JPH04319607A - Interatomic force microscope - Google Patents

Abstract

PURPOSE:To make it possible to align easily a thinly-narrowed light beam with the fore end of a cantilever and to improve the reliability and operability of an apparatus. CONSTITUTION:An interatomic force microscope is equipped with a cantilever 11 the base end part of which is fixed to a fixed end 15 and to the fore end part of which a probe 12 is fitted, a three-dimensional actuator 21 which makes a sample 30 approach the probe 12 and moves the sample 30 three-dimensionally and a displacement detecting mechanism of an optical lever type wherein a spot beam is applied to the fore end part of the cantilever 11, by a laser light projector 13, a reflected light terefrom is detected by PSD 14 and a bend of the cantilever 11 is measured therefrom. The projector 13 is so provided as to be movable forward and backward in the direction of projection of light, while the cantilever 11 is so provided that it can be displaced in the horizontal direction to the surface of the sample 30, and a screen 40 is provided on the opposite side to the projector 13 in respect to the cantilever 11. A spot image of the light and a shadow of the fore end of the cantilever 11 are formed on this screen 40.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic force microscope equipped with an optical lever type displacement detector, and more particularly to an atomic force microscope with improved means for aligning a light beam and a cantilever.

0002

2. Description of the Related Art In recent years, an atomic force microscope has been developed as a device capable of observing the surface shape of an insulating material with atomic level resolution. This atomic force microscope consists of an actuator that moves the sample three-dimensionally and a displacement detection mechanism that detects the vertical movement of the cantilever.

[0003] At the tip of the cantilever, a small tip with a sharp tip is attached to the sample side. When the cantilever and the sample surface are brought close to each other, an exchange repulsive force is created between the atoms at the tip of the tip and the atoms on the sample surface. acts, and the cantilever whose rigidity is lower than this force bends. When the actuator moves the sample in the in-plane direction, the bending of the cantilever changes depending on the repulsive force distribution on the sample surface.

[0004] Therefore, by reading the bending of the cantilever with a displacement detection mechanism, the shape of the sample surface can be determined with high resolution. In practice, the two-dimensional microscopic shape of the sample surface is often investigated by moving the sample side up and down using an actuator so that the exchange repulsive force acting between the cantilever and the sample surface always remains constant.

As a displacement detection mechanism, a scanning tunneling microscope is sometimes used, but from the viewpoint of design, operation, and replacement of samples and cantilevers, etc., an optical lever method using a laser diode and a position sensitive detector (PSD) is used. is advantageous. This optical lever method directs the laser beam to the tip of the cantilever (
However, it is used to detect changes in the position of the reflected light on the detector.

However, this type of atomic force microscope has the following problems. In other words, when using an optical lever-based displacement detection mechanism, in order to ensure the reliability and stability of the device, it is necessary to apply a narrowly focused light beam only to the tip of the cantilever, that is, to the back of the probe. . Even with an optical microscope, it is extremely difficult to align a beam that has been focused to a size smaller than the cantilever tip (~several tens of micrometers) so that it hits only the cantilever tip, making it difficult to operate when replacing the cantilever. In order to improve this, a simpler method is required.

[0007]

[Problem to be Solved by the Invention] When using a conventional optical lever type displacement detection mechanism, in order to ensure the reliability of the device, it is necessary to reliably align the narrowly focused beam with the tip of the cantilever. There is a need. An optical microscope is required for this positioning, which has been a factor in deteriorating the operability when replacing the cantilever.

The present invention was made in consideration of these circumstances, and its purpose is to easily align a narrowly focused light beam to the tip of a cantilever without using an optical microscope or the like. The object of the present invention is to provide an atomic force microscope that can improve the reliability and operability of the device.

[0009]

[Means for Solving the Problems] The gist of the present invention is to enlarge and project a spot image of a light beam irradiated onto a cantilever onto a screen, thereby allowing the light beam to be The purpose is to align with the cantilever.

That is, the present invention comprises a cantilever made of a spring-like thin film and whose base end is fixed to a fixed end, a probe attached to the tip of the cantilever, and a sample that is brought close to the probe and detected. A three-dimensional actuator that moves the sample three-dimensionally and a floodlight that focuses light onto a minute spot illuminate the tip of the cantilever with light, and the reflected light is detected by a light receiving element to measure the bending of the cantilever. In an atomic force microscope equipped with an optical lever-type displacement detection mechanism, a projector is installed so that it can move forward and backward with respect to the direction of light projection, and a cantilever is installed so that it can be displaced horizontally with respect to the sample surface, Another feature is that a screen is provided on the opposite side of the cantilever from the projector to project the spot image of the light and the shadow of the cantilever. Further, the present invention is preferably characterized in that the screen is desirably removable from the main body of the apparatus.

[0011]

[Operation] According to the present invention, by comparing the spot image of the light beam enlarged and projected onto the screen and the shadow of the cantilever, it is possible to visually confirm the positional relationship between them without the need for an optical microscope or the like. can. When the two are perfectly aligned, the cantilever and the light beam can be easily aligned by taking advantage of the fact that the enlarged spot of the light beam is not projected on the screen. .

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be explained below with reference to illustrated embodiments.

FIG. 1 is a perspective view showing a schematic configuration of an atomic force microscope according to an embodiment of the present invention. In the figure, 10 is a unit housing, and inside this housing 10 there are a cantilever 11, a probe 12, a laser beam projector 13, a position sensitive detector (PSD) 14, a fixed end 15, a receiving lens 16 (not shown), etc. It is accommodated. Reference numeral 20 denotes a case, and inside this case 20 there are a three-dimensional actuator 21 on which the sample 30 is placed, and an inch worm motor 22.
A magnet 23 and the like are housed therein.

The main structure of the above device will be explained in detail with reference to FIG. 2. The cantilever 11 is a cantilever beam with low rigidity, and a small probe 12 with a sharp tip is attached to the tip of the cantilever 11 on the sample 30 side. As shown in FIG. 3, the shape of the cantilever 11 is V-shaped in order to reduce rigidity, and the dimensions of each part are as shown in the figure.

The base end of the cantilever 11 is fixed to a fixed end 15, and the fixed end 15 is movable in the horizontal direction relative to the surface of the sample 30. Specifically, the fixed end 15 is horizontally movable by a sliding bearing or a rolling bearing, and is fixed to the housing 10 at a predetermined position by screwing or the like.

A laser beam projector 13 that irradiates the tip of the cantilever 11 with a laser beam is installed obliquely above the cantilever 11 so that it can move forward and backward in the direction in which the laser beam is projected. This projector 13 includes a laser diode 13a
and a focusing lens (or lens group) 13b, and the imaging position of the spot beam can be varied by moving the light projection direction. The reflected light from the cantilever 11 due to laser beam irradiation passes through the receiving lens 16 to the PSD 14.
Detected in Here, the portion surrounded by the dashed line in the figure, that is, the projector 13, the cantilever 11, and the PSD 14 constitute an optical lever type detection mechanism.

In front of the cantilever 11 with respect to the direction in which the laser beam is projected by the light projector 13, that is, the cantilever 11
A screen 40 is removably provided diagonally below. The screen 40 may be made of any material having a surface that diffusely reflects laser light, such as paper, and is not limited in any way to its material. On this screen 40, a spot image of the laser beam irradiated onto the cantilever 11 and a shadow of the cantilever 11 are projected. Then, the spot image of the laser beam and the shadow of the cantilever 11 can be visually confirmed.

The three-dimensional actuator 21 is, for example, formed by forming a common electrode on the inner circumferential surface of a cylindrical piezoelectric element and forming divided electrodes on the outer circumferential surface. (horizontal direction) and Z direction (vertical direction). Therefore, the sample 30 placed on this actuator 21 is movable in three-dimensional directions.

The unit housing 10 also includes a case 2.
It contacts three places: the magnet 23 (two places) provided at 0 and the shaft moved forward and backward by the motor 22, and is fixed by so-called three-point support. The distance between the housing 10 and the case 20 can be minutely changed by driving the motor 22, that is, the distance between the sample 30 and the probe 12 can be minutely varied. Next, a method of adjusting the alignment between the light beam and the cantilever 11 using the above device will be described with reference to FIG. 4.

A visible light laser was used as the laser diode 13a of the projector 13, the working distance of the projector 13 was 10 mm, and the minimum spot diameter was 30 μmφ. On the other hand, the dimensions of the cantilever 11 are as shown in FIG.

First, the projector 13 is fixed approximately 10 mm away from the tip of the cantilever 11. At this time, if the light beam and the cantilever 11 are not aligned, only the enlarged and projected spot light 41 is projected onto the screen 40, as shown in FIG. 4(a). This state is visually confirmed using an opening (not shown) provided in the housing 10.

Next, the fixed end 15 of the cantilever 11 is moved horizontally so that the shadow 42 of the tip of the cantilever 11 falls within the enlarged spot 41, as shown in FIG. 4(b). Next, move the floodlight 13 to display the image shown in FIG.
), the shadow 42 at the tip of the cantilever 11 is adjusted to its maximum size. As a result, the projector 13 is positioned at a working distance of 10 mm.

After the projector 13 is fixed in this state, the cantilever 11 is moved slightly in the horizontal direction toward the projector 13 again, so that the center of the tip of the cantilever 11 is irradiated with a light beam. At this time, the enlarged spot 41 of the light beam is not projected on the screen 40, as shown in FIG. 4(d).

By fixing the fixed end 15 in this state, the light beam and the cantilever 11 are accurately aligned, and the narrowed light beam is applied only to the tip of the cantilever 11, that is, the back surface of the probe 12. will be
Regarding the measurement of the sample surface, the light beam is not irradiated onto the sample side. Note that if the screen 40 becomes an obstacle during measurement of the sample surface, the screen 40 may be removed.

As described above, in this embodiment, the cantilever 1
A screen 40 is provided diagonally below the light beam 1, and a spot image 41 of the light beam and the cantilever 11 are formed on this screen 40.
By photographing the shadow 42 of the tip of the cantilever 11, the position of the light beam can be easily aligned with the cantilever 11. That is, the projector 13 and fixed end 15 are appropriately moved so that the shadow 42 of the cantilever 11 becomes maximum compared to the spot image 41, and both 13 and 15 are fixed at a position where the spot image 41 disappears from the screen 40. You can align the two using .

Therefore, according to this embodiment, the cantilever 1
It is no longer necessary to use an optical microscope to align the light beam with the light beam, and operability can be improved. This effect is especially great when replacing the cantilever 11. In addition, as for the device configuration, a screen 40 is added to the conventional device.
There is also an advantage that can be achieved with an extremely simple configuration that only requires the provision of.

Note that the present invention is not limited to the embodiments described above. In FIG. 2, the projector 13 and the fixed end 15 are shown to be moved via rolling bearings, but of course they may be moved using a sliding bearing method. Furthermore, these movements may be performed using a moving device or manually. Further, if the optical lever type displacement detection mechanism and the sample scanning mechanism are configured to be separated, there is no need to provide a screen in the apparatus, and the screen may be used only when adjusting the displacement detection mechanism. In addition, various modifications can be made without departing from the gist of the present invention.

[0028]

Effects of the Invention As described in detail above, according to the present invention, by enlarging and projecting the spot image of the light beam irradiating the cantilever onto a screen, the light beam can be narrowed down without using an optical microscope or the like. can be easily aligned with the tip of the cantilever, making it possible to realize an atomic force microscope with improved reliability and operability.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a schematic configuration of an atomic force microscope according to an embodiment of the present invention;

FIG. 2 is a sectional view showing the main part configuration of the above embodiment;

[Figure 3]
A plan view showing the specific configuration of the cantilever used in the above example,

FIG. 4 is a schematic diagram showing the relationship between a light beam spot and a cantilever shadow.

[Explanation of symbols]

10...Unit housing, 11...Cantilever, 12... Probe, 13...Laser beam projector, 14...position sensitive detector (PSD), 15...fixed end, 16...Receiving lens, 20...Case, 21...Three-dimensional actuator, 22...inch worm motor, 23...Magnet, 30...sample, 40...Screen.

Claims (1)

[Claims] Claim 1: A cantilever made of a spring-like thin film, the base end of which is fixed to a fixed end, a probe attached to the tip of the cantilever, and a sample brought close to the probe. An optical lever that irradiates the tip of the cantilever with light using a three-dimensional actuator that moves dimensionally and a projector that focuses light on a minute spot, and detects the reflected light with a light receiving element to measure the bending of the cantilever. In an atomic force microscope equipped with a displacement detection mechanism of the above-mentioned method, the projector is installed so as to be movable in the direction of light projection, and the cantilever is installed so as to be movable in the horizontal direction with respect to the surface of the sample. . An atomic force microscope characterized in that a screen for projecting a spot image of the light and a shadow of the cantilever is provided on a side opposite to the projector with respect to the cantilever.