JPH01127904A - Scanner for scanning tunnel microscope - Google Patents

Abstract

PURPOSE:To miniaturize the title scanner so that it can be integrated into a holder for a transmission type electron microscope TEM by using a thickness shift direction displacement of PZT for a displacement in each direction of X, Y and Z. CONSTITUTION:An X axis element EM 17 and a Y axis EM 18 consisting of a sheet of PZT are stuck and laminated, and to the surface of the EM 18, an insulator 14 is stuck and fixed. To the other surface of the insulator 14, Z axis EMs 16 (16a-16d) formed by laminating four sheets of PZT are stuck and fixed, and with respect to a displacement caused by a shift of the EM 16a, the EM 16b also generates a displacement caused by the shift, the shift displacement is superposed successively, and as a result, in the head part, a large displacement quantity is obtained. In such a way, as for a scanner body 11, the EM of one sheet each is thinned extremely (for instance, 0.3mm), and also, they are stuck by a thin adhesive layer, by which a natural frequency in a PZT simple substance scarcely drops, and a motion of each axis is independent each other, therefore, a displacement having no distortion is obtained. Accordingly, a miniature scanner can be constituted, and can be contained in a holder for TEM.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanner for a scanning tunneling microscope (STM).

[Prior Art] In general, when the probe is brought close to the sample to a point where the atoms at the tip of the probe overlap with the electron cloud of the sample atoms, and in this state a voltage is applied between the probe and the sample, a current is generated. flows. This current is called a tunnel current, and is about 1 to 10 nA when the voltage is from several mV to several square meters. The magnitude of this tunneling current changes depending on the distance between the sample and the tip, and by measuring the magnitude of the tunneling current, the distance between the sample and the tip can be measured with ultra-precision. , if the probe position is known, the surface shape of the sample can be determined. Furthermore, if the probe position is controlled so that the tunneling current is constant, the surface shape of the sample can be similarly measured based on the probe position locus.

Figure 5 is a diagram showing the schematic configuration of such a scanning tunneling microscope, in which 1 is a deep needle, 2 is a sample, 3 is a three-dimensional actuator, 4 is an XY scanning circuit, 5 is a water circuit, and 6 is a tunnel. Current amplifier, 7 is bias power supply, 8 is memory, 9 is C
PU, 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 probe 1 is moved and scanned in the Y-axis and Y-axis directions by sweeping the voltage applied to the Y-axis and the Y-axis piezoelectric element by the XY scanning circuit 4, and the probe 1 is moved and scanned in the Y-axis and Y-axis direction piezoelectric elements through the servo circuit 5. The tunneling current is controlled to be constant by controlling the voltage for the sample, and the voltage value at that time is read into 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, there is a cantilever type actuator in which the piezoelectric element 11 is connected to a tripod type by screws, etc. As shown in FIG. 7, a piezoelectric element 11 is also used in which the Y-axis is supported at both ends and the Y-axis is supported at one end.

[Problems to be solved by the invention]

However, the conventional tri-pot type has a low natural frequency of 1 to 3 K)[z, which makes it impossible to increase the scanning speed. Therefore, there is a problem in that it is easily affected by thermal drift and the like, resulting in a washed-out image. Furthermore, each movement of the Y-axis, Y-axis, and Y-axis affects the other axes, and if you try to reduce the distortion and increase the movement, there is a problem that the device inevitably becomes large.

By the way, in the case of a scanning tunnel microscope, it is difficult to tell which part of the sample is being observed, so a transmission electron microscope (TEM) is used.
) into a TEM or a reflection electron microscope (R
In addition to searching the field of view using the EM) method, it is desired to perform ultra-precise observation using a tunneling microscope, but it is impossible to mount the conventional tri-pot scanner on the TEM holder, and it is difficult to use the STM as a TEM. It could not be used by incorporating it into the sample chamber.

The present invention is intended to solve the above-mentioned problems. Each axis can independently reduce distortion, high-speed scanning is possible, and it can be incorporated into a TEM holder.
It is an object of the present invention to provide a scanner for a scanning tunneling microscope that can simultaneously observe an EM image or a REM image and a 37M image.

[Means to solve problems]

For this purpose, the scanner of the scanning tunneling microscope of the present invention is
A scanner consisting of a 3-axis piezo element made of a thin plate to which a driving voltage is applied so as to be displaced in each of three orthogonal axes, and the piezo element elements of two of the three orthogonal axes are laminated and bonded. and the other one-axis piezoelectric element is bonded to the other surface of the insulator bonded to the surface of the two-axis piezoelectric element, and is perpendicular to the two-axis piezoelectric element. The piezo element elements of each axis are driven to cause sliding displacement.

[Effect]

The present invention includes a three-axis piezo element element made of a thin plate to which a driving voltage is applied so as to be displaced in three orthogonal axes directions, and piezo element elements of two of the three axes are laminated and bonded, A piezoelectric element of another axis is bonded to the other surface of an insulator bonded to the surfaces of the piezoelectric element of the two axes, and is arranged so as to be orthogonal to the elements of the two axes, By driving the piezo element elements of each axis to cause sliding displacement, displacement is caused independently in the three axial directions, and the scanner can be configured to be extremely small.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the scanner of a scanning tunneling microscope according to the present invention, in which (a) is a plan view and (b) is a plan view.
is a side view, and 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 board, 13 is an insulating plate, 14 is an insulator, 16 is a Z-axis element, 17 is an X-axis element, 18 is a Y-axis element, 19
- 21 are terminals for the X, Y, and Z axes, 22 is a GND terminal, and 23 is a lead wire.

In the figure, an X-axis element 17 and a Y-axis element 18 made of PZT Fiui are fixed to the terminal plate 12 and laminated with each other with adhesive.
An insulator 14 is adhesively fixed to the surface of 8. Further, on the other surface of the insulator 14, a Z-axis element 16 made of four laminated PZT thin plates is adhesively fixed. Further, driving voltages are supplied from the terminal plate 12 through urethane-coated lead wires 23, respectively. For the displacements in each of the X, Y, and Z directions shown in the figure, the displacement in the thickness sliding (slip) direction of PZT is used. In addition, in the Z-axis direction, four sheets of PZT are stacked to form a laminated type.
This increases the displacement layer. A probe (not shown) is attached to the tip of this Z-axis element.

For example, to explain the displacement of the Z-axis, as shown in FIG.
The element 16b further undergoes displacement due to misalignment, and the misalignment displacements are sequentially superimposed, and as a result, a large displacement of ζ can be obtained at the tip.

In the scanner according to the present invention, by making the elements extremely thin and bonding them together using a very delicate adhesive I3, assembly is possible without substantially lowering the natural frequency of the PZT alone. It is possible to obtain a high vibration frequency of 250 KHz or more in a state where the Furthermore, since the movements of each Φ'1 are independent of each other, it is possible to obtain distortion-free displacement. In addition, each element is as thin as 0.3+n, and by making the adhesive layer extremely thin, the total size is approximately 1.6 am x 3 mm x 5.
It can be configured with a size of about +u.

FIG. 3 is a diagram showing a schematic configuration for obtaining a reflected image using a transmission electron microscope incorporating the scanner of the present invention, and FIG. 4 is a diagram showing the trajectory of an electron beam. In the figure, 31 is a holder, 32
3 is the sample, 33 is the test T4 fixing table, 34 is the STM scanning unit, 3
5 is the STM needle, 36 is the objective lens (OL) pole piece, 37 is the optical axis, 38 is the deflector, 38a, 38b are the first,
The second deflector 39 is an objective lens.

The holder 3I is moved by a side entry goniometer (not shown) to set the sample 32 at a predetermined position. Inside this holder 31, a sample 32 is attached to a sample fixing table 33 as shown in the figure, and an STM scanning section consisting of a piezo element is housed in the outside 4, and an STM needle 35 is provided facing the sample 31. . This STM
Scanning outside the scanning section 4 As mentioned above, about 1.6 cranes x 3 cranes x 5g
Since it is of a small size, it can be sufficiently stored in the holder 31.

In the above configuration, an electron beam emitted parallel to the sample surface along the optical axis is bent and focused by the forward magnetic field of the objective lens 39 and the deflector 38 installed above the objective lens, and is focused at an angle to the sample surface. The beam is irradiated in the form of a spot and reflected there, passing on the optical axis to form a reflected image below the objective lens. The reflected image is formed on a photosensitive surface (not shown), and the sample surface is observed. At this time, since the sample surface is parallel to the optical axis, the uneven portion casts a shadow on the electron beam, so that stripes are observed corresponding to the shape. The degree of unevenness of the surface can be determined by moving the outside of the STM scanning section.
The scanning needle 35 performs ultra-precise measurement. In this case, as mentioned above, the resolution of ST and M is in the atomic level, so
Although the permissible vibration amplitude of the STM needle is 0.1 Å or less, in the present invention, the sample and the needle are fixed in one holder, which is extremely advantageous in terms of vibration resistance. Also, ST
When bringing the M probe close to the sample, it can be observed as a TEM image, making it possible to prevent the STM probe from colliding with the sample surface.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to configure a compact scanner, so that the STM can be used as a TI? , it can be stored in the holder for M, and it can be carried out while observing the TEM or ItEM image when bringing the probe close to the sample.
EM and ST? By using vi together, TEM images and ST
Simultaneous observation of M images becomes possible. Furthermore, the scanner's natural frequency can be raised to enable high-speed scanning, making it possible to improve the TV quality of STM images.
Since observation is possible and each axis can be independently displaced, scanning can be performed with less distortion.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the 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 diagram showing an embodiment of the scanner of the scanning tunneling microscope according to the present invention. A diagram showing a schematic configuration when obtaining a reflected image with an electron W4 microscope, Figure 4 is a diagram showing the trajectory of an electron beam, Figure 5 is a diagram showing a schematic configuration of a scanning tunneling microscope, Figures 6 and 7
The figure shows a conventional tripod type scanner. 11... Scanner body, 12... Terminal board, 13.
14... Insulating plate, 16... Z-axis element, 17.
...X-axis element, 18...Y-axis element, 19
~21...X-axis, Y-axis, Z-axis terminals, 22...G
ND terminal, 2: (...Lead wire. Applicant: JEOL Ltd.

Claims (2)

[Claims] (1) A scanner consisting of a 3-axis piezo element made of a thin plate to which a drive voltage is applied so as to be displaced in each of the three orthogonal axes, in which the piezo element elements for two of the three orthogonal axes are laminated. The piezoelectric element of the other axis is bonded to the other surface of the insulator bonded to the surface of the piezoelectric element of the two axes, and the piezoelectric element of the other one axis is bonded to the other side of the insulator, and the piezoelectric element of the other one axis is bonded to 1. A scanner for a scanning tunneling microscope, characterized in that the piezo element elements on each axis are driven to cause sliding displacement. (2) A scanner for a scanning tunneling microscope according to claim 1, wherein the piezo element element for at least one of the three orthogonal axes is a stack of two or more piezo elements.