KR20020078787A - Scanning superconducting quantum interference device(squid) microscope - Google Patents

Abstract

PURPOSE: A superconducting quantum interference device scanning microscope is provided to allow for a continuous observation and prevent deterioration of resolution, while improving signal to noise ratio. CONSTITUTION: A superconducting quantum interference device scanning microscope, comprises a cryocooler(20) having a cryocooler head for a continuous cooling operation; an accommodation member for accommodating the cryocooler head, and which has an opening formed at the bottom of the accommodating member; a first bellows member(40) coupled to the bottom of the accommodation member in such a manner that the first bellows member is communicated to the accommodation member, and which is extendable/retractable in a vertical direction; a second bellows member(50) arranged at the bottom of the first bellows member in such a manner that the second bellows member is communicated to the first bellows member, and which has a transparent window(55) formed at the bottom of the second bellows member; a vacuum pump(26) for maintaining the accommodation member and the first and second bellows members at a vacuum state; a superconducting quantum interference member(60) accommodated into the second bellows member; a heat transfer member(65) an end of which is connected to the cryocooler head and the other end of which is connected to the superconductive quantum interference member; and a sample support(70) arranged underneath the second bellows member, and which supports a sample to move relatively to the transparent window.

Description

Superconducting quantum interference device scanning microscope {SCANNING SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE (SQUID) MICROSCOPE}

The present invention relates to a superconducting quantum interference device scanning microscope, and more particularly, it is possible to continuously observe the cooling temperature can be adjusted appropriately, as well as to broaden the application of the material of the superconducting quantum interference device, as well as the signal-to-noise ratio The present invention relates to a superconducting quantum interference device scanning microscope capable of increasing (SNR).

An electron microscope is an optical microscope that uses an electron beam and an electron lens instead of an optical microscope to form an enlarged image of an object on a fluorescent surface, and cannot be observed with an optical microscope whose resolution is limited by the wavelength of light. The subject can also be observed clearly.

Such electron microscopes are classified into various types depending on the imaging method and the purpose of use, but are generally classified into three types: transmission type, surface emission type, and scanning type.

Superconducting Quantum Interference Device (SQUID) is a so-called superconducting quantum interference device (SQUID), in which electrons pass through an insulating film by a tunnel effect when two superconductors are separated by a very thin insulating film. Using the Josephson Effect, it is possible to detect even minute magnetic fluxes, even the weakest magnetic field of about one hundred millionth of the earth's magnetic field. Such superconducting quantum interference devices have been applied to various fields such as measuring instruments, core magnetic fields, brain magnetic fields, submarine detectors, resource exploration devices, and non-destructive testers.

On the other hand, as a superconducting quantum interference device using such a superconducting scanning electron microscope is disclosed in US Patent Nos. 5491411, 5635836 and 5834938. In the superconducting quantum interference device scanning microscopes described above, a cryogenic refrigerant such as liquid helium (LHe) together with a superconducting quantum interference device to maintain a temperature at which the superconducting quantum interference device can cause a superconducting phenomenon (hereinafter referred to as ultra low temperature). Since the sample is to be observed in a state in which the sample is accommodated inside the cryogenic container in which the sample is accommodated, there is a problem that the sample is relatively limited.

In view of this problem, a superconducting quantum interference device scanning microscope for observing a sample at room temperature is disclosed in US Pat. No. 5894220 and Korean Patent Publication No. 99-58966 (published Jul. 26, 1999). have.

By the way, in such a conventional superconducting quantum interference device scanning microscope, a cryogenic container having a predetermined size is provided to cool the superconducting quantum interference device, and a refrigerant such as liquid helium is injected into the cryogenic container. When the refrigerant is consumed over time, the observation is stopped for replenishment of the refrigerant, which makes it difficult to continuously observe.

In addition, in such a conventional superconducting quantum interference device scanning microscope, there is a problem that the disturbance of the superconducting quantum interference device is generated due to the vibration transmitted from the cooling apparatus, including the "boiling phenomenon of the refrigerant" and the like, thereby causing the image to be blurred. .

In the conventional superconducting quantum interference device scanning microscope, temperature control is difficult, and thus the cooling state below the critical temperature of the superconducting quantum interference device can not be sufficiently stabilized, so that the signal-to-noise ratio (SNR) is reduced. Not only is it difficult to improve, but there is a problem that many restrictions are placed on the application of the superconducting quantum interference device having various critical temperatures.

Accordingly, an object of the present invention is to provide a superconducting quantum interference that can be continuously observed and the cooling temperature can be properly adjusted, thereby widening the application of the material of the superconducting quantum interference device and increasing the signal-to-noise ratio (SNR). It is to provide a device scanning microscope.

1 is a schematic diagram of a superconducting quantum interference device scanning microscope according to an embodiment of the present invention,

2 is an enlarged view illustrating main parts of FIG. 1;

3 is an enlarged view of the superconducting quantum interference device region of FIG. 2.

** Description of symbols for the main parts of the drawing **

10: receiving member 21: cylinder

26: vibration pump 40: the first bellows member

43: first bellows spring 50: the second bellows member

53: second bellows spring 65: heat transfer member

67 sapphire member 69 copper member

70: specimen support 75: adjustment bolt

77 spring member

The object is, according to the present invention, the cryogenic chiller having a cryogenic cooling head capable of continuous cooling action; A receiving member accommodating the cryogenic cooling head therein and having an opening formed at a lower end thereof; A first bellows member coupled to the bottom of the accommodating member in communication with the accommodating member and stretchable in an up and down direction; A second bellows member communicating with the first bellows member at the bottom of the first bellows member and being stretchable along a vertical direction and having a viewing window formed at the bottom thereof; Vacuum means for maintaining the interior of the receiving member, the first bellows member and the second bellows member in a vacuum; At least one superconducting quantum interference element accommodated in the second bellows member; Heat transfer means connected at one end to the cryogenic cooling head and connected at the other end to the superconducting quantum interference element so as to be heat-exchanged with each other; It is achieved by a superconducting quantum interference device scanning microscope characterized in that it comprises a specimen support spaced apart a predetermined distance below the second bellows member to support the specimen so as to move relative to the see-through window.

Here, the cryogenic cooling device is a cryocooler (Cryocooler), the cryogenic cooling head is preferably a cylinder of the cryocooler.

The heat transfer means has a length that extends longer than a length connecting the cryogenic cooling head and the superconducting quantum interference element at the shortest distance so that one end of the heat transfer means can correspond to the stretching of the first bellows member and the second bellows member. It is effective to include at least one copper (Cu) wire that is connected to the cryogenic cooling head and the other end is heat transferably connected to the superconducting quantum interference device.

Preferably, the copper wire is fixed to the bottom surface of the first bellows member so as to correspond to the expansion and contraction of the first bellows member and the second bellows member.

The heat transfer means may further include a sapphire member which is interposed between the copper wire and the superconducting quantum interference element and blocks the noise transmitted through the copper wire and is capable of conducting heat transfer.

And, it is preferable to further include a buffer support means for buffering at least one of the first bellows member and the second bellows member.

The buffer supporting means may include a first bellows spring having one end in contact with a bottom surface of the receiving member and the other end being in contact with a bottom surface of the first bellows member, and one end of the buffer supporting means being in contact with a bottom of the first bellows member. And the other end is effective to include a second bellows spring in contact with the bottom surface of the second bellows member.

In addition, it is preferable that the superconducting quantum interference device further comprises a position adjusting means for adjusting the relative position to the specimen.

Here, the position adjusting means is screwed so that one end is exposed to the outside of the second bellows member to allow the operation access from the outside of the second bellows member and the other end is capable of changing the position of the superconducting quantum interference element. It is effective to include a plurality of adjusting bolts and elastic means for applying an elastic force so that the superconducting quantum interference element is approached to the viewing window side.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

1 is a schematic diagram of a superconducting quantum interference device scanning microscope according to an embodiment of the present invention, FIG. 2 is an enlarged view of a main portion of FIG. 1, and FIG. 3 is an enlarged view of the superconducting quantum interference device region of FIG. As shown in these figures, the present superconducting quantum interference device scanning microscope is implemented in the form of a receiving member 10 to form a receiving space therein, and a cylinder 21 accommodated in the receiving member 10. A cryocooler 20 having an cryogenic cooling head, a first bellows member 40 and a second bellows member 50 which are elastically coupled to the lower side of the accommodating member 10 in a vertical direction; A vacuum pump 26 for maintaining the interior of the receiving member 10, the first bellows member 40 and the second bellows member 50 in communication with each other, the first bellows member 40 and the first The first bellows spring 43 and the second bellows spring 53 for buffering and supporting the second bellows member 50, and the superconducting quantum interference element 60 accommodated in the second bellows member 50. And a heat transfer member 65 for connecting the cryogenic cooling head and the superconducting quantum interference element 60 to each other so as to be capable of heat transfer with each other, and disposed below the second bellows member 50. It is configured to include a specimen support (70) for supporting the specimen 71 to enable adjustment of the relative position of the test piece 71 for quantum interference device (60). Here, the receiving member 10, the first bellows member 40 and the second bellows member 50 are such that the superconducting quantum interference element 60 accommodated therein can be prevented from being disturbed by an external magnetic field. It is formed of a magnetic shield member.

The cryocooler 20 ((Cryocooler) is a kind of cryogenic cooling apparatus using a Gifford-McMahon Cycle, and has various cooling temperature levels corresponding to the critical temperature of the superconducting quantum interference device 60. For example, the cryocooler 20 is generally manufactured to be used for more than 20,000 hours without refilling the refrigerant.

The cryocooler 20 includes a cylinder 21 in which a displacer (not shown) is slidably accommodated, a compressor 27 for compressing a refrigerant such as helium (He), and a regenerator ( 29) and a heat exchanger 31, each of which is connected in communication with each other to form a closed loop. In the drawings, reference numerals 33 and 35 denote surge volumes and valves, respectively.

A flange portion 23 extending in the radial direction is formed in the upper region of the cylinder 21, and a drive motor 25 is coupled to the upper portion of the flange portion 23 so as to elevate and displace the displacer stored therein. . The lower side of the flange portion 23 is coupled to the receiving member 10 having a tubular shape of which one side is opened, the receiving member 10, the first bellows coupled to communicate with each other in the upper region of the receiving member 10 A vacuum pump 26 is provided to maintain the interior of the member 40 and the second bellows member 50 in a vacuum state.

The receiving member 10 is formed to have an inner diameter extended along the radial direction so as to be spaced apart from the outer diameter surface of the cylinder 21 by a predetermined distance, and a through hole 12 is formed in the bottom central region. A first bellows member 40 which is stretchable in the up and down direction is coupled to a bottom surface of the receiving member 10, and a through hole 42 is formed in the central region of the bottom of the first bellows member 40. .

In the interior of the first bellows member 40, the first bellows spring 43 of a compression coil shape is accommodated in a vertical direction so as to buffer and support the first bellows member 40. Under the first bellows member 40, the second bellows member 50, which is reduced in the radial direction with respect to the first bellows member 40, is elastically coupled in the vertical direction. The second bellows spring 53 of the compression coil shape is accommodated in the second bellows member 50 so as to buffer the second bellows member 50.

Here, the second bellows member 50 and the second bellows spring 53 may be formed to have the same diameter as the first bellows member 40 and the first bellows spring 43, but mutually It is preferable to have a relatively small diameter compared to the first bellows member 40 and the second bellows spring 53 so as to buffer vibrations of other frequencies.

In addition, although each of the bellows members 40 and 50 and the bellows springs 43 and 53 are configured to have the same diameter at both ends along the up and down direction, the diameter is gradually changed, for example, a truncated conical shape. The image or center region may be configured to have a shape having a maximum diameter.

A through hole 52 is formed in the central region of the bottom of the second bellows member 50, and a see-through window 55 is formed in the bottom surface of the second bellows member to block the through hole 52 so that the inside can be maintained in a vacuum state. . The lower side of the see-through window 55 is provided with a specimen support 70 so as to support the specimen 71, the specimen support 70 is a specimen so that the position can be adjusted in the horizontal direction and the vertical direction A specimen support unit 73 for driving the support 70 is provided.

On the other hand, the inside of the second bellows member 50 can detect a fine magnetic field of the specimen 71 supported by the specimen support 70, which is installed to be movable in the up and down direction and the horizontal direction on the lower side of the see-through window 55. A superconducting quantum interference device 60 is disposed so that the superconducting quantum interference device 60 can analyze and display the driving circuit 61 for driving the superconducting quantum interference device 60 and the detected magnetic field. The analysis and display device 63 is connected.

On the upper side of the superconducting quantum interference device 60, a plurality of heat transfer members 65 formed so as to have a linear shape as a Cu member having one end capable of heat transfer to the bottom surface of the cylinder 21 are connected to each other so as to be capable of mutual heat transfer. The heat transfer member 65 has the shortest distance between the superconducting quantum interference element 60 and the bottom surface of the cylinder 21 so as to correspond to the expansion and contraction of the first bellows member 40 and the second bellows member 50. It is formed to have a length that is sufficiently extended compared to the length of the straight line to be connected, and is fixed to the bottom surface of the first bellows member 40 by a fixing bolt (66).

A plate-shaped sapphire member 67 is interposed between the heat transfer member 65 and the superconducting quantum interference element 60 to prevent noise (noise) from the cylinder 21 from being transmitted and to allow mutual heat transfer. A plate-shaped copper member 69 is interposed between the sapphire member 67 and the superconducting quantum interference element 60.

The copper member 69 is formed with a plurality of spring engaging portions 72 protruding along the plate surface direction, and each spring engaging portion 72 has a plurality of one end fixed to the bottom of the second bellows member 50. The other end of the spring member 77 is coupled. Each spring member 77 is composed of a tension coil spring so as to apply an elastic force to the copper member 69 close to the bottom surface of the second bellows member 50.

Here, each spring member may be configured in the form of a compression coil spring so that one end is in contact with the bottom surface of the first bellows member 40 and the other end is in contact with the top surface of the sapphire member.

The lower side of the copper member 69 is screwed up and down in the vertical direction to the bottom surface of the second bellows member 50 to adjust the relative position of the superconducting quantum interference element 60 with respect to the specimen (71) Each tip of the plurality of adjustment bolts 75 is in contact with each other.

By such a configuration, when the specimen 71 to be measured on the specimen support 70 is supported / fixed, the controller (not shown) controls the specimen support member 73 so that the specimen 71 is positioned at a predetermined measurement position. . Next, the control unit controls the vacuum pump 26 and the crycooler 20 to maintain the inside of the receiving member 10 in a vacuum state, and at the same time the superconducting quantum interference device 60 can operate Allow 60 to cool below the critical temperature.

At this time, the first bellows member 40, the second bellows member 50, the first bellows spring 43 and the second bellows spring 53 are generated during operation of the cryocooler 20. The vibration is buffered to suppress the fine motion of the superconducting quantum interference device 60.

On the other hand, the fine magnetic field emitted from the specimen 71 is detected by the superconducting quantum interference device 60 and the drive circuit 61, and is visualized through the analysis and display device 63 and displayed externally.

As described above, according to the present invention, an ultra low temperature cooling device such as a cryocooler capable of continuously performing a cooling operation without replenishing a refrigerant, and a receiving member disposed to form a vacuum around the cooling head of the ultra low temperature cooling device; And a first bellows member and a second bellows member elastically coupled to the lower side of the receiving member, a superconducting quantum interference element accommodated inside the second bellows member, and a cooling head and the superconducting quantum interference element. By providing a heat transfer member interposed between the heat transfer member and a specimen support formed at the lower side of the second bellows member to move the specimen in the horizontal and vertical directions, continuous observation without interruption of observation due to the replenishment of the refrigerant Superconducting quantum interference device scanning microscope capable of suppressing the degradation of the resolution caused by the vibration transmitted from the cooling device or the like. It is a ball.

In addition, according to the present invention, it is easy to adjust the temperature, thereby widening the application range of the superconducting quantum interference device, and cooling the temperature sufficiently below the critical temperature of the superconducting quantum interference device, thereby improving the signal-to-noise ratio (SNR). A device scanning microscope is provided.

Claims (9)

An ultra low temperature cooling device having an ultra low temperature cooling head capable of continuous cooling; A receiving member accommodating the cryogenic cooling head therein and having an opening formed at a lower end thereof; A first bellows member coupled to the bottom of the accommodating member in communication with the accommodating member and stretchable in an up and down direction; A second bellows member communicating with the first bellows member at the bottom of the first bellows member and being stretchable along a vertical direction and having a viewing window formed at the bottom thereof; Vacuum means for maintaining the interior of the receiving member, the first bellows member and the second bellows member in a vacuum; At least one superconducting quantum interference element accommodated in the second bellows member; Heat transfer means connected at one end to the cryogenic cooling head and connected at the other end to the superconducting quantum interference element so as to be heat-exchanged with each other; A superconducting quantum interference device scanning microscope, characterized in that it comprises a specimen support spaced apart a predetermined distance below the second bellows member to support the specimen so as to move relative to the viewing window. The method of claim 1, The cryogenic cooling device is a cryocooler (Cryocooler), the cryogenic cooling head is a superconducting quantum interference device scanning microscope, characterized in that the cylinder of the cryocooler. The method of claim 1, The heat transfer means has a length longer than a length connecting the cryogenic cooling head and the superconducting quantum interference element with the shortest distance, and one end of the cryogenic cooling is adapted to correspond to the stretching of the first bellows member and the second bellows member. A superconducting quantum interference device scanning microscope, characterized in that it comprises at least one copper (Cu) wire connected to the head and the other end of the superconducting quantum interference device. The method of claim 3, And the copper wire is fixed to the bottom surface of the first bellows member so as to correspond to the expansion and contraction of the first bellows member and the second bellows member. The method of claim 3, The heat transfer means, the superconducting quantum interference device scanning microscope interposed between the copper wire and the superconducting quantum interference device further comprises a sapphire member capable of heat transfer at the same time to block the noise transmitted through the copper wire. The method according to any one of claims 1 to 5, The superconducting quantum interference device scanning microscope, characterized in that it further comprises a buffer support means for buffering at least one of the first bellows member and the second bellows member. The method of claim 6, The buffer supporting means may include a first bellows spring having one end in contact with a bottom surface of the receiving member and the other end being in contact with a bottom surface of the first bellows member, and one end of the buffer supporting means being in contact with a bottom of the first bellows member. And the other end includes a second bellows spring contacting the bottom surface of the second bellows member. The method according to any one of claims 1 to 5, The superconducting quantum interference device scanning microscope, characterized in that it further comprises a position adjusting means for adjusting the relative position of the superconducting quantum interference device with respect to the specimen. The method of claim 8, The position adjusting means is screwed so that one end of the second bellows member is exposed to the outside of the second bellows member so as to allow operation access from the outside of the second bellows member, and the other end is variably arranged to position the superconducting quantum interference element. And a plurality of adjusting bolts and elastic means for applying an elastic force to approach the superconducting quantum interference device toward the see-through window side.