JP3836639B2 - Scanning probe microscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a scanning probe microscope such as an atomic force microscope or a friction force microscope that detects a displacement of a cantilever by irradiating the cantilever with a laser beam.
[0002]
[Prior art]
An atomic force microscope (AFM) is a device that measures the atomic force acting between a probe fixed to the tip of a cantilever and a sample by detecting the deflection of the cantilever, and detects the deflection of the cantilever using an optical lever method. In the atomic force microscope, laser light is irradiated on the back surface of the cantilever. Then, the laser beam reflected from the back surface of the cantilever is detected by a photodetector, and the displacement of the cantilever is detected.
[0003]
Since such a cantilever is usually a very small one having a length of about 0.2 mm and a width of about 0.03 mm, it is impossible to align the laser beam with the tip of the cantilever with the naked eye. Therefore, the conventional atomic force microscope is provided with an optical microscope for magnifying and observing the cantilever and an optical microscope with a CCD camera, and an operator observes the cantilever using these to irradiate the laser beam of the cantilever. Aligned with the tip.
[0004]
[Problems to be solved by the invention]
However, the cost of an apparatus equipped with such an optical microscope and an optical microscope with a CCD camera was high.
[0005]
The present invention has been made in view of these points, and an object thereof is to provide a low-cost scanning probe microscope capable of accurately aligning laser light with a cantilever.
[0006]
[Means for Solving the Problems]
The scanning probe microscope of the present invention that achieves this purpose irradiates the back surface of the cantilever with laser light from a laser light source, detects the laser light reflected on the back surface of the cantilever with a photodetector, and measures the displacement of the cantilever. in scanning probe microscope so as to, in the laser beam, and means for adjusting the irradiation position to the cantilever, which is disposed between the front Symbol cantilever and the light detector, the light detecting a laser beam from the cantilever A spot shape observing means comprising a half mirror or beam splitter that reflects toward the container, a screen that displays the spot shape of the laser light transmitted through the half mirror or beam splitter , and the spot shape confirming means, provided separately from the above, To check if the laser beam is hitting the cantilever Characterized in that a laser beam irradiation position checking means consisting of a convex lens positioned above the said cantilever.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0008]
FIG. 1 is a schematic view of an atomic force microscope shown as an example of a scanning probe microscope of the present invention.
[0009]
First, the configuration of FIG. 1 will be described.
[0010]
In FIG. 1, reference numeral 1 denotes a sample chamber, and a sample stage 3 that can move in the x, y, and z axis directions is disposed at the bottom of the sample chamber 2. A sample 4 is set on the sample stage 3.
[0011]
Reference numeral 5 denotes a cantilever facing the sample 4, and the cantilever 5 is supported by a cantilever holding member 6 fixed to the bottom of the sample chamber 2. A probe 7 is fixed to the end of the cantilever 5 on the sample side.
[0012]
Reference numeral 8 denotes an attachment hole formed in the ceiling of the sample chamber 1, and the attachment hole 8 is located immediately above the cantilever 5. A convex lens 9 that is a magnifying glass and a blue filter (glass) 10 are fixed in the mounting hole 8 by being vertically fitted, and the blue filter 10 is positioned on the sample chamber side. Note that both surfaces of the blue filter 10 are mirror surfaces.
[0013]
A half mirror 11 is disposed between the blue filter 10 and the cantilever 5, and the half mirror 11 is fixed to a laser light source 12. The half mirror 11 reflects the laser light from the laser light source 12 toward the cantilever 5. The laser light source 12 is attached to the irradiation position adjusting means 13, and the irradiation position adjusting means 13 is attached to the sample chamber 1.
[0014]
The irradiation position adjusting means 13 is configured to be rotatable about the x axis and is configured to be rotatable about a y ′ axis that is orthogonal to the x axis and parallel to the y axis. With such a configuration, if the irradiation position adjusting means 13 is rotated around the x axis, the laser light source 12 and the half mirror 11 are integrally rotated around the x axis along with the rotation. If the adjusting means 13 is rotated around the y ′ axis, the laser light source 12 and the half mirror 11 are integrally rotated around the y ′ axis in accordance with the rotation.
[0015]
Reference numeral 14 denotes a photodiode which is a photodetector attached to the side wall of the sample chamber. A half mirror 15 is disposed between the photodiode 14 and the cantilever 5, and the half mirror 15 reflects laser light reflected on the back surface of the cantilever 5 toward the photodiode 14.
[0016]
Reference numeral 16 denotes a mounting hole opened in the sample chamber 1, and a red screen 17 is fitted into the mounting hole 16 and fixed thereto. The red screen 17 projects the shape of the laser light that has passed through the half mirror 15. The red screen 17 is obtained by polishing and processing the portion of the red filter glass that is exposed to the laser light, that is, the surface of the sample chamber. Made. The surface of the red screen 17 opposite to the polished glass surface is a mirror surface.
[0017]
Reference numeral 18 denotes control means, and the control means 18 is connected to the sample stage 3 and the photodiode 14.
[0018]
The apparatus configuration of FIG. 1 has been described above. Next, a case where the laser beam is aligned with the tip of the cantilever in such an apparatus will be described.
[0019]
First, the operator turns on the laser light source 12. Then, red laser light (wavelength of about 670 nm) is generated by the laser light source 12, and the laser light from the laser light source 12 strikes the half mirror 11. Then, half of the laser light hitting the half mirror 11 is reflected by the half mirror 11 and travels toward the cantilever 5.
[0020]
In the apparatus of FIG. 1, when the laser beam irradiates the tip of the cantilever 5, the laser light source 12 and the half mirror 11 are adjusted in advance so that the laser beam is focused on the back surface of the cantilever 5. Look through the convex lens 9 and check whether the laser light is hitting the tip of the cantilever 5. The magnification of the convex lens 9 is about 10 times. If such a convex lens 9 is used, the position of the cantilever 5 can be specified. A convex lens exceeding this magnification cannot be used practically because the peripheral portion has a large distortion.
[0021]
By the way, although the apparatus of FIG. 1 is equipped with the blue filter 10, if the blue filter 10 is not arrange | positioned, it will be dazzled by the laser beam diffusely reflected on the cantilever 5, and an operator will not see the cantilever 5. As a result, the operator cannot confirm the laser light irradiation position on the cantilever.
[0022]
However, in the apparatus of FIG. 1, since the blue filter 10 that attenuates the laser light to about several percent is disposed, the operator does not see the laser light irregularly reflected on the cantilever, and the intensity of the most intense light on the cantilever. Only the high laser spot center point can be seen. For this reason, the operator can confirm the laser beam irradiation position on a cantilever correctly.
[0023]
When the laser beam does not hit the tip of the cantilever 5, the operator operates the irradiation position adjusting means 13 so that the laser beam hits the tip of the cantilever 5.
[0024]
In this way, when the laser beam hits the tip of the cantilever 5, the laser beam reflected by the back surface of the cantilever 5 hits the half mirror 15. Then, half of the laser light hitting the half mirror 15 is reflected by the half mirror 15 and enters the photodiode 14, and the other half passes through the half mirror 15 and hits the red screen 17.
[0025]
As described above, the surface of the red screen 17 to which the laser light hits is polished glass, so that the operator is not dazzled when looking from the opposite side of the polished glass, and the size of the laser light on the red screen is large. Is about 2 to 3 mm, the operator can clearly observe the shape of the laser spot projected on the red screen 17 with the naked eye. Then, the operator finely adjusts the irradiation position adjusting means 13 while looking at the red screen 17 so that the spot shape is a circle or an ellipse and the intensity of the laser beam is the strongest.
[0026]
As described above, the case where the laser beam is aligned with the cantilever in the apparatus of FIG. 1 has been described, but the laser beam is accurately positioned at the tip of the cantilever in the apparatus of FIG. Can be combined. Further, since the apparatus of FIG. 1 does not have to include an optical microscope or an optical microscope with a CCD camera, the cost of the apparatus is considerably lower than that of the conventional apparatus.
[0027]
When obtaining an atomic force image of the sample 4 in the apparatus of FIG. 1, the control means 18 makes the atomic force acting between the probe 7 and the sample 4 constant based on the signal from the photodiode 14. In this way, the sample stage 3 is scanned in the xy direction while feedback-controlling the z motion of the sample stage 3, and an atomic force image of the sample is obtained from the feedback control information.
[0028]
Although the apparatus of FIG. 1 has been described above, the present invention is not limited to this. For example, a beam splitter may be used instead of the half mirrors 11 and 15 in the apparatus of FIG.
[0029]
The present invention can be applied not only to an atomic force microscope but also to a scanning probe microscope such as a friction force microscope or a magnetic force microscope provided with a cantilever.
[Brief description of the drawings]
FIG. 1 is a schematic view of an atomic force microscope shown as an example of a scanning probe microscope of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sample chamber chamber, 2 ... Sample chamber, 3 ... Sample stage, 4 ... Sample, 5 ... Cantilever, 6 ... Cantilever holding member, 7 ... Probe, 8, 16 ... Mounting hole, 9 ... Convex lens, 10 ... Blue filter 11, 15 ... half mirror, 12 ... laser light source, 13 ... irradiation position adjusting means, 14 ... photodiode, 17 ... red screen, 18 ... control means

Claims (3)

In a scanning probe microscope that irradiates the back of the cantilever with laser light from a laser light source, detects the laser light reflected on the back of the cantilever with a photodetector, and measures the displacement of the cantilever.
Means for adjusting the irradiation position of the laser beam to the cantilever ;
Disposed between the front Symbol cantilever said photodetector, a half mirror or beam splitter is reflected toward the photodetector laser beam from the cantilever,
Spot shape observation means comprising a screen for projecting the spot shape of the laser light transmitted through the half mirror or beam splitter ;
A laser beam irradiation position confirmation unit comprising a convex lens located above the cantilever for confirming whether or not the laser beam hits the cantilever is provided separately from the spot shape confirmation unit. Scanning probe microscope.   The scanning probe microscope according to claim 1, further comprising a half mirror or a beam splitter that reflects laser light from the laser light source toward the cantilever between the laser light source and the cantilever.   The scanning probe microscope according to claim 1 or 2, wherein the laser light is a red laser, a blue filter is disposed between the convex lens and the cantilever, and the screen is a red screen.

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