JP2022134649A - Scanning type probe microscope, information processor, and program - Google Patents

Abstract

To provide a scanning type probe microscope capable of suppressing acquisition time of a surface image.SOLUTION: A scanning type probe microscope scans a surface of an observation object along an observation range with a probe, and obtains a surface image composed of pixels of m points in an X direction and n points in a Y direction for the observation range on the basis of interaction between the probe and the surface in each position being scanned. The scanning type probe microscope performs scanning by thinning out one portion of positions corresponding to the pixels in the m points in the X direction and the n points in the Y direction within the observation range so as to scan the observation range in a shorter time than when scanning positions corresponding to entire pixels in the m points in the X direction and the n points in the Y direction within the observation range. The scanning type probe microscope has information processing means for performing interpolation processing for restoring missing pixels on the basis of observation data in which partial pixels are missing from among the pixels in the m points in the X direction and the n points in the Y direction for the observation range.SELECTED DRAWING: Figure 6

Description

The present invention relates to scanning probe microscopes such as atomic force microscopes, and more particularly to scanning probe microscopes capable of reducing the time required to acquire surface images.

A scanning probe microscope (SPM) is a scanning microscope that obtains information on the surface of a sample by mechanically scanning a mechanical probe. It is a general term for magnetic force microscope (MFM), scanning capacitance microscope (SCaM), scanning near-field optical microscope (SNOM), scanning thermal microscope (SThM), and the like. A scanning probe microscope, in principle, has a sample stage, a probe, a scanner (actuator) that displaces the sample stage or the probe for scanning, and a detector that detects changes in physical quantities that occur in the probe. has as an element of A scanning probe microscope can perform raster scanning of a probe and a sample relative to each other in the XY directions, obtain surface information of a desired sample region through the probe, and map and display the surface information on a monitor. In this specification, the height direction of the sample is defined as the Z direction, and two orthogonal directions within a plane orthogonal to the Z direction are defined as the X direction and the Y direction.

A typical scanning probe microscope is an atomic force microscope. Atomic force microscopes use a cantilever tip (a member with a very small probe attached to the tip of the cantilever) as a probe.

In a scanning probe microscope, it is necessary to physically move the probe to scan, and it is necessary to stabilize the response signal detected by the detector and the feedback control using this response signal, etc. Therefore, there is a limit to shortening the time required to acquire the surface image. For example, it takes about 5 minutes to obtain the SPM image of the Si(111)7×7 surface shown in FIG. Since it takes a long time to acquire surface images, it is difficult to continuously acquire surface images in a short period of time to observe detailed temporal changes in phenomena occurring on the surface. In addition, at room temperature, there is a problem that the image is distorted due to the influence of thermal drift if it takes time to acquire the surface image.

Attempts have been made to solve such problems by various approaches.
For example, Japanese Unexamined Patent Application Publication No. 2002-100000 discloses a technique for increasing the speed of frequency signal detection by devising a signal detection circuit (phase detection circuit). Further, Japanese Patent Laid-Open No. 2002-200002 discloses a technique that enables a scanner device to perform high-speed scanning. Further, Patent Literature 3 discloses a technique of detecting a change in relative position between a probe and a sample to measure thermal drift and eliminating its influence. Non-Patent Document 1 discloses a scanning tunneling microscope that enables high-speed scanning by attaching a scanning piezoelectric member to the side of the probe that is lighter than the sample.

Patent No. 6025082 Patent No. 5268008 JP 2012-30358 A

e-JSSNT, 2020, Volume 18, p.146-151

Although various methods have been proposed to shorten the acquisition time of a surface image in a scanning probe microscope and eliminate the influence of thermal drift, further improvements are desired. An object of the present invention is to provide a scanning probe microscope that can solve the above problems.

In order to solve the above problems, in a scanning probe microscope according to one embodiment of the present invention, a scanning probe microscope scans a probe along an observation range on a surface of an observation target, and each position during scanning Based on the interaction between the probe and the surface in , a surface image composed of pixels of m points in the X direction and n points in the Y direction is obtained for the observation range. The scanning probe microscope thins out a portion of the positions corresponding to pixels of m points in the X direction and n points in the Y direction in the observation range, thereby scanning the observation range at m points in the X direction and n points in the Y direction. The observation range is scanned in a short time compared to the case of scanning positions corresponding to all n pixels.

In the present invention, the scanning probe microscope performs interpolation processing to restore missing pixels based on observation data in which some pixels are missing among m points in the X direction and n points in the Y direction in the observation range. It is preferable to provide information processing means for performing

In the present invention, the information processing means may collectively output a surface image composed of pixels of m points in the X direction and n points in the Y direction for the observation range by interpolation processing.

In the present invention, the information processing means performs interpolation processing in parallel with the scanning of the probe every time observation data is added by scanning the probe, and causes the display device to display the surface image obtained by the interpolation processing. good.

In the present invention, for example, the information processing means performs interpolation processing based on all acquired observation data each time observation data is added by scanning with the probe in interpolation processing performed in parallel with scanning of the probe. good.

Alternatively, in interpolation processing performed in parallel with the scanning of the probe, the information processing means, each time observation data is added by scanning with the probe, includes the latest addition data newly added among the acquired observation data, and Interpolation processing may be performed on missing pixels between the immediately preceding additional data and the latest additional data based on the immediately preceding additional data added immediately before the newly added observation data.

Further, an information processing apparatus according to an embodiment of the present invention is based on observation data in which some of the pixels of m points in the X direction and n points in the Y direction are missing, which are acquired by a scanning probe microscope. , an interpolation process for restoring missing pixels.

In the present invention, it is preferable to collectively output a surface image composed of pixels of m points in the X direction and n points in the Y direction by interpolation processing.

In the present invention, whenever observation data is added by scanning the probe by the scanning probe microscope, interpolation processing is performed in parallel with the scanning of the probe, and the surface image obtained by the interpolation processing is displayed on the display means. good.

In the present invention, for example, in interpolation processing performed in parallel with scanning with the probe, interpolation processing may be performed based on all acquired observation data each time observation data is added by scanning with the probe.

Alternatively, in the interpolation processing performed in parallel with the scanning of the probe, each time observation data is added by scanning with the probe, the latest addition data newly added among the acquired observation data and the newly added data Interpolation processing may be performed on missing pixels between the immediately preceding additional data and the latest additional data based on the immediately preceding additional data added immediately before the observed data.

A program according to an embodiment of the present invention causes a computer to function as the information processing apparatus according to any one of the above items.

It is a figure which shows the structure of an atomic force microscope typically. FIG. 10 is a diagram schematically showing the movement path of the probe in normal scanning; FIG. 10 is a diagram schematically showing an example of a moving path of a probe in thinned scanning; FIG. 10 is a diagram schematically showing another example of the moving path of the probe by thinning scanning; FIG. 10 is a diagram schematically showing still another example of the moving path of the probe by thinning scanning; 4 is a flow chart showing a procedure for obtaining a surface image by thinning scanning with the atomic force microscope of the first embodiment. FIG. 3 is a diagram showing observation data acquired by the atomic force microscope according to the first embodiment and a surface image restored from the observation data; It is a figure which shows typically the procedure of the interpolation process in 2nd Embodiment. 9 is a flow chart showing a procedure for obtaining a surface image by thinning scanning with the atomic force microscope of the second embodiment. FIG. 10 is a diagram showing observation data acquired by an atomic force microscope according to the second embodiment and a surface image restored from the observation data; It is a figure which shows typically the procedure of the interpolation process in 3rd Embodiment. FIG. 10 is a diagram showing observation data acquired by an atomic force microscope according to the third embodiment and a surface image restored from the observation data; It is an example of a surface image obtained by normal scanning.

[First Embodiment]
The configuration of a scanning probe microscope according to an embodiment of the present invention will be described below with reference to the drawings. In this specification, in each drawing showing the configuration of the scanning probe microscope, the shape, size, etc. of the constituent elements may be exaggerated or deformed in order to explain the main features. , The shape drawn in the drawing is not necessarily a faithful representation of the actual shape. FIG. 1 is a diagram schematically showing the configuration of a scanning probe microscope according to a first embodiment of the present invention, and shows a configuration example of an atomic force microscope 1 as a specific example of the scanning probe microscope. . In addition, in this specification, in each drawing, the shape, size, etc. of the constituent elements may be exaggerated or deformed in order to explain the main features, and the shape drawn in the drawing may be It is not necessarily a faithful depiction of the shape of the real thing.

The atomic force microscope 1 uses a cantilever tip 11 as a probe (a member having a probe 13, which is a very minute protruding needle, attached to the tip of the cantilever 12), and the interaction between the probe 13 and the surface of the sample S is performed. Changes in the cantilever 12 due to action (displacement of the tip portion of the cantilever 12 due to atomic force in the DC mode (contact mode or non-contact mode) and changes in the cantilever 12 in the AC mode (sometimes referred to as tapping mode) It is a microscope for imaging the state of undulations (surface image) in the observation range of the surface of the sample S through changes in vibration, etc.).

The atomic force microscope 1 exemplified in FIG.

As described above, the cantilever tip 11 is a member in which an extremely fine probe 13 is provided at the tip of the cantilever 12 . In this embodiment, the cantilever tip 11 is fixed to the microscope housing 10 via an excitation piezoelectric member 16 for vibrating the cantilever 12 in order to perform measurements in AC mode.

The scanner 14 has an actuator that displaces the stage 15 based on drive signals from the controller 18 . The scanner 14 displaces the stage 15 on which the sample is fixed in at least two directions of X and Y. As shown in FIG. The scanner 14 may also displace the stage 15 in the Z direction. Alternatively, as for the Z direction, the cantilever instead of the stage 15 may be displaced in the Z direction. The actuator may be of any type. For example, an actuator that drives by applying a voltage to a piezoelectric body may be used, or an optical actuator that generates displacement by irradiating a shape memory alloy or the like with intensity-modulated laser light may be used. .

The scanner 14 is detachably attached to the microscope housing 10 . With the scanner 14 attached to the microscope housing 10 , the stage 15 is arranged at a position facing the probe 13 at the tip of the cantilever 12 . A sample S to be measured (observed) by the atomic force microscope 1 is fixed to the stage 15 .

The optical sensor unit 17 is a detector that detects displacement of the cantilever 12 based on interaction between the probe 13 at the tip of the cantilever 12 and the surface of the sample S, and outputs a signal based on the displacement. The optical sensor unit 17 may, for example, comprise a sensor known as an optical lever optical sensor. This optical lever type optical sensor irradiates the back surface of the cantilever 12 with laser light through an optical system such as a lens and a mirror as necessary, and receives the reflected light with a photodiode. The optical lever type optical sensor detects the displacement of the cantilever 12 as the movement of the laser beam spot on the photodiode.

An optical sensor unit 17 that detects the displacement of the cantilever 12 is connected to an information processing device 19 .

The information processing device 19 is realized by a computer or the like. A control unit 191 , a storage unit 192 and an input/output interface 193 are provided.

The control unit 191 realizes the functions of the information processing device 19 by executing various programs stored in the storage unit 192 . In this embodiment, the control unit 191 implements at least interpolation processing, which will be described later. In addition, the control unit 191 may perform thinning determination that determines the degree of thinning in thinning scanning. The control unit 191 is implemented by, for example, a CPU.

The storage unit 192 is configured by a storage medium such as a RAM (Random Access Memory), HDD (Hard disk drive), SSD (Solid State Drive), or the like. The storage unit 192 stores programs executed by the control unit 191, data used in the programs, and the like. That is, the storage unit 192 stores an interpolation processing program that defines a processing procedure for interpolation processing, a scanning program that implements scanner scanning control including thinning scanning, a program that implements a thinning degree determination function, and these programs. Stores data used in Further, the storage unit 192 stores data obtained by measurement with the atomic force microscope 1 .

The input/output interface 193 is an interface to which an input/output device is connected. For example, an output device such as the monitor 20 or a printer, and an input device such as a keyboard and a mouse are connected. The monitor 20 is, for example, a display element such as a liquid crystal display or an organic EL display, and displays various information such as a surface image acquired by the atomic force microscope 1 and an operation screen.

The controller 18 includes, for example, a semiconductor laser drive circuit, a preamplifier circuit, an oscillation circuit, an AC/DC conversion circuit, a feedback circuit, a scanning control circuit, an actuator drive circuit, and the like. The controller 18, the information processing device 19, and the monitor 20 perform control driving of the atomic force microscope mechanism and signal processing, and finally display the unevenness information of the sample S on the monitor 20, so that the user can see the sample. It is possible to obtain knowledge about the surface information of S.

(normal scan)
FIG. 2 schematically shows the movement path of the probe in normal scanning. When acquiring a surface image composed of pixels of horizontal (X direction) m points x vertical (Y direction) n points in the observation range on the surface of the sample (observation target) by a normal method, the controller 18 controls the probe 13 After bringing the probe closer to the sample surface to the extent that interacts with the surface of the sample S, the observation range in the Y direction is equally divided into n rows corresponding to the number of pixels in the Y direction, and the first row in the Y direction ( For example, the probe 13 is scanned in the X direction (for example, from left to right) for each row, starting from the top row). A signal based on the displacement of the cantilever 12 output from the optical sensor unit 17 at each position obtained by equally dividing the observation range in the X direction by m corresponding to the number of pixels in the X direction during the scanning of each row in the X direction. is a value discretized by an AC/DC conversion circuit after undergoing signal processing as necessary. Then, the discretized value is taken into the information processing device 19 as a pixel value at the position. In this way, from the first row in the Y direction to the n-th row, which is the last row, the pixel values of m points are loaded into the information processing device 19 for each row. The image is stored in the storage unit 192 provided in the information processing apparatus 19 as a surface image of m points×vertical (Y direction) n points (for example, an image without missing points as shown in FIG. 13). This surface image is displayed on the monitor 20 .

In this way, according to normal scanning, scanning is performed so as to cover positions corresponding to all pixels, and the pixel values of all pixels within the observation range are sequentially acquired.

(thinning scan)
In the atomic force microscope 1 according to the present embodiment, in addition to the above-described normal scanning, scanning is performed by thinning out a part of positions corresponding to m points x n pixels in the observation range. Thinning scanning for scanning the observation range in a relatively short time is possible. It is arbitrary how the scanning is thinned. For example, thinning scanning can be performed by a scanning method such as the one schematically showing the movement path of the probe in FIGS.

The scanning method shown in FIG. 3 obtains missing data by thinning out rows in the Y direction from normal scanning and scanning in the X direction. That is, only one row of data is acquired for every predetermined number of rows (four rows in the example of FIG. 3). The method of FIG. 3 scans in the X direction in a common direction (all from left to right in the example of FIG. 3) in all rows from which data is acquired. The scanning method shown in FIG. 4 is common to FIG. 3 in that rows in the Y direction are thinned out from normal scanning and scanning in the X direction is performed. X-direction scanning is performed (for example, in the example of FIG. 4, left-to-right and right-to-left are alternately exchanged for each X-direction scanning). The scanning method shown in FIG. 5 scans along a triangular wave-like path. In this method, the scanning direction for acquiring data is no longer parallel to the X direction. When scanning as shown in FIG. 5, it is preferable to determine the pixel value of each pixel around the position of the probe by weighting according to the distance from the position of the probe.

The atomic force microscope 1 of this embodiment is configured to be able to select and use any one of these thinned scanning methods. For example, when only one row out of eight rows is scanned in the X direction by the scanning method shown in FIG. The time can also be reduced to about 1/8 compared to normal scanning. In the scanning method of FIGS. 3 and 4, it is preferable to scan the first and last rows in the Y direction in the X direction regardless of the degree of thinning. The similarity between the image obtained by normal scanning and the image restored by the interpolation process described later is evaluated using PSNR (Peak Signal to Noise Ratio) and SSIM (Structual SIMilarity) as indicators, and the image deterioration is within an acceptable level. The degree of thinning should be determined as follows.

During thinning scanning, pixel values at each position are captured by the information processing device 19 based on signals based on the displacement of the cantilever 12 at each position during scanning, as in the case of normal scanning.

For example, in the case of the scanning method shown in FIG. 3, among the first row to the n-th row, which is the last row in the Y direction, only the rows scanned in the X direction have m pixel values as information. It is taken into the processing device 19 and stored in the storage unit 192 . The format of the pixel value data fetched at this time is arbitrary. For example, it may be stored as an image (thinned image) of m horizontal (X direction) x n vertical (Y direction) points having the pixel value captured by each pixel. In this case, in the thinned-out image to be stored, the pixel values of rows not scanned in the X direction are missing (for example, filled with initial values of 0). Alternatively, in a format in which identification information of a scanned row (for example, a row number) is associated with a series of pixel values arranged in the X direction in the row, data on rows not scanned is not included. may be stored in

The degree of thinning in the thinning scanning (how many rows to scan in the X direction) may be determined by the user through trial and error, or may be determined by the information processing device 19 . For example, the information processing device 19 may acquire in advance a surface image obtained by normal scanning, and determine the degree of thinning based on the acquired surface image. Specifically, the pixel values are deleted (or the pixel values are set to an initial value (eg, 0)) while leaving the rows in the Y direction of a predetermined period (for example, every eight rows) in the surface image acquired in advance. ) Generate a simulated thinned image that simulates the thinning measurement, apply the interpolation processing described later to the simulated thinned image to obtain a restored image in which missing pixels are restored, and compare this with the original surface image. The degree of similarity may be evaluated using the aforementioned PSNR or SSIM as an index, and the degree of thinning that satisfies a predetermined criterion may be adopted. Alternatively, a spatial frequency spectrum may be obtained by two-dimensional Fourier transform or the like for a previously acquired surface image, and the degree of thinning may be determined based on the main frequency components in this spatial frequency spectrum. Such determination of the degree of thinning may be performed in the preparation stage before successive thinning scans.

(interpolation processing)
Observation data obtained by thinning-out scanning as described above has some pixels missing when forming a surface image with pixels of horizontal m points×vertical n points in the observation range. The information processing device 19 restores the surface image by interpolating the pixel values of the missing pixels by performing interpolation processing. The information processing device 19 may implement interpolation processing using an arbitrary algorithm, but it is preferable to perform interpolation using, for example, a DCT (discrete cosine transform) dictionary, cubic spline interpolation, or the like.

In this embodiment, the information processing device 19 applies interpolation processing to the observation data obtained by performing the thinning-out scanning for the entire observation range as described above, and obtains m points in the X direction and n points in the Y direction for the observation range. A surface image composed of point pixels is collectively restored and output.

FIG. 6 is a flow chart showing a procedure for obtaining a surface image by thinning scanning with the atomic force microscope 1 of the first embodiment. When performing observation by thinning scanning, first, a scanning pattern for thinning scanning is selected (step S01). Then, scanning is performed using the selected scanning pattern, and observation data including missing points is acquired for the entire observation range and stored in the storage unit 192 (step S02). Subsequently, interpolation processing is applied to the acquired observation data to restore a surface image in which the missing portions are interpolated (step S03), and the processing ends.

Note that steps up to step S02 (acquisition of observation data) and step S03 may be performed at completely different timings. That is, acquisition of thinned scanning observation data is continuously and repeatedly performed, and a plurality of continuous observation data at short time intervals are accumulated in the storage unit 192, and then interpolation processing is performed on the accumulated observation data. should be applied. By doing so, it is possible to observe continuous surface images at short time intervals.

FIG. 7 shows observation data acquired by the atomic force microscope 1 according to the first embodiment and a surface image restored from the observation data. That is, FIG. 7A shows an example of a thinned image obtained by thinning the scanning in the X direction to 1/8 (that is, scanning only one row out of eight rows in normal scanning). showing. FIG. 7(b) shows a surface image restored by applying interpolation processing using a DCT dictionary to the thinned image of FIG. 7(a). Although the image quality of the reconstructed surface image is degraded compared to the surface image obtained by normal scanning (e.g., FIG. 13), the surface image is sufficiently recognizable for the surface structure. Therefore, it becomes possible to acquire the image in a scanning time shortened by a factor of about 1/8.

[Second embodiment]
In the above-described first embodiment, interpolation processing is applied to observation data obtained by performing thinning-out scanning for the entire observation range as described above, and pixels of m points in the X direction and n points in the Y direction are applied to the observation range. The surface image composed of is collectively restored. While performing continuous observation using the method of the first embodiment, when attempting to perform real-time observation that updates the surface image displayed on the monitor 20 in real time, the scanning of the entire observation range is completed and interpolation processing is performed. is performed, the surface image displayed for the first time is updated. Therefore, the displayed surface image is not updated when scanning has been completed halfway through the observation range. Further, in the interpolation processing in the first embodiment, the amount of processing performed at one time is relatively large, and the processing may take a long time. For this reason, the time required for the interpolation processing may be rate-limiting in updating the displayed surface image.

The scanning probe microscope according to the second embodiment addresses the problem of the first embodiment in real-time observation. The scanning probe microscope of this embodiment has the same basic configuration as the scanning probe microscope of the first embodiment. In this embodiment, in order to perform real-time observation, scanning of the observation range and interpolation processing using observation data obtained by scanning are performed in parallel. At this time, the information processing device 19 performs interpolation processing in parallel with the scanning of the probe each time one line of observation data in the X direction is added by scanning the probe, and also performs surface image processing obtained by the interpolation processing. is displayed on the monitor 20.

In the present embodiment, in the interpolation processing performed in parallel with the scanning in the X direction, the information processing apparatus, as schematically shown in FIG. The surface image displayed on the monitor 20 is updated each time the interpolation process is completed.

FIG. 9 is a flow chart showing a procedure for obtaining a surface image by thinning scanning with the atomic force microscope 1 of the second embodiment. When performing observation by thinning scanning, first, a scanning pattern for thinning scanning is selected (step S11). Then, scanning is performed with the selected scanning pattern, and one row of observation data is acquired for the observation range and stored in the storage unit 192 (step S12). Rows that are not scanned according to the scanning pattern selected in step S11 are missing (missing measurements). Then, using the observation data for one line acquired in step S11, interpolation processing is performed to restore the surface image by interpolating the missing portions (step S13). Note that in the present embodiment, the interpolation processing in step S13 is performed based on all acquired observation data. Subsequently, if there is an unrestored portion (that is, a line to be scanned further) (step S14; Yes), the process returns to step S12. On the other hand, if there is no unrestored portion (that is, a line to be scanned further) (step S14; No), it means that the surface image of the entire observation range has been obtained, and the process ends.

FIG. 10 shows observation data acquired by the atomic force microscope 1 according to the second embodiment and a surface image restored from the observation data. 10(a-1) to (a-4) show observation data obtained by thinning the scanning in the X direction to 1/8 (that is, scanning only 1 row out of 8 rows in normal scanning). 10(b-1) to (b-4) show examples of interpolation processing by cubic spline interpolation for the observation data of FIGS. 10(a-1) to (a-4), respectively. The surface image obtained by applying and reconstructing is shown.

FIG. 10(a-1) shows observation data obtained by the first two scans in the X direction (scanning at positions in the Y direction corresponding to the 1st and 9th rows) in the observation range. 10(b-1) shows a surface image restored from the observation data of FIG. 10(a-1). When observation data is obtained by the second scanning in the X direction (that is, the scanning of the ninth line), interpolation processing is performed by the information processing device 19, and the surface image of FIG. 10(b-1) is displayed on the monitor 20. be done. The time required to restore the surface image of FIG. 10(b-1) by interpolation processing was 55 milliseconds. When scanning in the X direction is performed for the third and subsequent times, processing is performed on all acquired observation data. FIGS. 10(a-2) and 10(a-3) respectively exemplify the observation data obtained in the first five scans and the first nine scans in the X direction in the observation range, and FIG. 10(b -2) and FIG. 10(b-3) show surface images restored from the observation data of FIGS. 10(a-2) and 10(a-3), respectively. As observation data to be processed by the interpolation process and defects to be restored increase, the time required to restore the surface image by the interpolation process also increases. FIG. 10(a-4) shows observation data obtained up to the last scanning in the X direction in the observation range, and FIG. 10(b-4) is restored from the observation data of FIG. 10(a-4). A surface image is shown. When observation data is obtained by the last scanning in the X direction, interpolation processing is performed by the information processing device 19, and the surface image of FIG. 10(b-4) is displayed on the monitor 20. FIG. The time required to restore the surface image of FIG. 10(b-4) by interpolation processing was 1200 milliseconds. When Psnr was calculated to evaluate the image quality of FIG. 10(b-4), it was about 28.744.

As described above, according to the second embodiment, each time scanning in the X direction is performed, the displayed surface image can be updated up to the scanned portion as needed, even when scanning has been completed to the middle of the observation range. Real-time performance can be improved. In addition, in the interpolation processing that is performed each time observation data is added, the interpolation processing is performed based on the observation data that has been acquired up to that point. surface image can be reconstructed with the same degree of accuracy as

In the second embodiment, it is preferred that the interpolation process performed after one directional scan is completed before the next X-direction scan is completed. By doing so, it is possible to prevent the interpolation processing from becoming rate-limiting for the image acquisition speed in real-time observation. However, the closer to the end of the scanning of the observation range, the more observation data to be interpolated, and the longer the processing takes.

[Third Embodiment]
In the above-described second embodiment, the problems of the first embodiment in real-time observation are dealt with. Each time an object was added, an interpolation process was performed in parallel with the scanning of the probe, and the surface image obtained by the interpolation process was displayed on the monitor 20 . At that time, in interpolation processing, every time observation data was added, interpolation processing was performed based on all acquired observation data. In such interpolation processing, the closer to the end of scanning the observation range, the more observation data to be interpolated, and the more time it takes to process it. The same amount of processing is performed as in the case of collectively restoring the entire range in the first embodiment. Therefore, the time required for the interpolation processing (particularly in the second half of scanning the observation range) may be the rate-limiting factor in updating the displayed surface image.

The scanning probe microscope according to the second embodiment addresses the problems of the first and second embodiments. The scanning probe microscope of this embodiment has the same basic configuration as the scanning probe microscope of the first embodiment. In this embodiment, in order to perform real-time observation, scanning of the observation range and interpolation processing using observation data obtained by scanning are performed in parallel. At this time, as in the second embodiment, the information processing device 19 performs interpolation processing in parallel with the scanning of the probe each time one row of observation data in the X direction is added by scanning the probe, A surface image obtained by interpolation processing is displayed on the monitor 20 .

In the present embodiment, in the interpolation processing performed in parallel with scanning in the X direction, the information processing apparatus, as schematically shown in FIG. Among the data, the latest additional data newly added (that is, the observation data obtained by the latest scanning in the X direction), and the immediately preceding additional data added before the newly added observation data (that is, Based on the observed data obtained in the previous X-direction scan), the missing pixels between the immediately preceding additional data and the latest additional data are interpolated. Then, the surface image displayed on the monitor 20 is updated in such a manner that image fragments from the immediately preceding additional data to the latest additional data obtained as a result of the interpolation processing are combined with the previously obtained surface image.

The procedure for obtaining a surface image by thinning scanning with the atomic force microscope 1 of the third embodiment is basically the same as the order of obtaining the surface image in the second embodiment, and is performed according to the flowchart shown in FIG. . The third embodiment differs from the second embodiment in that the interpolation processing in step S13 is performed for missing pixels between the immediately preceding added data and the latest added data.

FIG. 12 shows observation data acquired by the atomic force microscope 1 according to the third embodiment and a surface image restored from the observation data. 12(a-1) to (a-4) show observation data obtained by thinning the scanning in the X direction to 1/8 (that is, scanning only 1 row out of 8 rows in normal scanning). 12 (b-1) to (b-4) show an example of applying interpolation processing by cubic spline interpolation to each of (a-1) to (a-4) observation data. surface image reconstructed by

FIG. 12(a-1) shows observation data obtained by the first two scans in the X direction (scanning at positions in the Y direction corresponding to the 1st and 9th rows) in the observation range. 12(b-1) shows a surface image restored from the observation data of FIG. 12(a-1). When observation data is obtained by the second scanning in the X direction (that is, the scanning of the ninth line), interpolation processing is performed by the information processing device 19, and the surface image of FIG. 12(b-1) is displayed on the monitor 20. be done. The time required to restore the surface image of FIG. 12(b-1) by interpolation processing was 55 milliseconds. When scanning in the X direction is performed for the third and subsequent times, interpolation processing is performed using newly acquired observation data and immediately preceding observation data. FIGS. 12(a-2) and 12(a-3) exemplify observation data to be interpolated after the fifth and ninth scans in the observation range, respectively. 12(a-2) and 12(a-3), respectively. 4 shows an updated surface image obtained by combining with . Since the amount of observation data to be interpolated and the defects to be reconstructed do not change even in the fifth and ninth interpolation processes, the time required to reconstruct the surface image by interpolation process is 55 milliseconds. Met. FIG. 12(a-4) shows observation data obtained in the last scanning in the X direction in the observation range, and FIG. 12(b-4) shows the surface restored from the observation data of FIG. FIG. 5 shows an updated surface image obtained by combining the image fragments with the previously acquired surface image. When observation data is obtained by the last scanning in the X direction, interpolation processing is performed by the information processing device 19, and the surface image of FIG. 12(b-4) is displayed on the monitor 20. FIG. The time required to restore the surface image of FIG. 12(b-4) by interpolation processing was also 55 milliseconds. When Psnr was calculated to evaluate the image quality of FIG. 10(b-4), it was about 27.073.

As described above, according to the third embodiment, each time scanning in the X direction is performed, even when scanning has been completed halfway through the observation range, the displayed surface image can be updated up to the scanned portion as needed. Real-time performance can be improved.

Also in the third embodiment, it is preferable that the interpolation processing performed after scanning in one direction is completed before the next scanning in the X direction is completed. By doing so, it is possible to prevent the interpolation processing from becoming rate-limiting for the image acquisition speed in real-time observation. In the third embodiment, unlike the second embodiment, the interpolation processing performed each time observation data is added is always based on the immediately preceding added data and the latest added data, so the processing time required for one interpolation processing is It is almost constant near the end of the scanning of the observation range. Therefore, according to the third embodiment, it is possible to more easily prevent the interpolation processing from becoming rate-limiting for the image acquisition speed in real-time observation (without using an information processing apparatus with high processing capability).

According to each of the embodiments of the present invention described above, it is possible to shorten the acquisition time of the surface image in the scanning probe microscope. Also, the influence of thermal drift in the scanning probe microscope can be suppressed.

[Modification of Embodiment]
Although each embodiment of the present invention has been described above, the present invention is not limited to these examples. For example, in the above embodiments, drive control in an atomic force microscope was described as an example, but the present invention is applicable to scanning probe microscopes other than atomic force microscopes (e.g., scanning tunneling microscopes (STM), scanning magnetic force microscopes). (MFM), scanning capacitance microscope (SCaM), scanning near-field optical microscope (SNOM), scanning thermal microscope (SThM), etc.).

In addition, additions, deletions, and design changes made by those skilled in the art to the above-described embodiments, and combinations of features of the embodiments as appropriate, do not include the gist of the present invention. to the extent possible are included within the scope of the present invention.

Reference Signs List 1 atomic force microscope 10 microscope housing 11 cantilever tip 12 cantilever 13 probe 14 scanner 15 stage 16 piezoelectric body for excitation 17 optical sensor unit 18 controller 19 information processing device 20 monitor

Claims (12)

The probe is scanned along the observation range on the surface of the observation target, and based on the interaction between the probe and the surface at each position during scanning, m points in the X direction and n points in the Y direction for the observation range. A scanning probe microscope for obtaining a surface image composed of pixels,
By thinning out part of positions corresponding to pixels of m points in the X direction and n points in the Y direction in the observation range and scanning, all of m points in the X direction and n points in the Y direction in the observation range are scanned. A scanning probe microscope that scans the observation range in a short time compared to scanning positions corresponding to pixels. Information processing means for performing interpolation processing to restore missing pixels based on observation data in which some of the pixels of m points in the X direction and n points in the Y direction are missing in the observation range. 2. A scanning probe microscope according to claim 1. 3. The method according to claim 2, wherein the information processing means collectively outputs a surface image composed of pixels of m points in the X direction and n points in the Y direction for the observation range by the interpolation processing. Scanning probe microscope as described. The information processing means performs the interpolation processing in parallel with the scanning of the probe each time observation data is added by scanning the probe, and causes the display device to display the surface image obtained by the interpolation processing. 3. The scanning probe microscope according to claim 2, characterized by: In the interpolation processing performed in parallel with the scanning of the probe, the information processing means performs the interpolation processing based on all acquired observation data each time observation data is added by the scanning of the probe. 5. The scanning probe microscope according to claim 4, characterized by: In the interpolating process performed in parallel with the scanning of the probe, the information processing means calculates the latest additional data newly added among the acquired observation data each time the observation data is added by the scanning of the probe. , and the immediately preceding additional data added immediately before the newly added observation data, performing the interpolation processing for missing pixels between the immediately preceding additional data and the latest additional data. 5. The scanning probe microscope according to claim 4, wherein: An information processing device that performs interpolation processing to restore missing pixels based on observation data obtained by a scanning probe microscope in which some pixels are missing among m points in the X direction and n points in the Y direction. 8. The information processing apparatus according to claim 7, wherein a surface image composed of pixels of m points in the X direction and n points in the Y direction is collectively output by the interpolation processing. Each time observation data is added by scanning the probe by the scanning probe microscope, the interpolation processing is performed in parallel with the scanning of the probe, and the surface image obtained by the interpolation processing is displayed on the display means. 9. The information processing apparatus according to claim 8, characterized by: In the interpolation processing performed in parallel with scanning with the probe, each time observation data is added by scanning with the probe, the interpolation processing is performed based on all acquired observation data. 10. The information processing device according to Item 9. In the interpolation processing performed in parallel with scanning with the probe, each time observation data is added by scanning with the probe, the latest addition data newly added among acquired observation data, and the newly added data 10. The interpolation processing is performed for missing pixels between the immediately preceding added data and the latest added data, based on the immediately preceding added data added immediately before the observation data obtained. The information processing device according to . A program that causes a computer to function as the information processing apparatus according to any one of claims 7 to 11.

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