JP2986304B2 - Sample cooling and holding device for scanning tunneling microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning tunnel microscope for scanning a sample surface with a probe and observing an image while detecting a tunnel current flowing between the probe and the sample while the sample is cooled to a low temperature. The present invention relates to a sample cooling and holding device.

[0002]

2. Description of the Related Art When observing a sample using an STM (scanning tunnel microscope), not only room temperature but also a low or high temperature environment may be required depending on the purpose. For example, when observing a sample in a superconducting state, it is necessary to keep the sample cooled to an extremely low temperature. In a conventional sample cooling holder for an STM (scanning tunnel microscope) used in such a case, the entire STM unit such as a sample stage, a probe, and a fixed base, or the entire container containing the STM unit is put in a refrigerant. There is a type in which the entire STM unit is cooled by cooling, and a type in which only the sample holder or only the sample stage is cooled.

[0003]

However, any of the sample cooling holders for STM described above has a problem that once cooling is started, if a problem occurs in the sample being cooled, the sample cannot be replaced immediately. . That is, in order to exchange the sample, the observation of the cooled STM image is stopped halfway, the temperature is returned to normal temperature, the STM unit is removed, and the sample is exchanged.
Cooling had to be performed again from the beginning to observe a cooled STM image. Therefore, it takes a lot of time and effort to exchange the sample, and the amount of wasted refrigerant increases.

[0004] Further, even in a type in which only the sample holder is cooled, the entire STM unit is covered with the container because the structure is exclusively for cooling STM, and the sample cannot be replaced immediately.

Further, since the stage has a dedicated shape for the cooling STM, it is not compatible with the sample holder for the room temperature and high temperature STM. Therefore, even if the room temperature and the high temperature STM are present, the cooling STM image observation is performed. In case, separate cooling STM
Had to be prepared, which was uneconomical.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a sample cooling and holding apparatus for a scanning tunnel microscope which can easily exchange a sample.

[0007]

For this purpose, the present invention performs image observation by scanning a sample surface with a probe while detecting a tunnel current flowing between the probe and the sample while the sample is cooled to a low temperature. A sample cooling and holding device for a scanning tunnel microscope, comprising: a sample holder for attaching a sample fixing portion to a holder case portion to fix a sample to the sample fixing portion; and a heat conducting portion disposed in a peripheral portion in contact with the sample fixing portion. It is characterized by comprising a sample stage having a heat insulating material for insulating the heat conducting portion from the main body and a cooling device for cooling the heat conducting portion, and configured to mount the sample holder from the back side.

[0008]

According to the sample cooling and holding device for a scanning tunnel microscope of the present invention, a sample holder is attached to a holder case and a sample is fixed to the sample holder. Since the sample holder includes a heat conducting part, a heat insulating material that insulates the heat conducting part from the main body, and a cooling device that cools the heat conducting part, the sample holder is configured to be mounted from the back side. It can be attached and detached from the back side of, and the sample can be easily exchanged.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing one embodiment of a sample cooling and holding device for a scanning tunnel microscope according to the present invention, wherein (A) is a side view of a sample holder, (B) is a side view of a sample stage, and (C) is a front view of the sample stage. FIG. 3D is a diagram showing a state where the sample holder is mounted on the sample stage. In the drawing, 1 is a sample holder, 2 and 18 are heat insulating materials, 3 is a sample fixing portion, 4 is a holder case portion, 5 is a sample, 11 is a sample stage, 12 and 13 are cooling devices, and 14 and 15 are heat conductors. , 16 are heat conducting parts, 1
7 denotes a heat conductive cover, and 19 denotes a stage body.

As shown in FIG. 1A, the sample holder 1 has a sample fixing part 3 attached to a holder case part 4 via a heat insulating material 2 and a sample 5 is fixed in the sample fixing part 3. . The sample fixing portion 3 covers the periphery of the rear surface of the sample 5 and has a window on the front surface for a probe to access, and is made of a material having good thermal conductivity such as Cu.

As shown in FIG. 1B, the sample stage 11 has a stage main body 1 having a heat conducting portion 16 and a heat insulating material 18.
9 and cooling devices 12, 13 and their heat conductors 14, 15
Consists of The stage body 19 has a cylindrical space so as to fit the sample holder 1 from the back side as shown in FIG. 1C, and holds the sample holder 1 as shown in FIGS. 1B and 1D. When the sample holder 1 is mounted, the heat conducting portion 16 is arranged at a portion in contact with the periphery of the sample fixing portion 3, and a heat insulating material 18 is provided in contact with the periphery of the heat insulating material 2 and further surrounds the heat conducting portion 16. The front surface of the sample 5 is left open.
And the heat conduction part 16 is the heat conductor 14 of the cooling device 12.
, And the stage body 19 is connected to the heat conductor 15 of the cooling device 13. The cooling device 12 performs cryogenic cooling using, for example, liquid helium, and the cooling device 13 performs low-temperature cooling using, for example, liquid nitrogen. The heat conductor cover 17 covers the heat conductor 14 and the heat conductor 16 at the temperature of the heat conductor 15.

A sample cooling and holding apparatus for a scanning tunnel microscope according to the present invention comprises a sample stage 1 as shown in FIG.
The sample can be easily exchanged by attaching and detaching the sample holder 1 to and from the rear surface by using, for example, an MGL (magnetic coupling type guide rod) device or the like. Moreover, when the sample holder 1 is mounted on the sample stage 11, the sample fixing portion 3 is cooled to a very low temperature by the cooling device 12 through the surrounding heat conducting portion 16 and is insulated by the heat insulating materials 2 and 18, and the surroundings are further cooled. Stage body 19 and holder case portion 4 that comes into contact with the
In step 3, auxiliary cooling is performed at a low temperature. That is, the heat insulating materials 2 and 1
The holder case 4 and the stage main body 19 form a thermal shield so as to surround the housing 8. Therefore, the radiation and heat radiation from the sample fixing unit 3 and the sample 5 are transferred to the heat insulating material and the stage body 18.
Therefore, the cooling effect of the sample 5 can be enhanced and the cooling temperature can be stabilized.

As shown in the figure, in the sample holder 1, a step is provided between the heat insulating material 2 and the sample fixing part 3.
, The attachment and detachment of the sample holder 1 to and from the sample stage 11, the contact between the heat insulating materials 2 and 8, the contact positioning between the sample fixing portion 3 and the heat conducting portion 16 can be facilitated, and cooling can be performed. Above all, the sample can be exchanged as in the conventional case.

FIG. 2 is a diagram schematically showing a sample holder stage for a normal temperature and high temperature STM.
Indicates a sample stage, and 23 indicates a sample.

As shown in FIG. 2, the sample stage 22 for the normal temperature and high temperature STM includes the cooling devices 12 and 13 shown in FIG.
In addition to eliminating the heat conductors 14 and 15, the heat conductors 16 and
The heat insulating material 18 is also eliminated, and the conventional normal temperature, high temperature S
It has the same shape as the TM sample stage. Therefore,
Using the conventional sample holder and the sample stage shown in FIG. 1 allows the sample to be cooled, and by replacing it with the sample stage shown in FIG. 2, it is possible to observe ordinary and high-temperature STM images as before. However, the cooling operation may be stopped.

FIG. 3 is a view showing another embodiment of the sample cooling / holding device for a scanning tunneling microscope according to the present invention, and FIG. 4 is another example in which a permanent magnet is mounted on the sample cooling / holding device for a scanning tunneling microscope according to the present invention. It is a figure showing an example.

The example shown in FIG. 3 omits the cooling device 13 and the heat conductor 15 in FIG. 1, and the example shown in FIG. 4 mounts the permanent magnet 32 on the holder case 31 of the sample holder. And a sample holder for applying a cooling magnetic field. 33 is a yoke and 34 is a thermal insulator.

When the sample is a superconducting material or the like, application of a magnetic field results in a portion where a magnetic flux passes through and a portion where no magnetic flux passes. In this case, the portion through which the magnetic flux passes is a defective portion that is not in a superconducting state. The properties and the like of the superconducting material change depending on the ratio of the defective portion to the whole, the arrangement thereof, and the like. Since an overcurrent due to the magnetic flux flows through the portion where the magnetic flux passes, the ITM
By examining the characteristics, the position of the defective portion and the IV characteristics can be found. For this reason, research on superconducting materials has required the application of a cooling magnetic field, but conventional cooling STMs do not yet have a holder that applies a magnetic field to the sample while cooling the sample. There is no.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above embodiment, the sample holder is configured so that the sample fixing unit 3 is attached to the holder case 4 via the heat insulating material 2.
The heat insulating material may be omitted.

[0020]

As is apparent from the above description, according to the present invention, the sample holder for attaching the sample fixing portion to the holder case and fixing the sample to the sample fixing portion, and the peripheral portion contacting with the sample fixing portion are provided. Since the sample stage includes a heat conducting portion disposed on the main body, a heat insulating material that insulates the heat conducting portion from the main body, and a cooling device that cools the heat conducting portion, the sample stage is configured to be mounted on the sample holder from the rear side. The holder can be freely attached and detached from the back side of the sample stage, and the sample can be easily exchanged even during cooling. Moreover, the sample can be cooled effectively. Furthermore, since it can take the same shape as that for normal temperature and high temperature STM, conventional MGL and parking for normal temperature and high temperature STM can be used, and a cooling-compatible sample stage, sample cooling holder, and normal temperature and high temperature STM holder are used. Then, S that can handle from high temperature to low temperature on the same stage
TM can be realized. Of course, if the cooling operation is stopped, the normal temperature and high temperature STM image observation as before becomes possible. Further, a cooling magnetic field can be applied to the sample.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a sample cooling and holding device for a scanning tunnel microscope according to the present invention.

FIG. 2 is a diagram schematically illustrating a sample holder stage for a normal temperature and high temperature STM.

FIG. 3 is a view showing another embodiment of the sample cooling and holding device for the scanning tunneling microscope according to the present invention.

FIG. 4 is a view showing another embodiment in which a permanent magnet is mounted on the sample cooling and holding device for a scanning tunnel microscope according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... sample holder, 2 and 18 ... heat insulating material, 3 ... sample fixing part,
4 ... holder case part, 5 ... sample, 11 ... sample stage,
12, 13 ... cooling device, 14, 15 ... thermal conductor, 16 ...
Heat conducting part, 17: heat conducting cover, 19: stage body

Claims (4)

(57) [Claims] 1. A sample cooling and holding device for a scanning tunnel microscope, wherein a sample surface is scanned with a probe to observe an image while detecting a tunnel current flowing between the probe and the sample while the sample is cooled to a low temperature. A sample holder for fixing the sample to the sample fixing part by attaching the sample fixing part to the holder case part, a heat conducting part disposed in a peripheral part in contact with the sample fixing part, and a heat insulating material for insulating the heat conducting part from the main body A sample cooling and holding device for a scanning tunneling microscope, comprising: a sample stage having a sample stage configured to mount a sample holder from the back side, and a cooling device for cooling a heat conducting portion. 2. A heat insulating material is provided between a holder case portion of a sample holder and a sample fixing portion.
A sample cooling and holding device for a scanning tunnel microscope according to the above. 3. The sample cooling and holding device for a scanning tunnel microscope according to claim 1, further comprising an auxiliary cooling device for cooling a main body insulated from the heat conducting portion by a heat insulating material of the sample stage. 4. The sample cooling and holding apparatus for a scanning tunnel microscope according to claim 1, wherein a permanent magnet is mounted on a holder case of the sample holder.