JPH04174312A - Interatomic force microscope apparatus - Google Patents

Abstract

PURPOSE:To make the apparatus compact in size by casting light to a cantilever from a projecting optical fiber, receiving the reflecting light by a detecting optical fiber, and detecting the displacement or vibration of the cantilever. CONSTITUTION:A light is cast to a cantilever 7 via a projecting optical fiber 62 from a light source 61. The light reflected from the cantilever 7 is, through a detecting optical fiber 64, detected by a photocell 63. At this time, the intensity of light returning to the detecting optical fiber 64 is changed by the gap between an end face of the fiber and the cantilever 7, and by utilizing this fact, the displacement or vibration of the cantilever 7 is detected. In this manner, the whole size of the interatomic force microscope can be made small, and moreover, the temperature drift can be restricted to be small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an atomic force microscope device, and particularly to an atomic force microscope device using a cantilever and an optical fiber displacement meter.

(Prior Art) In general, an atomic force microscope (AFM) is capable of displacing or vibrating the tip of the cantilever due to the atomic force generated between the sample and the tip of the cantilever when the cantilever is brought close to the sample on the order of angstroms. Detect and
This is used to measure the surface shape of a sample. In this case, the cantilever is formed from a thin metal foil, has a tip for detecting atomic force disposed at its tip, and has its terminal end fixed to the main body of the atomic force microscope apparatus.

By the way, in this type of atomic force microscope device, the method for detecting the displacement or vibration of the cantilever is to irradiate the cantilever with a light beam and receive the reflected light, in order to detect the displacement or vibration of the cantilever. A so-called optical lever method is often used. Furthermore, as another method, an optical heterodyne method is used in which a light beam is irradiated onto a cantilever and a phase change of the light applied from the cantilever is detected as a result.

However, in the former atomic force microscope device using the optical lever method, the light projecting part, the cantilever reflecting surface,
It is necessary to provide a large space on the detector surface. For example, if the distance between the light emitter and the cantilever surface is g, then g
is from several 10 dragons to several 100+sm. This value is obtained in order to magnify the minute displacement (0.1 to 100 m+*) of the cantilever. In other words, the work distance is large. If this work distance is large, when the atomic force microscope device is used in the atmosphere, air fluctuations in this area become noise and are detected by the detector, reducing cantilever displacement detection sensitivity.

In addition, the dimension of the entire device increases, and the temperature deformation value of the device decreases, which is a disadvantage.

On the other hand, the latter atomic force microscope device using the optical heterodyne method uses complicated and expensive optical components such as a black cell and a doped prism. Further, in this method, since the modulation frequency is as high as 80 MHz, a high-frequency detector is also required, which is also expensive. Furthermore, the size of the device is relatively large, ranging from several tens of millimeters to several hundred millimeters (however, compared to the former method, the work distance can be reduced to several liters). Therefore, the problem with this type of device is that it is very expensive and the dimension of the entire device is large, resulting in a low temperature drift value.

(Problem to be solved by the invention) As described above, in the conventional atomic force microscope device,
There were problems in that the entire device was large, the cantilever displacement detection sensitivity was low, the temperature drift value was decreased, and the price was high.

An object of the present invention is to provide an extremely low-cost atomic force microscope device that can reduce the size of the entire device, increase cantilever displacement detection sensitivity, and increase temperature drift value. .

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a cantilever that detects the atomic force generated between the sample and the sample provided at a predetermined distance. , an atomic force microscope device comprising a photodetector that is disposed opposite to the side of the cantilever opposite to the sample and detects displacement or vibration of the cantilever, the photodetector irradiates the cantilever with light. Optical fiber displacement is equipped with a light-emitting optical fiber and a light-receiving destination fiber that receives the light reflected by the cantilever, and detects the displacement or vibration of the cantilever by utilizing the amount of reflected light that changes depending on the position of the cantilever. I try to use a meter.

(Function) Therefore, in the atomic force microscope device of the present invention, light is irradiated from the light emitting optical fiber to the cantilever (-), the light reflected by the cantilever is received by the light receiving optical fiber, and the position of the cantilever is determined. By fully detecting the displacement or vibration of the cantilever using changes in the amount of reflected light, the overall size of the device can be made smaller than before.This also makes it possible to reduce the temperature drift value, and at the same time The influence on floor vibrations can also be reduced. In addition, the work distance is smaller than before, and the influence of air fluctuations is proportionally reduced, making it possible to increase cantilever displacement detection sensitivity.Furthermore, By using optical fibers, the effect of heat generation on the device can be reduced compared to the conventional method, and therefore temperature drift can also be equivalently reduced.

(Example) In the present invention, the displacement or vibration of a cantilever is detected by
This is done by emitting light from a light-emitting optical fiber onto a cantilever, and receiving the light reflected by the cantilever with a light-receiving optical fiber, making use of the fact that the amount of reflected light changes depending on the position of the cantilever.

In other words, the sample is irradiated with light from the light emitting optical fiber,
The light receiving optical fiber receives the reflected light from the cantilever. Here, the irradiated light spreads, and therefore the amount of reflected light, that is, the light intensity, changes depending on the position of the sample. Therefore, the position of the sample relative to the optical fiber is determined from this light intensity.

Hereinafter, an embodiment of the present invention based on the above concept will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of the configuration of an atomic force microscope apparatus according to the present invention. In FIG. 1, base 1 has x
A yz coarse movement mechanism 2 and an xyz fine movement mechanism 3 are provided.

In addition, the xyz fine movement mechanism 31; is equipped with a sample 4, and the Z drive mechanism 5 is equipped with an optical fiber displacement meter 6 of an atomic force microscope device.
has been established.

Further, the base 1 is provided with a cantilever 7 of an atomic force microscope device. This cantilever 7 is provided with a chip 8 for detecting atomic force on one surface (the side surface of the sample 4), and is placed between the sample 4 and the optical fiber displacement meter 6 to detect the atomic force generated between the sample 4 and the sample 4. It is designed to detect force.

In addition, in this atomic force microscope device, the xyz fine movement mechanism 3 is used so that the minute force (atomic force) of 10-9 to 10-''N acting between the cantilever 7 and the sample 4 is constant. is fed back in two directions and scanned in x and y to draw a topography.At this time, the xyz coarse movement mechanism 2 selects the measurement position of the sample 4 and the position where the atomic force acts (in two directions) on the sample. I am trying to perform an operation to move to 4.

FIG. 2 is a perspective view showing a detailed configuration example of the cantilever 7 and its vicinity. In FIG. 2, the cantilever 7 uses a metal plate (for example, tungsten, platinum, gold, nickel, etc.) having a thickness t of several micrometers to several tens of microliters as a base 7a. Further, on one surface of the base 7a, an atomic force detection chip 8 with a sharp tip (tip radius of about 0.1 μm) is provided.

Furthermore, an optical fiber displacement meter 6 is provided on the other surface of the base 7a so that the gap between it and the cantilever 7 is d. In this example, if the dimensions are taken as shown in Figure 2,
Length of cantilever 7 p1 Width of cantilever 7 W number 10
The gap d is several microns to several tens of microns, and the diameter of the optical fiber displacement meter 6 is several tens of microns, which corresponds to W.
---I'm taking a few steps.

FIGS. 3(a) and 3(b) are schematic diagrams showing detailed configuration examples of the optical fiber displacement meter 6. FIG. In FIG. 3, the optical fiber displacement meter 6 includes one light projecting optical fiber 62 that irradiates light from a light source 61 to the cantilever 7, and is arranged around this light projecting optical fiber 62, and the light is reflected by the cantilever 7. A plurality of light receiving optical fibers 64 (six in this example) receive light from the light emitting optical fiber 62 and emit the light to the photocell 63. Receive,
At this time, the gap δ between the fiber one end face and the cantilever 7
Therefore, the displacement or vibration of the cantilever 7 is detected by utilizing the change in the intensity of light returning to the light-receiving optical fiber 64.

Next, the operation of the atomic force microscope apparatus of this embodiment configured as described above will be explained.

In FIG. 1, the cantilever 7 is brought close to the sample 4 on the order of angstroms, and the cantilever 7 is caused by an atomic force generated between the sample 4 and the tip of the cantilever 7.
The displacement or vibration of the tip is detected by the optical fiber displacement meter 6, and the surface shape of the sample 4 is measured.

That is, light is irradiated from the light source 61 to the cantilever 7 through the light emitting optical fiber 62, and the light reflected by the cantilever 7 is received by the photocell 63 through the light receiving optical fiber 64. Due to the gap δ, the light receiving optical fiber 64
The displacement or vibration of the cantilever 7 is detected by utilizing changes in the intensity of the light returned to the cantilever.

In this case, the light intensity of the light-receiving optical fiber 64 becomes as shown in FIG. 4(a) based on the principle shown in FIG. 3(b). That is, in FIG. 4(a), the light intensity of the light-receiving optical fiber 64 is always below the light-receiving saturation value of the detector. At this time, the gap δ between the optical fiber and the cantilever 7 is δ−δB (Fig. 3(b)
It is maximum at the B place f). This position varies slightly depending on the characteristics of the optical fiber, but is approximately 100μ
It is about m. In normal usage (FIG. 3(a)), for example, it is used at an operating point of δ-δ□, and the displacement resolution at this time is about sub-μm. In the case of this embodiment, the gain of the detector is further increased and used as shown in FIG. 4(b). That is, at the point δ-δ8, the detector is saturated. However, on the O side from the B position, there is a part where the light intensity changes linearly with respect to the gap δ, as in the S region in Figure 4(b), and the operating point is at the G point in this region. (δ - δ6), the displacement of the cantilever 7 can be measured (for example, δ6 = 70 μs) By doing this, the resolution of the optical fiber displacement meter 6 can be increased from sub-μ to 1/100 μ to lnm1. can be improved, thus adding cantilever 7 to 10
A minute force of -9 to 10-2'N can be detected. This is because, if the spring constant of the cantilever 7 is k and the atomic force is F1 and the cantilever displacement is δ, F- is δ, k-1 ~ O, OIN/m, F-10-' ~ 10-''N
Then, δ-F/-(10-'~10-'')/(1~0.
01) -10-' to 10-20 [m. The previous 1/100 μ■ ~ 1n■ is 10-8 ~ 1
Since it is 0-'m, it corresponds to 10-7 to 10-'m in the above equation, and at this time, the atomic force of F-10-9 to 10-'N can be measured.

As described above, in this embodiment, the tip 8 for detecting atomic force is provided on one surface, and the cantilever 7 detects the atomic force generated between the sample 4 and the cantilever 7.
In an atomic force microscope device, the atomic force microscope device includes a photodetector that is disposed facing the other surface of the cantilever 7 and detects displacement or vibration of the cantilever 7. It is equipped with an optical fiber 62 for projecting light from a book, and a plurality of optical fibers 64 for receiving light that receive light reflected by the cantilever 7. An optical fiber displacement meter 6 is used to detect the displacement or vibration of the sensor.

Therefore, the following various effects can be obtained.

Cm) Light is irradiated from the light emitting optical fiber 62 to the cantilever 7, the light reflected by the cantilever 7 is received by the light receiving optical fiber 64, and the amount of reflected light changes depending on the position of the cantilever 7. 7 displacement or vibration, the size of the entire atomic force microscope device has been reduced from the conventional several tens of meters to several hundred mm.
This makes it possible to reduce the size to a fraction of the size. Thereby, the temperature drift value can also be reduced to a fraction of that.

At the same time, the influence on floor vibrations can also be reduced.

(b) Work distance is from several 10 mm to several 1
Compared to 00 dragon, the intestine is less than 100 μ and 1 to 10 times smaller.
The effect of air fluctuation becomes proportional to this value. In other words, the gap d is several lOμm.
In terms of degree, the conventional optical lever method has a number of IClem to a number of 1
Compared to the work distance of 00, it is possible to further reduce the dimension by 3 to 4 orders of magnitude. Thereby, the displacement detection sensitivity of the cantilever 7 can be increased.

(C) Since optical fibers are used, the effect of heat generation on the device can be reduced compared to the conventional method described above, and thereby the temperature drift value can also be equivalently reduced.

(d) Since there is only one optical fiber for light projection, the light spot is small and it is possible to easily accommodate smaller-sized cantilevers.

It should be noted that the present invention is not limited to the above embodiments, but can also be implemented as follows.

(a) As the optical fiber, the one having the configuration shown in FIG. 3(a) was used, but it is not limited to this.
Light projecting fibers as shown in a) to (C) may also be used.

In this case, since there are multiple light emitting fibers,
A larger amount of light can be obtained, and displacement detection sensitivity can be further increased.

(b) As a cantilever, one having a structure in which a tip 8 was provided on a base 7a as shown in FIG. 2 was used.
The present invention is not limited to this, and for example, as shown in FIG. 6, a device without a chip may be used.

(C) As a cantilever, the thickness t is from several μW to several 10
A μ layer glass plate may be used as the base 7a. When a glass plate is used as the cantilever, it is preferable to coat the surface with gold or the like so that light is well reflected.

(d) The number of fibers constituting the light-receiving optical fiber may be plural or singular.

[Effects of the Invention] As explained above, according to the present invention, as a photodetector,
It is equipped with an optical fiber for projecting light that irradiates light onto the cantilever, and an optical fiber for receiving light that receives light reflected by the cantilever, and uses the change in the amount of reflected light depending on the position of the cantilever to control the displacement or vibration of the cantilever. Since it uses an optical fiber displacement meter to detect Equipment can be provided.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing one embodiment of an atomic force microscope device according to the present invention, Fig. 2 is a schematic diagram showing a detailed configuration example near the cantilever in the same embodiment, and Fig. 3 is an optical fiber displacement in the same embodiment. FIG. 4 is a characteristic diagram for explaining the operation of the same embodiment, and FIGS. 5 and 6 show other embodiments of the atomic force microscope device according to the present invention. FIG. 1...Base, 2...xyz coarse movement mechanism, 3...x
yz fine movement mechanism, 4... sample, 5... Z drive mechanism, 6
...Optical fiber displacement meter, 7...Cantilever, 8
...Atomic force detection chip, 61...Light source, 62.
... Optical fiber for light projection, 63 ... Photocell, 64
...Optical fiber for light reception. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 (a) (b) Figure 3 (a) (b) Figure 1g4 (c) Figure 5

Claims (1)

[Scope of Claims] A cantilever for detecting atomic force generated between a sample and a sample provided at a predetermined distance; Alternatively, in an atomic force microscope device comprising a photodetector that detects vibration, the photodetector is a light projecting optical fiber that irradiates the cantilever with light, and a light that receives light reflected by the cantilever. An atomic force microscope device comprising a light-receiving optical fiber and using an optical fiber displacement meter that detects displacement or vibration of the cantilever by utilizing the amount of reflected light changing depending on the position of the cantilever. .