X-ray absorption analyzer

Abstract

In an X-ray absorption analyzer used in the conversion electron yield method, the noise of the conversion electron signal is reduced while allowing the sample to be heated. [Solution] The X-ray absorption analyzer 20 comprises an airtight housing 21, a lower electrode 27 and an upper electrode 29 provided in the housing 21, and a sample heater 34 that uses light irradiation. The heater 34 irradiates light onto the lower electrode 27 from the back surface 27b side opposite to the upper electrode 29, thereby heating the sample.

Description

Technical Field

[0001] The present disclosure relates to an X-ray absorption analyzer.

Background Art

[0002] As an analysis method using X-ray absorption fine structure (XAFS), the conversion electron yield method is known. In the conversion electron yield method, when a sample is irradiated with X-rays having a specific energy, Auger electrons are ejected, and the electrons reach an upper electrode disposed above the sample while ionizing the surrounding gas. The conversion electron yield method is an X-ray absorption analysis method for analyzing the chemical state of the outermost surface to about several hundred nm of a sample by analyzing the irradiation X-ray energy dependence of the current that replenishes the Auger electrons emitted from the sample irradiated with X-rays. Examples of the X-ray absorption analyzer capable of analyzing a sample by the above conversion electron yield method include those described in Patent Document 1.

[0003] The X-ray absorption analyzer described in Patent Document 1 has an X-ray incident part that transmits the irradiation X-rays to the sample, an X-ray emission part that emits the fluorescent X-rays generated by irradiating the sample to the outside, and an inflow part and an outflow part of an active gas, and includes a housing that houses the sample. This X-ray absorption analyzer has, inside the housing, a lower electrode on which the sample is disposed, an upper electrode disposed at a distance from the lower electrode with the sample interposed therebetween, and an electric heater capable of heating the sample via the lower electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a result of the inventors' diligent research on this type of X-ray absorption analyzer, it was found that when using an electrically heated heater, electromagnetic noise is easily superimposed on the conversion electron signal during switching in temperature control, due to the measurement principle of the conversion electron yield method. When electromagnetic noise is superimposed on the conversion electron signal, it becomes difficult to obtain the original XAFS spectrum, and the analytical accuracy is reduced.

[0006] In view of the above, this disclosure aims to reduce noise in the conversion electron signal while enabling heating of the sample in an X-ray absorption analyzer used in the conversion electron yield method. [Means for solving the problem]

[0007] According to one aspect of this disclosure, an X-ray absorption analyzer is Airtight enclosure (21) and A lower electrode (27) is provided within the housing on which the sample is placed, An upper electrode (29) is provided within the housing and is positioned at a distance from the lower electrode with the sample in between, The lower electrode has a back surface (27b) that is the side opposite to the upper electrode, and the heating mechanism (34) heats the sample by irradiating the lower electrode with light from the back surface side.

[0008] This X-ray absorption analyzer comprises a lower electrode on which the sample is placed, an upper electrode positioned at a distance from the lower electrode with the sample in between, and a heating mechanism that heats the sample by irradiating the lower electrode or the sample with light from the back side of the lower electrode opposite to the upper electrode. By using a heating mechanism that heats the sample with light irradiation instead of an electrically heated heater, the generation of electromagnetic noise caused by heating the sample is suppressed, thereby reducing noise in the conversion electron signal.

[0009] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows an overview of the XAFS analysis system according to the embodiment. [Figure 2] This is a perspective view of the housing that makes up an X-ray absorption analyzer. [Figure 3] This diagram shows the internal structure of an X-ray absorption analyzer. [Figure 4] This figure shows the measurement results of the internal and surface temperatures of the lower electrode after light irradiation. [Figure 5] This is a graph plotting the results from Figure 4. [Figure 6] This figure shows the results of XAFS analysis of copper foil using the transmission method. [Figure 7] This figure shows the results of XAFS analysis of copper foil using the XAFS analysis system according to the embodiment. [Figure 8] This figure shows the XAFS analysis results for Cu, Cu2O, and CuO samples using the XAFS analysis system according to the embodiment. [Figure 9] This is a perspective view showing a modified example of the lower electrode. [Figure 10] This figure shows the XAFS analysis results of copper foil containing copper oxide using an XAFS analysis system employing an electrically heated method in a comparative example. [Figure 11] This figure shows the results of scanning transmission electron microscopy observation of the prepared sample. [Figure 12] This figure shows the elemental analysis results of oxygen by energy-dispersive X-ray spectroscopy in the same field of view as the sample in Figure 11. [Figure 13] This figure shows the results of elemental analysis of copper by energy-dispersive X-ray spectroscopy in the same field of view as the sample in Figure 11. [Figure 14] This figure shows the results of XAFS analysis of the sample in Figure 11 using the transmission method and the XAFS analysis system of the embodiment. [Figure 15] This figure shows the results of XAFS analysis of the sample shown in Figure 11 at different temperatures in an active gas atmosphere using the XAFS analysis system of the embodiment. [Figure 16]This is a diagram showing the results of quantitatively evaluating copper and copper oxide for the sample in FIG. 11 by linear combination fitting of the XAFS spectrum. [Figure 17] This is a diagram showing a modified example of an X-ray absorption analyzer.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described based on the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals and described.

[0012] (Embodiment) The XAFS analysis system 1 according to the embodiment will be described.

[0013] The XAFS analysis system 1 of the present embodiment includes, for example, as shown in FIG. 1, an X-ray output device 10, an optical introduction device 11, an optical detection device 12, an X-ray absorption analyzer 20, and a heater 34.

[0014] In addition to analyzing a sample by the conversion electron yield XAFS method or the fluorescence XAFS method, the XAFS analysis system 1 can perform spectroscopic analysis of a sample using light having a wavelength different from that of X-rays and surface observation of the sample. Here, X-rays are electromagnetic waves having a range of energy from 10 eV to 100 keV and a range of wavelength from 124 nm to 12 pm. The conversion electron yield XAFS method irradiates a sample with X-rays having a specific energy and sweeps the energy while measuring the current flowing through the ionized active gas when Auger electrons emitted from the sample ionize the surrounding active gas. The fluorescence XAFS method measures the intensity of fluorescence X-rays emitted from the surface of the sample by irradiation with X-rays. Spectroscopic analysis irradiates a sample with, for example, ultraviolet light, visible light, or infrared light and measures the spectrum of the reflected light. Surface observation illuminates the sample surface with, for example, visible light and observes the sample surface visually or with a camera.

[0015] The X-ray output device 10 is an X-ray source capable of outputting X-rays with a specific energy, and for example, synchrotron radiation can be used. For the sake of explanation, the X-rays output from the X-ray output device 10 that enter the interior of the housing 21 constituting the X-ray absorption analyzer 20 will be referred to as "incident X-rays 100".

[0016] The light introduction device 11 emits light of a different wavelength than X-rays toward the sample 200 placed inside the housing 21. The light introduction device 11 has a known light source for spectroscopic analysis that generates laser light in wavelength ranges such as the ultraviolet, visible, or infrared regions. The light introduction device 11 is positioned in a different direction from the X-ray output device 10 and irradiates the sample 200 inside the housing 21 with light at a different angle from the incident X-rays 100. If visual or optical observation of the sample 200 is desired, the light introduction device 11 can simply illuminate the sample 200 with visible light instead of laser light, and the type of irradiated light can be changed according to the measurement purpose.

[0017] For the sake of explanation, the light emitted from the light introduction device 11 that enters the interior of the housing 21 will be referred to as "incident light 101". The light generated by the irradiation of the sample 200 with incident X-rays 100 or incident light 101 that is emitted outside the housing 21 will be referred to as "exit light 102". The exit light 102 may be fluorescent X-rays, ultraviolet light, visible light, infrared light, etc.

[0018] The photodetector 12 detects the emitted light 102 that is emitted from the housing 21 to the outside. The photodetector 12 is configured as an X-ray fluorescence detector to detect fluorescent X-rays produced by the X-ray irradiation of the sample 200, for example, when the sample 200 is irradiated with incident X-rays 100. The photodetector 12 is configured as an infrared photodetector to detect infrared light reflected from the surface of the sample 200, for example, when the sample 200 is irradiated with infrared laser light as incident light 101. The photodetector 12 is configured as a camera capable of imaging the sample 200, for example, when the sample 200 is irradiated with visible light as incident light 101. The photodetector 12 can be configured as an X-ray fluorescence detector, for example, by using a scintillation counter, proportional counter, Leytle detector (ionization chamber), semiconductor detector, etc. The photodetector 12 can use, for example, InGaAs, InSb, or PbS photoconductive elements in the case of an infrared photodetector, or silicon photodiodes or photomultiplier tubes in the case of a photodetector in the near-infrared to ultraviolet region. The photodetector 12 may be placed one at a time outside the housing 21, and its type may be changed depending on the measurement purpose, or multiple units of different types such as fluorescent X-ray detectors, infrared photodetectors, and cameras may be placed at the same time.

[0019] In X-ray fluorescence analysis, the fluorescent X-rays generated by irradiating sample 200 with X-rays are measured to obtain an XAFS spectrum. The wavelength of fluorescent X-rays is element-specific, and the element can be identified from the wavelength of the detected fluorescent X-rays, the concentration from the intensity, and the chemical bonding state from the dependence on the incident X-ray energy. In spectroscopic analysis, the light emitted by irradiating sample 200 with incident light 101 is divided into wavelengths and analyzed, and the components and properties of the molecules constituting sample 200 are analyzed quantitatively and qualitatively based on their unique wavelength spectra.

[0020] In the conversion electron yield XAFS method, sample 200 is excited by X-ray irradiation, and Auger electrons emitted from sample 200 ionize the active gas surrounding sample 200, releasing secondary electrons from the active gas. These secondary electrons then further ionize other active gases, resulting in a chain reaction of ionization and secondary electron emission, i.e., conversion, which amplifies the signal.

[0021] Here, in the case of the active gas, ionization and absorption of X-rays occur due to X-ray irradiation. When using a gas species with a larger atomic number or molecular weight than helium, the mass absorption coefficient of the gas is large, and it is ionized by the incident X-rays 100, so a current constantly flows through the lower electrode 27, increasing measurement noise. In addition, gas species with large atomic numbers and molecular weights shield the fluorescent X-rays emitted from the sample 200, making it difficult to increase the signal intensity of the measurement. For this reason, it is preferable to use a gas species with an atomic number and molecular weight of helium or less as the active gas, rather than a gas species with a large atomic number and molecular weight. Gas species with large atomic numbers and molecular weights such as oxygen, carbon dioxide, and water vapor can also be used, but considering the mass coefficient of the gas, it is preferable to use a mixed gas with a partial pressure of helium or lower as the base gas. The inflow / outflow of the active gas in the housing 21 is performed by the gas inflow section 25 and the gas outflow section 26, which will be described later.

[0022] In this embodiment, for example, hydrogen is used as the active gas, but a mixed gas of hydrogen and helium may also be used as the active gas, and the type of active gas can be changed as appropriate. Helium generally does not react well with other elements and therefore does not act well as a reducing gas, but hydrogen acts as a reducing gas that, for example, converts oxides on metal surfaces into metals. For this reason, when hydrogen is flowed as the active gas while heating the sample 200 with the heater 34, it becomes possible to measure while observing the reduction state of the outermost surface of the sample 200. This allows for dynamic observation of the sample 200, and enables real-time analysis of the electronic state changes of the element of interest in the sample 200, which cannot be confirmed by static observation.

[0023] The X-ray absorption analyzer 20 is equipped with a chamber-structured housing 21. The housing 21 is configured as a rectangular parallelepiped container with sides of approximately 15-20 cm, as shown in Figure 2, for example. The housing 21 is configured to measure the leak rate of helium gas by the suction method (sniffer method) at 5 × 10⁻¹⁰ -7 Pa·m 3The structure is airtight with a minimum of / s. The housing 21 has an X-ray inlet 22, a light outlet 23, and a heating window 24, each located at a different position, as shown in Figure 3, for example.

[0024] The X-ray incident section 22 is provided on the side surface 21c of the housing 21 facing the X-ray output device 10, and is an incident window that causes X-rays irradiated from the X-ray output device 10 to enter the interior of the housing 21. The X-ray incident section 22 is a plate-shaped or film-shaped member made of any material that has X-ray transparency, such as a polyimide film. As a polyimide film, for example, a Kapton® sheet can be used. The X-ray incident section 22 is made circular in shape with a diameter of about 5 to 30 mm from the viewpoint of optical adjustment and measuring any position of the sample. The X-ray transmittance of the X-ray incident section 22 is improved if the thickness of the member is thin, while the thickness is set to a range of about 1 to 150 μm from the viewpoint of ensuring sealing strength. The material, diameter and thickness of the X-ray incident section 22 described above are examples and are not limited to these.

[0025] The light emission unit 23 is an emission window that emits emitted light 102, which is light generated by the irradiation of the sample 200, to the outside of the housing 21. When incident X-rays irradiate the sample 200, the light emission unit 23 emits fluorescent X-rays as emitted light 102, and when incident light 101 irradiates the sample 200, it emits reflected light of the incident light 101 as emitted light 102. The light emission unit 23 is a plate-shaped or film-shaped member made of any material that is X-ray transparent or has light transmittance of wavelengths other than X-rays. For example, polyimide film or quartz glass can be used for the light emission unit 23, but a material with light transmittance is appropriately selected depending on the light to be emitted. In this embodiment, the light emission unit 23 is also configured to function as a light injector that directs light from the light introduction device 11 toward the sample 200. The light-emitting section 23 is provided, for example, on the upper surface 21a of the housing 21 facing the light introduction device 11 and the light detection device 12. The light-emitting section 23 is circular in shape with a diameter of approximately 5 to 30 mm, for example, from the viewpoint of optical adjustment and measuring an arbitrary position of the sample 200. The thickness of the light-emitting section 23 is, for example, in the range of approximately 1 to 150 μm in the case of a polyimide film, and approximately 1 mm in the case of plate-shaped quartz glass. Note that the material, diameter, and thickness of the light-emitting section 23 described above are examples and are not limited to these.

[0026] The heating window 24 is provided on the lower surface 21b of the housing 21 facing the heater 34, and is an inlet window that allows heating light irradiated from the heater 34 to enter the interior of the housing 21. The heating window 24 is a plate-shaped member made of any material that has light-transmitting properties to allow the irradiated light from the heater 34 to pass through, such as quartz glass.

[0027] In Figure 2, a representative example is shown where the X-ray incident section 22, the light emission section 23, and the heating window section 24 are all circular in shape. However, as long as the housing 21 can be reduced to a predetermined pressure or less, it may have other shapes such as a rectangle, or some of its shapes may be different. Furthermore, there may be multiple X-ray incident sections 22, light emission sections 23, and heating window sections 24.

[0028] The housing 21 is capable of introducing an active gas into its interior and, as shown in Figure 3, for example, has a gas inlet 25 and a gas outlet 26. The gas inlet 25 is provided to allow the active gas to flow into the housing 21 from the outside. The gas outlet 26 is provided to allow the active gas and the post-reaction gas to flow out of the housing 21 from the inside to the outside. The post-reaction gas is the gas generated inside the housing 21 when the sample 200 reacts with the active gas. A portion of the piping connected to the gas outlet 26 is connected to the gas analyzer 36. For example, if copper foil containing copper oxide is used as the sample 200 and hydrogen gas is introduced as the active gas to heat the sample 200, components such as water will be generated as post-reaction gas due to the reduction of copper oxide. In this case, the gas analyzer 36 can analyze the water and other components in the post-reaction gas.

[0029] The lower electrode 27 is located inside the housing 21 and is the electrode on which the sample 200 to be analyzed is placed. The lower electrode 27 is made of a conductive material such as carbon, tungsten, tantalum, or copper, and is in the shape of a circular plate. The lower electrode 27 forms a pair of electrodes with the upper electrode 29, which is placed at a distance from it. The side of the lower electrode 27 facing the upper electrode 29 is called the opposing surface 27a, and the side opposite the opposing surface 27a is called the back surface 27b, with the sample 200 placed on the opposing surface 27a of the lower electrode 27. The lower electrode 27 is supported by a support portion 28 provided on the side surface 21c of the housing 21, for example, and is insulated from the inner wall of the housing 21. The lower electrode 27 is connected to an ammeter 31 and a thermocouple 32, for example, making it possible to measure the current value and temperature of the lower electrode 27.

[0030] Furthermore, the housing 21 is lined with insulating ceramics, for example, on its inner walls and support parts 28, ensuring insulation between the lower electrode 27 and upper electrode 29 and other components. In addition, various wirings, such as the thermocouple 32, are covered with an insulating coating (not shown). This minimizes measurement noise from the ammeter 31, improving the measurement accuracy in XAFS analysis.

[0031] The lower electrode 27 has its back surface 27b facing the heating window 24, and heating by light irradiation from the heater 34 enables heating of the sample 200 placed on the opposing surface 27a. The lower electrode 27 can also be cooled via the support section 28 as the housing 21 is cooled by the chiller 35.

[0032] The upper electrode 29 is, for example, an annular shape with a through hole 291, allowing incident light 101 to be irradiated onto the sample 200 placed on the lower electrode 27 from the upper surface 21a side of the housing 21. In this embodiment, the through hole 291 of the upper electrode 29 also serves as a path for fluorescent X-rays generated by the irradiation of the sample 200 with incident X-rays 100. The upper electrode 29 can have any shape and configuration that ensures a path for the incident light 101 and the emitted light 102, and may be a frame shape other than an annular shape, or it may be a configuration divided into two or more parts. The upper electrode 29 is, for example, made of a conductive material such as carbon, tungsten, tantalum, or copper, similar to the lower electrode 27. The upper electrode 29 is held by the inner wall on the upper surface 21a side of the housing 21 and a support (not shown). The upper electrode 29 is positioned at a distance from the lower electrode 27 and is connected to the power supply 30 outside the housing 21.

[0033] The power supply 30 applies a voltage of approximately 300V to 1000V between the lower electrode 27 and the upper electrode 29. This suppresses the recombination of the activated gas, which has been ionized by Auger electrons emitted from the sample 200, with electrons when the activated gas is introduced into the housing 21 and the sample 200 is irradiated with X-rays.

[0034] The ammeter 31 measures the current generated when the active gas, ionized by Auger electrons from the sample 200, receives electrons at the lower electrode 27. The thermocouple 32 is a temperature measuring unit that measures the temperature of the sample 200 via the lower electrode 27. The thermocouple 32 is connected to the temperature controller 33 and is used to adjust the temperature of the sample 200. The temperature controller 33 is located outside the housing 21 and is connected to the thermocouple 32 and the heater 34, and adjusts the heating temperature of the sample 200 by the heater 34 as needed based on the temperature of the sample 200 measured by the thermocouple 32.

[0035] The heater 34 is located outside the housing 21 and is a light-irradiation type heating mechanism. The heater 34 is, for example, a halogen heater, but it is sufficient if it can irradiate light onto the back surface of the lower electrode 27 to heat it, and other known light-irradiation type heating mechanisms may also be used. The heater 34 is connected to the temperature controller 33, and the output such as the power value is arbitrarily adjusted according to the target temperature of the sample 200. The heater 34 irradiates heating light 103 onto the back surface 27b of the lower electrode 27 through the heating window 24. As a result, compared to the case where an electric heater is used, the generation of electromagnetic noise during heater temperature control is suppressed, and the measurement accuracy of the ammeter 31 is improved.

[0036] It is also conceivable to heat the sample 200 by directly irradiating the surface with light. However, in this case, if the reflectivity of light on the surface of the sample 200 differs, the light absorption efficiency will change, resulting in an unstable surface temperature of the sample 200. Therefore, the heater 34 irradiates light onto the back surface 27b of the lower electrode 27, heating the sample 200 via the lower electrode 27 to stabilize the surface temperature of the sample 200. If achieving a higher temperature is more important than the stability of the surface temperature of the sample 200, in addition to heating the sample 200 via the lower electrode 27 by the heater 34, heating by directly irradiating the surface of the sample 200 with light using another light source may also be performed.

[0037] The chiller 35 is a cooling mechanism provided in the housing 21. The chiller 35 is, for example, positioned on the lower surface 21b side of the housing 21 and connected to an external refrigeration cycle (not shown), to which a low-temperature refrigerant is supplied. By cooling the housing 21, the chiller 35 can bring the area excluding the vicinity of the sample 200 to a constant temperature, thereby improving the measurement accuracy of the ammeter 31. The chiller 35 may also be attached to the upper surface 21a side, for example, and its attachment location can be changed as appropriate.

[0038] The gas analyzer 36 is connected to the gas outlet 26 and is a gas analysis unit that analyzes the introduced active gas and the post-reaction gas. For example, when hydrogen is used as the active gas, the gas analyzer 36 may use a quadrupole mass spectrometer or an infrared absorption detector capable of detecting hydrogen components and other post-reaction gas components, but it is not limited to this and may be appropriately changed depending on the type of gas to be detected.

[0039] The above describes the basic configuration of XAFS analysis system 1.

[0040] [Heating by light irradiation] The back surface 27b of the lower electrode 27 was heated by the heater 34, and the internal temperature of the lower electrode 27 and the surface temperature of the opposing surface 27a were measured. The results shown in Figures 4 and 5 were obtained. This heating test was conducted under the following conditions.

[0041] <Test Conditions> • Active gas: A mixed gas based on helium, containing 3.8% hydrogen. • Flow rate of activated gas: 20 sccm • Temperature measurement: The temperature inside the lower electrode 27 and the opposing surface 27a are measured using a thermocouple. • Heater: Halogen lamp HSH-60 / F30 (manufactured by Fintech Co., Ltd.) The halogen lamp has a voltage of 24V, an outer diameter of φ60mm, a power of 300W, a focal length of f30, a beam diameter of φ7.2mm, and a power density of 135W / cm². 2 The following was used. In addition, the lower electrode 27 was made of carbon.

[0042] As a result of the heating test, it was confirmed that the temperature of the opposing surface 27a (hereinafter referred to as "electrode surface temperature") was heated to at least 612°C, although the temperature of the lower electrode 27 was lower than the internal temperature of the lower electrode 27, as shown in Figure 4. Specifically, when the internal temperature of the lower electrode 27 was 49°C, 125°C, 219°C, 317°C, 412°C, 498°C, 582°C, and 668°C, the electrode surface temperatures were 47°C, 119°C, 207°C, 298°C, 385°C, 462°C, 536°C, and 612°C, respectively. Furthermore, when the internal temperature of the lower electrode 27 and the electrode surface temperature were plotted, a nearly linear relationship was obtained between these temperatures, as shown in Figure 5. Note that "lower electrode surface temperature" in Figures 4 and 5 refers to the electrode surface temperature. Furthermore, when the temperature of the lower electrode 27 was controlled by raising its temperature at a rate of 10°C / min up to the set temperature, the internal temperature of the lower electrode 27 was measured at set temperatures of 200°C, 250°C, 300°C, 350°C, and 400°C, and in all cases the internal temperature matched the set temperature.

[0043] Furthermore, while the lower electrode 27 has a thickness on the order of millimeters, for example several millimeters (4 mm in this embodiment), the sample 200 has a thickness on the order of micrometers, for example several tens of micrometers, making it significantly thinner than the lower electrode 27. Therefore, the sample 200, which is placed on the surface 27a opposite the lower electrode 27, has a temperature that is approximately the same as the electrode surface temperature. These results suggest that the surface temperature of the sample 200 can be controlled to a desired value by heating the back surface 27b of the lower electrode 27 with a light-irradiation heater 34 from outside the housing 21.

[0044] [Noise reduction using XAFS analysis system] Next, we will explain the results of XAFS analysis performed using copper foil as sample 200.

[0045] As a comparative example, XAFS analysis of copper foil was performed using a general transmission method, yielding the results shown in Figure 6. The above transmission method involved using BL2S3 at the Aichi Synchrotron Radiation Center, performing XAFS measurements of the K absorption edge of Cu while sweeping the light energy in the range of 8800 eV to 10000 eV at 0.31 eV intervals. Furthermore, the results shown in Figure 6 were measured at 25°C and represent the XANES region, which is sensitive not only to the local structure but also to the chemical state.

[0046] In transmission spectroscopy, the copper foil exhibited two characteristic peaks: (A) a shoulder peak around 8980 eV, and (B) a white line peak splitting around 9000 eV, both of which represent the metallic state of copper, as shown in Figure 6. In Figure 6 and Figure 7 (described later), the peak positions are indicated by arrows to make the peak positions easier to understand. The XAFS spectra in Figures 6 and 7 were normalized by fitting the signal before the absorption edge using Victoreen's equation, subtracting it as background, and ensuring that the value after the absorption edge is 1.

[0047] Next, using the XAFS analysis system 1, sample 200 (copper foil) was heated to 25°C by light irradiation with heater 34, and the conversion electron yield was measured using XAFS. The results shown in Figure 7 were obtained. In the conversion electron yield XAFS method using the XAFS analysis system 1, as shown in Figure 7, the copper foil showed peak splitting of (A) a shoulder peak around 8980 eV and (B) a white line around 9000 eV, yielding results similar to those obtained by the transmission method.

[0048] Furthermore, using copper oxide powder (Cu2O), in which Cu is in a monovalent chemical state, and copper oxide powder (CuO), in which Cu is in a divalent chemical state, as sample 200, XAFS measurements were performed using the XAFS analysis system 1, and the results shown in Figure 8 were obtained. The peak near the rise of the K absorption edge of Cu, enclosed by the dashed line in Figure 8, shifted to the higher energy side in the order of Cu, Cu2O, and CuO, that is, as the valence of Cu increased. In addition, the two split peaks of the white line around 9000 eV observed for metallic Cu became one peak for Cu2O and CuO, and the peak became higher as the valence of Cu increased. Thus, the XAFS analysis system 1 can measure chemical states other than the metallic state of Cu and can also distinguish between those chemical states.

[0049] For powder samples 200, XAFS analysis is possible by preparing a lower electrode 27 having multiple recesses 271 on the opposing surface 27a side, as shown in Figure 9, and placing the sample in the recesses 271. The multiple recesses 271 are, for example, fine cylindrical in shape, and their diameter and depth can be determined according to the size of the sample 200 so that powder or particulate samples 200 can be placed in them. For example, in the case of cylindrical recesses 271, it is preferable that both the diameter and depth be about 1 to 30 μm, taking into account the processing time. Note that Figure 9 shows only the central region of the lower electrode 27 where the sample 200 is placed.

[0050] Furthermore, when XAFS measurements were performed on copper foil containing copper oxide and metallic copper using the comparative example's XAFS analysis system, which heats the lower electrode and the sample using an electrically heated heater, the results shown in Figure 10 were obtained. The comparative example's XAFS analysis system has the same configuration as, for example, the one described in Patent Document 1, and an electrically heated heater is placed near the lower electrode where the sample is placed. In the comparative example's XAFS analysis system, the XAFS spectrum, as shown in Figure 10, was an oscillating waveform with numerous noises that are not material-derived components with an intensity distribution of 0.1 or higher. This is thought to be due to the fact that when an electrically heated heater is used, electromagnetic noise is easily superimposed on the conversion electron signal during switching during temperature control, due to the measurement principle of the conversion electron yield method. In such an XAFS spectrum, it is difficult to identify the structure of the shoulder peak and white line and the material components.

[0051] On the other hand, since the XAFS analysis system 1 employs a heating method using light irradiation from the heater 34, as described above, noise in the XAFS spectrum is reduced, and the chemical state can also be determined.

[0052] [Comparison with the transmission method] Next, we will describe the results of a comparison between transmission method and XAFS measurement using XAFS analysis system 1, using copper foil coated with copper oxide as sample 200.

[0053] First, a 3 μm thick copper foil was heated in air at 250°C to prepare sample 200. A portion of sample 200 was thinned using focused ion beam (FIB) to prepare a cross-sectional sample. Scanning transmission electron microscope (STEM) images, shown in Figure 11, and elemental composition (EDS) images of oxygen and copper in the same field of view, shown in Figures 12 and 13, were obtained from this sample. In Figures 11 to 13, the left side is the surface of the sample, and the right side is the bulk. According to the STEM image in Figure 11, sample 200 was a film with varying density, but a surface layer with a thickness of approximately 150 nm to 200 nm was formed from the surface. Furthermore, as shown in Figure 12, a large amount of oxygen was detected mainly in the surface layer of sample 200, and as shown in Figure 13, copper was detected in the surface layer and in regions deeper than the surface, with a large amount of copper detected in the deeper regions. Therefore, the surface layer was copper oxide, and the bulk was metallic copper.

[0054] Then, XAFS measurements were performed on the above sample 200 using the transmission method and the XAFS analysis system 1, and the results shown in Figure 14 were obtained. The example shown in Figure 14 was obtained using the XAFS analysis system 1. In the general transmission method, as shown in Figure 14, a shoulder peak at 8980 eV and a peak splitting of the white line around 9000 eV were observed, which are due to metallic copper, while no peaks due to copper oxide were observed. In contrast, in the example, a shoulder peak at 8980 eV and a single broad peak around 9000 eV were observed. These results indicate that the XAFS analysis system 1 can observe the chemical state of copper at a depth of several hundred nanometers from the surface, which is difficult to observe with the transmission method.

[0055] Next, a gas mixture of helium gas and 3.8% hydrogen was used as the active gas, and this active gas was circulated through the housing 21 at a rate of 20 sccm. Subsequently, the internal temperature of the lower electrode 27 was heated from 25°C to 400°C using the heater 34, and the reduction reaction process of copper on the surface of the sample 200 was analyzed. The XAFS measurement results obtained using this XAFS analysis system 1 are shown in Figure 15. The XAFS spectrum shows a single white line peak around 9000 eV between 300°C and 350°C, indicating a change from copper oxide to metallic copper. The surface temperatures of sample 200 in this analysis were 280°C, 325°C, and 371°C at 300°C, 350°C, and 400°C, respectively, for the lower electrode 27.

[0056] Furthermore, in order to quantitatively evaluate the proportion of copper oxide, linear combination fitting (LCF) was performed on the XAFS spectra of metallic Cu and Cu2O, yielding the results shown in Figure 16. As the temperature increased from 25°C to 400°C, the proportion of metallic Cu increased while the proportion of Cu2O decreased. These results indicate that the XAFS analysis system 1 can evaluate the reduction process of copper at a depth of several hundred nanometers from the surface by heating with a gas containing hydrogen, which has reducing properties, as the active gas, and performing surface analysis during the gas reaction during heating.

[0057] According to this embodiment, the XAFS analysis system 1 comprises a lower electrode 27 on which the sample 200 is placed, and a heater 34 that heats the sample 200 by irradiating the lower electrode 27 with light from the back surface 27b side opposite to the upper electrode 29. In this XAFS analysis system 1, by providing the heater 34 as a heating mechanism that heats the sample 200 by light irradiation instead of an electrically heated heater, the generation of electromagnetic noise caused by the heating of the sample 200 is suppressed, and thus the noise of the conversion electron signal can be reduced.

[0058] Furthermore, the X-ray absorption analyzer 20, which constitutes the XAFS analysis system 1, further comprises a housing 21, a gas inlet 25 into which an active gas can be introduced into the housing 21, and a gas outlet 26 for releasing the active gas to the outside of the housing 21. The X-ray absorption analyzer 20 further comprises a gas analyzer 36 for analyzing the active gas flowing out from the gas outlet 26. This allows for dynamic observation of the sample 200 when a gas containing hydrogen, which has a reducing effect, is used as the active gas, and enables real-time analysis of changes in the sample 200 that cannot be confirmed by static observation.

[0059] The XAFS analysis system 1 further includes a photointroduction device 11 that irradiates the sample 200 with light of a different wavelength than X-rays, and a photodetector 12 that detects the light generated by the irradiation. This allows for the irradiation of the sample 200 with light other than X-rays, such as ultraviolet light, visible light, or infrared light, and the detection of the light generated by this irradiation with the photodetector 12, enabling analyses other than X-ray analysis, such as spectroscopic analysis, and other evaluations such as visual observation.

[0060] If the X-ray absorption analyzer 20 has a lower electrode 27 with a recess 271, a sample 200 in powder or particulate form can be placed in the recess 271. Furthermore, because the lower electrode 27 has a recess 271, electrical contact is ensured even when the conductivity of the sample 200 is low, and the sample 200 can be stably fixed even when heating or introducing an active gas.

[0061] (Other embodiments) This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence range. In addition, various combinations and forms, as well as other combinations and forms including one, more, or less of those elements, fall within the scope and concept of this disclosure.

[0062] In the above embodiment, the XAFS analysis system 1 had both the photointroducer 11 and the photodetector 12 positioned on the upper surface 21a of the housing 21, but their arrangement may be changed. The XAFS analysis system 1 may include, for example, a photodetector 12 for detecting fluorescent X-rays and a photodetector 12 for detecting infrared rays, and these may be positioned facing different surfaces of the housing 21, as shown in Figure 17. In this case, for example, the housing 21 may have a configuration having two light-emitting sections 23, which are provided on the upper surface 21a and the side surface 21c, respectively. The XAFS analysis system 1 only needs to be configured to allow heating of the sample 200 by light irradiation from the back surface 27b of the lower electrode 27, and other components related to the detection of emitted light 102 and the inflow and outflow of active gas may be changed as appropriate.

[0063] It goes without saying that, in each of the above embodiments, the elements constituting the embodiment are not necessarily essential unless explicitly stated to be particularly essential or unless they are clearly considered essential in principle. Furthermore, in each of the above embodiments, when numerical values ​​such as the number, numerical values, quantities, or ranges of the components of the embodiment are mentioned, the embodiment is not limited to those specific numbers unless explicitly stated to be particularly essential or unless it is clearly limited to a specific number in principle. Furthermore, in each of the above embodiments, when the shape, positional relationship, etc., of the components are mentioned, the embodiment is not limited to those shapes, positional relationships, etc., unless explicitly stated or unless it is clearly limited to a specific shape, positional relationship, etc., in principle. [Explanation of symbols]

[0064] 12...Photodetector, 21...Housing, 22...X-ray inlet, 23...Light outlet, 25...Gas inlet, 26...Gas outlet, 27...Lower electrode, 27b...Back, 271...Recess, 29...Upper electrode, 34...Heater (heating mechanism), 36...Gas analyzer

Claims

1. A sealed enclosure (21) and A lower electrode (27) is provided within the housing on which the sample is placed, An upper electrode (29) is provided within the housing and is positioned at a distance from the lower electrode with the sample in between, An X-ray absorption analyzer comprising: a heater (34) that heats the sample by irradiating the lower electrode with light from the back side, with the side of the lower electrode opposite to the upper electrode being the back side (27b).

2. The housing is provided with an X-ray injector (22) that injects X-rays into the interior of the housing toward the sample, The X-ray absorption analyzer according to claim 1, further comprising: a light incident section (23) provided in the housing at a position different from the X-ray incident section, which causes light of a different wavelength than X-rays to be incident into the housing toward the sample.

3. The housing is provided with a gas inlet (25) through which an active gas can be introduced inside, The X-ray absorption analyzer according to claim 1, further comprising a gas outlet (26) provided in the housing for releasing the active gas introduced into the housing to the outside of the housing.

4. The X-ray absorption analyzer according to claim 3, wherein the gas inlet allows the active gas containing hydrogen to be introduced into the housing.

5. The X-ray absorption analyzer according to claim 3 or 4, further comprising a gas analysis unit (36) for analyzing the active gas flowing out from the gas outlet.

6. The X-ray absorption analyzer according to claim 1, further comprising a photodetector (12) for detecting light from the sample.

7. The X-ray absorption analyzer according to claim 6, wherein the photodetector is an X-ray fluorescence detector for detecting X-ray fluorescence.

8. The X-ray absorption analyzer according to claim 6, wherein the light detection device is an infrared photodetector for detecting infrared rays.

9. The X-ray absorption analyzer according to claim 1, wherein the lower electrode has a recess (271) in which the sample is placed.

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