JP2968993B2 - X-ray spectrometer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an X-ray spectrometer capable of performing X-ray diffraction measurement using X-rays of a plurality of wavelengths at a time.

[Conventional technology]

X-ray diffraction is a general evaluation method in structural analysis of crystals and amorphous materials. In X-ray diffraction, an X-ray spectroscope is used to monochromatic or collect X-rays. As the X-ray spectrometer, there are known a reflection type perfect crystal, a transmission type perfect crystal, a mosaic crystal, a curved crystal (Johanson type, Johan type) and the like. In addition, in the reflection type flat perfect crystal, an asymmetric cut type, a channel cut type, or a combination thereof is generally used.

On the other hand, in the X-ray diffraction, the anomalous dispersion method is a powerful method for analyzing the structure of a substance composed of a plurality of types of elements. In this case, measurement is repeated a plurality of times using X-rays having a wavelength near the absorption edge of each atom constituting the substance.

[Problems to be solved by the invention]

As described above, when performing X-ray diffraction by the anomalous dispersion method, the same measurement must be repeated a plurality of times while changing the X-ray source (wavelength). Therefore, it takes a long time to measure the weak diffraction intensity, and the material changes during the measurement.
At present, various difficulties are occurring.

The present invention has been made in view of such problems,
It is an object of the present invention to provide an X-ray spectrometer capable of performing X-ray diffraction of a plurality of wavelengths at one time.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, a crystal layer on the surface is composed of a plurality of stacked crystal layers, the crystal layer on the surface has a larger lattice spacing than the crystal layer on the lower side, and diffracts a long wavelength component of the incident X-ray beam. The thickness of each crystal layer is set so as to be equal to or slightly larger than the extinction distance determined by the X-ray wavelength at which each crystal layer causes diffraction and the index of reflection. An X-ray spectrometer is provided.

[Action]

In the X-ray spectrometer of the present invention, since a crystal layer closer to the surface has a longer lattice spacing, it is sequentially diffracted from long wavelength components, and short wavelength components reach the crystal layer where diffraction occurs and are diffracted. At this time, since the thickness of each crystal layer is set to a specific value, it is possible to efficiently extract each diffraction X-ray. Therefore, an X-ray flux having sufficient intensity including only a specific plurality of wavelengths can be obtained, and the above-mentioned problem is solved by using this X-ray spectroscope.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples. FIG. 1 is a conceptual diagram of an X-ray spectrometer of one embodiment according to the present invention, corresponding to two wavelengths. This X-ray spectrometer is composed of a crystal layer a on the surface and a crystal layer b on the lower part. The crystal layer a is made of a substance having a larger lattice spacing than the crystal layer b.
The thickness of each of the crystal layers a and b is equal to the extinction distance (generally, this distance is several μm to several tens μm) determined by the X-ray wavelength at which each crystal layer causes diffraction and the index of reflection. Or slightly larger.
By doing so, most of the wavelength components diffracted by the respective crystal layers a and b are diffracted and can be efficiently extracted, and an X-ray flux with high intensity can be obtained.

In the X-ray spectrometer having the above configuration, continuous X
When a line is incident at an angle θ, λ _a = 2d _a sin θ (d _a
X-rays having a wavelength determined by the lattice spacing of the a layer) are diffracted,
lambda _a more short-wave X-rays transmitted through, with b layer lambda _{b =} 2d _b sin [theta
(D _b is the lattice spacing of the layer b) X-ray of the wavelength of the diffracted.
Therefore, the direction of the angle 2θ from the incident X-ray lambda _a and lambda _b
Are diffracted.

Next, a specific example of the measurement using the X-ray spectrometer will be described. Here, the X-ray spectrometer is of a Bragg case (FIG. 2 (A)).

Using a Si (111) crystal (d _a = 3.1355 °) for the a layer and a LiF (200) crystal (d _b = 2.01 °) for the b layer, the surfaces of the two crystals are pressed without gaps, and X-rays are applied. The spectroscope 1 was used. The thickness of each layer is as follows: a layer 5.7 μm (extinction distance 5.67 μm), b layer 7
μm (extinction distance 7.00 μm). Here, it is needless to say that the two layers a and b should be formed by epitaxial growth as long as they are crystals that can be epitaxially grown.

The measurement system was arranged as shown in FIG. 2 is a continuous X-ray source,
3 is a sample and 4 is a detector. In this example, sample 3 is AS
_{A 2} Se ₃ film was used. The K absorption edge of As is 11.865 KeV (λ = 1.045
Å). In FIG. 2, if θ = 15.14 °, λ _a
= 1.6379 °, λ _b = 1.05 °, and the detector 4 can measure the anomalous variance with respect to As at one time.
As the detector 4, an energy-resolved detector such as a semiconductor detector or a multi-channel detector is used.

Although the transmission method is used in the above description, the same applies to the reflection method.

In the above description, the case where the X-ray spectrometer is a Bragg case is described. However, in the case of the Laue case (FIG. 2 (B)), the thickness of each crystal layer is represented by an odd number of the extinction distance. By making it twice, the intensity of the diffracted wave can be maximized.

FIG. 4 is a diagram showing another configuration example of the X-ray spectrometer according to the present invention. As shown in the figure, when the lattice planes of the layers a and b are not parallel, the diffracted X-rays λ _a and λ _b are not parallel, but λ _a ′ and λ _b ′ are formed by using a channel cut type or two crystals.
Can be parallel rays.

FIG. 5 shows an X-ray spectrometer formed by laminating n crystal layers C ₁ ,..., Cn having different lattice spacings. In this case, by configuring d ₁ > d ₂ ‥‥> dn (di: the i-th lattice spacing), diffraction can be caused up to the shortest wavelength component, and X using the n wavelengths is used. Line diffraction becomes possible.

〔The invention's effect〕

According to the present invention, since the X-ray spectrometer is composed of a plurality of crystal layers, continuous X-rays can be converted into an X-ray flux containing only specific plural wavelengths.

Further, since the crystal layer closer to the surface has a longer lattice spacing, the longer wavelength (lower energy) component is sequentially diffracted, and the shorter wavelength (higher energy) component reaches the crystal layer where diffraction occurs and is diffracted.

Further, the thickness of each crystal layer is configured to be equal to or slightly larger than the extinction distance determined by the X-ray wavelength and the index of reflection at which each crystal layer causes diffraction. Diffraction lines are extracted efficiently, and attenuation of intensity can be suppressed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an X-ray spectrometer according to an embodiment of the present invention, FIGS. 2 (a) and (b) are explanatory diagrams of a Bragg case and a Laue case, and FIG. FIG. 4 schematically shows a measuring system used, FIG. 4 shows another configuration example of the X-ray spectrometer according to the present invention, and FIG. 5 shows another configuration example of the X-ray spectrometer according to the present invention. Action. 1 X-ray spectrometer 2 Continuous X-ray source 3 Sample 4 Detector

Claims (1)

(57) [Claims] A crystal layer on the surface has a lattice spacing larger than that of a lower crystal layer, diffracts a long-wavelength component of an incident X-ray beam, and includes a plurality of crystal layers. The thickness of each layer is determined by X
An X-ray spectrometer characterized by being set to be equal to or slightly larger than an extinction distance determined by a line wavelength and a reflection index.