JP2004226292A - Scanning hall probe microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To widen a scanning range by adopting a mechanism for providing a driving part piezoelectric element for a sample or a Hall probe element in an ambient temperature portion to evade performance deterioration of the piezoelectric element under low temperature, and for providing only the Hall probe element of a sensor part and the sample in a low temperature portion. <P>SOLUTION: This scanning Hall probe microscope is provided with a chamber 2, a cooling means 14 for cooling an inside of the chamber, a support member 3 for supporting the sample or the Hall probe element in a prescribed positional relation inside the chamber, a sample or Hall probe element mounting block 6 provided to be opposed to a tip of the support member, and actuators 9-11 for moving the support member horizontally or vertically in an ambient temperature area outside the chamber. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a scanning Hall probe element microscope for observing a sample surface using a Hall probe element at a low temperature.
[0002]
[Prior art]
As a scanning Hall probe element microscope for observing a sample surface using a Hall probe element at a low temperature, the one described in Non-Patent Document 1 and the like are known.
[0003]
[Non-Patent Document 1] 1324 Appl, Phys, Lett. 69 (9) August 1996 [Real-time scanning Hallprobe microscopy]
[0004]
The existing scanning Hall probe element microscope (SHPM) disclosed in the above document is an essential measuring device for quantitative observation of magnetic domains. The schematic configuration of this scanning Hall probe element microscope apparatus (SHPM) will be briefly described with reference to the drawings. FIG. 6 is an overall configuration diagram of the apparatus, FIG. FIG. 8 is an explanatory view of the operation state of the PZT tube, FIG. 9 is an explanatory view of the scanning (moving) state of the Hall probe element, and FIG. 10 is a sample observed with a conventional scanning Hall probe element microscope (SHPM). FIG.
[0005]
In the figure, 51 is a PZT tube (PlEZO ELECTR1C TUBE), 52 is a Hall probe element attached to the tip of the tube 51, 53 is a sample (sample), 54 is a controller, 55 is a display device, and 56 is a personal computer. In the figure, the Hall probe element 52 is shown in an enlarged state at the center in the figure.
The PZT tube 51 is provided with an X, Y direction piezo actuator and a Z direction piezo actuator, and is tilted at a predetermined angle with respect to the sample as shown in FIG. , The PZT tube can be swung about the fulcrum 51C to scan substantially horizontally. A well-known hole probe element 52 as shown in an enlarged manner in the center of FIG. 6 is attached to the tip of the PZT tube 51, and a tip bias is applied to the hole probe element 52 as shown. Thus, a tunnel current can be detected.
[0006]
The main part of the scanning Hall probe element microscope apparatus will be further described with reference to FIG. 7. The scanning Hall probe element microscope apparatus includes a cryostat 58 for low-temperature cooling, and a chamber 59 is provided in the cryostat 58. Are located. A well-known vacuum / exchange gas space 60 is formed above the chamber, and a support member 61 made of a material such as a glass material is disposed in the chamber. A PZT tube 51 having a piezo actuator 51a for moving in the Z direction and a piezo actuator 51b for moving in the X and Y directions is attached. Below the PZT tube 51, a sample holding table 62 is attached at an angle. The sample 53 is placed on the table 62, and the magnetic domain observation of the sample is performed by a hole probe element 52 provided at the tip of the PZT tube 51. Can be done.
[0007]
In the vicinity of the hole probe element 52 provided in the PZT tube 51, a cryogen storage tank (for example, liquid nitrogen, liquid helium, etc.) 64 is arranged in order to make the periphery of the PZT tube 51 a cooling area A as shown in FIG. I have. A space (outlet for gas discharge) 66 through which the cryogen flows is formed around the chamber 59, and the cryogen is supplied from the cryogen storage tank 64 into the space 66. In this example, a valve 65 is arranged in a flow path that communicates the cryogen storage tank with the space, so that the supply of the cryogen can be controlled. Further, the cryogen (for example, helium gas) is provided in the chamber 59. Is satisfied.
[0008]
In the microscope, the X- and Y-direction piezo actuators 51b constituting the PZT tube 51 swing about the fulcrum 51C with respect to the sample 53 as shown in FIG. That is, the Hall element is attached to the tip of the tube type PZT tube 51 for detecting the tunnel current, and when measuring in the lift mode, the PZT tube 51 is inclined with respect to the sample as shown in FIG. Need to measure. In this measurement, as shown in FIG. 9, magnetic domain observation is performed by moving the Hall probe element 52 above the sample surface by 0.34 μm. A scanning range of about 50 μm × 50 μm is possible at room temperature.
[0009]
However, in this measurement method, since the PZT tube 51 is swung about the fulcrum 51C for scanning, the Hall probe element 52 gradually moves from the sample as shown in FIG. As a result, there is a problem that the image becomes unclear as the Hall probe element is gradually separated from the sample as shown in FIG.
In order to observe a vortex of a superconducting material or the like, it is necessary to cool the sample and the Hall probe element (liquid He temperature) as described above, but the scanning range of the existing SHPM is the piezoelectric element (piezo element). Due to the limitation of physical properties, only about 1 μm × 1 μm can be obtained at low temperature, and observation over a wide range cannot be performed. Therefore, there is a problem that practically low temperature application is difficult.
[0010]
[Problems to be solved by the invention]
The problems of the scanning Hall probe element microscope are summarized as follows.
1. The sample (sample) and the PZT tube (X, Y, Z piezo actuator) are arranged close to each other in the cooling area as shown in FIG. 7, and when the sample is cooled, the piezo actuator is also cooled. Therefore, the displacement range (measurement range) becomes narrower at lower temperatures due to the temperature characteristics of the piezo actuator.
2. When the Hall probe element is brought closer to the sample, the hole probe element and the sample are inclined by about 1.5 ° because the tunnel current is detected using the corner of the tip of the Hall probe. The Hall probe element is attached to the end face of the piezo actuator, and the PZT tube swings around 51C as shown in FIG. 8, so that the height from the sample surface is fixed. In the measurement (lift mode) in which the XY plane is scanned by scanning, the distance between the hole probe element and the sample is gradually increased, and the resolution of the measurement image is deteriorated and blurred in the scanning direction (see FIGS. 9 and 10; Is an image of 50 μm on one side).
3. Since scanning is performed only by the piezo actuator, it is impossible to perform a wide range of measurement.
4. Since the piezo actuator is installed in the same space as the sample, when replacing the heat exchange gas, it is necessary to pay attention to discharge breakdown due to the high voltage applied to the piezo actuator.
5. The movement mechanism for fine movement and coarse movement in the Z direction that detects tunnel current adopts a movement method that uses a voltage change and friction applied to a piezo actuator called a slip stick mechanism. However, friction changes depending on temperature. Movement becomes unstable.
6. Since a PZT tube type piezo actuator is employed, it is difficult to use an electromagnet that can be easily used as a method of applying an external strong magnetic field in the Z direction. There are problems such as.
[0011]
Therefore, an object of the present invention is to solve the above-mentioned conventional problems by proposing a scanning Hall probe element microscope apparatus capable of performing a wide range measurement even at a low temperature.
More specifically, the SHPM device of the present invention has a driving unit piezoelectric element for a sample or a Hall probe element installed at a room temperature to avoid performance degradation of the piezoelectric element at a low temperature, a hole probe element and a sample in a sensor unit. By adopting a mechanism for installing only the low-temperature portion, it is possible to widen the scanning range. In addition, a stepping motor is used for coarse adjustment of the probe for detecting the tunnel current, and a piezoelectric element (piezo element) is finely used. Thus, the scanning Hall probe element microscope apparatus enables a wide range of measurements even at low temperatures, enabling a wider range of applications.
[0012]
[Means for Solving the Problems]
For this reason, the technical solution adopted by the present invention is:
A scanning hole probe element microscope, in which an actuator for driving the hole probe element or the sample is set in a room temperature region so that the actuator is not affected by the sample temperature. -A probe element microscope.
In a scanning Hall probe element microscope, a Hall probe element and a sample are arranged in a cooled chamber, and an actuator for driving either the Hall probe element or the sample is provided in a room temperature region outside the chamber. It is a scanning Hall probe element microscope characterized by being arranged.
A chamber, cooling means for cooling the inside of the chamber, a support member for supporting the sample or the hole probe element in a predetermined positional relationship within the chamber, and a sample or a hole provided opposite to the tip of the support member. A scanning Hall probe element microscope, wherein a probe element mounting table and an actuator for moving the support member horizontally or vertically are provided in a room temperature region outside the chamber.
Further, there is provided a scanning Hall probe element microscope in which the chamber has two layers and a cryogen is further disposed outside the chamber.
Further, the scanning Hall probe element microscope is characterized in that the actuator is constituted by a combination of a stepping motor and a piezoelectric element.
A scanning Hall probe element microscope is characterized in that, among the actuators, a piezo actuator is used for fine movement and a stepping motor is used for coarse movement.
The scanning Hall probe element microscope is characterized in that the chamber is evacuated and the entire vacuum chamber is placed in a strong magnetic field to facilitate the application of a magnetic field.
[0013]
Embodiment
The configuration of the scanning Hall probe element microscope according to the present invention will be described with reference to the drawings. FIG. 1 is an enlarged view of a main part of the scanning drive system of the present invention, and FIG. FIG. 3 is a diagram for explaining a state in which the sample is moving, FIG. 3 is a diagram for explaining the relationship between the hole probe element and the sample during scanning, and FIG. FIG.
[0014]
In FIG. 1, 1 is a low-temperature cryostat, 2 is a two-layer chamber, 3 is a Hall probe element support member, 4 is a Hall probe element, 5 is a sample, 6 is a sample support, and 7 is a vacuum / exchange gas. Room. An actuator mounting table 8 is provided on the upper part of the two-layer chamber 2, and an X, Y-direction piezo actuator 9, an X, Y-direction stepping motor 10 for driving the Hall probe support member 3 on the mounting table 8. , A Z-direction piezo actuator 11 and a Z-direction stepping motor 12. The Hall probe element 4 is attached to the Hall probe element support member 3 at a predetermined angle (about 1.5 °).
[0015]
In this microscope, an X, Y-direction piezo actuator 9, an X, Y-direction stepping motor 10, a Z-direction piezo actuator 11, and a Z-direction stepping motor 12 for driving the Hall probe element 4 in a room temperature region outside the two-layer chamber 2 are provided. Even if the sample 5 is cooled by a cryogen during observation, the displacement range (measurement range) becomes narrower at lower temperatures due to the temperature characteristics of the piezo actuator because the piezo actuator in the X, Y, and Z directions is in the room temperature range. Problem can be solved.
[0016]
A space 13 in which the cryogen flows is formed around the outer periphery of the two-chamber chamber in the cryostat 1, and the cryogen is supplied from the cryogen storage tank 14 into the space 13. In addition, a valve 15 is disposed in a flow path that connects the cryogen storage tank 14 and the space 13, and the supply of cryogen can be controlled by a valve operating member 15A. Further, a cryogen is appropriately supplied into each of the layers 2a and 2b of the two-layer chamber 2, and the inside of the chamber is filled with a cooling gas, and these form a cooling means in the chamber. Thus, the cooling area A is formed around the sample.
[0017]
In the microscope described above, the X- and Y-direction piezo actuators 9 and the X and Y-direction stepping motors 10 provided on the mounting table 8 are used to move the Hall / probe element support member 3 horizontally to the sample surface as shown in FIG. Scan in the direction. At this time, in this microscope, the hole probe support member 3, which supports the hole probe element 4 with a predetermined inclination, moves horizontally as shown in FIGS. It moves on the sample while maintaining a fixed distance while maintaining the state. Therefore, the distance between the sample surface and the Hall probe element is always constant, and a clear image can be obtained over the entire surface of the sample even in the measurement (lift mode) in which the XY plane is scanned as shown in FIG.
In addition, since the piezo actuators in the X, Y, and Z directions are installed in the room temperature area outside the chamber, the piezo actuators are not affected by the sample temperature. Can be measured.
[0018]
FIG. 5 shows a second embodiment.
The second embodiment is characterized in that the configuration of the first embodiment is further simplified and the device is downsized.
In FIG. 5, 21 is a vacuum chamber, 22 is a cooling stage, 23 is a sample, 24 is a Hall probe element, 25 is an X and Y direction piezo actuator, 26 is an X and Y direction stepping motor, 27 is a Z direction piezo actuator, 28 is a Z-direction stepping motor, 29 is a vacuum region, 30 is a Hall probe element support member, and 31 is a mounting table of the whole apparatus. The Hall probe element 24 is attached to the Hall probe element support member 30 at a predetermined angle (about 1.5 °).
[0019]
In this microscope, the X, Y-direction piezo actuator 25, the X, Y-direction stepping motor 26, the Z-direction piezo actuator 27, and the Z-direction stepping motor 28 are arranged in a room temperature region outside the vacuum chamber 21. Even when cooled by the stage 22, the piezo actuators in the X, Y, and Z directions are not affected by low temperatures, and the problem that the displacement range (measurement range) becomes narrower at lower temperatures due to the temperature characteristics of the piezo actuators can be solved. Has become.
Note that an appropriate method can be selected as a method for supplying the cryogen to the cooling stage.
[0020]
Although the embodiment of the present invention has been described above, it is also possible to mount the sample on the support member side and fix the Hall probe element on the chamber side, in contrast to the above-described embodiment. Can be easily replaced. Further, the shape of the chamber, the cooling area in the chamber, the cooling method, and the like can be arbitrarily set depending on the device. Further, it is also possible to make the chamber a vacuum and install the entire vacuum chamber in a strong magnetic field to facilitate the application of a magnetic field.
Furthermore, the present invention may be embodied in any other form without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely an example in all aspects and should not be interpreted in a limited manner.
[0021]
【The invention's effect】
According to the present invention as described in detail above,
1. Since the piezo actuator for driving one of the sample and the Hall probe element is installed in the room temperature region, the piezo actuator is not affected by the sample temperature, and the same range as the room scan region can be measured even at a low temperature.
2. Since independent piezo actuators are used for each of the XYZ axes, the movement is linear and the measured image does not blur depending on the location.
3. Scanning is performed by a piezo actuator, but a wide range of measurement is possible because a stepping motor can be used for movement.
4. Since the piezo actuator is installed at room temperature, there is no fear of causing discharge breakdown due to high voltage.
5. Tunnel current detection uses a piezo actuator for fine movement and a stepping motor for coarse movement, so accurate movement is possible and operation can be performed at room temperature. Since the moving mechanism is installed at room temperature, it is not affected by temperature at all.
6. Since the temperature variable section and the moving mechanism section can be manufactured compactly, a magnetic field can be applied by an electromagnet.
And other excellent effects.
[Brief description of the drawings]
FIG. 1 is an enlarged view of a main part of a scanning drive system of the present invention.
FIG. 2 is a diagram illustrating a state in which a Hall probe element moves on a sample.
FIG. 3 is a diagram illustrating the relationship between a hole probe element and a sample during scanning.
FIG. 4 is a view showing a state where a sample is measured by a scanning Hall probe element microscope according to the present invention.
FIG. 5 is an enlarged view of a main part of a scanning drive system according to a second embodiment of the invention.
FIG. 6 is an overall configuration diagram of a conventional Hall probe element microscope.
FIG. 7 is an enlarged view of a main part of a conventional microscope.
FIG. 8 is an explanatory diagram of an operation state of a conventional PZT tube.
FIG. 9 is an explanatory diagram of a scanning (moving) state of a conventional Hall probe element.
FIG. 10 is a view of a sample observed by a conventional scanning Hall probe element microscope (SHPM).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Low temperature cryostat 2 Two-layer chamber 3 Hall probe element support member 4 Hall probe element 5 Sample 6 Sample support table 7 Vacuum / exchange gas chamber 8 Actuator mounting table 9 X, Y direction piezo actuator 10 X, Y direction Stepping motor 11 Z-direction piezo actuator 12 Z-direction stepping motor 13 Space (outlet for gas discharge)
14 cryogen 15 valve

Claims (7)

A scanning hole probe element microscope, in which an actuator for driving the hole probe element or the sample is set in a room temperature region so that the actuator is not affected by the sample temperature. -Probe element microscope. In a scanning Hall probe element microscope, a Hall probe element and a sample were arranged in a cooled chamber, and an actuator for driving either the Hall probe element or the sample was arranged in a room temperature region outside the chamber. A scanning Hall probe element microscope, characterized in that: A chamber; cooling means for cooling the inside of the chamber; a support member for supporting the sample or the Hall probe element in a predetermined positional relationship within the chamber; A scanning Hall probe element microscope, wherein a mounting table and an actuator for moving the support member horizontally or vertically are provided in a room temperature region outside the chamber. The scanning Hall probe element microscope according to claim 2 or 3, wherein the chamber has two layers, and a cryogen is further arranged outside the chamber. The scanning Hall probe element microscope according to any one of claims 1 to 4, wherein the actuator comprises a combination of a stepping motor and a piezoelectric element. 6. The scanning Hall probe element microscope according to claim 5, wherein a piezo actuator is used for fine movement and a stepping motor is used for coarse movement. The scanning Hall probe element microscope according to any one of claims 2 to 6, wherein the chamber is evacuated, and the entire vacuum chamber is placed in a strong magnetic field to facilitate application of a magnetic field.

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