JPH067469B2 - Electron microscope equipped with X-ray prevention means by energy filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-sensitivity and high-quality recordable electron microscope, and more particularly to an electron microscope for preventing generation of a center spot due to X-rays. is there.

[Conventional technology]

Generally, in a transmission electron microscope, a sample is irradiated with a focused electron beam, the diffraction pattern of the sample is formed on the back focal plane of the objective lens by the electron beam transmitted through the sample, and the diffracted electron beam is caused to interfere again. It is designed to form a magnified image of the sample. If this magnified image is projected on the fluorescent surface by the projection lens, a magnified transmission image of the sample is observed, and if the focal plane behind the objective lens is projected, the magnified sample diffraction pattern is observed. Further, if an intermediate lens is arranged between the objective lens and the projection lens, a magnified transmission image or a diffraction pattern can be arbitrarily obtained by adjusting the focal length of the intermediate lens. In order to observe the enlarged transmission image or diffraction pattern (hereinafter referred to as transmission electron beam image) formed in this way, a photographic film is placed on the image plane of the conventional projection lens to expose the transmission electron beam image. Alternatively, an image intensifier is arranged to amplify and project a transmission electron beam image.

[Problems to be solved by the invention]

However, photographic film has the disadvantage of low sensitivity to electron beams and troublesome development processing.On the other hand, when an image intensifier is used, the sharpness of the image is low and the image is distorted. There is a problem that it is easy.

By the way, recently, there has been proposed a recording medium having extremely high sensitivity, which is capable of releasing the accumulated electron beam energy as light when the irradiated electron beam energy is accumulated and then light irradiation or heating is performed.

FIG. 3 is a cross-sectional view of a stimulable phosphor (stimulable phosphor) sheet excited by light irradiation suitable for such a recording medium, 21 is a stimulable phosphor sheet, and 22 is a support. Body, 2
Reference numeral 3 is a stimulable phosphor layered on the support.

In the figure, the support 22 has a thickness of 100 to 200.
μ-sized polyethylene sheet, plastic film,
An aluminum plate of 0.5 to 1 mm, a glass plate of 1 to 3 mm, or the like is used, and it may be transparent or opaque. In the case of opacity, light emission is detected from the side to which excitation light is applied.
When transparent, luminescence can be detected from the side on which the excitation light is applied, the opposite side, or both sides. As such a stimulable phosphor used in the stimulable phosphor sheet, for example, described in _{JP-A-55-12143 (Ba 1-xy, Mg} x, Ca y) FX: aEu ²⁺
(However, X is at least one of Cl and Br, x and y are 0 <x + y ≦ 0.6, and xy
≠ 0, a is 10 ⁻⁶ ≦ a ≦ 5 × 10 ⁻² ),
BaF described in JP-A-59-56479
X · xNaX ′: aEu ²⁺ (where X and X ′ are
At least one of Cl, Br, and I, and x and a are 0 <x ≦ 2 and 0 <, respectively.
a ≦ 0.2) and other stimulable phosphors. Then, such a stimulable phosphor is dispersed in an appropriate binder and applied onto the support 22 so as to have a thickness of about 10 to 1000 μm. It should be noted that if the stimulable phosphor layer is self-supporting, it can itself be a stimulable phosphor sheet.

When the stimulable phosphor sheet thus formed is irradiated with radiation such as an electron beam, a part of the energy of the radiation is accumulated in the phosphor, and then the phosphor is irradiated with excitation light such as visible light. , The fluorescent body emits fluorescent light (stimulated emission light) according to the accumulated energy. Further, instead of the above-mentioned stimulable phosphor that is excited by light irradiation, a thermofluorescent substance that emits radiation energy accumulated by heating as heat fluorescent light may be used. In this case, for example, Na ₂ SO ₄ , MnS
A compound obtained by adding at least one of a small amount of additives such as Mn, Dy, and Tm to a sulfuric acid compound such as O ₄ , CaSO ₄ , SrSO ₄ , and BaSO ₄ may be used. Similar to the fluorescent sheet.

Therefore, a recording medium such as a stimulable phosphor sheet or a thermoluminescent sheet is arranged on the image plane of the electron microscope to store and record a transmitted electron beam image, and the recording medium is excited by an exciting light such as visible light. When scanning or sweep heating is performed to generate fluorescence, and this fluorescence is photoelectrically read, an electric signal corresponding to the transmitted electron beam image is obtained. If the electric image signal thus obtained is used, an electron microscope image is displayed on a display such as a CRT or permanently recorded as a hard copy, and further, the image signal is temporarily stored on a magnetic tape, a magnetic disk or the like. It is possible to leave it.

By the way, when the recording medium as described above is used, a black dot (hereinafter referred to as a center spot) is generated at the center of the recorded image. This phenomenon is mainly caused by X-rays generated as a result of electrons being scattered by a sample or the like because the sensitivity of the recording medium described above is dramatically higher than that of the conventional photographic film. It does not occur when is used.

The present invention is to solve the above-mentioned problems and uses a recording medium such as the above-mentioned accumulative phosphor sheet or thermoluminescent sheet which is extremely sensitive to electron beams and the like, and does not cause a center spot. It is an object of the present invention to provide an electron microscope equipped with an X-ray prevention means by an energy filter capable of high sensitivity recording.

[Means for solving problems]

Therefore, an electron microscope provided with an X-ray prevention means by an energy filter of the present invention is a lens system for enlarging and projecting a transmitted electron beam image obtained by irradiating a sample with an electron beam emitted from an electron gun. And an X-ray shutter that is solid or movably arranged on the optical axis and blocks X-rays generated from a sample, etc., and is arranged at a predetermined position of the lens system. X-ray and the X-ray
And an energy filter for avoiding the line shutter and returning it to the original optical axis.

[Action]

An electron microscope equipped with an X-ray prevention means by an energy filter of the present invention converges an electron beam emitted from an electron gun and irradiates a sample, and magnifies and projects a transmitted electron beam image at a predetermined position of a lens system. When an energy filter is provided, the orbit is bent to separate the electron beam from the X-ray when the energy filter is driven, and the X-ray shutter fixed or movable on the optical axis is avoided, whereby Even if a high-sensitivity recording medium such as a stimulable phosphor sheet or a thermoluminescent sheet is used, the center spot does not occur, by blocking with a shutter and projecting and recording only the transmitted electron beam image on the recording medium. In addition, a sharp image can be obtained, and the X-ray shutter can be moved to retract it, and the energy filter is not driven, so that it can be used as an electron microscope using a normal film. The ability.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of an electron microscope equipped with an X-ray shutter according to the present invention. In the figure, 1 is an electron gun, 2 is an electron beam, 3 is a converging lens, 4 is a sample, 5 is an objective lens, 6
a, 6b, and 6c are magnetic poles, 7 is a shutter, 8 is an intermediate lens, 9 is a projection lens, 10 is a high-sensitivity recording medium, and 11 is X.
A line, 12 is an optical axis, and 13 is a detection slit.

In the figure, an electron beam 2 emitted from an electron gun 1 and accelerated is converged by a converging lens 3 and irradiated on a sample 4, and a transmission electron beam image is formed by an objective lens 5. At this time, the electron beam is the magnetic pole 6 forming the Ω type energy filter.
The orbit is changed to the Ω shape by a, 6b, and 6c, the shutter 7 is avoided, and the optical path is returned to the optical axis 12.
3, the electron beam image passes through the intermediate lens 8 and the projection lens 9.
And is recorded as an energy filter image on the high-sensitivity recording medium 10.

On the other hand, the X-rays generated by the sample 4 are the magnetic poles 6a, 6b, 6c.
Since it is not affected by the magnetic field due to, the light travels along the optical axis 12 and is blocked by the shutter 7 arranged on the optical axis. As a result, the image is not projected on the recording medium 10 and the occurrence of the center spot is prevented.

It should be noted that the shutter 7 is configured to be movable and retracted so that the magnetic poles 6a, 6b, 6c constituting the energy filter are formed.
If is not excited, the electron beam goes straight and can be used as an electron microscope using a normal film.

FIG. 2 is a view showing another embodiment of the present invention using a reflection type (castan-only type) energy filter, in which 14 is a magnetic pole and 15 is an electrode.

In the figure, the orbit of the electron beam 2 is bent by the magnetic field by the magnetic pole 14 and advances toward the electrode 15, but is decelerated and repelled by the electric field by the electrode 15 and is reflected on the electrode surface to form an A or B orbit. The shutter 7 is drawn to avoid it, and the optical axis 12 is returned. Then, the electron beam that has passed through the detection slit 13 has a first
As in the case of the figure, the energy filter image is recorded by being projected on the recording medium 10. On the other hand, the X-ray 11 travels along the optical axis and is blocked by the shutter 7 to prevent the center spot from being generated.

〔The invention's effect〕

As described above, according to the present invention, an energy filter is provided at a predetermined position of the lens system to bend the trajectory of the electron beam, separate the electron beam and the X-ray, and fix or move only the X-ray on the optical axis. It is possible to block only the energy filter image by blocking the electron beam by the X-ray shutter provided in the above and projecting the electron beam on the recording medium while avoiding the X-ray shutter. Therefore, even if a high-sensitivity recording medium such as a stimulable fluorescent sheet or a thermoluminescent sheet is used for recording an electron microscope image, a center spot due to X-rays generated from a sample or the like does not occur, and only an electron beam is emitted. It becomes possible to obtain a sharp image. Further, by retracting the X-ray shutter and not driving the energy filter, it can be used as an electron microscope using a normal film.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the electron microscope according to the present invention using the energy filter according to the present invention, and FIG. 2 is a diagram showing a main part of the electron microscope according to the present invention using a reflection type energy filter. The figure is a cross-sectional view of a stimulable phosphor sheet used in the present invention. 1 ... Electron gun, 2 ... Electron beam, 3 ... Converging lens, 4 ... Sample,
5 ... Objective lens, 6a, 6b, 6c ... Magnetic pole, 7 ... Shutter, 8 ... Intermediate lens, 9 ... Projection lens, 10 ... High sensitivity recording medium, 11 ... X-ray, 12 ... Optical axis, 13 ... Detection slit, 14 … Magnetic pole, 15… Electrode

Claims (1)

[Claims] 1. A lens system for enlarging and projecting a transmission electron beam image obtained by irradiating a sample with an electron beam emitted from an electron gun, and a solid or movable arrangement on the optical axis,
An X-ray shutter that blocks X-rays generated from a sample and the like is arranged at a predetermined position of the lens system, and when driven, deflects the electron beam to separate it from the X-rays on the optical axis, and avoids the X-ray shutter An electron microscope provided with an X-ray prevention means by an energy filter having an energy filter for returning the light beam to the original optical axis.