JPH0132288Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a sample position control device for a side entry goniometer for an electron microscope.

Electron microscopes are equipped with side entry goniometers to move and tilt the sample. This goniometer supports a sample holder inserted through the side wall of a sample chamber on a stage, and the rotation of the goniometer rotates the sample holder and tilts the sample with respect to the optical axis. The above-mentioned sample tilt axis is arranged within the pole piece, and the height Z ₀ of the sample tilt axis from the lower pole is usually called the sample position.

In conventional goniometers, Z ₀ is fixed due to the stage design. Conventional adjustment of the optical axis direction involves tilting the sample tilting axis itself with respect to the stage using a spherical bearing in order to correct the unevenness of the sample inserted in the sample holder. I was making adjustments.

There are usually two ways to use this conventional adjustment of the optical axis direction.If you want to properly align the inserted sample at Z ₀ , the sample being examined will always be on the optical axis even if the sample is tilted. Therefore, the electron beam irradiation position on the sample is constant, and there is no image deviation due to tilt.
However, when observing with Z ₀ shifted, the optical axis is deviated from the sample tilt axis, so the electron irradiation position on the sample is different from that at Z ₀ , and there are drawbacks such as image omission due to tilt. It was hot.

In addition, in conventional goniometers, the sample position is determined by a stage, and the stage is fixed in the vertical direction, so the pole piece must be replaced when observing a transmission electron image and when observing a convergent electron diffraction image. However, there were drawbacks such as the need to expose the sample to the atmosphere during this time.

This idea was developed to improve the above-mentioned conventional drawbacks, and by providing a mechanism that moves the stage up and down in a vacuum-sealed state to adjust the sample position, it prevents the image from escaping due to the tilt of the sample. Another object of the present invention is to provide a goniometer sample position control device that allows observation of transmission images and diffraction images without replacing pole pieces.

This invention consists of a sample holder 7 inserted into the sample chamber 1 through the side wall, a stage 13 that supports the sample holder 7 in the sample chamber 1 so as to be able to rotate around the sample tilting axis 8, and this stage. Two leaf springs 2 connected to the top and bottom of 13 via sealing material
1, 22, a male thread 25 formed on the outer periphery of the stage 13, a rotatable ring-shaped worm wheel 26 having a female thread 27 on the inner periphery that engages with the male thread 25, and this worm wheel 26.
a worm 30 that can be adjusted from the outside to rotate the worm wheel; a mechanism that allows vertical movement of the stage 13 and prevents rotation so as to convert the rotation of the worm wheel 26 into vertical movement of the stage 13; A goniometer comprising a bush 31 having a tapered surface provided on the outer periphery of the stage 13, and a screw 16 for horizontal position adjustment and fixing of the stage 13 provided opposite to the bush 31. This is a sample position control device.

Hereinafter, the present invention will be explained with reference to illustrated embodiments. FIG. 1 is a partially cutaway plan view of a side entry goniometer for a transmission electron microscope according to an embodiment of the present invention, and FIG. It is a vertical sectional view taken by cutting at , and the cut plane is changed as appropriate for ease of understanding.

In the drawing, reference numeral 1 denotes a sample chamber, which is partitioned at the center by upper and lower lens pole pieces 2 and 3, and at the periphery by a yoke 4 and a non-magnetic spacer 5 connected to these. .

Reference numeral 6 denotes a goniometer, which has a sample holder 7 inserted into the sample chamber 1 through its side wall. The center axis of the sample holder 7 is a sample tilting axis 8, and a sample stage 9 is attached to the tip of the sample holder 7 so as to be located between the pole pieces 2 and 3, into which a sample 10 is inserted. ing. A moving rod 12 of a sample moving mechanism 11 is connected to the other end of the sample holder 7.

Reference numeral 13 denotes a donut-shaped stage, which is installed in the periphery of the sample chamber 1 so as to be movable up and down.
A moving rod 12 is slidably inserted therethrough, and the deviation between the sample tilting axis 8 and the optical axis Z can be adjusted using a screw 16. The stage 13 is supported by two plate springs 21 and 22 via O-rings 17, 18 and 19, 20 at the top and bottom, and is vacuum-sealed with respect to the yoke 4 and the spacer 5.
The vertical movement is caused by the elastic deformation of the two leaf springs 21, 22, and the two leaf springs 21, 22 and the O-ring 17~
The sliding movement of 20 allows movement in the horizontal plane.

23 is a screw that fixes the stage 13 in a predetermined plane position, and is screwed to the spacer 5 through the through hole 23a of the stage 13, and the stage 13
The stage 13 is allowed to move up and down and prevented from rotating, and the stage 13 is pressed by a spring 24. A pin 32 is attached to the spacer 5, and is inserted into a pin hole 32a of the stage 13. Like the screw 23, the pin 32 allows the stage 13 to move up and down, but prevents it from rotating. A male thread 25 is provided on the outer periphery of the stage 13, and a worm wheel 26 is provided on the outer periphery.
It engages with a female thread 27 provided on the inner periphery. The worm wheel 26 has a low-friction material 28 attached to its bottom surface so as to slide on the spacer 5, and is engaged with a worm 30 which can be adjusted from the outside through a gear portion 29 on its outer periphery. stage 1
A bush 31 having a tapered surface is provided at a portion facing the screw 16 of No. 3, so that the stage 13 can be fixed to the worm wheel 26 after adjustment.

In the goniometer sample position control device configured as described above, when the worm 30 is rotated from the outside with the screw 16 loosened, the worm wheel 26 engaged with the worm wheel 26 rotates, The stage 13 is moved up and down via the male screw 25 engaged with the female screw 27, which changes the height _Z0 of the sample tilt axis 8, thereby controlling the sample position. At this time, the stage 13 is O-ring 17,1
Since it is supported by two plate springs 21 and 22 via 8, 19, and 20, it moves up and down while maintaining a vacuum-sealed state. After adjusting Z ₀ to the specified position, screw 16
Tighten to secure stage 13 and keep Z ₀ in place.

The stage 13 can be moved in the horizontal plane by rotating the screw 16, but this movement is to adjust the deviation from the optical axis Z, and the moving distance is extremely small.
The engagement with 5 is such that it cannot be disengaged. In order to make this movement possible, the stage 13 is fitted with O-rings 17 to 20 and two leaf springs 2.
1 and 22, and a small gap is created between the screw 23 formed in the stage 13 and the through hole 2a, and between the pin 32 and the pin hole 32a.

In order to tilt the sample 10, the sample holder 7 is moved to the sample tilt axis 8 by rotating the goniometer 6.
When rotated about the central axis, the sample 10 on the sample stage 9 is tilted with respect to the optical axis Z. Further, movement of the sample stage 9 in the horizontal direction is possible by operating the goniometer 6 and the sample moving mechanism 11, but the details will be omitted.

In this way, it is possible to adjust Z ₀ arbitrarily by operating the worm 30, and in this case, even if Z ₀ is changed, the sample 10 is inserted on the sample tilt axis 8, so the sample 10 can be adjusted. Even if the image is tilted, the image will not disappear.

Figure 3 is a curve diagram showing an example of the characteristics of the pole piece, where C _S is the spherical aberration coefficient, C _C is the chromatic aberration coefficient,
f ₀ is the focal length, C/O is the condenser objective condition, d is the beam diameter, and α is the sample irradiation angle. When observing a transmission image with an electron microscope, the values of the spherical aberration coefficient C _S , the chromatic aberration coefficient C _C , and the focal length f ₀ are preferably smaller, and in the example shown in Fig. 3, Z ₀ = 2 to 2.5.
There is an optimum condition in mm.

By the way, when the sample is held within the objective lens field, there is a front magnetic field that operates as a condenser lens above and below the sample, and a rear magnetic field that operates as an objective lens, so that the incident electron beam parallel to the optical axis of the lens is directed toward the sample surface. The condition is that the electron beam is focused at the top, and the electron beam emitted from this point becomes parallel when it exits the objective lens.
That is, the capacitor objective condition C/O
There is a sample position where Z ₀ = 1.5 mm in Figure 3.
It's time. Under these conditions, the parallel electron beam is entirely focused on the sample, so the beam diameter d becomes very small and the sample irradiation angle α becomes very large. In order to achieve this, the sample irradiation area is small, the irradiation area is difficult to control, and the irradiation area moves with a slight horizontal deflection magnetic field, resulting in _poor operability. 2.5mm is chosen.

On the other hand, when observing a diffraction image, it is necessary to obtain a diffraction image of a minute area, and it is better to capture more information inside the sample by irradiating this area with the largest possible illumination angle, so the diffraction image is a condenser object. It is necessary to observe the specimen under conditions close to the active conditions. For this reason, in the past, another C/O pole piece was prepared and the pole piece was replaced when observing the diffraction image, but in the present invention, the pole piece is adjusted by moving the stage 13 up and down to adjust Z ₀ . The usage conditions of the pole piece can be arbitrarily selected without replacing the pole piece.

As explained above, according to the present invention, the stage supporting the sample holder is provided with a mechanism that moves the stage supporting the sample holder up and down in a vacuum-sealed state to adjust the sample position. This makes it possible to prevent image deviation even when the sample is tilted, and to freely control the sample position to suit transmission and diffraction images.
By replacing the pole piece, you can select the optimum conditions for the desired pole piece without exposing the sample to the atmosphere. In addition, since the vertical movement mechanism combines a worm wheel mechanism and a screw mechanism, the stage can be moved up and down smoothly while maintaining the horizontal position, and a mechanism for adjusting and fixing the horizontal position of the stage is provided. It is easy to adjust the deviation from the optical axis.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway plan view of a side entry goniometer for a transmission electron microscope according to an embodiment of the present invention, FIG. FIG. 3 is a curve diagram showing an example of the characteristics of the pole piece. In each figure, the same reference numerals indicate the same or equivalent parts. 1 is the sample chamber, 2 and 3 are the pole pieces, 4 is the yoke, 5 is the spacer, 6 is the goniometer, 7 is the sample holder, 8 is the sample slope, and 9 is the sample holder. Sample stand, 10
is a sample, 13 is a stage, 21 and 22 are two leaf springs, 25 is a male screw, 26 is a worm wheel, 2
7 is a female thread, 30 is a worm, and 31 is a bush.

Claims (1)

[Scope of utility model registration request] A sample holder 7 is inserted into the sample chamber 1 through the side wall, and the sample holder 7 is connected to a sample tilting axis 8.
A stage 13 supported within the sample chamber 1 so as to be able to rotate around the stage 13, two plate springs 21 and 22 connected to the upper and lower sides of the stage 13 via sealing materials,
A male screw 25 formed on the outer periphery of the stage 13
a rotatable ring-shaped worm wheel 26 having a female thread 27 on the inner circumference that engages with the male thread 25; a worm 30 that can be adjusted from the outside to rotate the worm wheel 26; A mechanism that allows the stage 13 to move up and down and prevents its rotation so as to convert the stage 13 into vertical movement; a bush 31 that has a tapered surface provided on the outer periphery of the stage 13; A goniometer sample position control device comprising screws 16 for adjusting and fixing the horizontal position of a stage 13 provided to face each other.