JPH0616014B2 - Positron annihilation analysis method and analyzer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a positron annihilation analysis method and an analysis apparatus for analyzing a sample by using a positron annihilation analysis method, and particularly to a positron with high accuracy at an analysis point of a sample. It is to irradiate.

[Background of the Invention]

In the positron annihilation method, a positron is injected into a sample, the positron is pair-annihilated with the electron in the sample, and the γ-rays emitted at that time are detected to obtain information on the electronic structure, lattice defects, and other information in the sample. Is the way. A positron is a particle that has the same rest mass as an electron and has a charge that has the same absolute value and opposite sign as the electron's charge (negative charge). The positron source is a sealed + β-decaying radioisotope (eg, ²² Na). When a positron of several hundred KeV emitted from this positron source is irradiated onto the sample, the positron that jumps into the sample becomes ions or electrons. Repeatedly collided with
^-The positron has thermal energy (~ 0.
025 eV). When the sample is a metal, the thermalized positron annihilates with the electron with a lifetime of 100 to 300 PS. At this time, two 511 keV (that is, positron and energy corresponding to the rest mass of the electron) γ rays are emitted in almost opposite directions. From the total energy including mass at the time of pair annihilation and the conservation law of total momentum, the angle and energy made by the two γ-rays are the momentum possessed by the positron and electron pair at the time of pair annihilation (the momentum of the positron is almost ignored). Depending on the electron momentum), the two γ-rays will be distributed in a slight angular range (within ± 25 mrad) centered on the 180 degree direction, and the energy will also be centered on 511 keV. It shows a Doppler width of several keV. Therefore, by precisely measuring the angular distribution of the two γ-rays (measurement of the γ-γ angular correlation) or by measuring the energy distribution of the γ-rays (Doppler width), You can know the momentum distribution.

Hereinafter, the conventional positron annihilation analysis method (see Experimental Materials Course 11 "Lattice Defects" (Kyoritsu Shuppan), pages 163-175 (1978)) will be described with reference to FIGS. 14 and 15.

FIG. 14 is a diagram showing a conventional annihilation γ-ray (γ-ray generated by pair annihilation of positron and electron) energy spectrum measuring apparatus. The sample 34 is irradiated with positrons 21 emitted from the positron source 12 (for example, ²² Na), the reduced γ rays 22 are detected by the γ ray detector 19, and the energy spectrum of the annihilated γ rays is measured. The energy of two photons emitted at the time of annihilation is about 511 keV. The kinetic energy of the annihilation partner's electron is only a few eV, so the energy of the proof γ-ray deviates from 511 keV. In the laboratory system, the energy width δ _E of the annihilation γ-ray energy spectrum becomes CP _l / 2 due to the Doppler effect. Where C is the speed of light, P _l
Is the momentum component in the emission direction. Therefore, the energy width δ _E spreads to about 2 keV, and as the γ-ray detector 19, for example, G. This energy width δ _E can be measured by using a (L _i ) solid state detector (SSD). FIG. 15 schematically shows the energy spectrum of annihilation γ rays. The S parameter is used to measure the energy spectrum of annihilation γ rays. S
The parameter is expressed by the following equation using the central area A of the spectrum and the areas B ₁ and B ₂ of both ends shown in the drawing of FIG.

S = A / (B ₁ + B ₂ ) ... (1) The central part A of the spectrum is a region where γ-rays due to pair annihilation of a positron and a free electron are mainly contributing, and both end parts B ₁ , B ₂ is γ due to pair annihilation of the positron and the core electron
The area where the line contributes. S-parameter measurement is a very effective means for studying lattice defects, especially those having a low ionic concentration such as atomic vacancies and tensile stress portions of edge dislocations.

Consider, for example, atomic vacancies in a metal. Atomic vacancies
Since it has no cations, it is more negatively charged than a perfect crystal. Since the positron is positively charged, it is captured when the positron approaches the atomic vacancy due to Coulomb interaction. When the concentration of atomic vacancies is about 10 ⁻⁴ , most of the positrons are captured by the atomic vacancies and disappear near the atomic vacancies. Potential energy due to only electrons by ions in atomic vacancies becomes nearly flat and electrons become free electrons. Therefore, as the number of positrons annihilated in the atomic vacancies increases, the pair annihilation with free electrons increases, and the S parameter increases (the central part A of the spectrum is at both ends B ₁ , B).
Is relatively larger than _2. ) When a plurality of atomic vacancies are aggregated to form vacancies, the electrons become more free electrons, and the S parameter becomes larger.

As described above, the S parameter is effective for investigating the generation and recovery process of electron vacancies. For example, copper (Cu) 3M
When irradiation with eV electrons is performed at 10 K, the S parameter increases with irradiation. This is because the copper atoms are repelled from the lattice points by the fast electrons, and then atomic vacancies are generated. After irradiation, the temperature was raised to recover the damage caused by the grace and the S-parameter was set to stage III.
(Temperature range where atomic vacancies can move) increases (S. Mantle et.al: Phys.
Rev. Left) 34 p1554 (1975)). This is Stage II
This is because vacancy clusters are formed because the atomic vacancy moves in I.

In addition to the annihilation γ-ray energy spectrum measurement described above, the positron annihilation method has an analysis method by γ-γ angle correlation measurement or positron lifetime measurement, and is a very effective means for lattice defect research as described above. I'm running. However, since any conventional positron annihilation method simply irradiates the sample with positrons emitted from the positron source, the information obtained is that the positron-irradiated surface of the sample, that is, the irradiated surface is usually several mm ² Since it is up to several cm ² , it has a drawback that it leads to averaged information on such a wide range.

[Object of the Invention] An object of the present invention is to obtain a positron annihilation analysis method and an analysis device capable of implanting positrons in a fine local region of a sample to be analyzed with high accuracy.

[Outline of Invention]

The inventors have noticed that the magnetic field lens of the electron microscope has the same focal length for positrons and electrons of the same energy, and if the positron is driven into the sample set in the microscope using the imaging lens of the electron microscope. , It was discovered that the positron beam can be precisely applied to the electron microscope observation position in the sample.

That is, the feature of the present invention is that the sample to be analyzed is set in an electron microscope, and then the positron beam is passed through the imaging lens system of the electron microscope from the direction opposite to the traveling direction of the electron beam of the electron microscope. The energy of the positron beam passing through the imaging lens system is made substantially equal to the energy of the electron beam, and further, the energy of the positron beam passing through the imaging lens system is decelerated to about thermalization energy. In the positron proof analysis method, the sample is analyzed by irradiating the sample with a positron beam and measuring annihilation γ rays generated in the sample.

Another feature of the present invention is an electron gun, an imaging lens system, an imaging surface,
And an electron microscope provided with a sample setting unit and the like, and an electron microscope provided in the microscope, which passes through the imaging lens system in a direction opposite to the electron beam passing direction, and the energy when passing through the imaging lens system. Positron irradiation device for irradiating the sample set in the sample setting section with a positron beam having a substantially equal energy of the electron beam of the electron beam, and a positron provided between the image forming system and the sample setting section and having passed through the image forming system. A positron deceleration means for decelerating the energy of the beam to about thermalization energy, and an annihilation γ-ray measuring device for measuring annihilation γ-rays generated when the sample set in the sample setting section is irradiated with positrons. It is in a positron annihilation analyzer.

Example of Invention

Recently, in the study of irradiation damage, in order to investigate the kinetics of the generation process of irradiation damage, attempts have been made to directly observe the defect generation process by irradiating the sample with a transmission electron microscope directly with ions. However, electron microscopes (hereinafter referred to as electron microscopes) use single lattice defects (point defects) such as atomic vacancies.
Although it is possible to observe secondary defects such as voids and dislocation loops that are formed by aggregation of the defects, it is not possible to observe the rolling defects themselves.

If information such as the concentration of point defects near these secondary defects can be obtained by using the positron annihilation method described above,
It is very effective for clarifying the kinetics of the radiation damage generation process. Further, if information on the local electronic structure of the electron microscope observation position and the like can be obtained, dramatic progress can be expected in physical property research. However, for that purpose, the positron must be precisely driven into the position in the sample corresponding to the desired image in the observation field of the electron microscope. However, at present, there is no technology capable of accurately injecting positrons into minute local areas in a sample.

The configuration and principle of a transmission electron microscope (abbreviated as transmission electron microscope) will be briefly described.

FIG. 16 is a device configuration diagram of a transmission electron microscope. The transmission electron microscope includes an irradiation system for irradiating a sample with an electron beam and an imaging system for expanding the electron beam passing through the sample and forming an image on a fluorescent plate (imaging surface). The irradiation system includes an electron gun 1, an accelerating tube 2, a condenser lens 3 and the like. The image forming system includes an objective lens 5, intermediate lenses 6 and 7, projection lenses 8 and 9, and the like. The intermediate lens is composed of a first intermediate lens and a second intermediate lens, and the projection lens is
It is composed of a first projection lens and a second projection lens. The condenser lens 3 of the irradiation system has a function of converging the electron beam into a parallel beam, the objective lens 5 of the image forming system has a function of determining the focal length, and the intermediate lenses 6 and 7 and the projection lenses 8 and 9 have a function of determining the magnification of the image. Have.

The electron beam 20 emitted from the electron gun 1 is accelerated by the accelerating tube 2 to a sufficient energy to pass through the sample 4 (usually, the sample thickness is 0 to 5000Å, the electron beam energy is about 50 to 200 keV). . The electron beam 20 accelerated to a predetermined energy is converged by the condenser lens 3 so as to be a parallel beam, and is irradiated onto the sample 4. The beam diameter at this time is several μm. When passing through sample 4,
The electron beam is scattered and diffracted according to the tissue in the sample. As a result, the cross section of the electron beam after passing through the sample has information on the structure of the sample in the form of light and shade of the beam density (scattered rays and diffraction rays are cut by slits). , Objective lens 5, intermediate lens 5,
6 and the projection lenses 8 and 9 are used to enlarge and image on the fluorescent plate 11. On the fluorescent plate 11, since the fluorescence intensity changes according to the density of the beam density (that is, information about the tissue), it is possible to visually observe an enlarged image of the tissue of the sample. FIG. 17 shows how the electron beam expands after passing through the sample. Each lens of the image forming system is configured to further magnify a part of the image formed by the lens in the preceding stage, and a final image 24 is obtained.

The above is the basic configuration and principle of the transmission electron microscope. In recent years, in addition to this transmission electron microscope, many electron microscopes having multiple functions such as a scanning electron microscope function and a characteristic X-ray analysis function have been proposed and put into practical use. Has been done.
However, there is currently no electron microscope that adds the function of analysis using the positron annihilation method to these electron microscopes.

Next, a specific embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing an embodiment of the device of the present invention, in which a positron annihilation analysis function is added to a transmission electron microscope. That is, the structure is such that a positron irradiation device and an annihilation gamma ray measuring device are added to the conventional transmission electron microscope. The positron irradiation device includes a positron source 12 and a thermalizing plate 1 loaded on the surface of the positron source 12.
3, Positron accelerator tube (including extraction electrode 14, converging lens 1
5, a collimator 16 and the like. As the positron source 12, a ²² Na source (positron energy range: 0
˜540 keV) and an aluminum foil is used as the heat plate 13. The annihilation γ-ray measuring device 19 is provided obliquely behind the sample when viewed from the direction of the positron irradiation device, and is composed of one annihilation γ-ray detector (G. (L _i ) detector).

The transmission electron microscope is composed of an electron gun 1, an accelerating tube 2, a condenser lens 3, a sample setting section 4 ', an image forming lens system 10, an image forming surface 11 and the like. 17 is the image plane 11
The film chamber provided on the back side of the
The positron irradiation device is provided on the side opposite to the image forming plane.
Reference numeral 18 denotes a positron deceleration tube provided between the imaging lens system 10 and the sample set portion 4 ', before the positron emitted from the positron irradiator is injected into the sample set in the sample set portion 4'. To decelerate the positron to prevent the positron from penetrating the sample.
8'is a correction coil.

A constant voltage V _{0 in} the range of ₀ to 200 kV is applied to the accelerating tube 2 of the transmission electron microscope. Voltage V _0/2 is applied to the positron acceleration tube 14 and positron deceleration tube 18. However, the polarities of the voltage applied to the positron deceleration tube 18 and the polarities of the accelerating tube 2 and the positron accelerating tube 14 are opposite. The image plane (fluorescent plate) 11 is provided with a small hole 11 'in the central portion of the fluorescent plate in order to pass the positron beam emitted from the positron irradiation device.

The positron irradiation device irradiates a sample with positrons emitted from a positron source, and the annihilation gamma ray measuring device 19
Is for detecting and counting annihilation γ rays generated when positrons disappear in a sample. The imaging lens system 10 magnifies and forms an image of the electron beam that has passed through the sample, and includes an objective lens 5, a first intermediate lens 6, a second intermediate lens 7, and a first intermediate lens 7.
It is composed of a projection lens 8 and a second projection lens 9. It should be noted that hitting a positron beam (or an electron beam) from the image forming surface (fluorescent plate) 11 side through the image forming lens system 10 to the sample in reverse is called reverse image forming, and an image formed on the sample is reverse image forming. Called.

Next, the scanning procedure of the device of the present invention will be described. Figure 2 shows the first
It is a figure which shows the schematic structure of the apparatus shown in the figure, and it demonstrates below using this FIG.

Voltage V ₀ (kV) in the accelerating tube 2 and positron decelerating tube 18 Voltage is applied. Electron beam 20 energy V ₀ emitted from the electron gun 1 _(keV) is, after passing through the sample 4 is decelerated by the positron deceleration tube 18, the energy V _0/2 (ke
V) electron beam. The positron deceleration tube 18 is for decelerating the positron beam, but since the electron beam passes through the positron deceleration tube 18 in the opposite direction to the positron beam,
The electron beam is decelerated as well as the positron beam. Thus the energy V _0/2 (keV) of summer was electron beam, based on the principle described above, an image is formed on the fluorescent screen 11 through an imaging lens system 10, to TEM observation of a sample tissue. If there is a portion to be analyzed by the positron annihilation method in the observed image, the position of the sample 4 is finely adjusted so that the portion is located at the center of the fluorescent plate, that is, the position of the small hole 11 '.
Then, loaded with positron source 12 positron irradiation apparatus applies the voltage V _0/2 (kV) to the positron acceleration tube 14. In this way, the positrons (energy range: 0 to 540 keV) emitted from the positron source 12 are made incident on the thermalizing plate 13 to be heated and the energy distribution width is set to the order of 1 eV, and then the positron accelerating tube 14 uses the positrons. by accelerating, making energy _V 0/2 monochrome positron beam 21 (keV). (Refer to "Physics Frontline 5" (Kyoritsu Shuppan) p58 (1983) for a method of generating a positron beam of monochromatic energy by combining the heating plate 13 and the accelerating tube 14.) This positron beam 21 is used by the focusing coil 15. And focuses on a small hole 11 'in the center of the fluorescent plate (image plane) 11. That is, when the positron beam 21 passes through the small hole 11 ', the beam is narrowed down most. The positron beam 21 that has passed through the small hole 11 'is formed into an image by the imaging lens system 10 on the basis of the principle described later, that is, an image formed in the region of the small hole 11' in the center of the fluorescent plate 11 based on the principle. The positron beam 21 is bombarded at the corresponding position in the sample. Here Importantly, the energy of the positron beam 21 as it passes through the imaging lens system 10 and V _0/2 (keV), the electron beam energy V ₀ which passes through the imaging lens system 10 in the opposite direction / It is the same as 2 (keV). here,
The positron moderator tube 18 has the following two functions.

In order to reverse-image the positron beam, the energy of the positron beam passing through the imaging lens system 10 must be the same as that of the electron beam. Therefore, the positron region tube 18 changes the energy of the electron beam 20 to V ₀ (ke
Energy value _V 0/2 from V) positron beam 21 (ke
V) to slow down. Since the electron beam energy when passing through the sample is V ₀ (keV), the sample penetrating power of the electron beam as an electron microscope is not impaired.

If the positron beam 21 is Gyakuyui image to the sample 4 through the image-forming lens system 10, if you leave the energy of the positron beam 21 is V _0/2 (keV), similarly to the electron beam 20, also mostly positron beam 21 Penetrates the sample 4. Therefore, the positron deceleration tube 18 acts to decelerate the energy of the positron beam 21 from V 0/2 (keVL) to about thermal energy (up to ₀ keV), and the positron beam is then driven into the sample. Electron beam 20 passing through sample 4
If is a parallel beam, the positron beam 2 which is imaged in reverse
1 is also a parallel beam. However, if the electron beam 20 is not a perfect parallel beam, the positron beam 21 that forms the reverse image is also not a parallel beam, and when the electron beam 20 is decelerated by the positron deceleration tube 18, the electric field and the velocity in the vertical direction remain. There is an error. For this reason, the correction coil 18 'is provided to correct the trajectory of the positron beam 21 when the reverse image is formed.

In this way, the energy distribution of the annihilation γ-rays caused by the positrons implanted in the sample 4 is measured by the annihilation γ-ray detector 19 and a predetermined positron annihilation analysis is performed.

For example, a 1 _m C ₁ ²² Na source is used as the positron source 12,
If the probability that the generated positrons are guided to the positron accelerating tube 14 through the thermalization plate 13 is 10 ⁻⁴ and the probability that the converged positron beam 21 is lost before being hit by the sample is ½, the sample 4 has About 1000 positrons can be injected per second. At this time, if the annihilation γ-ray energy distribution measurement of 100 channels is performed for 100 seconds, data with a statistical error of 5% or less for each channel can be obtained.

A positron irradiation device in which the axial center of the positron irradiation device (defined as the same as the axial center of the positron accelerating tube 14) coincides with the axial center of the imaging lens Keno as in this embodiment described above is called a linear axial center irradiation device. I will decide.

Next, the principle of the present invention will be described with reference to FIGS. FIG. 3 shows the principle of reverse imaging. Object 2 now
Consider a case where the final magnified image 24 of the image of 3 (sample) is obtained by the imaging lens system 10. Position P _{0 with} object 23
Is successively imaged by each lens, and is imaged at P ₁ in the image 25, and finally stored at the point P. Considering the lens 9, the light emitted from the point P ₁ (electron beam in this case) is focused on the point P by the lens 9. On the contrary, the light emitted from the point P (electron beam in this case) is
In exactly the same manner, the light is focused by the lens 9 to form an image at the point P ₁ . On the other hand, the magnetic lens has the same focal length for electrons and positrons of the same energy, as shown below. Therefore, when the positron 21 is emitted from the point P (point on the fluorescent screen) of the image 24 toward the lens 9 ', an image is formed at the point P _{1 of the} image 25,
Further, an image is formed on the points P ₂ , P ₃ , and P _4, and finally an image is formed (reverse image formation) on the point P ₀ .

Next, it will be described with reference to FIGS. 4 to 6 that the magnetic field lens has the same focal length for electrons and positrons having the same energy.

FIG. 4 shows how the magnetic field lens focuses.
The electron beam 20 emitted from A passes through the magnetic field lens 29 while turning to the left and forms an image at a point P. On the other hand, the positron beam 21 emitted from A turns to the right on the contrary, but forms an image at the same point P. This is as follows by Lorentz force [V × B]
(Fleming's left-hand rule). First, consider the orbit of the electron with reference to FIG. Considering where the electron exiting the point A in FIG. 5 (a) comes to the point B, the radial component H _r of the magnetic field acts on the axial velocity component V _z to move from the front side to the back side of the paper. The force, -e (V _z × H _r ) appears.
As a result, the electron has V _z , and at the same time, Fig. 5 (b)
As shown in (4), the rotation about the axis is started with the velocity component V _θ (in this case, turning to the left with respect to the traveling direction). When a component H _{z in} the axial direction of the magnetic field acts on the velocity component V _θ , a force F _r (= −e (V _θ × H _z )) for converging there occurs, and this force causes a point P (FIG. 4). Image). On the other hand, the case of the positron is similarly considered at the point B in Fig. 6 (a).
Assuming that the positron has the same energy as the electron described in FIG. 5, the axial component of the velocity at point B is V _z . The force generated by the action of this component V _z and the radial component H _r of the magnetic field is [+ e (V _z × H _r )] in the case of positron,
The size is the same as that of the electron, but the direction is opposite. Therefore positron starts to rotate about the axis at a velocity component -V _theta (turning to the right with respect to the traveling direction) as shown in Figure No. 6 (b). When the axial component H _z of the magnetic field acts on −V _θ , a focusing force F _r ′ = + e ((−V _θ ) × H _z ) is generated.

F _r ′ = + e ((− Vθ) × H _z ) = − e (Vθ ×
H _z ) = F _r (2) From equation (2), the focusing force _r ′ acting on the positron is exactly the same as the focusing force F _r acting on the electron, and therefore the rotation is the opposite but the same point. Imaged in Z, it can be seen that the magnetic lens has the same focal length for positrons and electrons of the same energy. A detailed calculation shows that the lens formula holds for the magnetic lens.

Where f is the focal length, a and b are the object and lens,
The distance between the lens and the image.

Further, f is expressed by the following equation.

Where E is the electron (or positron) energy (ke
V) and I are currents (AT) flowing through the magnetic field coil, and k is a constant determined by the pole piece shape of the magnetic field lens.

In the case of the present embodiment, since positrons are driven in through a small hole 11 'provided at the center of the fluorescent plate (imaging plane) 11, all images successively formed by the respective lenses are on the axis of the magnetic field lens. Yes, this is not a problem, but generally it is a fluorescent screen (image plane) 11
When trying to inject a positron from any place in the image, the problem is the rotation of the image. In the case of normal optics, it is either an inverted image or an erect image, but in the case of a magnetic field lens, the image generally rotates as shown in FIG. This is because there is a rotation (Vθ or −Vθ) for producing the focusing force F _r of the magnetic field lens as described above.
Therefore, if the electron image is rotated by the angle φ, it is easily understood that the positron image is rotated by the angle −φ.

This rotation angle φ is given by the following equation.

Where Φ ₀ is the acceleration voltage, B (Z) is the magnetic flux density on the axis, and Z _a
And Z _b are the Z-axis coordinates of the object and the image, respectively.
An example of calculation of equation (5) is shown in FIG. In the figure, NI is a current (AT) flowing through the magnetic lens. Further, φ ₀ represents rotation by the objective lens, and φ _p represents rotation by the projection lens. From FIG. 8, the total rotation angle φ _total can be adjusted to π (rad) by adjusting the values of the currents flowing through the objective lens and the projection lens, respectively.
It can be easily adjusted. Thus the rotation angle φ
_By setting _total to π (rad), that is, 180 °, the rotation angle of the positron also becomes −180 ° (that is, 180 °), and the electron image and the positron image can be matched. In this way, the problem of image rotation due to the magnetic field lens can be solved.

In the present embodiment, the method of inserting the positron source 12 at the time of irradiation of the positron beam is adopted. With electrodes,
With this deflection electrode, the beam is always avoided at another place, and a small hole 11 'formed in the fluorescent plate only during irradiation (measurement).
It goes without saying that a method of passing through or a combination of these methods may be used. In this embodiment, the position resolution of the positron annihilation analysis is about the area of the small hole 11 'in the observed image. That is, the magnification M, the area of the small hole 11 'is A
Then, the position resolution is about A / M ² . Therefore, the position resolution can be adjusted by adding a diaphragm function to the small hole 11 'of the fluorescent plate (imaging surface) 11 and making the size of the small hole 11' variable. Of course, the resolution can be changed by changing the magnification of the electron microscope. Next, another modification will be described with reference to FIGS. In each of the drawings, the parts denoted by the same reference numerals as those in the above-mentioned embodiment are the same or corresponding parts.

FIG. 9 shows a second embodiment of the present invention, which is an example in which the deflection magnet 30 is used in the positron irradiation device. The positron beam emitted from the positron source 12 is heated, accelerated,
After being converged, it is deflected by the analysis magnet and the small hole 11 '.
It is driven into the sample 4 through. This embodiment also has small holes 1
Since positrons are implanted through 1 ', there is essentially no difference from the above-mentioned embodiment, but in this embodiment it is easy to secure a space for the positron irradiation system, and the heat plate 13, the accelerating tube 14, etc. Annihilation γ caused by positron hitting
Lines (stray light) can be easily shielded and the S / N ratio of measurement can be improved. As in the second embodiment, the path of the electron beam 21 from the electron source 12 to the fluorescent plate (image plane) 11 is deflected, and then the electron beam 21 is passed through the axial center of the imaging lens system 10. The electron irradiation device as described above will be referred to as a deflection type axial center irradiation device.

FIG. 10 shows a third embodiment of the present invention, which includes an electron source 12, a thermalization plate 13, a positron accelerator tube 14, and a focusing coil 15.
It shows an example in which a positron irradiating device including the above is movable. In this embodiment, the fluorescent plate (imaging surface) 11 is not provided with small holes, and the fluorescent plate 11 is made of a transparent plate coated with fluorescent paint on both front and back surfaces thereof, and the back surface of the fluorescent plate 11 is irradiated with a positron beam. By doing so, fluorescence is emitted, and the position of the positron beam on the fluorescent plate can be confirmed. The positron irradiation device is movable so that the positron beam 21 can be irradiated to any position on the fluorescent plate 11. Further, the fluorescent plate 11 has a structure that can be opened and closed as shown by a broken line in the figure.

Next, the operation procedure of this embodiment will be described. First, the positron irradiation device is moved so that the fluorescent spot (spot) by the positron beam comes to the place where the positron annihilation analysis of the observation image is desired. Next, the fluorescent plate 11 is flipped up in the same manner as when taking a photograph, and the positron beam 21 is shot into the sample 4 through the imaging lens system 10. According to this embodiment, there is an effect that an arbitrary position of the observation image can be analyzed without moving the sample position. The positron irradiator is moved by a goniometer so that the positron beam always faces the pole piece of the projection lens 9 after passing through a predetermined phosphor screen position. In conjunction with this, the current of the converging lens 15 is changed to the positron beam 21.
Is automatically adjusted so that the beam diameter becomes the smallest when passing through a predetermined phosphor screen 11. The positron irradiation device of the type that moves the irradiation position of the positron beam 21 in this way will be referred to as a moving-source scanning scanning irradiation device.

It is possible to easily scan the positron beam 21 by combining the deflection electrodes without moving the positron irradiation device, and this is called a deflection electrode type scanning irradiation device.

FIG. 11 is a view showing a fourth embodiment of the present invention, in which a positron source 1
2 is attached to a support movable in the XY directions, and the fluorescent plate (imaging surface) 11 is directly scanned. The energy of positrons emitted from the positron source 12 is continuously distributed from 0 to 540 keV, but in the case of reverse imaging, the positrons having a large energy difference from the electron beam energy have a greatly deviated orbit and are inserted between the lenses in the middle. Excluded with the slits that have been. Therefore, positrons having energy close to the electron beam energy are preferentially implanted in the sample 4. This embodiment is effective as a simple method when the accuracy of the position where the positron is driven is not required so much. The positron deceleration tube 18
However, if the implantation amount of positrons may be small, it may not be provided.

FIG. 12 shows a fifth embodiment of the present invention, which is effective when accuracy is not required so much as the embodiment of FIG. In this embodiment, as shown in FIG.
A decelerator plate 32 is used instead of the positron deceleration tube 18 (see FIG. 2). The reduction plate 32 is, as shown in FIG.
It has a large number of holes and can rotate. In the case of normal electron microscope observation, the electron beam 20 is passed through this hole, and in the case of positron annihilation analysis, the reduction plate 3
The positron beam 21 is made to impinge on this plate 32 by rotating 2 by an appropriate angle, and is decelerated so that the positron is blocked by the sample 4. The speed reducing ability can also be adjusted by changing the thickness of each part of the speed reducing plate 32.

The various kinds of examples of the transmission electron microscope of the present invention have been described above. However, the present invention can be similarly applied to any electron microscope having an imaging lens system such as a radiation electron microscope or a projection electron microscope in addition to the transmission electron microscope.

FIG. 13 shows a sixth embodiment of the present invention, which is an embodiment when the present invention is applied to an electron mirror type electron microscope. In FIG. 13, (a) shows a configuration diagram of this embodiment, and (b) shows an electron mirror. In this type of electron microscope, an electron beam 20 is bent by a deflecting magnetic field and put into an electron mirror, and a sample is placed on the bottom of the mirror. The incident electrons 20 are driven back near the sample surface,
It is bent by the deflection magnetic field, and an image is formed on the fluorescent screen 11 by the projection lens 33. When an electron is reflected, it is extremely sensitive to an electric field in the vicinity thereof, and therefore, the image is contrasted with slight irregularities on the sample surface. In such an electron mirror electron microscope,
When a positron is driven from the fluorescent plate 11 side to the projection lens 33 side (this lens corresponds to the image forming lens system of the above-described embodiment), a reverse image is formed on the sample 4 according to the same principle as that of the above-described embodiment, which is the same as the electron reflection point. A positron hits the position. At the reflection point, the positron has an electric charge opposite to that of the electron, so that the positron is sucked toward the surface of the sample and strikes the sample 4. In this way, positrons can be driven into the surface position of the sample 4 corresponding to the electron image on the fluorescent plate.

In the present invention, as the annihilation γ-ray detector, an example of measuring the annihilation γ-ray energy spectrum is shown, but (1) a pair of γ-ray detectors on both sides of the sample (at least one of which is the sample Fine movement is possible on the circumference of the center (±
(About 50 mrad)), so that γ−
Measurement of γ-angle correlation (2) It is also possible to measure the lifetime of positrons by injecting the positron beam intermittently on the order of several PS.

According to the present invention, since positrons can be driven into the electron microscope observation position of the sample, it becomes possible to measure physical properties in a microscopic region (approximately electron microscope resolution) using the positron annihilation method.

〔The invention's effect〕

As described above in detail, in the present invention, the positron beam is applied to the sample through the imaging lens system of the electron microscope, so that the positron can be injected with high precision in a fine local region of the sample observed by the electron microscope. Therefore, there is an effect that a positron annihilation analysis method and an analysis device capable of performing minute local analysis of a sample to be analyzed can be obtained.

[Brief description of drawings]

1 to 8 are views for explaining the first embodiment of the present invention.
FIG. 1 is a longitudinal sectional view of the device of the present invention, FIG. 2 is a schematic configuration diagram of the device shown in FIG. 1, FIGS. 3 to 8 are views for explaining the principle of the present invention, and FIGS. FIGS. 9A and 9B are schematic configuration diagrams respectively explaining other embodiments of the present invention. FIG. 9 is a second embodiment of the present invention, FIG. 10 is a third embodiment, and FIG. 11 is a fourth embodiment.
FIG. 12 is a diagram showing a fifth embodiment, FIG. 13 is a diagram showing a sixth embodiment, FIG. 14 is a system diagram of a conventional positron annihilation analyzer, and FIG. 15 is a diagram explaining the principle of the positron annihilation analysis method, 16th
FIG. 17 is a schematic configuration diagram of a general transmission electron microscope, and FIG. 17 is a diagram explaining the principle of the transmission electron microscope shown in FIG. 1 ... Electron gun, 2 ... Accelerator tube, 3 ... Condenser lens, 4 ... Sample, 4 '... Sample set part, 5 ... Objective lens, 6 ... First intermediate lens, 7 ... Second Intermediate lens,
8 ... First projection lens, 9 ... Second projection lens, 10 ...
... Imaging lens system, 11 ... Fluorescent plate (imaging surface), 11 '...
… Small holes, 12 …… Positron source, 12 ′ …… Positron source support, 13 …… Thermalization plate, 14 …… Positron accelerator tube, 15 ……
Converging lens, 16 ... Collimator, 17 ... Film chamber, 18 ... Positron deceleration tube, 18 '... Correction coil, 1
9: annihilation gamma ray detector, 20: electron beam, 21 ...
… Positron beam, 22 …… Disappearing γ-rays, 23 …… Object, 2
4 to 28 ... Image, 29 ... Magnetic lens, 30 ... Deflection magnet, 31 ... X-Y movable support, 32 ... Decelerator plate, 33 ... Projection lens (imaging lens), 34 ... Sample.

Claims (27)

[Claims] 1. A transmission electron microscope for irradiating a sample to be analyzed with an electron beam to analyze the sample is provided with a positron source for irradiating a positron beam from a direction opposite to the traveling direction of the electron beam. Further, the positron beam passes through the image forming lens system of the transmission electron microscope, and the energy of the positron beam passing through the image forming lens system and the energy of the electron beam are made substantially equal to each other. The energy of the positron beam that has passed through the system is decelerated to about thermalization energy through a positron deceleration means, the sample is irradiated with the positron beam, and the annihilation γ-ray generated in the sample is measured to analyze the sample. A positron annihilation analysis method characterized by performing. 2. The transmission electron microscope according to claim 1, wherein the transmission electron microscope is an electron gun, an acceleration tube, a condenser lens,
A positron annihilation analysis method comprising a sample setting unit, an imaging lens system, and an imaging surface. 3. The positron beam according to claim 1, wherein the positron beam is made incident on a thermalizing plate to be heated, the energy distribution value is on the order of 1 eV, and the positron is accelerated to obtain a monochromatic positron. A positron annihilation analysis method, which comprises irradiating the image forming surface side to the image forming lens system side after forming the beam. 4. The positron beam according to claim 1, wherein the positron beam is heated, accelerated, converged, and then deflected to irradiate the positron beam from the image forming surface to the image forming lens system side. A positron annihilation analysis method characterized by: 5. The positron annihilation analysis method according to claim 1, wherein the transmission electron microscope is an electron mirror electron microscope. 6. A transmission electron microscope provided with an electron gun, an imaging lens system, an imaging surface, a sample setting section, and the like, and a transmission electron microscope provided in the transmission electron microscope, wherein the imaging lens system passes through an electron beam. And a positron irradiation device for irradiating the sample set in the sample setting section with a positron beam whose energy when passing through the imaging lens system is substantially equal to the energy of the electron beam of the electron microscope, Positron deceleration means provided between the imaging system and the sample setting unit for decelerating the energy of the positron beam that has passed through the imaging system to about thermal energy, and positrons for the sample set in the sample setting unit. An annihilation γ-ray measuring device for measuring annihilation γ-rays generated when irradiated with a positron annihilation analyzer. 7. The transmission electron microscope according to claim 6, wherein the transmission electron microscope is an electron gun, an acceleration tube, a condenser lens,
A positron annihilation analyzer characterized by comprising a sample setting section, an imaging lens system and an imaging surface. 8. The positron irradiating device according to claim 6, wherein the positron source emits a positron, a thermalizing plate that heats the positron emitted from the positron source, and the heated positron. A positron annihilation analyzer characterized by comprising a positron accelerating tube for accelerating the beam and a converging lens for converging the accelerated positron beam. 9. The positron annihilation analyzer according to claim 8, further comprising a collimator on the image plane side of the converging lens in the positron irradiation device. 10. The annihilation γ-ray measuring device according to claim 6, wherein the annihilation γ-ray detector is provided obliquely behind the sample when viewed from the direction of the positron irradiation device. Positron annihilation analyzer. 11. The positron annihilation analyzer according to claim 6, wherein the image plane is made of a fluorescent plate. 12. The positron annihilation analyzer according to claim 11, wherein the fluorescent plate is provided with a small hole for passing a positron beam in a central portion thereof. 13. The positron annihilation analyzer according to claim 12, wherein the small hole has an opening / closing structure and is opened when the sample is irradiated with a positron beam. 14. The positron annihilation analyzer according to claim 6, wherein the imaging lens system is composed of an objective lens, a central lens, and a projection lens. 15. The positron annihilation analyzer according to claim 6, further comprising a correction coil provided between the imaging lens system and the positron deceleration means for correcting the trajectory of the positron beam. . 16. The positron annihilation analysis device according to claim 6, wherein the positron irradiating device is a linear axis center irradiating device whose axial center coincides with the axial center of the imaging lens system. apparatus. 17. The positron annihilation analysis device according to claim 8, wherein the positron source is of a system inserted into a positron irradiation device at the time of positron beam irradiation. 18. The positron annihilation device according to claim 8, wherein the positron irradiation device is provided with a positron beam shutter in front of the positron source, and the shutter is opened during positron beam irradiation. Analysis equipment. 19. The positron annihilation analyzer according to claim 8, wherein the converging lens is provided with a deflection magnet in front of the converging lens to deflect the path of the positron beam from the positron source to the image plane. 20. The positron irradiating device according to claim 6, wherein the path of the positron beam from the positron source to the image plane is deflected, and then the positron beam passes through the axial center of the image forming lens system. A positron annihilation analysis device, which is a deflection type axial center irradiation device as described above. 21. The positron annihilation analyzer according to claim 6, wherein the positron irradiating device is a radiation source moving scanning irradiating device having a structure capable of moving parallel to an image plane. . 22. The positron annihilation analyzer according to claim 11, wherein the fluorescent plate is composed of a transparent plate coated with fluorescent paint on both front and back surfaces thereof. 23. The positron annihilation analyzer according to claim 6, wherein the positron irradiation device is a deflection electrode type scanning irradiation device having a structure in which a positron beam is scanned by a combination of deflection electrodes. . 24. The positron annihilation analyzer according to claim 6, wherein the positron irradiator has a structure in which a positron source moves in the XY directions on the imaging plane. 25. The positron deceleration means according to claim 6, wherein the positron deceleration means is a deceleration tube for applying a negative voltage provided between the imaging lens system and the sample setting section. Positron annihilation analyzer. 26. The positron annihilation analyzer according to claim 25, wherein the deceleration tube has a large number of holes and has a rotatable structure. 27. The positron annihilation analyzer according to claim 6, wherein the transmission microscope is an electron mirror electron microscope.