JPS6335480Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sample cooling device for an electron microscope or the like that can check the temperature of a cooled sample.

In electron microscopy, cooling a sample is extremely important for researching the physical properties of the sample, and has been in practice for a long time. In conventional equipment, the sample is held and fixed in a holder, the holder is connected to a refrigerant tank through a heat conduction plate and a heat conduction rod, and liquid nitrogen or liquid helium is injected into the refrigerant tank to keep the sample at a nitrogen temperature. Alternatively, it is designed to be cooled to near the helium temperature, and the temperature at that time is measured by a thermocouple attached to the holder.

In such an apparatus, the sample is cooled to a predetermined temperature, but the temperature is measured by a thermocouple attached to the holder, so when the electron beam is irradiated during observation, the sample is If the temperature of the sample increases due to an increase in temperature or some kind of accident, the measurement result may be significantly different from the actual sample temperature, causing a problem.

The present invention has been devised in view of the above points, and provides an apparatus that can accurately confirm that the sample has been cooled to a predetermined temperature or lower during observation of the cooled sample.

The configuration of the present invention includes a holder that holds a sample with good heat conduction, a mechanism that movably supports the holder,
In an apparatus comprising a refrigerant tank filled with a refrigerant, a means for thermally connecting the sample holder and the refrigerant tank, and a temperature measuring means attached to the sample holder, the temperature is directed toward the surface of the sample held in the holder. The present invention is characterized by a sample cooling device such as an electron microscope, which is provided with means for flowing a gas that solidifies at a temperature higher than or comparable to a predetermined cooling temperature of the sample.

An embodiment of the present invention will be explained in detail below based on the drawings.

Figure 1 is an overall sectional view of the present invention;
The figure is an enlarged sectional view of a portion thereof. In these figures, reference numeral 1 denotes an objective lens, and the objective lens is composed of a yoke 2, an excitation coil 3, and a magnetic pole piece 4. A sample holder 5 is arranged in the magnetic gap between the magnetic pole pieces in a direction perpendicular to the optical axis of the electron beam. The holder is supported by a holder 7 attached to a sample stage 6 placed above the objective lens (around the magnetic pole pieces). The holder is taken out of the vacuum and connected to a refrigerant tank 8 filled with liquid nitrogen or liquid helium. Further, a sample moving mechanism 9 is attached to the stage opposite to the holder and engages with the holder 5. The holder 5 is provided with an electron beam passage hole 10, into which a mesh 13 holding a sample 12 is attached via thermally conductive holding pieces 11a and 11b. The holder is connected to one end of a heat conduction rod 15 via a heat conduction plate 14. The conduction rod is held thermally insulated inside the holder 7, and the other end is thermally connected to the refrigerant in the refrigerant tank 8.

A sample chamber 16 is placed above the objective lens, and a gas supply source 17 is fixed to its side wall. A pipe 18 extends into the sample chamber from this gas supply source, and a thin tube 19 is taken out from the tip of the pipe, the open end of which is close to and opposite the upper surface of the sample 12 held in the holder 5. A gas for checking the cooling temperature (for example, nitrogen gas) is emitted from the open part toward the sample. A thermocouple 20 is fixed to the holder 5, and its lead wire is taken out of the mirror body through the holder 7.
Connected to an indicator (not shown).

In such a configuration, cooling the sample and measuring the sample temperature using a thermocouple are the same as in the prior art. Then, the temperature of the sample is assumed to be higher than the temperature of the holder, and a gas having a solidification point higher than that temperature is blown onto the surface of the sample from the thin tube 19. Now, when the sample is cooled with liquid helium, nitrogen gas is used as the confirmation gas. The solidification point of the nitrogen gas is 63°, so if the sample is cooled below that point, the gas will solidify on the sample surface and adhere to it. Therefore, an electron beam is irradiated onto the sample in a cooled state, and an electron beam diffraction image of the sample is first observed. Then, while blowing the gas onto the surface of the sample from the thin tube 19, changes in the electron beam diffraction image of the sample are observed. At this time, if the temperature of the sample is higher than the solidification point of the gas, the gas will not solidify, and therefore no change will appear in the electron beam diffraction image of the sample. However, if the sample is cooled below the solidification point of the gas, the gas will solidify and adhere to the sample surface, and an electron diffraction image of the sample and the solidified gas will be observed. The diffraction image will be clearly different from the diffraction image of the sample alone. Therefore, by performing the above observation, it can be confirmed that the sample temperature has decreased to the solidification point of the blown gas.

With the configuration described above, the thermocouple 20
This makes it possible to easily and reliably detect unexpected accidents and increases in sample temperature due to electron beam irradiation that cannot be checked by measuring the temperature of the holder.
It is also possible to discover when a thermocouple is out of order, and it can also be used to calibrate the thermocouple temperature.

Note that the above is an example of the present invention, and various changes can be made when implementing the invention. For example, in the illustrated example, the sample is inserted from a direction perpendicular to the optical axis, but the present invention can be similarly applied to an apparatus in which the sample is inserted from above the objective lens. Further, the gas emitted from the thin tube 19 toward the sample is not limited to the illustrated nitrogen gas, but can be arbitrarily selected depending on the cooling temperature of the sample. Furthermore, although the structure is shown in which the gas is introduced from the sample chamber, the present invention is not limited to this, but it may be blown out from the sample holder 5, or a thin tube may be installed in the holder that supports the objective aperture placed directly below the sample. Alternatively, the gas may be blown onto the sample from the objective aperture. Furthermore, it is convenient to prepare a plurality of types of gases and select and use them according to the sample temperature.

[Brief explanation of drawings]

FIG. 1 is an overall sectional view showing an embodiment of the present invention;
FIG. 2 is a sectional view of the main part of FIG. 1. 1: Objective lens, 4: Magnetic pole piece, 5: Sample holder, 6: Stage, 7: Holder, 8: Coolant tank,
9: Moving mechanism, 12: Sample, 15: Heat conduction rod, 1
6: sample chamber, 17: gas supply source, 18: pipe,
19: Thin tube, 20: Thermocouple.

Claims (1)

[Scope of utility model registration request] A holder for holding a sample with good thermal conductivity, a mechanism for movably supporting the holder, a refrigerant tank filled with refrigerant, a means for thermally connecting the sample holder and the refrigerant tank, and a mechanism attached to the sample holder part. An apparatus, such as an electron microscope, which is equipped with a temperature measuring means, which is equipped with a means for flowing a gas that solidifies at a temperature higher than or about the same as the predetermined cooling temperature of the sample toward the surface of the sample held in the holder. Sample cooling device.