JPH058800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an X-ray spectroscopy element using an artificial cumulative film as an X-ray diffraction material.

[Conventional technology]

Fluorescence X-ray analyzers excite a sample with primary X-rays or electron beams, and detect the wavelength of secondary X-rays generated from the sample. An X-ray spectroscopy element using a diffraction material made of a plate or an artificial cumulative film is required.
This X-ray spectroscopy element changes the angle of incidence by utilizing the fact that diffraction occurs only when X-rays are incident at a certain angle determined by the wavelength and the lattice spacing of the element, and the X-rays are efficiently reflected. This allows X-rays of a desired wavelength to be separated into spectra.

The X-ray diffraction conditions in the above X-ray spectroscopic element are as follows:
As is well known, it is given by the Bragg equation below.

2dsinφ=nλ d: Interplanar spacing of the grating φ: Incident angle, diffraction angle λ: wavelength of fluorescent X-ray n: order of reflection [Problem to be solved by the invention] By the way, an X-ray spectroscopic element made of an artificial cumulative film has the following properties: Appropriate 2 on a single crystal plate (substrate) such as silicon
It has a laminated structure in which more than one substance is deposited alternately by vacuum evaporation or sputtering, and because the interplanar spacing d of the lattice is large, it is used for spectroscopy of soft X-rays with a long wavelength λ. Since the surface of this X-ray spectroscopic element forms a mirror surface, when the incident angle of X-rays is made small, total reflection of the X-rays occurs on the surface.
As the intensity of the rays increases and they enter the X-ray detector together with the diffracted X-rays, the signal-to-noise ratio decreases.

Here, in the case of a spectroscopic crystal consisting of a single crystal,
The lattice spacing d in the Bragg equation mentioned above is determined by the size of the molecule and is therefore extremely small. Therefore, as can be seen from Bragg's equation, the angle of incidence φ that causes diffraction becomes relatively large, making it difficult for the aforementioned total internal reflection to occur.

On the other hand, an artificial cumulative film has many molecular layers in one film (layer), so the lattice spacing d
is significantly larger than that of a spectroscopic crystal. Therefore,
As can be seen from Bragg's equation, it is necessary to set the incident angle φ that causes diffraction to be significantly smaller than that of the spectroscopic crystal, so the intensity of the aforementioned totally reflected X-rays increases significantly and the S/N ratio decreases. Moreover, as mentioned above, the X-ray spectroscopic element having an artificial cumulative film is
It is used to separate X-rays with long wavelengths, and therefore, the X-rays incident on the X-ray spectrometer include X-rays with shorter wavelengths than the X-rays to be separated, so total internal reflection of X-rays is not possible. Since the intensity increases, SN
There is a significant decrease in the ratio.

The present invention was made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an X-ray spectroscopic element having an artificial cumulative film that reduces total internal reflection of X-rays and has a high signal-to-noise ratio. shall be.

[Means to solve the problem]

In order to achieve the above object, the present invention forms a surface layer of a material having a lower density than the material constituting the artificial cumulative film on the surface of the artificial cumulative film.

[Effect]

Hereinafter, the principle of the present invention will be explained before explaining the embodiments.

The total reflectance I of X-rays by the mirror surface increases as the incident angle ψ decreases, and becomes 1 at 0 degrees. Further, the incident angle at which the total reflectance I is approximately 0.5 is given by 0.094λ√ degree, where the wavelength of the X-ray is λ (Å) and the density of the reflector is ρ (g/cm ³ ). Therefore,
By forming on the surface of the artificial cumulative film a surface layer of a substance whose density ρ is smaller than the density of the molecules constituting the artificial cumulative film, the intensity of the totally reflected X-rays can be reduced. Therefore, the intensity ratio between the diffracted X-rays of a certain wavelength and the total reflected X-rays containing various wavelengths, that is, the S/N ratio can be increased. Note that when the surface of the surface layer is made rough, the total reflected X-rays are further reduced, and this effect is further enhanced.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 1 is a diagram showing an example of the configuration of an X-ray fluorescence spectrometer using an X-ray spectroscopy element 1 according to an embodiment of the present invention, and FIG. It is shown in That is, the spectroscopic element 1 is
Silicon and tungsten are alternately vacuum-deposited or sputtered on a substrate 2 made of a silicon single crystal wafer to form an artificial cumulative film consisting of thin layers 3 and 4, and a density ρ is further applied to the surface of the artificial cumulative film. A surface layer 5 of carbon, which is smaller than silicon and tungsten, is formed by vacuum evaporation to a thickness of about 1000 Å.

The apparatus shown in FIG. 1 includes such an X-ray spectroscopic element 1.
is supported rotatably in the direction of arrow q by an axis perpendicular to the plane of the paper through the center point d of its front surface, and a solar slit 6, a fluorescent X-ray analysis sample 7, and this sample 7 are attached to one side of the support. An X-ray tube 8 and the like are provided for exciting and generating fluorescent X-rays. Further, on the other side of the spectroscopic element 1, a solar slit 9 and an X-ray detector 10 such as a proportional counter tube are provided, and the base 11 is connected to the spectroscopic element 1 as indicated by the arrow q.
The elements are connected to the drive source of the element so as to rotate in the same direction about point p at a speed twice the rotational angular velocity of . In other words, among the fluorescent X-rays generated from the sample 7, those that pass through the solar slit 6 have an incident angle φ
(indicated by "" in the drawing)) enters the spectroscopic element 1, and diffraction occurs in the X-rays with a constant wavelength λ determined by this incident angle φ, so this diffracted X-ray
The line passes through the solar slit 9 and is detected by a detector 10.

For example, if we use the above device to detect the intensity of the characteristic X-ray Mg-Kα ray of magnesium (Mg) using sample 7, which is cast iron containing about 0.05% magnesium by weight, the signal X The characteristic X-ray Fe-L line of iron is a noise component having a wavelength λ _o relatively close to the wavelength λ _s of the line. Figures 3 and 4 are the first
By rotating the base 11 of the spectroscopic element 1 and detector 10 shown in the figure, the incident angle φ of the fluorescent X-rays with respect to the spectroscopic element 1 is determined.
At the same time, the output of the detector 10 is further applied to the pulse height analyzer to obtain the X _{- ray} intensities I
The curves S and N are shown when measured separately, and the scale on the vertical axis is 1 when the incident angle φ is 0, that is, the intensity at 100% total reflectance. Note that FIG. 3 shows a case where a conventional X-ray spectroscopic element without the carbon surface layer 5 in FIG. 2 is used,
FIG. 4 shows a case where the X-ray spectroscopic element shown in FIG. 2 is used.

Here, the Mg-Kα ray of wavelength λ _s causes diffraction at the position of incident angle φ _s , and the Fe-L ray of wavelength λ _o diffracts at the position of ψ _o , producing peaks at these positions. However, by measuring the true height of the peak at the incident angle ψ _s , the intensity of the Mg-Kα ray can be accurately determined. However, as mentioned above, the angle at which an X-ray with wavelength λ (Å) enters a substance with density ρ (g/cm ³ ) and about 50% of it is totally reflected is 0.094λ√
Since it is given by ρ degrees, for example, in a conventional X-ray spectroscopic element, X
When the ray is directly incident, the angle of total reflection becomes large. On the other hand, when the light is incident on the carbon layer 5 having a density ρ of 2.2, the angle at which 50% of the light is totally reflected is reduced to about one-third. That is, if the half-value angles of the total reflection part in the case where the surface layer 5 of the carbon layer is not provided are ψ _0s and ψ _0o for curves S and N, respectively, and ψ _1s and ψ _1o in the case where the carbon layer 5 is provided, then As shown in FIGS. 3 and 4, the latter angle is about one third of the former angle.

Furthermore, since the X-ray of wavelength λ _s and the noise component of X-ray of wavelength λ _o for which the intensity of the diffracted X-ray at the incident angle ψ _s is to be measured are simultaneously incident on the detector 10, the intensity of the diffracted X-ray can be measured. The sum is represented by the dashed line in each figure. Therefore, in a conventional spectroscopic element not provided with the carbon surface layer 5, an extremely large error component x due to total reflection is added to the true peak value to be measured as shown in FIG. On the other hand, when the X-ray spectroscopic element of the present invention provided with the carbon surface layer 5 is used, as shown in FIG. 4, the error component y becomes extremely small and accurate measurements can be performed.

[Effects of the Invention] As described above in detail with respect to the embodiments, the present invention provides an X-ray spectroscopic element having an artificial cumulative film in which the diffraction angle is small due to the large lattice spacing. Because we provided a surface layer of a material with a lower density than the material that makes up the artificial cumulative film,
The intensity of the totally reflected X-rays can be made extremely small, resulting in a high signal-to-noise ratio and a marked improvement in the accuracy of spectroscopy.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of a fluorescent X-ray spectrometer using the X-ray spectroscopic element of the embodiment of the present invention, and FIG.
The figure is an enlarged view of a part of the cross section of the X-ray spectrometer in Figure 1, and Figure 3 is an enlarged view of the X-ray incident angle, reflection, and diffraction of X-rays when using a conventional X-ray spectrometer.
The curve shown in FIG. 4 showing the relationship with the ray intensity is the same curve as in FIG. 3 when the X-ray spectroscopic element of the embodiment of the present invention is used. In the figure, 1 is an X-ray spectroscopic element, 2 is a substrate, 3 is a silicon layer, 4 is a tungsten layer, and 5 is a carbon layer (surface layer).

Claims (1)

[Claims] 1. On the surface of an X-ray diffraction material consisting of an artificial cumulative film in which two or more types of substances are alternately deposited on a substrate, a surface layer of a substance having a lower density than the substance constituting the artificial cumulative film is formed. An X-ray spectroscopy element characterized by: