JPH0298033A - Cylindrical piezoelectric actuator - Google Patents

Abstract

PURPOSE:To enable a high speed scanning in a slight range in the case of using a cylindrical piezoelectric actuator as a three-dimensional fine adjusting mechanism or the like by axially superposing electrodes in a multiple stage, and driving the electrodes in such a manner as not to generate an angular variation in deviation at a tip. CONSTITUTION:An angular variation at the tip of an element caused by a control voltage applied to an A electrode 1 is counterbalanced by applying a voltage of an opposite phase and the same amplitude to a B electrode 2 having an identical electrode arrangement. Thereat, a high frequency component having a relatively small amplitude is superposed on a control voltage applied to the B electrode 2 so that a high speed deviation in a slight region at the tip of the element is generated without angular variations in such a state that a rough deviation over the whole element is kept. Therefore, a cylindrical piezoelectric actuator can be used for a three-dimensional fine adjusting mechanism such as a scanning tunnel microscope, and a high speed scanning can be performed.

Description

[Detailed Description of the Invention] [Industrial Application Field J] The present invention generally relates to a cylindrical piezoelectric actuator,
More specifically, the present invention relates to a fine movement element used in a scanning tunneling microscope and devices to which it is applied.

[Prior Art] In recent years, research on scanning tunneling microscopes (STM) has become active, and a cylindrical piezoelectric actuator (FIG. 2) is generally used as its fine movement mechanism.

Most cylindrical piezoelectric actuators are made of dinicotitanate/lead acid (PbTi0.-PbZrO,:
Ceramics (abbreviated as PZT) are used. Generally, a voltage is applied in the thickness W direction, and expansion and contraction in the length L direction is utilized. When used as an actuator in the radial direction (X, Y directions), the electrodes on the surface of the element are divided and arranged as shown in Figure 3, and voltages with different polarities are applied to the opposing electrodes to cause the expansion and contraction of each electrode part. Due to the difference in polarity (direction), the element is bent into an arc shape to obtain radial displacement.

[Problem to be solved by the invention 1 However, this cylindrical piezoelectric actuator is
When used as a three-dimensional micro-motion mechanism such as M, there were the following problems.

This element has a characteristic that when scanning is performed with a large displacement (up to several μm), the large displacement and the natural frequency of the element are contradictory. (Noboru Ichinose: Ap
plication of Electronic C
eramics for STM engineering
ts, Journal of the Japan Society of Precision Engineering, 54/7/1988) From this, even when using the drive voltage as shown in Figure 4 with an offset and then scanning a minute area (general usage in STM), There is a problem in that the scanning speed of the probe is limited by the natural frequency of the entire element.

Furthermore, since the tip of the element undergoes arc-shaped displacement, the angle between the probe tip, which is normally fixed at the tip of the element, and the sample surface is not constant, so the S/
There was a problem that N deteriorated.

[Means and effects for solving the problem] The present invention arranges electrodes in multiple stages in the axial direction of a cylindrical piezoelectric actuator, and drives one set (two stages) with the same electrode arrangement with voltages of opposite phase. This is a cylindrical piezoelectric actuator that allows displacement in the radial direction and prevents angular changes in the displacement of the tip. Hereinafter, each component of the present invention will be explained in detail in Examples.

[Example 1] FIG. 1 is a schematic diagram that best represents the features of the present invention.

The angle change of the tip of the element that is supposed to be caused by the control voltage applied to the A electrode part l provided close to the end of the fixed side 3 of the element is the same as that of the A electrode part l provided close to the tip part. A electrode part 1 added to B electrode part 2 with an electrode arrangement of
The control voltage applied to is canceled out by the displacement of the B electrode section 2 caused by the control voltages having opposite phases and the same amplitude.

By increasing the distance between the A electrode section 1 and the B electrode section 2, displacement occurs in a direction perpendicular to the element tip axis. In this state, by superimposing a high frequency component with a relatively small amplitude on the control voltage applied to the B electrode section 2, the tip of the element is caused to undergo high-speed displacement in a minute area while maintaining the general displacement of the entire element.

[Example 2] Next, another example will be shown. FIG. 5 is a schematic diagram showing the electrode arrangement of a cylindrical piezoelectric actuator when the present invention is applied to STM.

When voltages with opposite phases are applied to the large stroke drive electrode 6 and the angle correction electrode 8, the probe 4 is displaced while maintaining its angle with the sample 5. At that time, the probe is also displaced in the axial direction. Since the amount increases as the length L in FIG. 5 increases, the change in the distance between the sample and the probe cannot be ignored. (A large displacement in the X or Y direction can be obtained.) Therefore, correction is made by applying a voltage to the biaxial drive electrode 7. As a result, the probe 4 can be displaced in the X or Y direction while maintaining the distance to the sample 5 and the angle it forms with the sample 5. In that state, the high-speed scanning electrode 9
If an AC voltage is applied to the element, the part that operates in an AC manner is the tip side (probe side) after the high-speed scanning electrode 9 of the element, so the effective resonance frequency is higher than the resonance frequency of the entire element6.
that's all.

By providing a Z-axis driving electrode, not only can the angle between the probe and the sample be kept constant (the distance between the two can also be kept constant), but the angle of the high-speed scanning signal can be corrected. By separately providing high-speed scanning electrodes without overlapping the electrodes, we were able to improve the accuracy of element displacement during high-speed scanning.In addition, the arrangement of each electrode in the buttocks (element in the X and Y directions) (arrangement for causing displacement) is not limited to the electrode arrangement of this example;
andD, P, E, Sm1th: Scanning
Tunneling Microscopy.

Rev, Sci, Instrum, 57.
(1986) 168B) can be used.

Further, the cylindrical piezoelectric actuator in the present invention is
Recording and reproducing device applying STM (Japanese Patent Application Laid-Open No. 63-1615
It is clear that the invention can also be used in Japanese Patent No. 52 and Japanese Patent Application Laid-open No. 63-161553.

[Effects of the Invention] As explained above, by using the correction electrode of the present invention, even if the entire element is enlarged to take a large stroke in the X and Y directions and the resonant frequency of the entire element is reduced, High-speed scanning of minute areas becomes possible.

Furthermore, since the angle and distance between the probe attached to the tip of the element and the sample are maintained, the stability of the detected tunnel current increases, that is, the accuracy can be improved in measurements such as STM.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the features of the present invention (Embodiment 1), Fig. 2 is a schematic diagram showing the shape of a general cylindrical piezoelectric actuator, and Fig. 3 is a schematic diagram showing the shape of a general cylindrical piezoelectric actuator. A schematic diagram, FIG. 4 is a schematic diagram showing an example of how a cylindrical piezoelectric actuator is used in a scanning tunneling microscope, and FIG. 5 is an actuator of an investigative tunneling microscope in which the present invention (Example 2) is implemented. , is a schematic diagram showing the state between samples. 1-A electrode part 2-B electrode part 3-fixed side 4-probe 5-sample 6-large stroke drive electrode 7-Z-axis drive electrode 8-angle correction electrode 9-high-speed scanning electrode

Claims (2)

[Claims] (1) A cylindrical piezoelectric actuator characterized in that electrodes are arranged in multiple stages in the axial direction, and at least one set (two stages) of electrodes having the same electrode arrangement can be driven with voltages of opposite phase. (2) The cylindrical piezoelectric actuator according to claim 1, further comprising an axial drive electrode for performing axial correction between the pair of electrodes.