JPH02243907A - Piezoelectric element driving type probe and its driving method - Google Patents

Abstract

PURPOSE:To improve the resolution by providing a piezoelectric element part which is displaced periodically as the displacement sum of plural piezoelectric bodies in the direction of one of two X and Y axes and >=2 driving voltage terminals which controls the displacement of the piezoelectric element part. CONSTITUTION:A specific voltage is applied between the probe 1 and a sample 2 and a Z-axial control element 4 is so controlled that a tunnel current flowing through the probe 1 becomes constant, so that the probe 1 can trace the surface shape and electron state density of the sample 2. At this time, X-axial and Y-axial control circuits 8 and 9 control the X-axial and Y-axial piezoelectric elements and while the probe 1 is put in scanning operation in the X and Y directions, the element 4 is controlled so that the tunnel current becomes constant; and the displacement quantity is displayed to obtain a three-dimensional image on a display device 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a probe that is the key to an apparatus for observing surface conditions using a probe, such as a scanning tunneling microscope (STM), and a method for driving the probe. It is something.

(Prior art) The conventional scanning tunneling microscope is described in Applied Physics Vol. 56 (1).
9B? ) pp. 1126-1137 (Applied Physics, 56
．． As explained in Nα9゜(19B?) 1126-1137), the probe was
ZT) can be attached to piezoelectric ceramics to measure the tunneling current and observe the electronic state on the surface of the material, or to move the tip minutely in response to changes in the tunneling current to measure the distance between the tip and the sample surface. I keep it constant and observe the surface shape.

The scanning tunneling microscope was originally developed to observe surface conditions in ultra-small areas, such as atomic images, without contact, but its scope of application is rapidly expanding. Normally, in order to observe atomic images, a narrow region of several 1100 nanometers is sufficient, but depending on the application, a region of 10 to 100
It is desired to scan an area larger than μm. For this reason, drive voltage elements having various scanning ranges are being developed, but those with wide scanning ranges usually have poor resolution.

Therefore, when observing a wide range and when observing a high-resolution image such as an atomic image, it is necessary to replace the probes attached to different drive voltage elements. For this reason, when the probe is replaced, the measurement location shifts, making it difficult to enlarge or reduce the same location for observation. That is, it is difficult to observe an image of the same location while changing the magnification as with a normal optical microscope or scanning electron microscope.

Furthermore, in general, as the scanning range of the driving voltage element becomes wider, the weight of the driving voltage element increases, so the resonant frequency becomes lower and there is a problem that high-speed scanning becomes impossible.

(Problems to be Solved by the Invention) An object of the present invention is to provide a piezoelectric element-driven probe having a wide scanning range and high resolution, and a method for driving the same.

(Means for Solving the Problems) A piezoelectric element-driven probe of the present invention includes a probe disposed at a distance from a measurement sample, and two probes connected to the probe, X and Y.
It is composed of a piezoelectric element section that applies periodic displacement as the sum of displacements of a plurality of piezoelectric bodies in at least one axis direction, and two or more drive voltage terminals that control the displacement of this piezoelectric element section.

Furthermore, the method for driving the piezoelectric element-driven probe of the present invention is characterized in that displacement/
A low-frequency drive voltage is applied to a drive voltage terminal that drives a piezoelectric material with a large drive voltage, and a high-frequency drive voltage is applied to a drive voltage terminal that drives a piezoelectric material with a small displacement/drive voltage to scan over a wide scanning range. , the probe is scanned with a resolution on the atomic order, or one or more of the drive voltage terminals are selected corresponding to a desired scanning range, and drive voltages are simultaneously applied to the terminals to scan the probe. .

The conventional technology has a resolution of about 10-4 of the maximum scanning range, and has the disadvantage that the resolution worsens as the scanning range becomes wider. For example, when observing an atomic image, the maximum scanning range was about 1 μm. For this reason, it has been difficult to measure the same measurement location while greatly changing the magnification. Furthermore, as the scanning range becomes wider, the driving piezoelectric element cannot scan at high speed, so there is a drawback that it takes an increasingly longer time to collect measurement data.

On the other hand, the piezoelectric element-driven probe of the present invention has a resolution of about 10-b to 10-7 or more of the maximum scanning range, and maintains high resolution even when the scanning range is wide. That is, it has a resolution that allows observation of atomic images over a maximum scanning range of 100 am or more. Therefore, it is possible to measure the same location while changing the magnification. Furthermore, even if the scanning range becomes wider, scanning can be performed without reducing the scanning speed, so measurement data can be collected at high speed.

(Function) Bring the sample and the probe closer together so that the distance between the sample and the probe is in the tunnel region. By applying a predetermined voltage between the sample and the probe in this region and driving the piezoelectric element in the Z direction perpendicular to the sample surface so that the tunneling current remains constant, the distance between the probe and the sample can be kept constant. can be kept. In this state, if the probe is scanned like a TV raster using the piezoelectric element in the two directions x and y, the tip of the needle will move by tracing the density of the local state density of electrons attached to the atoms on the sample surface. (In the case of a sample with uniform physical properties such as work function,
(equivalent to keeping the distance between the probe and the sample surface constant)
. Therefore, if the voltage changes applied to the piezoelectric micro-tremor element in the Z direction are extracted and imaged, the surface structure and shape of the material can be estimated by approximately 10
It can be determined with an accuracy of pm.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Figure 1 is a block diagram showing an embodiment of the present invention, in which 1 is a probe, 2 is a sample, 3 is a stage, 4 is a Z-axis pressure type element, and 5 is a block diagram showing an embodiment of the present invention.
(5-1, 5-2) are X-axis pressure type elements, 6 (6-1,
6-2) is a Y-axis pressure type element, 7 is a Z-axis control circuit, 8 is an X-axis control circuit, 9 is a Y-axis control circuit, and 10 is a display device.

The piezoelectric scanning section to which the probe is attached includes an X-axis pressure type element 5,
It is composed of a Y-axis pressure type element 6.

The X and Y axis piezoelectric elements 5 and 6 are a high precision wide scanning piezoelectric element section 5.
-1.6-1 and a piezoelectric element section 52.6-2 for coarse adjustment. High precision wide scanning piezoelectric element section 5-1.6-
1 is 10 to 10 for a driving voltage of ±150 to 250
It has a resolution of about to pm in a scanning range of 100 μm or more, and has a resolution of about 10 -6 to 10 -7 in the maximum scanning range, and its specific configuration will be described later. The piezoelectric element section 5-2゜6-2 for coarse adjustment is a laminated type piezoelectric element that has a large displacement at low voltage, and is capable of a large displacement of about 10 to 100 μm with a driving voltage of 100 μm. This is used for rough alignment (offset) of the measurement location.

This coarse adjustment piezoelectric element section 5-2.6-2 does not need to be directly coupled to the direct integration wide scanning piezoelectric element 5-1.6-1, and the piezoelectric scanning section can be roughly adjusted in the X and Y directions. Any mechanism may be used as long as it has an additional mechanism that can do this.

With this configuration, a predetermined voltage is applied between the probe 1 and the sample 2, and the Z-axis pressure type element is controlled by the Z-axis control circuit 7 so that the tunnel current flowing through the probe 1 is constant. 4, the probe 1 can trace the surface shape and electronic state density of the sample 2. That is, if the surface condition is constant, the topography of the sample surface can be measured, and if the surface is extremely flat, the electronic state density can be measured. At this time, the X and Y axis control circuits 8 and 9 control the X and Y axis piezoelectric elements, and the probe 1
If the Z-axis pressure type element 4 is controlled so that the tunnel current becomes constant while scanning in the X and Y directions, and the amount of displacement is displayed, a three-dimensional image can be displayed on the display device 10. In theory, the distance between the probe 1 and the sample 2 is kept constant, and the tunnel current flowing between them is displayed. Specifically, by applying a driving voltage to the rough adjustment piezoelectric element section 5-2, 6-2, the measurement sample is aligned to the center position of the measurement scanning range, and then the large-diameter high-precision adjustment is performed. The measurement area is X with the wide scanning piezoelectric element section 5-1.6-1.

Perform a rask scan in the Y direction. Since the display device 10 can normally display only about 250 to 1000 pixels in one direction, the display resolution is determined depending on the scanning range. Therefore, by changing the X and Y scanning range, the displayed magnification changes, and by reducing the scanning range, 1. High-magnification, high-resolution images can be obtained. for example,
If the size of the display surface is 100 mm square and the scanning range of the high-precision, large-diameter scanning piezoelectric element is enabled from 1 nm to 1 mm, the magnification can be varied in the range of 102 to 103. That is, an image with variable magnification can be easily obtained at a desired location, equivalent to an optical microscope or a scanning electron microscope. The X and Y scanning ranges change in proportion to the magnitude of the drive voltage applied to the piezoelectric element. Since high-resolution measurement data can be collected even when the scanning range is large, it goes without saying that the measurement data can be stored in the storage device and the area to be displayed later on the display device can be displayed as a variable magnification image through software processing. .

Next, the configuration of the high-precision wide-scanning piezoelectric element, which is the basic component of the present invention, and its control method will be described.

Figure 2 (a) is an example in which two piezoelectric elements with different displacement/voltage characteristics are combined, and the displacement of each piezoelectric element part (1) and (2) can be controlled independently, and the overall effect is obtained by superimposing them. The amount of displacement can be controlled. Each piezoelectric element part (1),
The displacement ratio for the drive voltage in (2) is assumed to be 1:100.

For example, the maximum displacement amount for the maximum drive voltage: ±150 to 250 V is set to ±0.5 nm and ±50 nm. When a driving voltage as shown in FIG. 2(b) is applied to each piezoelectric element part (1) and (2) of the piezoelectric element having such a configuration,
A large displacement with high accuracy as shown in FIG. 2(C) can be obtained. That is, in the piezoelectric element part (2), -50, -49° -48, ...49.50 nm in units of lnm.
On the other hand, the piezoelectric element part (1) changes as 10 p
If the scanning range is 1 μm with a resolution of m, by combining these two piezoelectric elements, it is possible to have a resolution of 10 pm with a maximum scanning range of 100 pm. In other words, the maximum displacement amount is determined by the characteristics of the piezoelectric element part (2) with large displacement/piezoelectric characteristics, while the resolution is determined by the characteristics of the high-resolution piezoelectric element part (1), so a wide scanning range with high precision can be achieved. functions as an actuator with

The combination is not limited to the combination of two piezoelectric elements, but it is possible to create a large number of combinations.Also, as a combination of the displacement ratio of the two piezoelectric elements, a D/A conversion circuit, etc. 2. When controlling with a computer using
It is best to use a combination that is a base system, that is, a ratio that is a multiple of 2.

FIG. 3(a) is a side view of another high-precision, wide-scanning piezoelectric element. High-precision piezoelectric elements are combined, and the displacement of the l-tal is determined as the superposition of the displacements of each element. For example, the characteristics of each piezoelectric element are determined by the maximum drive voltage ±150~
Assuming that the maximum displacement amount for 250 V is ±0.5 μm, there are about 10 pieces. As shown in FIG. 3(b), a voltage of V sin is first applied to the piezoelectric element having such a configuration, and then each piezoelectric element (1) to (11
) By sequentially changing the driving voltage applied to the two terminals, the amount of displacement shown in FIG. 3(C) can be obtained. At this time, the maximum displacement is
Since it is determined by the displacement/voltage characteristics of each piezoelectric element and the number thereof, by combining high-precision piezoelectric elements, it can be used as a piezoelectric actuator with high precision and a wide scanning range.

FIG. 4 shows a configuration example of a simple scanning range selection type piezoelectric element according to another embodiment of the present invention. Figure 4(a) shows the displacement/
Elements with different voltage characteristics (1).

An example combining (2) and (3) is shown below. For example, the displacement range for the maximum drive voltage is 1 μm and 3 μm.

If the maximum scanning range is 10 μm, the maximum scanning range can be selected and used as an actuator having different scanning ranges such as 1.3 μm, 4.10°11, and 13.14 μm. In this case, unlike the high-precision wide-scanning piezoelectric elements shown in FIGS. 2 and 3, as the scanning range becomes wider, the resolution generally deteriorates. Fourth
Figure (b) shows piezoelectric elements (1) with the same displacement/voltage characteristics.
An example of combining (10) is shown below. For example, if the displacement range for the maximum drive voltage is a combination of 10 piezoelectric bodies of 1 μm, the maximum scanning range is 1.2.・・・・・・、
It can be selected and used as an actuator having different scanning ranges such as 9.10 and 1/11. In the embodiment shown in Fig. 3, it was necessary to scan the two piezoelectric elements in synchronization, but in the embodiment shown in Fig. 4, the selectable scanning range is fixed, and the two piezoelectric elements are This eliminates the need to synchronize the piezoelectric elements described above.

Next, a specific example of the structure of the piezoelectric element will be shown. FIG. 5(a) shows an example in which the length of the region to which voltage is applied to the piezoelectric body 11 is changed, and the lengths of the electrodes 12, 13, and 14 are different.
The scanning range varies in proportion to the area to which the voltage is applied. Figure 5(b) shows voltage elements 15.16.17 with different characteristics.
This shows an example of a configuration in which drive voltages can be applied to the electrodes 20 of each piezoelectric element by connecting them through insulators 18, 19, etc., and piezoelectric bodies with various characteristics can be used in combination. These correspond to a configuration in which piezoelectric elements having different displacement/voltage characteristics are combined as shown in FIGS. 2 and 4(a). FIG. 5(c) shows an example in which electrodes 22 are attached to piezoelectric elements 21 at equal intervals, and shows a configuration example in which piezoelectric elements 21 having the same characteristics are arranged in parallel. Furthermore, FIG. 5(d) shows an example of a stacked piezoelectric element, in which a voltage can be applied to each electrode 24 at both ends of the piezoelectric body 23, and elements with the same characteristics are arranged in parallel. It can be used equivalently to Mochi theory,
If the thickness and voltage characteristics of each layer are changed, Figures 5(a) and (b)
) can be obtained. Figure 5(c),
(d) corresponds to an example in which voltage bodies having the same characteristics as those shown in FIGS. 3 and 4 (b) are arranged. Such a composite piezoelectric element can be used as a high-precision wide-scanning piezoelectric element or a scanning range selection type piezoelectric element, and can be used for the x and y axes of a tri-pot fine movement mechanism, a cross-shaped fine movement structure, and a tower-type fine movement mechanism.
An X-Y scanning actuator can be configured.

FIG. 6 shows a tube-type example of a specific configuration of another piezoelectric element of the present invention. Figure 6(a) shows a tube-shaped y
An example is shown in which the length of the electrode 25 that controls the drive of the axial and Y-axis scans is changed, and 26 is an electrode that controls the drive of the Z-axis scan. FIG. 6(b) shows an example in which a large number of electrodes 30 of the same length are arranged in parallel, and 31 is an electrode that controls the Z-axis scanning drive. Figure 6 (a) corresponds to the configuration that combines piezoelectric elements with different displacement/voltage characteristics shown in Part 2 and Figure 4 (a). , X and Y scanning can be performed over a wide range with high precision. On the other hand, FIG. 6(b) corresponds to an example in which piezoelectric bodies having the same characteristics as those in FIGS. 3 and 4(b) are arranged.

FIG. 7 is a diagram showing another embodiment of the present invention combining different piezoelectric fine movement mechanisms. FIG. 7 shows an example in which a wide-range scanning cross-shaped fine movement mechanism 35 and a high-precision tube-type fine movement mechanism 36 are combined. The tube type fine movement mechanism 36 has an outer diameter of 2 mmφ and a length of about 10 mm, and can constitute a piezoelectric element with a characteristic of about 80 people/V. Therefore, 2400 at ±15V
Can scan the range of people. Therefore, if the cross-shaped fine movement mechanism can scan a wide scanning range, it can be used as a high-precision, wide-scanning piezoelectric element. Moreover, the tube type fine movement mechanism
Since it is very small and can scan at a high speed of 10 kHz or more, it can be used as a high-speed piezoelectric actuator.

The combination of such different piezoelectric fine movement mechanisms is not limited to the example described here, and various combinations are possible.

(Effects of the Invention) As explained above, the piezoelectric element-driven probe of the present invention has the following features:
By driving two types of piezoelectric elements simultaneously, X-Y 2
Can perform dimensional scanning. Therefore, images can be observed by changing the magnification over a wide range of 10 to 107. Furthermore, by using a high-speed scanning piezoelectric element as one piezoelectric element, high-speed scanning becomes possible, so the range of application is wide.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention. FIGS. 2 and 3 are explanatory diagrams of the high-precision wide-scanning piezoelectric element section and scanning control method of the present invention. FIG. 4 is a diagram of the variable scanning range piezoelectric element of the present invention. 5, 6, and 7 are side views of the specific configuration of the piezoelectric element portion of the present invention. 1... Probe 2... Sample 3... Stage 4... Z-axis piezoelectric element... X-axis piezoelectric element 6... Y-axis pressure type element 5-1.6-1... High Precision wide scanning piezoelectric element section 5-2.6-2...Piezoelectric element section for tIl adjustment 7...Z-axis control circuit 8...X-axis control circuit 9...Y-axis control circuit 10... Display device 11... Piezoelectric body 15, 16.17... Piezoelectric element 20... Electrode 22... Electrode 24... Electrode 30.31... Electrode 36... Tube type fine movement mechanism 12, 13.14... Electrode 18.19... Insulator 21... Piezoelectric element 23... Piezoelectric body 25.26... Electrode 35... Cross-shaped fine movement mechanism

Claims (1)

[Claims] 1. A probe disposed at a distance from the measurement sample, and a total displacement of a plurality of piezoelectric bodies connected to the probe in at least one of the two axes X and Y. A piezoelectric element-driven probe comprising a piezoelectric element section that applies periodic displacement, and two or more drive voltage terminals that control the displacement of the piezoelectric element section. 2. A probe disposed at a distance from the measurement sample, and a probe connected to the probe to apply periodic displacement as the sum of displacements of a plurality of piezoelectric bodies in at least one of the two axes, X and Y. In a method of driving a piezoelectric element-driven probe having a piezoelectric element portion that controls displacement of the piezoelectric element portion, and two or more drive voltage terminals that control displacement of the piezoelectric element portion, a drive voltage terminal that drives a piezoelectric body with a large displacement/driving voltage. A low-frequency drive voltage is applied to the drive voltage terminal that drives the piezoelectric material with small displacement/drive voltage, and a high-frequency drive voltage is applied to the drive voltage terminal to scan the probe with atomic-order resolution over a wide scanning range. A method for driving a piezoelectric element-driven probe characterized by: 3. A probe disposed at a distance from the measurement sample, and a probe connected to the probe to impart periodic displacement as the sum of displacements of a plurality of piezoelectric bodies in at least one of the two axes, X and Y. In a method for driving a piezoelectric element-driven probe having a piezoelectric element section that controls the displacement of the piezoelectric element section, and two or more drive voltage terminals that control the displacement of the piezoelectric element section, one or more of the A method for driving a piezoelectric element-driven probe, characterized by selecting a drive voltage terminal and simultaneously applying a drive voltage to the terminal to scan the probe.