JP2556533B2 - Scanning tunneling microscope scanner - Google Patents

Description

The present invention relates to an electron microscope scanner equipped with a scanning tunneling microscope (STM).

[Conventional technology]

In general, when the probe is brought close to the sample until the atom at the tip of the probe and the electron cloud of the atoms of the sample overlap by about 1 nm, and a voltage is applied between the probe and the sample in this state, a current flows. This current is called the tunnel current, and when the voltage is 1 mV, 1 to 1
It is about 0mA. The magnitude of this tunnel current changes depending on the distance between the sample and the probe, and by measuring the magnitude of the tunnel current, the distance between the sample and the probe can be measured ultra-precision. If the needle position is known, the surface shape of the sample can be obtained. Further, if the probe position is controlled so that the tunnel current becomes constant, the surface shape of the sample can be measured in the same manner by the trace of the probe position.

FIG. 5 is a diagram showing a schematic configuration of such a scanning tunneling microscope. 1 is a probe, 2 is a sample, 3 is a three-dimensional actuator, 4 is an XY scanning circuit, 5 is a servo circuit, 6 is a tunnel current amplifier. , 7 is a battery, 8 is a memory, 9 is a CPU, and 10 is a display device.

The three-dimensional actuator 3 is constructed by hollowing out one piezoelectric element, and is controlled through the CPU 9 and memory 8
The scanning circuit 4 sweeps the applied voltage to the X-axis and Y-axis direction piezoelectric elements to move the probe 1 in the X-axis and Y-axis directions for scanning, and also through the servo circuit 5 to the Z-axis direction piezoelectric elements. The tunnel current is controlled to be constant by controlling the voltage, and the voltage value at that time is read by the CPU and displayed on the display device 10, so that the surface shape of the sample can be observed.

As such a three-dimensional actuator 3, as shown in FIG. 6, a cantilever type in which a piezoelectric element 11 is connected to a tripod type by screwing or the like, or in order to make the rigidity higher than this, As shown in FIG. 7, the piezoelectric element 11 is
An X-axis and a Y-axis are supported at both ends, and a Z-axis is supported at one end.

[Problems to be solved by the invention]

However, the conventional tripot type has a low natural frequency of 1 to 3 KHz, so that the scanning speed cannot be increased. Therefore, there is a problem that the image is liable to be affected by thermal drift, etc. Also X
The movements of the axes, the Y-axis, and the Z-axis affect the other axes, and there is a problem that the distortion becomes small and the movement becomes large when the movement is increased.

By the way, in the case of a scanning tunneling microscope, it is difficult to know where the sample is being observed.
It is hoped that the field of view will be searched by TEM or backscattered electron microscope (REM) method by incorporating it in M) and observe with a tunnel microscope with higher precision. It was not possible to mount the STM in the TEM sample chamber and use it.

The present invention is for solving the above problems, each axis can independently reduce the strain, high-speed scanning is possible, and can be incorporated in the TEM holder, TEM
An object of the present invention is to provide a scanner for a scanning tunneling microscope capable of simultaneously observing an STM image or an REM image.

[Means for solving problems]

Therefore, the scanner of the scanning tunneling microscope of the present invention is a scanner having an integrated structure in which three piezo element elements to which a driving voltage is applied so as to displace the probes in the directions of three axes orthogonal to each other are integrated. , Said 3
For two of the piezo element elements, a sliding displacement is generated in a direction orthogonal to the stacking direction of the piezo element elements, and a displacement is generated in the stacking direction for the other one piezo element element. And at least the above-mentioned 3
One of the piezo element elements has two or more piezo elements stacked.

[Operation] A scanner having an integrated structure in which three piezo element elements to which a driving voltage is applied so as to respectively displace the probes in the directions of three axes orthogonal to each other is provided. Two of these piezo element elements are configured to cause sliding displacement in a direction orthogonal to the stacking direction of the piezo element elements, and the other one piezo element element is configured to cause displacement in the stacking direction. Since at least one of the three piezo element elements has two or more piezo elements laminated, the scanner of the scanning tunnel microscope can be downsized and the resonance frequency can be increased. Therefore, high-speed scanning becomes possible.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

1A and 1B are views showing an embodiment of a scanner of a scanning tunneling microscope according to the present invention. FIG. 1A is a plan view, FIG. 1B is a vertical side view, and FIG. 1C is a side view. FIG. 2 is a diagram for explaining the Z-axis displacement of the scanner. In the figure, 11 is the scanner body, 12 is a terminal plate, 13, 14, 15 are insulating plates, 16
Is a Z-axis element, 17 is an X-axis element, 18 is a Y-axis element, 19 to 21 are X-axis, Y-axis and Z-axis terminals, and 22 is a GND.
Terminals and 23 are lead wires.

In the figure, the scanner body 11 is a PZT bonded with an adhesive.
The X-axis and Y-axis elements 17 and 18 made of PZT and the Z-axis element 16 made of PZT which are insulated from each other by the insulating plate 14 and laminated and adhered to each other by the lead wire coated with urethane from the terminal plate 12. A drive voltage is supplied to each. Although the scanner body 11 and the terminal plate 12 are shown separately in the figure, they may be integrated. Then, the displacement in the thickness slip (deviation) direction of the PZT is used for the displacement in the Y direction and the Z direction, and the displacement in the thickness direction is used for the displacement in the X direction. In addition, the Z-axis element 16 is a laminated type in which four PZTs are stacked.
Thereby, the amount of displacement in the Z direction is increased. A probe (not shown) is attached to the tip of this Z-axis element.

For example, when explaining the displacement of the Z axis, as shown in FIG. 2, with respect to the displacement caused by the displacement of the Z axis element 16a,
The element 16b is further displaced due to the displacement, and the displacement displacement is sequentially superimposed, and as a result, a large displacement amount can be obtained at the tip portion.

In such a scanner according to the present invention, each element is made extremely thin, and when these very thin adhesive layers are used for adhesion, the natural frequency of 250 KHz or more is hardly reduced without substantially reducing the natural frequency of the PZT simple substance. You can get a number. Further, since the movements of the respective axes are independent of each other, it is possible to obtain a displacement without distortion. In addition, each element is as thin as 0.3 mm, and by making the adhesive layer extremely thin, it is possible to form a total size of about 1.6 mm x 3 mm x 5 mm.

FIG. 3 is a diagram showing a schematic configuration when a reflection image is obtained by a transmission electron microscope incorporating the scanner of the present invention, and FIG.
The figure shows the trajectory of the electron beam. In the figure, 31 is the holder, 32 is the sample, 33 is the sample fixing base, 34 is the STM scanning unit, 35 is the STM needle, and 36
Is an objective lens (OL) pole piece, 37 is an optical axis, 38 is a deflector, 38a and 38b are first and second deflectors, and 39 is an objective lens.

The holder 31 is moved by a side entry goniometer (not shown) to set the sample 32 at a predetermined position. In this holder 31, a sample 32 is attached to a sample fixing base 33 as shown in the figure, an STM scanning section 34 made of a piezo element is housed, and an STM needle 35 is provided facing the sample 31. Since the STM scanning unit 34 is about 1.6 mm × 3 mm × 5 mm as described above, the holder 3
It can be fully stored in 1.

In the above structure, the electron beam emitted parallel to the sample surface along the optical axis is bent and focused by the front magnetic field of the objective lens 39 and the deflector 38 installed above the objective lens to form an angle on the sample surface. The beam radiated in a spot shape and reflected there forms an image reflected below the objective lens through the optical axis. The reflected image is formed on a photosensitive surface (not shown) to observe the sample surface. At this time, since the sample surface is parallel to the optical axis, the concave and convex portions are shaded with respect to the electron beam, and thus fringes are observed corresponding to the shape.
The degree of the unevenness is measured with high precision by the STM scanning needle 35 by driving the STM scanning unit 34. In this case, as described above, ST
Since the resolution of M is an atomic lens, the allowable vibration amplitude of the STM needle is 0.1 Å or less, but in the present invention, the sample and the needle are fixed in one holder, which is extremely advantageous in terms of vibration resistance. Becomes Further, when the STM probe is brought close to the sample, it can be observed as a TEM image, so that it is possible to prevent the STM probe from colliding with the sample surface.

〔The invention's effect〕

As described above, according to the present invention, the drive voltage is applied so as to displace the probes in the directions of the three orthogonal axes.
A scanner having an integrated structure in which three piezo element elements are laminated, and two of the three piezo element elements are subjected to sliding displacement in a direction orthogonal to a laminating direction of the piezo element elements. In addition, the other one piezo element element is configured to be displaced in the stacking direction, and at least one of the three piezo element elements has two or more piezo elements. Since they are stacked, the scanner of the tunnel microscope can be downsized and the resonance frequency can be increased while maintaining the displacement of the probe at a sufficient amount, which enables high-speed scanning.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a scanner of a scanning tunneling microscope according to the present invention, FIG. 2 is a diagram for explaining the Z-axis displacement of the scanner, and FIG. 3 is a transmission electron incorporating the scanner of the present invention. FIG. 4 is a diagram showing a schematic configuration when a reflection image is obtained by a microscope, FIG. 4 is a diagram showing a trajectory of an electron beam, FIG. 5 is a diagram showing a schematic configuration of a scanning tunneling microscope, FIG. 6 and FIG. It is a figure which shows the tripot type scanner of. 11 …… Scanner body, 12 …… Terminal plate, 13, 14, 15 ……
Insulation plate, 16 ... Z-axis element, 17 ... X-axis element, 18 ... Y-axis element, 19-21 ... X-axis, Y-axis, Z
Axis terminals, 22 ... GND terminal, 23 ... Lead wire.

Front Page Continuation (72) Inventor Ikuya Nishimura 3-1-2 Musashino, Akishima-shi, Tokyo Nihon Electronics Co., Ltd. (56) Reference JP-A-60-257776 (JP, A) JP-A-60- 59980 (JP, A) Actual development Sho 58-196834 (JP, U)

Claims (1)

(57) [Claims] 1. A scanner having an integrated structure in which three piezo element elements to which a drive voltage is applied so as to respectively displace the probes in the directions of three orthogonal axes are laminated, and the three piezo elements are provided. Two of the elements are configured to cause sliding displacement in a direction orthogonal to the stacking direction of the piezoelectric element elements, and for another one piezoelectric element element to be displaced in the stacking direction. In addition, at least one of the three piezoelectric element elements is a scanner of a scanning tunneling microscope in which two or more piezoelectric elements are laminated.