6 or greater, a scintillator can be manufactured that achieves both high luminescence intensity and high-speed response.

[0084] Furthermore, the scintillator S of Example 1 includes a plurality of light-emitting layers 21 and barrier layers 22. While it is desirable for all pairs of adjacent light-emitting layers 21 and barrier layers 22 to have a ratio b / a of 6 or greater, this does not necessarily have to be the case. For example, if b / a ≥ 6 is satisfied for any thickness a of the light-emitting layer 21 and any thickness b of the barrier layer 22, the aforementioned effects can be achieved for these pairs.

[0085] A scintillator that achieves both high luminous intensity and high-speed response can cope with high-speed scanning, and a charged particle beam device that can obtain a sufficient S / N ratio even with high-speed scanning can be provided.

[0086] Furthermore, the relationship between the number of light-emitting layers 21 and the total thickness of the quantum well structure 3 has the following effects. Figure 11 2 shows the change in the emission intensity with respect to the total thickness of the quantum well structure 3 in this embodiment.

[0087] This figure shows an example of irradiation using an electron beam accelerated at 10 kV as a charged particle beam. It can be seen that the luminescence intensity reaches its maximum when the overall thickness of the quantum well structure 3 is between 200 nm and 600 nm. Furthermore, the relationship between layer thickness and luminescence intensity shows that, when using an electron beam accelerated at 10 kV, the characteristics remain roughly the same even when the number of light-emitting layers 21 is varied between 5 and 30 layers. This indicates that the overall thickness of the quantum well structure 3 has a significant effect on the change in luminescence intensity, while even a certain degree of variation in the number of light-emitting layers 21 has little effect.

[0088] Furthermore, it can be seen that the relationship between the overall thickness of the quantum well structure 3 and the luminescence intensity varies depending on the accelerating voltage of the charged particle beam being irradiated. The distance that the charged particle beam penetrates into the irradiated material varies with the accelerating voltage. In this embodiment, the penetration distance of the electron beam accelerated at 10 kV is approximately 1 μm. This shows that the depth at which the electron beam produces luminescence is a crucial factor in determining luminescence intensity. The thickness of the quantum well structure 3 that produces luminescence can be set within a range of at least one-fifth and no more than three-fifths of the penetration distance of the electron beam.

[0089] Furthermore, since fewer layers in the light-emitting layer 21 reduce the disorder of the resulting crystals, fewer crystal defects that can cause unwanted light emission, thereby improving the light-emitting properties. While the number of layers in the light-emitting layer 21 has some degree of freedom, it has been shown that keeping the number of layers within a certain range improves light-emitting properties. The inventors' research has revealed that maintaining the number of layers in the light-emitting layer 21 within a range of 5 to 30 achieves excellent light-emitting properties.

[0090] Research by the inventors of the present invention has revealed that by appropriately designing the thickness of the topmost layer of the quantum well structure 3 and the portion above it in the scintillator S, stable characteristics are achieved. For example, if the combined thickness of the portion from the conductive layer 2 to the light-emitting layer 21 located closest to the incident side of the quantum well structure 3 (including the oxygen-containing layer 23 and, if necessary, the barrier layer 22) is set to 200 nm or greater, stable characteristics are achieved. Below 100 nm, there is some variation in characteristics, but above 100 nm, this variation is reduced. Above 200 nm, the characteristics reach a usable level.

[0091] As described above, according to the scintillator S according to the first embodiment, the light emission intensity can be improved.

[0092] The scintillator S of Example 1 is mounted on a mass spectrometer and used as a detector for detecting mass-separated ions. As a modified example, the scintillator S can also be used in other measurement devices.

[0093] Figure 12 This figure shows the basic structure of an electron microscope 40 according to this modification. A sample 43 is irradiated with a primary electron beam 42 emitted from an electron source 41, emitting secondary particles 44 such as secondary electrons or reflected electrons. These secondary particles 44 are attracted and incident on a scintillator S. The scintillator S is used in the electron microscope 40 as a detector for detecting electron beams emitted from an object to be evaluated (e.g., the sample 43).

[0094] When secondary particles 44 are incident on the scintillator S, light is emitted from the scintillator S. The light emitted from the scintillator S is guided by the light guide 45 and converted into an electrical signal by the light receiving element 46. The scintillator S, light guide 45, and light receiving element 46 are collectively referred to as a detection system.

[0095] The signal obtained by the light receiving element 46 is converted into an image corresponding to the irradiation position of the electron beam and displayed. The electron microscope 40 includes an electron optical system (i.e., a deflector, lens, aperture, objective lens, etc.) for converging the primary electron beam 42 and irradiating the sample 43, but this is not shown in the figure.

[0096] The electron optical system is provided in the electron optical lens column 47. The sample 43 is placed on a sample stage so as to be movable, and the sample 43 and the sample stage are arranged in a sample chamber 48. The sample chamber 48 is generally kept in a vacuum state during electron beam irradiation.

[0097] Although not particularly shown, the electron microscope 40 is connected to a control unit that controls the overall operation and the operation of each component, a display unit that displays images, an input unit for a user to input operation instructions for the electron microscope, and the like.

[0098] The electron microscope 40 is an example of an electron microscope configuration. Electron microscopes equipped with a scintillator, a light guide, and a light-receiving element can also have other configurations. Furthermore, secondary particles 44 also include transmitted electrons, scanning transmitted electrons, and the like. For simplicity, only one detector (scintillator S) is shown, but detectors for detecting reflected electrons and for detecting secondary electrons can be provided separately. Furthermore, multiple detectors can be provided to detect different azimuth or elevation angles.

[0099] Another charged particle beam apparatus may be configured as another modified example of Example 1. In such a charged particle beam apparatus, a scintillator S is used as a detector for detecting charged particles obtained by irradiation with a charged particle beam emitted from a charged particle source.

[0100] Captions

[0101] 1…Light-emitting part

[0102] 2…conductive layer

[0103] 3…Quantum well structure

[0104] 4…GaN layer

[0105] 5…Interface

[0106] 6…Sapphire substrate

[0107] 21…luminescent layer

[0108] 22…Barrier layer

[0109] 23…Oxygen layer

[0110] 24…holes

[0111] 30…Mass analysis device

[0112] 31…Ion source

[0113] 32…Mass separation unit

[0114] 33…Conversion dynode

[0115] 34…Amplifier

[0116] 35…Signal output

[0117] 40…Electron microscope

[0118] 41…Electron source

[0119] 42…primary electron wire

[0120] 43…sample

[0121] 44…Secondary particles

[0122] 45…Light guide

[0123] 46…Light receiving element

[0124] 47…Electron optical tube

[0125] 48…Sample Room

[0126] S…Scintillator

[0127] a, b, c...thickness

[0128] All publications, patents, and patent applications cited in this specification are incorporated herein by reference as if fully intact.

Claims

1. A scintillator, characterized in that: have: substrate; A GaN layer, disposed on the incident side relative to the substrate, comprising GaN; a quantum well structure provided on the incident side relative to the GaN layer; and a conductive layer disposed on the incident side relative to the quantum well structure, In the quantum well structure, multiple light-emitting layers containing InGaN and multiple barrier layers containing GaN are alternately stacked. An oxygen-containing layer containing oxygen is provided between the quantum well structure and the conductive layer. The interface resistance between the conductive layer and the quantum well structure is 10 -1 ~10 -5 Ωcm 2 within the range.

2. A scintillator, characterized in that: have: substrate; A GaN layer, disposed on the incident side relative to the substrate, comprising GaN; a quantum well structure provided on the incident side relative to the GaN layer; and a conductive layer disposed on the incident side relative to the quantum well structure, In the quantum well structure, multiple light-emitting layers containing InGaN and multiple barrier layers containing GaN are alternately stacked. An oxygen-containing layer containing oxygen is provided between the quantum well structure and the conductive layer. In the quantum well structure, a plurality of holes are formed in at least the light-emitting layer located closest to the incident side among the light-emitting layers. The density of the holes is 10 4 pieces / cm 2 Above and 10 10 pieces / cm 2 Within the following range.

3. The scintillator according to claim 1 or 2, characterized in that The oxygen-containing layer includes Ga oxide.

4. The scintillator according to claim 1 or 2, characterized in that The thickness of the oxygen-containing layer is in the range of 1 nm to 100 nm.

5. The scintillator according to claim 1 or 2, characterized in that The total thickness of a portion including the conductive layer and the light-emitting layer provided on the most incident side in the quantum well structure is 200 nm or more.

6. The scintillator according to claim 1 or 2, characterized in that: The conductive layer includes at least one of Al, Au, Ag, Ti, Pd, W, and Nb.

7. The scintillator according to claim 1 or 2, characterized in that: With respect to any thickness a of the light-emitting layer and any thickness b of the blocking layer, b / a≧6.

8. The scintillator according to claim 1 or 2, characterized in that: The number of the light-emitting layer is in the range of 5 to 30.

9. A measuring device, characterized in that: In a charged particle beam apparatus including a detector for detecting charged particles obtained by irradiation with a charged particle beam emitted from a charged particle source, the detector is the scintillator according to claim 1 or 2 .

10. A mass analysis device, characterized in that: In a mass spectrometer including a detector for detecting mass-separated ions, the detector is the scintillator according to claim 1 or 2.

11. An electron microscope, characterized in that In an electron microscope including a detector for detecting electron beams emitted from an object to be evaluated, the detector is the scintillator according to claim 1 or 2.

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