JPH06258016A - Actuator and scanning tunneling microscope - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide an actuator having high rigidity and a scanning tunneling microscope capable of speeding up observation time. [Structure] In the actuator of the present invention, rigidity is increased by engaging a plurality of plate-shaped single crystal piezoelectric elements to form a three-dimensional structure. Further, the scanning tunneling microscope of the present invention has a separating means for separating the probe from the sample surface during the blanking period by more than the predetermined gap distance, and a probe separated from the sample surface by the separating means. And a moving means for moving the needle at a speed faster than the scanning speed to shorten the retrace time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator and a scanning tunneling microscope.

[0002]

2. Description of the Related Art First, the structure of a conventional scanning tunneling microscope will be briefly described with reference to FIG.

In the conventional scanning tunneling microscope shown in FIG. 8, a coarse movement inchworm mechanism 33 is provided on a main body base 31, and a fine movement mechanism 35 for holding a probe tip 27 is constructed on the coarse movement inchworm mechanism 33. The sample 41 is held by the XY drive mechanism 37 so that it can be driven in the XY directions. The heater 39 is for heating the sample 41.

Next, an observing method will be described by taking as an example the case of observing the state of the solid surface at a high temperature with a scanning tunneling microscope. First, the sample heater 41 is heated by the heater 39 to reach a constant temperature, and then the coarse motion inchworm mechanism 3 is used.
The probe tip 27 is approached by 3 until a tunnel current flows. Next, the XY drive mechanism 37 scans the sample in the XY directions, and at the same time, the fine movement mechanism 35 is operated so that a constant tunnel current flows between the sample 41 and the probe 27. By monitoring the operating voltage at this time, the state of the sample surface can be known.

However, when the sample is heated to a high temperature, the fine movement mechanism 35 is provided in the immediate vicinity of the sample 41 and the probe 27. Therefore, when the sample 41 is heated to a high temperature, the fine movement mechanism 35 also becomes a high temperature. . Therefore, a driving element used for the fine movement mechanism 35 is a piezoelectric element using a piezoelectric single crystal such as lithium niobate or lithium tantalate as a high Curie temperature element that can be used even at high temperatures.

Since this piezoelectric element is a single crystal, it has a thin plate shape as shown in FIG. In the conventional actuator shown in FIG. 7, electrodes 103 are provided on both side surfaces of a plate-shaped lithium niobate crystal 101, and an end portion of the lithium niobate crystal 101 is held by a probe holder 105. The probe 107 is provided.

Next, a schematic structure of a conventional scanning tunneling microscope will be described with reference to FIG. By applying the bias voltage of the bias voltage source 57 to the sample 59 and controlling the applied voltage of the Z-axis drive source piezo element 51, the probe 55 is brought close to the sample 59 to the gap through which the tunnel current flows. A servo system is configured to control the voltage of the Z-axis driving piezo element 51 so that the tunnel current becomes constant.

The tunnel current detected by the probe 55 is converted into a voltage signal in the current / voltage converter 61.
Since this tunnel current is inversely proportional to the square of the distance between the probe 55 and the sample 59, the gap value between the probe 55 and the sample 59 is linearized by passing through the log amplifier 63. After that, it compares with the comparison reference voltage of the comparison reference voltage source 165,
The error voltage is amplified by the error amplifier 67, further amplified by the high voltage amplifier 69 to a voltage capable of driving the piezo element, and applied to the Z-axis driving piezo element 51.

By constructing such a servo system, the probe 55 and the sample 59 are proportional to the comparison reference voltage 165 set.
A constant tunnel current can flow between them. This keeps the gap between the probe 55 and the sample 59 constant.
Further, the state of the surface of the sample 59 can be known by measuring the applied voltage to the Z-axis piezo element 51 while scanning the probe 55 with the piezo element 53 in the XY directions.

FIG. 10 shows a time chart of the waveforms of the scanning voltages Vx and Vy and the tunnel current comparison reference voltage VR. As is clear from the time chart shown in FIG. 10, conventionally, when scanning the probe 55 in the XY directions, the blanking is performed at the same time as the observation time for capturing the signal.

This is because it depends on the servo system responsivity of the entire apparatus, and there is a possibility that the probe may come into contact with the sample unless the blanking period is returned for a certain period of time like the observation time.

[0012]

However, since the thin plate-shaped single crystal piezoelectric element used in the conventional actuator has a low rigidity in the X-axis direction, noise due to vibration in this direction is very large. Become.

The probe is fixed by inserting the probe into a probe holder similar to an injection needle by deforming the insertion portion of the probe. That is, since the probe is simply inserted into the probe holder, the holding force is weak and there is a problem in that contact noise is generated due to vibration.

Further, in the observation with the conventional scanning tunneling microscope, the retrace time is long, which impedes the speeding up of the observation time.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an actuator having high rigidity and a scanning tunnel microscope capable of speeding up observation time.

[0016]

In order to achieve the above object, the actuator of the first invention of the present application is summarized as a three-dimensional structure by engaging a plurality of plate-shaped single crystal piezoelectric elements.

The actuator of the second invention of the present application is summarized in that a plate-shaped single crystal piezoelectric element is housed in a ceramic case.

The third invention of the present application is a scanning tunneling microscope for observing the state of the sample surface by scanning the sample surface in one direction with a probe while maintaining a predetermined gap, and in a blanking period. In that case, a separating means that separates the probe from the sample surface by a distance greater than the predetermined distance and a probe that is separated from the sample surface by the separating means are moved at a speed faster than the scanning speed, and a retrace time. It is a gist to have a moving means for shortening.

Further, this scanning tunneling microscope is preferably equipped with a tunnel current measuring servo circuit, and the tunnel current when the sample surface is scanned keeps the gap between the probe and the sample surface constant while keeping the gap between the sample surface and the sample surface constant. The separation means applies a control signal to the comparison reference signal of the tunnel current measuring servo circuit to set the gap between the probe and the sample surface, which is held constant, to an arbitrary distance for control. The main point is to do.

[0020]

The actuator of the first invention of the present application has a high rigidity because it is formed three-dimensionally by engaging a plurality of plate-shaped single crystal piezoelectric elements.

The actuator of the second invention of the present application has a high rigidity because the plate-shaped single crystal piezoelectric element is housed in a ceramic case.

In the scanning tunneling microscope of the third invention of the present application, during the blanking period, the probe is separated from the surface of the sample by a distance larger than the gap distance for the predetermined period, and the probe is moved at a speed faster than the scanning speed. Shorten the return time. As a result, the probe is positively separated from the sample, and even if the probe is returned at high speed, contact between the probe and sample can be prevented.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the structure of an actuator according to the present invention.

As shown in FIG. 1, four plate-shaped single crystal piezoelectric elements 1 are combined in a box shape to form a single actuator.

Further, the actuator shown in FIG. 2 has two plate-shaped single crystal piezoelectric elements 11c and 11d arranged to face each other.
Is a combination of two plate-shaped single crystal piezoelectric elements 11a and 11b, which are similarly opposed to each other, which are slightly depressed from both end faces and project from the both end faces. The combination shape of these plate-shaped single crystal piezoelectric elements is not limited to the above two examples, and various three-dimensional configurations such as a triangular prism shape or a pentagonal prism shape can be used.

Further, FIG. 3 shows an actuator section 20 in which the actuator shown in FIG. 2 is incorporated in a ceramics holder 21. That is, one end of the actuator is fixed to the ceramic holder 21, and the other end is fixed to the ceramic probe holder 25 to be integrated. At this time, the actuator is fixed to the ceramic holder 21 by fitting the projecting both ends of the plate-shaped single crystal piezoelectric elements 11a and 11b into the guide groove 23 of the ceramic holder 21. As a result, it becomes possible to prevent the vibration due to the vibration in the direction orthogonal to the guide groove 23. Further, the probe holder 25 has a hole into which the probe 27 can be inserted, and the probe 27 can be fixed with a fixing screw 29.

Next, FIG. 4 shows the actuator section 2 shown in FIG.
The scanning tunneling microscope which adopted 0 is shown. Note that FIG.
The same parts as those of the conventional scanning tunnel microscope shown in FIG. In FIG. 4, the actuator unit 20 is provided at the tip of the fine movement mechanism 35. That is, since the probe 27 can be reliably fixed by providing the actuator section 20 having the structure shown in FIG. 3, a tunnel current signal without contact noise due to vibration can be obtained.

Next, an example of the scanning tunneling microscope will be described with reference to FIG. The same parts as those of the conventional scanning tunneling microscope shown in FIG. 9 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, a reference voltage generation source 65 that generates a reference voltage is provided instead of the comparison reference voltage source 165 that outputs the comparison reference voltage.

The operation will be described below with reference to the time chart of the scanning voltage waveform and the probe control voltage shown in FIG. Figure 6
As shown in, the reference voltage generation source 65 generates a comparison reference voltage for tunnel current setting during the observation period and the blanking period according to the scanning voltage waveform, and applies it. In the servo system of the system, the probe 55 scans the surface of the sample 59 according to this reference voltage. Therefore, during the observation period, the tunnel current flows so as to reach the set reference voltage value.
5 is controlled along the surface of the sample 59 so that the surface of the sample 59 can be observed. On the other hand, in the blanking period, the comparison reference voltage is set to 0V, so that the probe 55 is separated from the sample 59 and the sample 59 is returned to the scanning start point at high speed.
It will not come into contact with.

As another method, the probe 55 is moved to the sample 5 in synchronism with the input of the piezo driving high voltage amplifier 69 in the blanking period.
Even if a control voltage for separating from 9 is applied, the same effect can be obtained.

[0031]

As described above, the actuator of the present invention has a three-dimensional structure to increase the rigidity, and by incorporating it into a ceramic holder, the rigidity can be further increased. Therefore, when incorporated in the fine movement mechanism, it is possible to reduce noise generated by the vibration generated in the fine movement mechanism.

Further, the scanning tunneling microscope of the present invention is
When the sample surface is scanned, the probe is separated and moved at high speed, so that the retrace time can be shortened, and therefore the sample surface can be observed at high speed.

[Brief description of drawings]

FIG. 1 is a perspective view showing a basic structure of the present invention.

FIG. 2 is a perspective view showing a structure for assembling into a ceramics holder.

FIG. 3 is a perspective view showing a structure for integrating the basic structure of a ceramics holder, a piezoelectric element, and a probe holder.

FIG. 4 is a fine movement driving mechanism using the single crystal shown in FIG.

FIG. 5 is a block diagram showing a basic configuration of a scanning tunneling microscope.

6 is a diagram showing a drive time chart of the scanning tunneling microscope shown in FIG.

FIG. 7 is a perspective view showing the shape of a conventional probe holder.

FIG. 8 is a diagram showing a configuration of a conventional fine movement drive mechanism.

FIG. 9 is a block diagram showing a basic configuration of a conventional scanning tunneling microscope.

FIG. 10 is a diagram showing a drive time chart of a conventional scanning tunneling microscope.

[Explanation of symbols]

 1, 11 Single crystal element 3, 15 Electrode 5 Electric wire 20 Actuator 21 Ceramics holder 23 Guide groove 25 Probe holder 27 Probe 29 Probe fixing screw 31 Main body base 33 Coarse inch worm mechanism 35 Fine movement mechanism 37 XY drive mechanism 39 Heater 41 Sample 51 Z-axis piezo element 53 Piezo element 55 Probe 57 Bias voltage 59 Sample 61 Current / voltage converter 63 Log amplifier 65 Reference voltage source 67 Error amplifier 69 High voltage amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Kobayashi 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center (72) Inventor Tatsuaki Kuroda Komukai-shiba, Kawasaki-shi, Kanagawa 1 Incorporated Toshiba Research and Development Center

Claims (3)

[Claims] 1. An actuator comprising a plurality of plate-shaped single crystal piezoelectric elements engaged with each other to form a three-dimensional structure. 2. An actuator comprising a plate-shaped single crystal piezoelectric element housed in a ceramic case. 3. A scanning tunneling microscope for observing the state of a sample surface by scanning the sample surface in one direction while maintaining a predetermined gap, wherein the probe is in the blanking period. Separating means for separating the sample surface from the sample surface by a distance greater than the predetermined distance, and moving means for moving the probe separated from the sample surface by the separating means at a speed faster than the scanning speed to shorten the retrace time. A scanning tunneling microscope having.