JP3428403B2 - Friction force probe microscope and method for identifying atomic species and materials using friction force probe microscope - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls a magnetic substance provided in a cantilever by a magnetic field control mechanism in order to measure a frictional force acting between a sample and a probe, and a direction perpendicular to a longitudinal direction of the cantilever. The present invention relates to a friction force probe microscope for keeping the flexure of a cantilever constant by feedback-controlling the flexure displacement amount of the.

[0002]

2. Description of the Related Art In recent years, an atomic force microscope (AFM) has been developed as an apparatus capable of observing a solid surface with atomic resolution. Hereinafter, referring to FIG. 1, AFM and A
An observation method using FM will be described. In the AFM, the length 10 having the probe 10 is used to detect a minute force (Van de Waals force, magnetic force, Coulomb force, atomic force, etc.).
A cantilever 5 of about 0 μm is used. When the sample 4 is brought closer to the probe 10, bending occurs in the direction in which the cantilever 5 is attracted to the sample 4 by the atomic force acting between the probe 10 and the sample 4. Further, when the sample 4 is brought closer to the probe 10, the cantilever 5 suddenly largely bends and jumps, and the probe 10 and the sample 4 come into contact with each other.

After that, when the sample 4 is further contacted, the cantilever 5 bends in the opposite direction to the above. In order to keep this amount of bending constant, the piezoelectric body driving device 9 is passed through the control signal generating circuit 8.
Scanning is performed along the surface of the sample 4 while controlling the piezoelectric body 3 in the Z direction by. The scanning is performed by the piezoelectric body driving device 9 and the piezoelectric bodies 1 and 2 in the X and Y directions. The control amount in the feedback corresponds to the unevenness of the surface of the sample 4, and if this control amount is imaged by the computer 11 or the like, the AF
An M image can be obtained. The amount of bending of the cantilever 5 is measured by a two-divided photodiode 7 which is a displacement measuring unit. For the displacement measuring unit, a method such as an optical lever, laser interference, tunnel current or the like is usually used. The resolution of the AFM depends on the tip curvature radius and the tip angle of the probe 10, and the smaller these are, the higher the resolution is.

[0004]

During the scanning of the sample or the probe, friction due to atomic force, adsorption force, elastic force, viscous force, Coulomb force, van der Waals force, etc., acting between the probe and the sample The force acts to bend the cantilever in a direction perpendicular to the longitudinal direction, and the cantilever sharply bends immediately above the sample having a large friction coefficient. Therefore, there is a problem that it is impossible to control the frictional force between the probe and the sample. Further, it is impossible to measure the absolute value of the shear stress, and there is a problem that the contact area between the probe and the sample changes depending on the type of material.

[0005]

In order to solve this problem, a friction force probe microscope of the present invention is a cantilever with a probe having a magnetic body, and a cylindrical position control mechanism for controlling the position of a sample. And a small displacement measurement mechanism for measuring the amount of deflection of the cantilever due to van der Waals force, magnetic force, Coulomb force, atomic force, etc., and a magnetic field control mechanism for arbitrarily controlling the lateral deflection of the cantilever. The force acting in the direction perpendicular to the longitudinal direction is controlled by feedback control of the deflection of the cantilever in the direction perpendicular to the longitudinal direction with an external magnetic field generated from the magnetic field control mechanism during scanning of the probe or sample. It can be detected by a magnetic field.

Further, the cantilever is vibrated in a direction perpendicular to the longitudinal direction by an AC external magnetic field generated from a magnetic field control mechanism, the degree of vibration damping of the cantilever is measured, and the hardness of the sample in the lateral direction is imaged. Then, the second information can be obtained.

Further, by directly feedback controlling the voltage or current required for generating the magnetic field to the magnetic field control mechanism, the magnitude of the vertical vibration of the cantilever is always constant in the direction perpendicular to the longitudinal direction. By doing so, the shear stress can be measured.

Further, while mechanically controlling the cantilever at the resonance frequency, the magnetic field feedback control is performed so that the bending in the direction perpendicular to the longitudinal direction generated in the cantilever during scanning the sample surface is zero. A clear image with high N can be obtained.

In the present invention, the magnetic field control mechanism is a coil, and when the magnetic field control mechanism is installed in the cylindrical position control mechanism, it is desirable not to contact the sample, the sample stage and the magnetic field generation mechanism.

Further, if a device for generating a static magnetic field in the direction perpendicular to the longitudinal direction of the cantilever is installed, the static magnetic field aligns the magnetic poles of the ferromagnetic substance and soft magnetic substance of the cantilever in the lateral direction of the cantilever. Therefore, it is possible to easily supply force to the cantilever by the magnetic field of the magnetic field control mechanism.

Further, by applying a static magnetic field from the lateral direction while depositing the magnetic material on the cantilever, a cantilever with a magnetic material can be produced in which the magnetic poles are oriented in the lateral direction. In this case, the cantilever is a piezoelectric body, a piezoelectric thin film,
The device can be made smaller if configured with either a capacitance sensor or a piezoresistor.

If the probe provided at the tip of the cantilever is a conductive probe capable of controlling the electric potential and capable of passing a current, a contact current depending on the contact area can be passed.

Since the present invention is an AFM / STM (scanning tunneling microscope) having an active cantilever capable of arbitrarily controlling the amount of bending in the direction perpendicular to the longitudinal direction of the cantilever by using a magnetic field, it is possible to use one atom to measure It is possible to measure up to frictional force and shear stress on the metric order and the micrometer order, and it is possible to identify atomic species and materials by using such a lot of information.

[0014]

DETAILED DESCRIPTION OF THE INVENTION FIG.
It is a schematic diagram showing one embodiment of a force probe microscope. The sample 4 is a piezoelectric body 1 in three directions of X, Y, and Z,
The coil with an iron core, which is the magnetic field control mechanism 12, is installed on the cylindrical fine movement mechanism formed by 2 and 3 within the range where it does not come into contact with the sample 4 or the cylindrical fine movement mechanism. The scanning of the sample 4 in the horizontal plane is performed by applying the voltage generated by the piezoelectric body driving device 9 to the piezoelectric bodies 1 and 2 in the X and Y directions. The semiconductor laser 6 having an output of 5 mW and the two-divided photodiode 7 are for irradiating the cantilever 5 with laser light and detecting the reflected light, and constitute an optical lever. The displacement (deflection) of the cantilever 5 is measured by this optical lever, and the force converted between the spring constants of the cantilever 5 is detected to detect the force acting between the sample 4 and the probe 10. it can.

The cantilever 5 is made of titanium and is conductive and has a triangular shape having a thickness of 600 nm, a length of 200 μm and a width of 500 μm, and a magnetic thin film having a thickness of 1 μm on the back end.
It is vapor-deposited by supplying a static magnetic field with a side of 10 μm by a sputtering method. In addition, this thin film cantilever 5
The opposite side of the probe 10 is fixed by a fixed end 14. Further, a magnetic substance cantilever can be manufactured using a bulk material such as iron or samarium cobalt without using a magnetic thin film. In this case, it is necessary to align the magnetic poles in a direction perpendicular to the longitudinal direction with a static magnetic field before measurement. Alternatively, it may be performed while applying a static magnetic field during measurement (scanning).

The sample 4 is fixed to the conductive sample table 15.
The contact current flowing through the probe 10 and the sample 4 due to the voltage application from the voltage generator 16 is detected by the current measuring device 17. Incidentally, reference numeral 13 in FIG. 2 is a lens for focusing the laser light emitted from the semiconductor laser 6 on the cantilever 5.

The distance between the sample 4 and the cantilever 5 is reduced by applying a control voltage to the piezoelectric body 3 in the Z direction using the piezoelectric body drive device 9. After the contact between the probe and the sample, the sample is scanned and imaging is performed. At that time, when a large frictional force between the probe of the cantilever and the sample acts, the cantilever is largely bent in the direction perpendicular to the longitudinal direction ( Figure 3
(See (a) and (b)). Therefore, by applying an electric current to the magnetic field control mechanism 12, a magnetic field is generated to restore the twist of the probe to the original value, and the twist of the cantilever is returned to zero (see FIGS. 3C and 3D). By monitoring the current required to generate the magnetic field at that time, it is possible to image the frictional force using the magnetic force.

Next, the fine movement mechanism is moved in the Y-axis direction to acquire the following data. Furthermore, if there is a material with a large friction coefficient in the sample, it is necessary to reduce the deflection of the cantilever to zero.
Apply the duckback to restore the original bending. By repeating this operation, the frictional force between the sample and the probe at each point can be observed. At the same time, a voltage difference of 1 V can be maintained between the probe 10 and the sample 4, and a contact current image at each point of the sample 4 can be mapped. This makes it possible to confirm the conductivity due to the difference in the material, and to obtain the difference in the contact area in the case of the same material. Further, since the sample can be rotated in an arc, characteristics of the sample 4 in all directions can be observed. Further, the material can be identified by utilizing the fact that the degree of attenuation of the vibration of the cantilever varies depending on the material by scanning while the cantilever vibrates in the direction perpendicular to the longitudinal direction by the generated AC external magnetic field. Further, the shear stress of the material can be determined from the magnetic field by feeding back the vibration damping to the magnetic field control mechanism (see FIG. 4).

FIG. 5 shows a samarium-cobalt permanent magnet, which is a static magnetic field generator 20, installed in a direction perpendicular to the longitudinal direction of the cantilever. By aligning the magnetic poles of the Ni (nickel) magnetic thin film 18 on the cantilever with this static magnetic field, the cantilever can be oscillated by 30 nm with a 10 Gauss magnetic field generated from the magnetic field control mechanism.

[0020]

According to the friction force probe microscope of the present invention, since it is an AFM / STM having an active cantilever capable of arbitrarily controlling the lateral deflection of the cantilever by using a magnetic field, one atom or It is possible to measure frictional force and shear stress on the order of nanometers to micrometers, and it is possible to identify atomic species and materials by using this much information.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a conventional atomic force microscope.

FIG. 2 is a schematic diagram illustrating a friction force probe microscope according to an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a friction force probe microscope according to an embodiment of the present invention.

FIG. 4 is a diagram showing a state in which a cantilever is vibrated in a direction perpendicular to a longitudinal direction using the friction force probe microscope according to the embodiment of the present invention.

FIG. 5 is a view showing a state where magnetic poles are aligned in a direction perpendicular to the longitudinal direction of a magnetic body provided at the tip of a cantilever used in a friction force probe microscope according to an embodiment of the present invention.

[Explanation of symbols]

1 X direction piezoelectric 2 Piezoelectric body in Y direction 3 Z-direction piezoelectric body 4 samples 5 cantilevers 6 Semiconductor laser 7 Two-segment photodiode 8 Control signal generation circuit 9 Piezoelectric drive device 10 probe 11 computer 12 Magnetic field control mechanism 13 lenses 14 fixed end 15 Conductive sample table 16 Voltage generator 17 Current measuring device 18 Magnetic thin film 19 Direction of magnetic pole 20 Static magnetic field generator

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01B 21/30 G01N 13/16 G01N 19/02

Claims (12)

(57) [Claims] 1. A cantilever with a probe having a magnetic material, a cylindrical position control mechanism for controlling the position of a sample, a minute displacement measuring mechanism for measuring the amount of deflection of the cantilever, and a deflection of the cantilever. Or a magnetic field control mechanism for arbitrarily controlling the distance between the sample and the probe, wherein the magnetic body provided at the tip of the cantilever has magnetic poles aligned in a direction perpendicular to the longitudinal direction. Characteristic friction force probe microscope. 2. A cantilever with a probe having a magnetic body, a cylindrical position control mechanism for controlling the position of a sample, a minute displacement measuring mechanism for measuring the amount of deflection of the cantilever, and a deflection of the cantilever. Or a magnetic field control mechanism for arbitrarily controlling the distance between the sample and the probe, and when the magnetic substance is provided at the tip of the cantilever, the magnetic pole is applied while applying a static magnetic field in the direction perpendicular to the longitudinal direction. A friction force probe microscope characterized by having 3. The friction according to claim 1, wherein the probe provided at the tip of the cantilever is a conductive probe capable of controlling an electric potential and allowing a current to flow. -Force probe microscope. 4. The friction force probe microscope according to claim 1, wherein the magnetic field control mechanism includes a coil. 5. The magnetic field control mechanism, when installed in the cylindrical position control mechanism, is not in direct contact with any of the sample, the sample stage, and the cylindrical position control mechanism. The friction force probe microscope according to any one of 1, 2, 3, and 4. 6. The cantilever is configured to include one selected from a piezoelectric body, a piezoelectric thin film, a capacitance sensor, and a piezoresistor. The friction force probe microscope described in 1. 7. The static magnetic field generator is installed in the vertical direction of the cantilever, 1, 2, 3,
The friction force probe microscope according to any one of 4, 5, and 6. 8. A cantilever with a probe having a magnetic body, a cylindrical position control mechanism for controlling the position of a sample, a minute displacement measuring mechanism for measuring the amount of deflection of the cantilever, and a deflection of the cantilever. Or, using a friction force probe microscope having a magnetic field control mechanism for arbitrarily controlling the distance between the sample and the probe,
While scanning the probe or the sample, the force acting in the vertical direction is detected by the magnetic field by feedback-controlling the bending in the direction perpendicular to the longitudinal direction of the cantilever with the external magnetic field generated from the magnetic field control mechanism. A method for identifying atomic species and materials using a friction force probe microscope. 9. A cantilever with a probe having a magnetic body, a cylindrical position control mechanism for controlling the position of a sample, a minute displacement measuring mechanism for measuring the amount of bending of the cantilever, and a longitudinal direction of the cantilever. Using a friction force probe microscope having a magnetic field control mechanism for controlling deflection perpendicular to the direction, the cantilever is vibrated in a direction perpendicular to the longitudinal direction by an alternating external magnetic field generated from the magnetic field control mechanism. And measuring the degree of attenuation of the cantilever, a method for identifying atomic species and materials using a friction force probe microscope. 10. A cantilever with a probe having a magnetic body, a cylindrical position control mechanism for controlling the position of a sample, a minute displacement measuring mechanism for measuring the amount of deflection of the cantilever, and a deflection of the cantilever. Or, using a friction force probe microscope having a magnetic field control mechanism for arbitrarily controlling the distance between the sample and the probe,
While scanning the probe or the sample, the cantilever is oscillated in the vertical direction by using the magnetic field control mechanism, and the voltage or current required to generate the magnetic field is directly feedback-controlled to the magnetic field control mechanism to laterally move. Identification of atomic species and materials using a friction force probe microscope characterized by measuring shear stress by making the magnitude of vibration in the direction perpendicular to the longitudinal direction of the cantilever always constant Method. 11. A cantilever with a probe having a magnetic body, a cylindrical position control mechanism for controlling the position of a sample, a minute displacement measuring mechanism for measuring the amount of deflection of the cantilever, and a deflection of the cantilever. While using a friction force probe microscope having a magnetic field control mechanism for arbitrarily controlling, while scanning the sample surface while mechanically controlling the cantilever at a resonance frequency,
A method for identifying atomic species and materials using a friction force probe microscope, characterized in that magnetic field feedback control is performed so that the bending of the cantilever in the direction perpendicular to the longitudinal direction is zero. 12. A cantilever with a probe having a magnetic body, a cylindrical position control mechanism for controlling the position of a sample, a minute displacement measuring mechanism for measuring the amount of deflection of the cantilever, and a deflection of the cantilever. While using a friction force probe microscope having a magnetic field control mechanism for arbitrarily controlling, while scanning the sample surface while mechanically controlling the cantilever at a resonance frequency,
Magnetic field feedback control is performed so that the bending of the cantilever in the direction perpendicular to the longitudinal direction becomes zero, and the minute displacement measuring mechanism for measuring the amount of bending of the cantilever is rotated in an arc to form a crystal direction / crystal axis. A method for identifying atomic species and materials using a friction force probe microscope, which is characterized by measuring the shear stress for each of the.