Patent Grant
8787525
1. Field of the Invention
The present invention relates to an X-ray monochromator, a method of manufacturing the same and an X-ray spectrometer using such an X-ray monochromator.
2. Description of the Related Art
An X-ray monochromator is employed in an X-ray spectrometer having a configuration as illustrated in
2d sin θ=nλ (Formula 1)
(where d: structural period, θ: incident angle, angle of diffraction (Bragg angle), n: degree of diffraction, λ: X-ray wavelength).
The X-ray monochromator 110 has a structural periodicity directed to point B at each reflection position thereof so as to satisfy the requirement of the formula 1, the structural period being d in the formula 1. Namely, the X-ray monochromator 110 is formed by using a member that is curved with a radius of curvature equal to the diameter (2R) of the Rowland circle 14 and made of a material that shows a periodicity in the normal directions of the curved surface.
Additionally, the X-ray monochromator 110 preferably has a surface profile stretching along the Rowland circle 14 so that reflected X-rays 17 are focused at the position of the X-ray detector 13. A monochromator arranged in such a way is referred to as Johansson monochromator. However, Johann monochromators having a surface profile stretching along a circle 15 with a radius equal to the diameter (2R) of the Rowland circle as illustrated in
When the wavelengths of X-rays are relatively long, artificial multilayer film mainly made of an inorganic material and having a structural period of several nanometers is often selected as structurally periodic material to be used for an X-ray monochromator from the viewpoint of easiness of modifying the structural period. A material having a low electron density such as an organic material for artificial multilayer film in order to improve the spectroscopic performance of X-rays can be used. Japanese Patent Application Laid-Open No. S63-94200 discloses an X-ray monochromator using clay having a layered structure and including organic cations in layered spaces and mica minerals as structurally periodic material.
On the other hand, Japanese Patent Application Laid-Open No. 2005-246369 (which corresponds to U.S. Pat. No. 7,618,703) discloses a porous film having a periodic structure formed via self-assembly of molecules and an application thereof to X-ray optical elements. The disclosed porous film shows a symmetric reflection plane that is directed in a same direction over the entire film and has an axis of rotation (n=6). X-ray diffractions in in-plane directions of such a porous film attributable to the symmetry of the film are applied to X-ray devices. A splitter for which X-rays are made to enter such a porous film on the condition of total reflection so that the splitter separates totally reflected X-rays from X-rays diffracted in-plane and a modulator utilizing that the in-plane intensity of diffracted X-rays changes as a function of the direction of X-rays entering such a porous film have been reported.
However, the inventions of the above listed patent literatures have problems and require improvements. An X-ray monochromator disclosed in Japanese Patent Application Laid-Open No. S63-94200 can sometimes show a limitative spectroscopic performance of X-rays because the X-ray monochromator employs an organic substance for a layer having a low electron density. A material having an electron density lower than an organic substance is required to improve the X-ray spectroscopic performance.
On the other hand, it is very difficult to form a porous film disclosed in Japanese Patent Application Laid-Open No. 2005-246369 on a curved surface. A so-called rubbing process of rubbing a polymer layer formed on a substrate in a single direction is needed to form such a porous film. However, it is difficult to uniformly execute a rubbing process on a curved surface such as a curved surface of an X-ray monochromator and hence it is difficult to apply a porous film of Japanese Patent Application Laid-Open No. 2005-246369 to an X-ray monochromator.
In view of the above-identified technical background, it is therefore the object of the present invention to provide an X-ray monochromator showing an excellent X-ray spectroscopic performance. In an aspect of the present invention, there is provided an X-ray monochromator including: a substrate having a concave surface; and an inorganic oxide film formed on the concave surface and having a plurality of pores, in which the plurality of pores of the inorganic oxide film are laid periodically in a stacked manner in the normal directions of the concave surface, and in which the plurality of pores are cylindrical.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Now, preferred embodiments of the present invention will be described below by referring to the accompanying drawings.
As a result of intensive research efforts, the inventors of the present invention found that an X-ray monochromator showing an X-ray spectroscopic performance than ever and an X-ray spectrometer including such an X-ray monochromator can be provided by using, a porous inorganic oxide film having a plurality of cylindrical pores, or a porous inorganic oxide film having a plurality of spherical pores showing a local porous structure with different symmetric reflection planes facing to directions that are different from each other.
An embodiment of X-ray monochromator and that of X-ray spectrometer according to the present invention will be described by referring to
The X-ray monochromator of this embodiment is formed by using a porous inorganic oxide film that is characterized by containing air having an electron density much lower than organic substances and forming a periodic structure. For this reason, the conditions on which X-ray diffraction (reflection) takes place, or the incident angle of X-rays and the wavelength range of X-rays, are narrowed according to Darwin-Prins formula so that the wavelength resolution of X-rays can be improved.
The porous inorganic oxide film of this embodiment is prepared by applying a precursor reactive solution onto the top surface of the substrate and by way of a reaction. Therefore, the smallest arrangement for forming the film including molecules or atoms and then the porous inorganic oxide film becomes very flat and smooth. From this point of view, the present invention can provide an X-ray monochromator having an excellent X-ray wavelength resolution.
For the purpose of this embodiment, pores (cylindrical pores and spherical pores) refer to those whose insides are void and whose outer walls are covered by an inorganic oxide. While some of the pores may shrink during the manufacturing process as the film contracts, the pores (the cylindrical pores or the spherical pores) of this embodiment can show an aspect ratio of not less than 0.30 in order to make them have a uniform structural period in the normal directions.
The porous inorganic oxide film of this embodiment can be manufactured by means of a hydrothermal method of bringing a reactive solution containing a surface active agent including an organic substances for providing templates of pores, a precursor of the inorganic component and acid into contact with the top surface of a substrate and holding it there or a process of applying a solution containing a surface active agent, a precursor of an inorganic oxide, acid and a solvent onto a substrate so as to cause an organic-inorganic complex film to be formed while the solvent evaporates. A technique of spin coating or dip coating may be employed for applying the solution (reactive solution).
To obtain a porous film, the organic substance is removed from a film prepared in the above-described manner to produce pores in the parts where the organic substance existed. The organic substance can be removed by any known means. For example, a technique of baking the film in an oxygen atmosphere, a technique of extracting the organic substance by means of a solvent or a technique of ozone oxidation may be employed. While a baking process is generally employed, a process of extraction by solvent or ozone oxidation may alternatively be adopted to remove the organic substance when it is not allowed to expose the film and the substrate to high temperatures at the time of baking.
A porous inorganic oxide film that can be used for this embodiment may be a film where the organic substance remains in the insides of (some of) the pores formed in the inorganic oxide or a porous film from which the organic substance has been completely removed so long as it can provide the required function of an X-ray monochromator. When the structural periods in the normal directions are reduced as the porous film contracts in the normal directions of the top surface of the substrate as a result of removal of the organic substance, the structural periods in the normal directions can be adjusted by selecting an appropriate process for removing the organic substance in terms of baking temperature so as to accommodate the X-ray wavelength region that is the object of spectrometering.
A porous inorganic oxide film to be used for this embodiment can be formed by way of a relatively short process of applying a precursor solution onto a substrate. Thus, the manufacturing time can be reduced so that an X-ray monochromator can be provided at low cost. Furthermore, a porous inorganic oxide film to be used for this embodiment can be prepared by way of a wet process as described above unlike artificial multilayer films that are generally prepared by way of a dry process, so that an X-ray monochromator can be provided in an easy manner without requiring any accurate process control.
Inorganic oxides that can be used for the multiple inorganic oxide film of this embodiment include silica, titania and zirconia, although they are not subjected to any particular limitations so long as they can form a porous film. A material having a low electron density can be employed from the viewpoint of X-ray wavelength resolution so long as the inorganic oxides serves to detect reflected X-rays with a sufficient intensity. For example, the X-ray wavelength resolution can be improved by using silica.
Additionally, since the porous film of the X-ray monochromator of this embodiment is formed by using an inorganic oxide, the porous film is free from the fear of degradation of spectroscopic performance of X-rays due to oxidation/degradation that arises as a result of X-ray irradiations. Thus, the present invention can provide a stable X-ray monochromator.
Organic substances for providing templates of pores for forming a porous inorganic oxide film for this embodiment are not subjected to any particular limitations so long as they can form a film for the purpose of this embodiment. Examples of such organic substances include amphiphilic molecules such as those of surface active agents. When the organic substance to be used is appropriately selected, the sizes of the aggregates of the organic substance in the film can be controlled to control the structural periods in the normal directions of the film. For example, if a nonionic surface active agent containing polyethylene oxide as hydrophilic part is employed for organic molecules, the structural periods in the normal directions of the film increase as the chain length of the polyethylene oxide increases. Thus, the structural periods in the normal directions can be adjusted by selecting appropriate organic molecules according to the X-ray wavelength region that is the object of spectroscopy.
Materials that can be used for the substrate are not subjected to any particular limitations, for example, including glass, so long as the materials are not damaged in the process of preparing the film.
In this embodiment, the profile of the top surface of the substrate is a curved concave surface with a radius of curvature equal to the diameter of the Rowland circle. In
The top surface of the substrate is a surface where the film is formed and can be subjected to a surface treatment in order to improve the wettability of the reactive solution so as to prepare a uniform and smooth film. When, for example, a hydrophilic reactive solution is employed, the organic substance on the surface may be removed typically by ozone asking in order to make the top surface of the substrate hydrophilic. Note that the film on the concave surface can produce cracks when the top surface of the substrate is subjected to a rubbing process particularly if the film has spherical pores.
The characteristics of an X-ray monochromator formed by using a porous film having cylindrical pores (porous film with cylindrical pores) and those of an X-ray monochromator formed by using a porous film having spherical pores (porous film with spherical pores) will be described below. It recommended to select an X-ray monochromator having an appropriate film by considering these characters and the specifications of the X-ray monochromator that is required for an X-ray spectrometer (the size of the monochromator, the diameter of the Rowland circle, the wavelength range, the wavelength resolution and the X-ray reflection intensity and so on).
Table 1 shows the characteristics of porous films having cylindrical pores and those of porous films having spherical pores. The X-ray reflection intensity, the X-ray wavelength resolution and so on are determined in a complex manner by these characteristics.
Now, an X-ray spectrometer formed by using this embodiment of X-ray monochromator will be described below.
The X-ray spectrometer of this embodiment is characterized by including this embodiment of X-ray monochromator, an X-ray source and an X-ray detector.
In the X-ray spectrometer, an X-ray source 12, an X-ray detector 13 and an X-ray monochromator 11 are arranged in a manner as illustrated in
When the wavelengths of X-rays are relatively long, X-rays can be absorbed and/or scattered by the gas in the spectrometer depending on the optical path lengths of X-rays. Therefore, the parts where the X-ray source, the X-ray detector and the X-ray monochromator are arranged can be covered by a chamber and the internal pressure can be reduced.
While this embodiment is described below by low of examples, this embodiment is by no means limited to the examples.
In this example, a cylindrically curved monochromator of a porous film having cylindrical pores is prepared by applying a reactive solution containing a surface active agent and a silica precursor onto a substrate.
Firstly, a glass substrate 33 having a curved concave surface as illustrated in
A reactive solution for preparing a porous film having cylindrical pores is prepared. 22.9 g of polyethylene oxide 10 hexadecyl ether is dissolved in 900 mL of isopropyl alcohol, while being stirred, and 28 mL of hydrochloric acid (0.1 M), 35 mL of ultrapure water and 156 mL of tetraethoxysilane are added thereto to prepare a reactive solution. The reactive solution is held to room temperature for 2 hours while the reactive solution is being stirred.
The glass substrate 33 is immersed in the reactive solution with the surface 3R thereof illustrated in
When the prepared X-ray monochromator is analyzed by way of a θ-2θ scanning X-ray diffraction observation with a Bragg-Brentano arrangement, using an X-ray microbeam (3 μmφ, 8 keV), a diffraction peak indicating that the structural period in the normal direction is 5.24 nm at each position of films can be confirmed.
The X-ray monochromator is introduced into an electric furnace and the temperature is raised at a rate of 2° C./minute until the temperature gets to 400° C. When the temperature gets to 400° C., the X-ray monochromator is held to that temperature for 10 hours and then the temperature is lowered at a rate of 2° C./minute until the temperature gets to room temperature. After the baking, the monochromator is analyzed by way of a θ-2θ scanning X-ray diffraction observation with a Bragg-Brentano arrangement, using an X-ray microbeam (3 μmφ, 8 keV), it can be confirmed that the structural period in the normal direction is contracted to 3.33 nm at each position of films. Additionally, it can be confirmed that the organic substance is removed from the X-ray monochromator by means of an infrared absorption spectrum.
An X-ray source 12 (fluorescent X-rays from a sample containing carbon, nitrogen and hydrogen respectively by 30%, 10% and 60%), an X-ray detector 13 and the prepared X-ray monochromator 11 are arranged on a Rowland circle with a radius of 100 nm as illustrated in
In this example, a cylindrically curved monochromator of a porous film having spherical pores is prepared by applying a reactive solution containing a surface active agent and a silica precursor onto a substrate.
Firstly, a glass substrate 33 having a curved concave surface as illustrated in
A reactive solution for preparing structure films is prepared. 27.5 g of polyethylene oxide 10 hexadecyl ether is dissolved in 500 mL of ethanol, while being stirred, and 25 mL of hydrochloric acid (0.1 M), 25 mL of ultrapure water and 112 mL of tetraethoxysilane are added thereto to prepare a reactive solution. The reactive solution is held to room temperature for 2 hours while the reactive solution is being stirred.
The glass substrate 33 is immersed in the reactive solution with the surface 3R thereof illustrated in
When analyzed by way of a θ-2θ scanning X-ray diffraction observation with a Bragg-Brentano arrangement, using an X-ray microbeam (3 μmφ, 8 keV), a diffraction peak indicating that the structural period in the normal direction is 5.65 nm at each position can be confirmed. Additionally, a diffraction pattern can be detected, if weak, in in-plane directions of a porous of films prepared on a silicon wafer plane under similar experimental conditions by a φ-2θX scanning X-ray diffraction observation (X-ray incident angle: 0.2°) and no remarkable peak can be found on the rocking curve as a result of φ scanning at the position (2θX=1.23°) where the diffraction pattern is detected. This means that a plurality of local pore structures with different symmetric reflection planes exist in a spherical pore silica porous film prepared under these experimental conditions.
The X-ray monochromator is introduced into an electric furnace and the temperature is raised at a rate of 2° C./minute until the temperature gets to 550° C. When the temperature gets to 550° C., the X-ray monochromator is held to that temperature for 10 hours and then the temperature is lowered at a rate of 2° C./minute until the temperature gets to room temperature. After the baking, the monochromator is analyzed by way of a θ-2θ scanning X-ray diffraction observation with a Bragg-Brentano arrangement, using an X-ray microbeam (3 μmφ, 8 keV), it can be confirmed that the structural period in the normal direction is 4.26 nm at each position of films. Additionally, it can be confirmed that the organic substance is removed from the X-ray monochromator by means of an infrared absorption spectrum or the like.
An X-ray source 12 (fluorescent X-rays from a sample containing carbon, nitrogen and hydrogen respectively by 30%, 10% and 60%), an X-ray detector 13 and the prepared X-ray monochromator 11 are arranged on a Rowland circle with a radius of 100 nm as illustrated in
In this comparative example, a spherically curved monochromator is prepared by using synthetic mica and the performance thereof is examined.
Firstly, a glass substrate 33 having a curved concave surface as illustrated in
Then, a coating solution to be applied to the substance is prepared. 10 g of synthetic mica sodium taeniolite is added to 50 mL of n-butylamine hydrochloride solution (0.4 M) and the solution is stirred for 2 hours. After being washed for several times with purified water and subjected to a starring process, 200 mL of aqueous solution of polyoxyethylene lauryl amine hydrochloride (5 wt %) is added and subjected to an ion exchange process for 24 hours. The obtained suspension is dehydrated under reduced pressure by means of a Büchner funnel and washed for several times with purified water. The washed product is dried at 80° C., put into benzene and dispersed by means of a homogenizer. The benzene suspension is applied to the above substrate and dried firstly at room temperature and subsequently at 110° C.
When the prepared X-ray monochromator is analyzed by way of a θ-2θ scanning X-ray diffraction observation, using an X-ray microbeam (3 μmφ, 8 keV), it can be confirmed that the structural period in the normal direction is 3.48 nm at each position of films. It can also be found by means of a contact surface profilometer that the surface coarseness of the film is 850 nm at maximum height Ry.
Then, an X-ray source 12 (fluorescent X-rays from a sample containing carbon, nitrogen and hydrogen respectively by 30%, 10% and 60%), an X-ray detector 13 and the prepared X-ray monochromator 11 are arranged on a Rowland circle with a radius of 100 nm as illustrated in
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Applications No. 2009-272882, filed Nov. 30, 2009, No. 2010-202048, filed Sep. 9, 2010 which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-272882 | Nov 2009 | JP | national |
| 2010-202048 | Sep 2010 | JP | national |
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| Number | Date | Country | |
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