JP3210187B2 - Scanning method of scanning probe microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning system for a scanning probe microscope such as a scanning tunnel microscope and an atomic force microscope, and more particularly to a scanning system for obtaining an atomic level image over a wide range of sample surfaces.

[0002]

2. Description of the Related Art Microscopes using a probe include a scanning tunneling microscope (STM), an atomic force microscope (AFM), and others. It is known that both STM and AFM have an atomic level resolution (0.1 nm or less). STM
Utilizes the fact that the tunnel current between the tip of the probe and the sample is very sensitive to the size of the gap, so that the tunnel current is kept constant while scanning the deep needle in the X and Y directions along the sample surface. In some cases, by controlling the height (Z direction) of the probe, an uneven image of the surface is obtained. In addition, the AFM detects the micro-deformation of the micro-beam deformed by the atomic force acting between the tip of the micro-beam (micro-beam) and the sample surface by an optical method or an STM dependent on the micro-beam, and detects the micro-beam. While correcting the position in the Z direction so that the deformation becomes constant, the sample or microbeam is
The surface shape of the sample is obtained by scanning in the direction. In any of the microscopes described above, a piezoelectric body is generally used for scanning the probe and controlling the position in the direction.

FIG. 6 shows a schematic configuration of the STM. In the figure, 42 is a sample, 43 is a probe, 44 is a head,
6 is a Z-axis direction piezoelectric element, 48 is an X-axis direction piezoelectric element, 49
Is a Y-axis direction piezoelectric element, 45 and 47 are insulating plates, 51 is an electrode, 52 is an XY scanning circuit, 53 is a servo circuit, 54 is a tunnel current voltage conversion circuit, 55 is a bias power supply, 56 is a microcomputer, and 57 is a memory. , 58 indicate a display device.

In FIG. 6, a probe 43 is mounted on a head 44 of an STM unit.
47 and piezoelectric elements 46, 48, 49. The piezoelectric elements 46, 48, and 49 constitute a three-dimensional actuator including an X axis, a Y axis, and a Z axis. The piezoelectric element 46 drives the Z axis, the piezoelectric element 48 drives the X axis, and the piezoelectric element 49 drives the Y axis. It is. A driving voltage is applied to the electrodes 51 disposed on both sides of the piezoelectric elements 46, 48, and 49 constituting the three-dimensional actuator. To control the three-dimensional actuator, the probe 43 is moved in the X-axis and Y-axis directions by sweeping the voltage applied to the piezoelectric elements 48 and 49 in the X-axis and Y-axis directions by the XY scanning circuit 52 to perform two-dimensional scanning. The voltage to the Z-axis direction piezoelectric element 46 is controlled through the servo circuit 53 so that the tunnel current becomes constant while performing this scanning. Therefore, the control voltage value is sampled by the microcomputer 56 in synchronization with the scanning of the probe 43 and is displayed on the display device 58 while being stored in the memory 57, so that the surface shape (concavo-convex image) of the sample 42 is obtained.
Can be observed.

As described above, it is known that the STM and the AFM can obtain an atomic level resolution. However, when scanning is performed in the maximum scanning range (200 nm to 100 μm) of the probe, the atomic level resolution is reduced. It is impossible to get. Because, usually, the vertical and horizontal resolution of such a scanning probe microscope is a maximum of 51 due to the capacity of the memory.
Since it is composed of pixels of about 2 (9 bits) × 512 (9 bits), when scanning is performed in the maximum scanning range of 200 nm, the distance between the two pixels is about 0.4 nm, which is larger than the size of one atom. This is because Therefore, in general, when obtaining an image at the atomic level, it is necessary to scan with a reduced scanning range.

[0006]

Conventionally, when an atomic level image is to be obtained over a wide range of the sample expression, the scanning range is reduced to such an extent that the resolution at the atomic level can be obtained (up to about 50 nm). Then, the observation field of view is moved by moving the sample, and the same scanning is repeated again, thereby joining the images obtained last.

In such a method, in order to scan one scanning range and determine the next scanning range, it is necessary for the operator to set parameters and the like, which requires much time and labor. ing. If it takes a long time for this, there arises a problem that the sample drifts during this time and stable observation cannot be performed.

The present invention has been made to solve such problems of the prior art.
M, AFM, etc. are divided into several partial areas within the maximum scanning range of the probe of the scanning probe microscope, and sequentially scanned.
An object of the present invention is to provide a scanning method for obtaining an image having an atomic-level high resolution within the maximum scanning range of the probe by joining the obtained images.

[0009]

According to the scanning method of the scanning probe microscope of the present invention which achieves the above object, a scanning method for obtaining a signal relating to irregularities on a sample surface by scanning a deep needle with a piezoelectric element along the sample surface. In the scanning probe microscope, the maximum scanning range of the probe is
An offset signal for sequentially changing the divided partial areas, and while this offset signal is in one partial area,
A scanning signal for scanning the partial area is superimposed and applied.

In this case, the value of at least one of the offset signal and the scanning signal may be set so that the partial area partially overlaps the adjacent partial area.

[0011]

According to the present invention, there is provided an offset signal for causing the piezoelectric element for scanning the probe to sequentially change a partial area obtained by dividing the maximum scanning range of the probe by n, and a method of controlling the offset signal while the offset signal is present in one partial area. And a scanning signal for scanning the partial area is superimposed and applied.
High resolution at the atomic level can be obtained in a partial region. By connecting the images of the partial areas, a high resolution can be obtained over the entire maximum scanning range. Further, since the image of each partial area is obtained in a predetermined order by dividing the maximum scanning range in this manner, the joining of the captured images can be automated, and manual adjustment and setting are not required, and the search can be performed in a short time. An image with atomic-level high resolution can be obtained within the maximum scanning range of the needle.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle of the present invention is that, as shown in FIG. 2, the maximum scanning range of the probe of the scanning probe microscope is automatically set to n.
That is, the partial area is sequentially scanned, and the obtained images are joined together to obtain an image having a high resolution at the atomic level within the maximum scanning range of the probe.

Hereinafter, the STM will be described as an example.
The same applies to FM. FIG. 1 shows a schematic configuration of an STM according to one embodiment. The difference from the conventional example shown in FIG. 6 is that the X-direction and Y-direction drive signals output from the XY scanning circuit 52 are X-direction and X-direction drive signals as described later. Offset signal, X
A scan signal, a Y offset signal, and a Y scan signal are output, and among these, the X offset signal and the X scan signal are superimposed by an adder circuit 11 as shown in the figure to form an X-axis direction piezoelectric element 48. , Y
The only difference is that the offset signal and the Y scanning signal are superimposed by the adding circuit 12 as shown in the figure and applied to the Y-axis direction piezoelectric element 49, and the other points are the same.

The XY scanning circuit 52 outputs an X offset signal, an X scanning signal, a Y offset signal, and a Y scanning signal having waveforms as illustrated in FIG. However, in the case of this example, the X direction and the Y direction are each divided into three equal parts, and the signal voltage 1 is a voltage necessary to scan the divided one-third side.

That is, the X offset signal and the Y offset signal output from the XY scanning circuit 52 are signals for sequentially changing the partial area within the maximum scanning range obtained by equally dividing the maximum scanning range into n parts in each direction. . And
The X-scanning signal and the Y-scanning signal output from the XY scanning circuit 52 are signals for performing two-dimensional sweep scanning in the partial area while the X-offset signal and the Y-offset signal are in one partial area. It is the same as the conventional one. Therefore, the scanning range of each partial area becomes 1 / n in one side direction compared to the maximum scanning range.
The interval between the sampling points of the control voltage value applied to the Z-axis direction piezoelectric element 46 through 3 can be reduced accordingly, and the resolution increases.

FIG. 4A is a waveform diagram in which the X offset signal and the X scanning signal shown in FIG. 3 are combined, and FIG.
FIG. 9 is a waveform diagram in which an offset signal and a Y scanning signal are synthesized. The uneven images of each partial region obtained by scanning with such a probe driving signal are sequentially taken into a memory 57 via a microcomputer 56, and When the scanning of the partial area is completed, those image signals are connected by the microcomputer 56 and displayed on the display device 58. In this way, as shown in FIG.
The entire observation area extends to the maximum scanning range of the probe, and
In the entire range, a high resolution, for example, an atomic level, which is n times higher than the resolution obtained by scanning the maximum scanning range of the probe at a time, can be obtained.

By the way, due to the characteristics of the scanning device, when the images of the partial areas actually scanned are connected and displayed, the images become discontinuous or partially overlapped. It can be considered. In order to prevent this, as shown in FIG. 5, the scanning range of each partial area is slightly widened and scanning is performed so that the scanning range partially overlaps with the adjacent partial area, and the overlapped portion is overlapped during display. You may make it. To perform such overlapping scanning, the voltage value and the amplitude of at least one of the offset signal and the scanning signal may be adjusted.

The scanning method of the scanning probe microscope of the present invention has been described based on several embodiments.
The present invention is not limited to these embodiments, and various modifications are possible.

[0019]

As is apparent from the above description, according to the scanning method of the scanning probe microscope of the present invention, the partial area obtained by dividing the maximum scanning range of the probe by n is sequentially provided on the piezoelectric element for scanning the probe. Since the offset signal for changing the offset signal and the scanning signal for scanning the partial area while the offset signal is in one partial area are superimposed and applied, the partial area has an atomic level. High resolution can be obtained. By connecting the images of the partial areas, a high resolution can be obtained over the entire maximum scanning range. Further, since the image of each partial area is obtained in a predetermined order by dividing the maximum scanning range in this manner, the joining of the captured images can be automated, and manual adjustment and setting are not required, and the search can be performed in a short time. An image with atomic-level high resolution can be obtained within the maximum scanning range of the needle.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a scanning tunneling microscope that performs a scanning method according to one embodiment of the present invention.

FIG. 2 is a diagram for explaining a basic principle of the present invention.

FIG. 3 is a waveform diagram of a signal output from the XY scanning circuit in FIG. 1;

FIG. 4 is a diagram illustrating a waveform diagram and a synthesized screen obtained by synthesizing the offset signal and the X-scan signal of FIG. 3;

FIG. 5 is a view similar to FIG. 4 of another embodiment.

FIG. 6 is a diagram showing a schematic configuration of a conventional scanning tunneling microscope.

[Explanation of symbols]

 11, 12 Adder circuit 42 Sample 43 Probe 44 Head Z-axis piezoelectric element 48 X-axis piezoelectric element 49 Y-axis piezoelectric element 45, 47 Insulating plate 51 Electrode 52 XY scanning Circuit 53 Servo circuit 54 Tunnel current voltage conversion circuit 55 Bias power supply 56 Microcomputer 57 Memory 58 Display device X offset signal X scanning signal Y offset signal Y scanning signal

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-281002 (JP, A) JP-A-1-216204 (JP, A) JP-A-6-34313 (JP, A) JP-A-6-31313 160076 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21/00-21/24 G01B 11/30 G01B 21/30 H01J 37/28 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A scanning probe microscope which obtains a signal related to irregularities on a sample surface by scanning a deep needle with a piezoelectric element along a sample surface.
An offset signal for sequentially changing a partial area obtained by dividing the maximum scanning range of the probe by n is superimposed on a scanning signal for scanning the partial area while the offset signal is in one partial area. A scanning method of a scanning probe microscope, wherein the scanning method is applied. 2. The method according to claim 1, wherein at least one of the offset signal and the scanning signal is set so that a partial area partially overlaps an adjacent partial area.
The scanning method of the scanning probe microscope described.