JPH05187862A - Surface analyzing device - Google Patents

Abstract

PURPOSE:To analyze the surface of a sample by detecting the two-dimensional displacement of a lever caused by an interatomic force working on the lever. CONSTITUTION:When a lever 11 is set above a sample 10, an interatomic force works between the sample 10 and lever 11 and the lever 11 is two-dimensionally displaced. The two-dimensional displacement of the lever 11 is detected by means of, for example, an optical position detector 12c in a displacement detecting means 12 and the coefficient of friction of the lever 11 against the sample 10 is found by means of an analyzing means 13 from the detected two-dimensional displacement.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an atomic force microscope (AF).
M) is used for the surface analysis device.

[0002]

2. Description of the Related Art As shown in FIG. 7, an atomic force microscope has a lever 2 arranged several nm above a sample 1, and an atomic force (van der Waals force or the like) acting between the sample 1 and the lever 2. ), The displacement amount of the lever 2 which is displaced is detected to measure the atomic arrangement and shape of the sample surface.

FIG. 8 is a schematic configuration diagram of the atomic force microscope using the optical lever method. A lever 2 is arranged above the sample 1, and a mirror 3 is provided on the lever 2. The lever 2 is made of tungsten wire. On the other hand, a He—Ne laser oscillator 4 is provided, the laser light output from the laser oscillator 4 is applied to the mirror 3, and the reflected laser light is received by the optical position detector 5. Then, the displacement of the lever 2, that is, the surface shape of the sample 1 is obtained from the output signal of the optical position detector 5.

Other atomic force microscopes include those using an optical interference method, those using a scanning tunneling microscope (STM), and an optical displacement meter. It should be noted that the lever 2 includes, for example, one using a leaf spring in addition to one formed of a tungsten wire, and the lever 2 is manufactured by micromachine leg processing.

On the other hand, in the atomic force microscope, the technique of separately measuring the attraction force and the friction force is described in "Tribologist".
Vol. 34, No. 1, (1989) P19-P22 for scanning tunneling microscopes and atomic force microscopes. This technology detects the vertical force and the horizontal force of the lever at different timings by changing the detection direction of the optical sensor by 90 °, and measures the attraction force and the friction force.

By the way, in the field of magnetic recording, it is required to analyze the surface at the atomic level, but it is difficult to analyze the surface only by measuring the surface shape of the sample with the atomic force microscope.

Further, in the atomic force microscope for measuring the attraction force and the friction force, since the attraction force and the friction force are detected at different timings, the positional relationship between the attraction force and the friction force is unclear. Surface analysis is difficult.

[0008]

As described above, it is difficult to analyze the surface of the sample. Therefore, it is an object of the present invention to provide a surface analysis apparatus capable of performing surface analysis of a sample by detecting a two-dimensional displacement amount of the lever due to an atomic force acting on the lever.

[0009]

The present invention relates to a sample,
At least the lever arranged at an interval where the atomic force acts between the sample, the displacement detecting means for detecting the two-dimensional displacement amount of the lever, and the two-dimensional displacement amount detected by the displacement detecting means. A surface analysis apparatus, which is provided with an analyzing means for obtaining a coefficient of friction of a lever with respect to a sample and which is intended to achieve the above object.

In this case, the displacement detection means includes at least one laser oscillator, at least one mirror that responds to the displacement of the lever, and at least one optical position that detects the position of the reflected laser light output from the laser oscillator from the mirror. And a detector.

[0011]

By providing such means, when the lever is arranged above the sample, an atomic force acts between the sample and the lever, and the lever is displaced in two dimensions. The two-dimensional displacement amount of the lever is detected by, for example, an optical position detector in the displacement detection means, and at least the friction coefficient of the lever with respect to the sample is obtained by the analysis means from the detected two-dimensional displacement amount.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the surface analysis apparatus. A two-dimensional lever 11 is arranged above the sample 10. This two-dimensional lever 11 is made by bending the tip of a tungsten quadrangular prism (1 side is 1 to 100 μm, length is 0.1 to several mm).
The tip of the tip is sharply processed by electrolytic etching so that the tip has a radius of several nm to several 100 nm.
The two-dimensional lever 11 is arranged such that its longitudinal direction is the same as the y direction, and scans in the x direction in this state. Further, the upper surface Sx of the two-dimensional lever 11 is arranged parallel to the surface in the x direction, and the one side surface Sz is arranged parallel to the surface in the z direction. Note that the sample 10 is, for example, several 100 n in the xyz direction by a cylindrical piezoelectric element (not shown).
It is possible to move minutely within the range of m to several 100 μm.

The displacement detecting means 12 is the two of the two-dimensional lever 11.
It has a function of detecting a dimensional displacement amount, and is composed of a laser diode 12a, a rotating mirror 12b, and an optical position detector (PSD) 12c. Of these, the rotary mirror 12b is a minute one having a size of 10 μm to several mm and is provided on the upper surface Sx of the two-dimensional lever 11.
And the reflecting surface is arranged in the same direction as the x direction.
The output laser light from the laser diode 12a is the rotating mirror 1
The optical position detector 12 is arranged so as to irradiate 2b.
c is arranged at a position for receiving the reflected laser light from the rotating mirror 12b. The light position detector 12c is a four-divided light position detector, and has an analog voltage Vi proportional to the coordinates (Px, Pz) of the spot of the received reflected laser light.
It has a function of outputting (i = x, z).

On the other hand, an analysis device 13 is provided. The analysis device 13 has a function of inputting the analog voltage Vi from the optical position detector 12c and obtaining the friction coefficient G of the two-dimensional lever 11 with respect to the sample 10 and the surface material Mi of the sample 10 from the analog voltage Vi. There is. The acting force resolving unit 14 has a function of obtaining the forces Fx and Fz acting on the two-dimensional lever 1 in the x direction and the z direction from the analog voltage Vi.

The friction coefficient calculator 15 receives the forces Fx and Fz, and the friction coefficient G and the phase information θ are calculated from these forces Fx and Fz.
Is calculated by the following equation: G = | Fx | / | Fz | (1) θ = tan ⁻¹ (| Fz | / | Fx |) (2)

The material analyzing unit 16 receives the friction coefficient G and the phase information θ, compares the friction coefficient G and the phase information θ with the friction coefficient GMi and the phase information θMi corresponding to the various materials Mi stored in advance, and matches them. It has a function of obtaining the surface material Mi of the sample 10 as two-dimensional information from the friction coefficient GMi and the phase information θMi. In this case, the surface material Mi is

[0018]

[Equation 1] Search for something that is related to. Next, the operation of the device configured as described above will be described.

The two-dimensional lever 11 is arranged at an interval of 10 nm or less with respect to the sample 10. At this interval, an atomic force, that is, an attractive force or repulsive force of 10 ⁻⁸ N or less acts between the two-dimensional lever 11 and the sample 10. And the two-dimensional lever 1
When 1 scans the upper side of the sample 10 in the x direction, the two-dimensional lever 11 exerts each force F in the x direction and the z direction on the two-dimensional lever 11, as shown in FIG.
x and Fz act.

These forces Fx and Fz bend the two-dimensional lever 11 in the θx and θz directions. At this time, the relationship between the flexure amounts δx and δz of the tip of the two-dimensional lever 11 and the respective forces Fx and Fz is Fi = (3E · Ii / L ³ ) Δi (4) where i = x, z, E is Young's modulus, Ii is the second moment of area in the i direction, and L is the length of the two-dimensional lever 11.

The rotation angle θi of the rotary mirror 12b at this time is θi = (3 / 2L) δi (5). However, when a force acts on the tip of the two-dimensional lever 11, the two-dimensional lever 11 bends and the rotating mirror 12
b rotates by the rotation angle θi.

In this state, the laser light output from the laser diode 12a is reflected by the rotating mirror 12b and reaches the optical position detector 12c. Spot position (Px, Pz) of the reflected laser light received by this optical position detector 12c
Is a position corresponding to the rotation angle θi of the rotating mirror 12b. The optical position detector 12c has an analog voltage V proportional to the spot position (Px, Pz) of the received reflected laser light.
Output i.

By the way, the rotation angle θi of the rotating mirror 12b is obtained from the analog voltage Vi. That is, Vi = κ · Pi (κ = proportional constant between position and voltage) (6) Pi = H (2θi) (7)

If the distance between the laser diode 12a and the rotating mirror 12b is H according to the above equations (4) to (7), then Vi = (L ² · H · κ / E · Ii) Fi (8) holds, and from this formula (8), the analog voltage Vi is the force Fi.
It can be seen that and are proportional.

Here, the detection resolution of each force Fx, Fz is obtained. For example, in the case of a tungsten wire having one side of the two-dimensional lever 11 of 10 μm and a length of 1 mm, from the above formula (8), δFi = (E · Ii / L ² ・ H · κ) δVi (9) is obtained. Therefore, δV is 1 mV and κ is 1 mV / μ
m, H is 50 mm, L is 1 mm, E (Young's modulus of tungsten) is 50 × 10 ¹⁰ N / m ² , Ii is r ⁴ Substituting / 12 (r is the length of one side of the two-dimensional lever 11 of 10 μm) into the equation (9),

[0026]

[Equation 2] Therefore, the detection resolution of each force Fx, Fz is 10 ⁻⁸ N.

On the other hand, when the two-dimensional lever 11 scans the sample 10 in the x direction, the optical position detector 12 at this time is scanned.
The analog voltage Vi output from c is the action force decomposition unit 14
Sent to.

This acting force decomposing unit 14 is operated by the analog voltage Vi.
The forces Fx and Fz acting on the two-dimensional lever 1 in the x direction and the z direction are calculated from the above and sent to the friction coefficient calculation unit 15. These forces Fx and Fz are obtained as two-dimensional information on the xy plane, and FIG. 3 shows the two-dimensional information of the force Fx.
It should be noted that the two-dimensional information of the force Fz can be similarly obtained. The friction coefficient calculator 15 receives the respective forces Fx and Fz, and calculates the above equation (1) from these forces Fx and Fz to obtain the friction coefficient G and the phase information θ.

The material analyzing unit 16 receives the friction coefficient G and the phase information θ, and compares the friction coefficient G and the phase information θ with the friction coefficient GMi and the phase information θMi corresponding to various materials Mi stored in advance. , The surface material Mi of the sample 10 is obtained as two-dimensional information from the matched friction coefficient GMi and phase information θMi.

Thus, according to the above-mentioned embodiment, the sample 1
Not only the two-dimensional shape of 0 but also the friction coefficient G and the phase information θ on the surface of the sample 10 can be obtained in real time, and the surface material Mi of the sample 10 can be obtained on the atomic level order. In addition, the resolution of analysis of the surface material Mi can be very high at several μm to 0.01 μm.
Further, the memory capacity can be reduced only by storing the friction coefficient GMi and the phase information θMi.

The present invention is not limited to the above-mentioned one embodiment, and may be modified within the scope of the invention. For example, as shown in FIG. 4, the displacement detecting means 30 irradiates the upper surface of the two-dimensional lever 11 with laser light Q1 and Q2 from two directions, and the respective reflected laser light is divided into two light position detectors 30 and 31. You may receive light. In this case, one optical position detector 30 detects the position Px of the reflected laser spot in the x direction, and the other optical position detector 31 detects the position Pz of the reflected laser spot in the z direction. Further, the optical position detectors 30 and 31 may be formed by combining two one-dimensional optical position detectors.

Further, although the rotating mirror 12b is provided in the above-mentioned embodiment, as shown in FIG. 5, a flat portion 33 having a small surface roughness is formed on the bent portion of the two-dimensional lever 32, and the flat portion 33 is formed. It may be used as a mirror.

Further, as shown in FIG. 6, mirrors 34 and 35 are provided in directions orthogonal to each other with respect to the two-dimensional lever 32, and these mirrors 34 and 35 are irradiated with laser beams to reflect the reflected laser beams. It may be detected by a position detector.
In this case, instead of the mirrors 34 and 35, flat parts may be formed on the two-dimensional lever 32 to be used as mirrors.

On the other hand, instead of the laser diode 12a, L
A combination of an ED and an optical lens or a gas laser such as a HeNe laser may be used, and the laser light may be guided by an optical fiber to irradiate the rotating mirror 12b or the like. A four-division photo detector may be used as the optical position detector.

[0035]

As described in detail above, according to the present invention, it is possible to provide a surface analysis apparatus capable of detecting the two-dimensional displacement amount of the lever due to the atomic force acting on the lever and analyzing the surface of the sample.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a surface analysis apparatus according to the present invention.

FIG. 2 is a schematic diagram showing each force acting on a two-dimensional lever in the same device.

FIG. 3 is a diagram showing two-dimensional information of a force in the x direction obtained by the device,

FIG. 4 is a configuration diagram showing a modified example of the device.

FIG. 5 is a configuration diagram showing a modified example of the device.

FIG. 6 is a configuration diagram showing a modified example of the device.

FIG. 7 is a diagram showing a positional relationship between a lever and a sample.

FIG. 8 is a schematic configuration diagram of an atomic force microscope.

[Explanation of symbols]

10 ... Sample, 11 ... Two-dimensional lever, 12 ... Displacement detecting means, 12a ... Laser diode, 12b ... Rotating mirror,
Reference numeral 12c ... Optical position detector, 13 ... Analysis device, 14 ... Acting force decomposition unit, 15 ... Friction coefficient calculation unit, 16 ... Material analysis unit.

Claims (2)

[Claims] 1. A lever arranged at an interval between the sample and an atomic force between the sample and the sample, a displacement detector for detecting a two-dimensional displacement amount of the lever, and a detector for detecting the displacement. And a means for determining at least the friction coefficient of the lever with respect to the sample from the two-dimensional displacement amount. 2. The displacement detection means includes at least one laser oscillator, at least one mirror that responds to displacement of a lever, and at least one position that detects the position of laser light reflected from the mirror and output from the laser oscillator. The surface analysis device according to claim 1, further comprising an optical position detector.