JPH02107952A - X-ray diffraction measurement for powder - Google Patents

Abstract

PURPOSE:To enable accurate measurement of a diffraction profile of a small amount (about 0.1-1mg) of a sample at a high accuracy by setting an angle of incidence of X rays into a sample support substrate at the sum of an angle preset and a critical angle of the sample support substrate. CONSTITUTION:X rays R1 generated from an X-ray source 2 is incident into a total reflection mirror 1 at an angle alpha passing through a double-crystal spectroscope 3. X rays R3 reflected are detected 6 as voltage pulse to be amplified 12 and after a noise is removed with a pulse height analyzer 13, they are counted 14 to be sent to an arithmetic circuit 15. X rays R6 diffracted by a sample C adhering to the mirror 1 and detected 8 likewise and counted 11 to be sent to the circuit 15. The circuit 15 computes a critical angle alphac from the intensity of the reflected X rays and the angle alpha to determine a sum alpha=alphac+DELTAalpha with an angle DELTAalpha preset and sends a control signal to an X-Y stage 4. Detectors 6 and 8 are arranged in a triply coaxial vertical type goniometer separately to vary the angle alpha and an angle for measuring intensities of reflected and diffracted X rays roughly centering around the sample C continuously by a signal of the circuit 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an X-ray diffraction measurement method used to analyze the crystal structure of a minute powder sample.

[Prior Art] Conventionally, total internal reflection fluorescent X-ray analysis has been used as a method for nondestructively analyzing the components of a minute sample (Advances in X-ray Analysis, [1 (198B) 217).

In the total internal reflection X-ray fluorescence analysis method, a sample is deposited on the total internal reflection mirror of a fluorescent X-ray analyzer, and the X-rays are directed onto the mirror at an incident angle below the critical angle at which the incident X-rays on the total internal reflection mirror cause total internal reflection. Fluorescence X of the elements contained in the sample generated from the sample when irradiated with
This is a method of detecting lines.

On the other hand, X-ray diffraction is used to analyze the crystal structure of a sample, and known methods include the diffractometer method, which is the θ-2θ method, the X-ray diffraction method using photographs, and the oblique incidence xIa method. ing. In the diffractometer method, the following formula (1
) The X-ray diffraction intensity and diffraction angle 2θ profile are determined based on Bragg's equation, and unknown substances are identified and lattice constants, strain, etc. are measured.

2dsinθ=nλ - (1) where d: lattice spacing θ Nibragg angle n: reflection order λ: wavelength of the X-ray used However, the diffractometer method is
There was a problem in that the ray diffraction intensity decreased and a direct X-ray diffraction profile could not be obtained using an X-ray diffraction detector.
Therefore, in order to obtain the X-ray diffraction profile of a very small amount of sample, a high-sensitivity film was used to take a photograph using the Debye-Scherer method, and based on the relationship between the density of the film and the diffraction angle 2θ, a microphotometer was used to obtain the X-ray diffraction profile. Normal X-ray diffraction is performed (refractories, F (19
86)686).

The oblique angle incidence X-ray diffraction method is a diffractometer method in which X-rays are incident at an oblique angle (an angle of shallow incidence that almost approaches the sample surface) to analyze the structure of thin films and thin layers. 1. The X-ray diffraction profile of the polycrystalline phase near the sample surface can be obtained (^PP1.5urf, Sc
i, 26 (1986) 12).

[Problem to be solved by the invention]

The analytical measurement of a sample using the total internal reflection fluorescent X-ray apparatus described above has the advantage of being able to measure a minute amount, but is limited to elemental composition analysis and cannot analyze the crystal structure of the sample.

In addition, in the diffractometer method, crystal structure analysis can be performed using X-ray diffraction, but if the sample is small, it is necessary to rely on the X-ray diffraction method using photographs, which is time-consuming and therefore not commonly used. isn't it. Furthermore, oblique angle incidence X
Linear diffraction is effective for structural analysis of thin films and thin layers, but this method cannot be applied to microscopic powder samples because it requires appropriate conditions for the X-ray optical system. .

The present invention has been made in view of the above circumstances, and the present invention has been made in view of the above circumstances.
It is an object of the present invention to provide a powder X-ray diffraction measurement method that allows highly sensitive and accurate measurement of the diffraction profile of a very small sample amount of about 1 to 1 mg.

[Means to solve the problem]

The powder X-ray diffraction measuring method according to the present invention irradiates a powder sample attached to a sample support substrate on a sample support stand of a goniometer with X-rays, and based on the intensity of the obtained diffracted X-rays, the powder In the method of identifying the crystal structure of a sample, the sample supporting substrate is irradiated with X-rays, the critical angle αc of the sample supporting substrate is determined from the relationship between the X-ray incident angle and the reflected X-ray intensity, and the critical angle αc of the sample supporting substrate is determined. Angle Δα where the incident angle α of X-rays is set in advance
It is characterized by setting the sum α=αゎ+Δα.

[Effect]

In the method of the present invention, since the X-ray incident angle is set near the critical angle of total reflection of the sample support substrate, diffracted X-rays can be efficiently detected and scattered X-rays in the sample support substrate are suppressed.
Diffraction profiles of minute amounts of samples can be obtained with high sensitivity and accuracy.

〔principle〕

Figure 4 compares the theoretical value Ir of the diffracted X-ray intensity on the surface of a flat sample made of 1000 Fe specimens when the X-ray is incident at an oblique angle and when the θ-2θ method, that is, the diffractometer method. This graph shows the diffraction angle 2θ degrees on the horizontal axis and the diffraction X-ray intensity 1r on the vertical axis. The theoretical value 1r was determined by Pe1ser et al. (X-ray Di
ffraction' by Polycrystal
lineMaterials, In5t, Phys,
+ London, (1955) 159) The following formula (2) % formula %) However, o: Diffraction X-ray intensity per unit area of the sample when there is no absorption S: Cross-sectional area of the incident X-ray flux μ: Line of the sample Absorption coefficient α: Angle between the sample surface and the incident X-ray β: Angle between the sample surface and the diffracted X-ray 2θ: Diffraction angle α + β L: Sample thickness (film thickness) , In Fig. 4, when the X-ray is incident at an oblique angle, the incident angle α-pi 2°, 4
The calculation results at ``, 10'', 20°, and 40' are shown by solid lines, and the calculation results when the θ-2θ method is used are shown by broken lines.

...(2) As is clear from this graph, the diffracted X-ray intensity 1r for a thin film with a constant thickness and a constant oblique angle is determined by the diffraction angle 2θ.
It shows a constant intensity regardless of the angle of incidence α
The smaller the diffraction X becomes, 0', 20°, 10°...
It can be seen that the line intensity Ir increases.

On the other hand, the diffracted X-ray intensity 1r in the θ-2θ method increases inversely as the diffraction angle 2θ decreases, but it does not show a large value at α-1° or α-2° at oblique angle of incidence. . This shows that if the incident angle of X-rays is made small and the X-rays are irradiated at a constant rate, the diffracted X-ray intensity of the layer near the surface of the sample can be obtained with extremely high sensitivity.

FIG. 5 is a schematic diagram when X-ray R2 is irradiated to the substrate 1 whose surface has been mirror-polished, and the total reflection critical angle αゎ is (Anal
, Chem, 4:L, (1975) 852), it is known that it is given by the following formula (3).

Zρ αo〜(5,4Xl0IOλ2)"" ・(3) However, ρ: Density of substrate (gram") Z: Atomic number of substrate A: Atomic weight of substrate λ: Wavelength of incident X-ray (c+n) ), when the X-ray incident angle α is larger than the total reflection critical angle αc, the X-rays R2 deeply enter the substrate I, resulting in a large amount of scattered X-rays.Also, as shown in FIG. When the X-ray incident angle α is smaller than the total reflection critical angle αc, the incident X-ray R2 is totally reflected on the substrate 1. In this case, FIG. is a schematic diagram showing the diffraction situation of incident X-ray R2, and as shown in this diagram, the X-ray diffracted by sample C has a substrate 1.
The incident X-ray R2 incident at an angle α with respect to the reflecting surface P is
Diffracted X-rays R are reflected at an angle α on the reflecting surface P, and the reflected X-rays R3 are further projected onto the sample C on the substrate 1.
4 and diffracted X-rays R6 generated by the projection of the X-rays R9 directly incident on the sample C on the substrate 1. Here, if the incident angle of the directly incident X-ray R6 to the sample C is θ, the diffraction angle of the directly incident diffracted X-ray R6 at X1%R is 2θ, and the reflected X-ray at the reflecting surface P is The diffraction angle of the diffracted X-ray R4 generated at R3 is 2θ+2α, so the reflection surface P
The diffraction angle caused by the reflected X-ray R6 is shifted by 2α to the higher angle side, and a diffraction profile representing a normal distribution as shown in FIG. 7 is obtained. In Figure 7, the horizontal axis is the diffraction angle 2θ
, the vertical axis shows the X-ray diffraction intensity, the solid line (2) in the figure is the diffraction line due to reflected X-rays, and the solid line (E) is the diffraction line due to incident X-rays. This is a diffraction line, and the dashed line (h) is the actually measured diffraction profile. As is clear from the figure, the diffraction angle 2 when the X-ray diffraction intensity of the diffraction line (d) due to reflected X-rays is maximum
θ is shifted to the higher angle side than the diffraction angle 2θ when the X-ray diffraction intensity of the diffraction line (E) due to the incident X-rays is maximum, and the actually measured diffraction profile (E) is
It has a form in which diffraction lines (d) due to reflected X-rays are superimposed on (e). The diffracted X-rays due to the reflected X-rays can be removed by arithmetic processing, but based on the knowledge found through experiments by the present inventor, the X-ray incident angle α is set by Δα from the total reflection critical angle αc.
It has been found that if the angle is increased by about -0.05 to 0.1 degrees, the diffracted X-rays generated by the reflected X-rays are removed, and the diffracted X-rays of the powder sample caused by the incident X-rays can be efficiently detected without performing calculation processing. ing.

This means that the incident X-rays do not penetrate deep into the matrix (1 μm
This is presumed to be due to the fact that noise and hackground intensity caused by X-rays scattered by the substrate, fluorescent X-rays, etc. can be reduced, and diffracted X-rays due to total internal reflection development can be removed.

Therefore, in order to efficiently detect the diffracted X-rays of the powder sample deposited on the substrate 1 and to reduce the amount of scattered X-rays caused by the deep penetration of the X-rays into the substrate, it is necessary to As shown in figure (b), the X-ray incident angle α is α−
It is effective to make Δα=0.05 to 0.1° larger than αc.

Note that αc can be roughly estimated using the previous equation (3), but it must be determined accurately during measurement due to equipment errors such as deviations in the optical system of the total reflection surface.
Total internal reflection X-ray fluorescence spectrometry (e.g. advances in X-ray analysis,
lu (1988) 217. Japanese Patent Publication No. 634781
The value of αc is determined from the reflected X-ray intensity according to the method described in No. 7).

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 is a schematic diagram showing a method of performing X-ray diffraction measurement of powder according to the present invention. 2 in the diagram is X! The X-ray source section 2 is an X-ray source that generates 'il, and an X-ray emitting portion 2a of the X-ray source section 2 is provided with a shielding plate 2b that can be released when emitting X-rays. , X-rays R1 generated by the X-ray source 2 pass through a double-crystal spectrometer 3 that monochromates the X-rays into Cod, 1, etc., and are incident at an angle α on the sample support substrate, that is, the total reflection mirror 1, on which the sample C is attached. let The total reflection mirror 1 is placed on an XY stage 4 which is a sample support.

FIG. 2 is a schematic plan view showing a state in which the total reflection mirror 1 is placed on the X-Y stage 4, and FIG. 3 is a schematic cross-sectional view seen from the side of FIG. As shown in FIGS. 2 and 3, it is arranged in three coaxial vertical goniometers (not shown) for fine adjustment. The XY stage 4 includes a sample stage (not shown) that can rotate clockwise around the sample C, that is, in the direction of the outlined arrow, and can also move in the X-axis and Y-axis directions perpendicular to each other in a horizontal plane. It is possible. The X-ray R3 reflected by the total reflection mirror 1 placed on the χ-Y stage 4 passes through the double slit collimator 5 attached to the reflected χ-ray intensity detector 6, and is detected as a voltage pulse by the detector 6. Ru. The detected voltage pulse is amplified by an amplifier 12, and a pulse height analyzer 13 removes noise and the like and extracts only pulses with a certain range of wave heights.

The number of pulses is counted by a counter 14, and the arithmetic circuit 1
Sent to 5.

On the other hand, the X-ray R6 diffracted by the sample C attached to the total reflection mirror 1 passes through the Solar slit 7 attached to the diffraction X-ray intensity detector 8, and is detected as a voltage pulse by the detector 8, and its value is As in the case of detection, amplifier 9. Wave height analyzer10. The signal is sent to the arithmetic circuit 15 via the counter 11. The arithmetic circuit 15 calculates the reflection
The critical angle αc is calculated from the ray intensity and the chi-ray incident angle α, and the sum α=αc+Δα with a preset angle Δα is determined, and a control signal is sent to the XY stage 4 connected to the calculation circuit 15. A reflection x-ray intensity detector 6 equipped with a double slit collimator 5 and a diffraction X-ray intensity detector 8 equipped with a solar slit 7 are respectively arranged in three coaxial vertical goniometers for fine adjustment. The goniometer continuously measures the incident angle α of x wAR2 and the angle for measuring the reflected X-ray intensity and the diffracted X-ray intensity in the circumferential direction with the sample C as the center based on the signal from the calculation circuit 15. change to

The arithmetic circuit 15 is connected to the X-ray source 2. It is also connected to the two-crystal spectrometer 3, and sends control signals for measurement operations.

Next, the measurement procedure of the present invention will be specifically explained.

X-ray R generated from incident source 2 with a preset output
, are separated by a crystal spectrometer 3 made of Si (100) single crystal, for example, and set to a wavelength necessary for measurement. After measuring the intensity of the incident X-ray R2 with the reflected X-ray intensity detector 6 with the incident angle α of the X-ray R2 having the set wavelength set as α-〇, the shielding plate 2b of the X-ray source emission part 2a is closed. to stop the X-ray irradiation. A powder sample is deposited on the total reflection mirror 1, and the total reflection mirror 1 is installed on a rotating sample stage (not shown) installed in the X-Y stage 4, and a part of the total reflection mirror on which the amount of sample C attached is particularly small is measured. is set in the optical path of the X-ray R2, and the reflected X-ray intensity is measured by double angle scanning of α-2α. At this time, the reflectance, which is the value obtained by dividing the reflected X-ray intensity by the incident X-ray intensity, is determined by the arithmetic circuit 15, and the reflectance is normally 0.
01, the incident angle α is fixed to a predetermined value of incident angle α−αゎ+0.075°. Next, X-Y
The stage 4 is operated to move the portion to which the sample powder C has sufficiently adhered into the optical path of the X-ray R2, and the diffraction profile obtained by scanning only at the diffraction angle 2θ is recorded.

FIGS. 8 and 9 are diffraction profiles obtained by measurement according to the method of the present invention. A first example showing a method of carrying out the present invention
In the figure, a CO tube is used as the X-ray source 2, an amorphous quartz plate with a diameter of 30 mm is used as the total reflection mirror 1, and approximately 1 mg of S
It shows the results of the diffraction profile measured for the i powder standard sample, and in both Figures 8 and 9, the horizontal axis is the diffraction angle 2θ (degrees).
, the vertical axis represents the X-axis diffraction intensity. As is not clear from Fig. 8, when scanning the diffraction angle 2θ from 10° to 100°, diffraction profiles are obtained at both α-0, 2° and α-0, 35°, but α It can be seen that a clearer diffraction profile can be obtained at -o and 35 degrees. In the θ-2θ method, the background noise is large overall, and the diffraction lines are not clear.

The total reflection critical angle αc of quartz (SiOz), which is the total reflection mirror 1 used here, is αゎ−0.2 for CoK and X-rays.
Since the angle is 75°, scattering due to amorphous quartz (Sing) is observed near 2θ-25° of the α-0,375° diffraction profile. Also, α−0,2° α−o,
The bank ground intensity increases near 2θ=10° at each angle of 35″′, and this is caused by scattering of incident X-rays on the quartz surface, which is the substrate.

Figure 9 shows the incident angle α of the diffraction profile of the Si (111) plane by scanning the diffraction angle 2θ from 31″ to 36°.
This is a measurement of changes associated with As is clear from the graph, when the incident angle α is larger than the total reflection critical angle α°-0.275°, diffraction lines due to reflected X-rays are generated, the peak becomes broad, and the diffraction angle shifts to the higher angle side. Therefore the 8th
From the results shown in the graphs in Figure 9 and Figure 9, it can be seen that the X-rays scattered by the sample supporting substrate are small (a clear diffraction profile can be obtained) at α-〇, 35°.

Note that when X-rays are incident at oblique angles, the X-ray measuring optical system is likely to shift, so it is preferable to set the incident angle α for each sample.

〔effect〕

As detailed above, according to the method of the present invention, the X-ray incident angle α
Since it is set to the sum of the critical angle αc of the total reflection mirror and the preset angle Δα, α−αゎ+Δα, the diffracted X-ray intensity increases, and the scattered X-rays on the sample support substrate are suppressed, so that the sample is in a very small amount. The present invention exhibits excellent effects such as being able to obtain a diffraction profile with high sensitivity and accuracy even when using a wafer.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the method of carrying out the present invention, and FIG. 2 is an X-
A schematic plan view showing the sample support substrate placed on the Y stage, Figure 3 is a schematic cross-sectional view from the side of Figure 2, and Figure 4 shows the diffraction X-ray intensity and diffraction angle based on the theoretical calculation results of the incident angle α. Graph showing the relationship with 2θ, Figure 5 is a schematic diagram showing the relationship between X-ray reflection and refraction, Figure 6 is a schematic diagram showing how incident X-rays are diffracted in a sample, and Figure 7 is a schematic diagram showing the relationship between X-ray reflection and refraction. Figures 8 and 9 are diagrams showing the diffraction profiles obtained by the phenomenon shown in the figure, and Figures 8 and 9 are diagrams showing the X-ray diffraction profiles obtained by depositing a standard Si sample on an amorphous quartz plate. ■...Sample support substrate 4...X-Y stage 5.
...Double slit collimator 6...Reflection chi-ray detector 7...Solar slit 8...Diffraction X-ray detector C...Sample patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Kono To Noboru x Seikaikaidan Ikumiya

Claims (1)

[Claims] 1. A powder sample attached to a sample support substrate on a sample support stand of a goniometer is irradiated with X-rays, and the crystal structure of the powder sample is determined based on the intensity of the obtained diffraction X-rays. In the identification method, the sample support substrate is irradiated with X-rays, the critical angle α_c of the sample support substrate is determined from the relationship between the X-ray incident angle and the reflected X-ray intensity, and the incident angle of the X-rays on the sample support substrate is determined. A method for measuring X-ray diffraction of powder, characterized in that α is set as a sum of α and a preset angle Δα=α_c+Δα.