JPH11142105A - Friction force probe microscope and identifying method of atomic species and material by using friction force probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable measuring the frictional force and shearing stress and identifying atomic species and material, by constituting a scanning tunneling microscope having an active cantilever which can arbitrarily control deflection in the direction perpendicular to the longitudinal direction of the cantilever by using a magnetic field. SOLUTION: Distance between a specimen 4 and a cantilever 5 is reduced by applying a control voltage to a piezoelectric member 3 in the Z direction by using a piezoelectric member driving equipment 9. After contact of a probe and the specimen 4, the specimen is scanned and imaged. At this time, in the case that a large frictional force acts on the probe and the specimen 4, the lever 5 is deflected in the direction perpendicular to the longitudinal direction. Torsion of the lever 5 is returned to zero by making a current flow to a magnetic field controlling equipment 12. The frictional force using a magnetic force can be imaged by monitoring a current needed fro generating a magnetic field at that time. By vibration-scanning the lever 5 in the direction perpendicular to the longitudinal direction with a generated AC external magnetic field, material can be identified by using the degree of attenuation of the vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, an atomic force microscope (AFM) has been developed as a device capable of observing a solid surface with an atomic order resolution. Hereinafter, AFM and A will be described with reference to FIG.
An observation method using FM will be described. In the AFM, in order to detect a small force (Van der Waals force, magnetic force, Coulomb force, atomic force, etc.), a length 10 having a probe 10 is used.
A cantilever 5 of about 0 μm is used. When the sample 4 is brought closer to the probe 10, bending occurs in a direction in which the cantilever 5 is drawn toward the sample 4 by an 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 bends sharply greatly, jumps, and the probe 10 comes into contact with the sample 4.

Thereafter, when the sample 4 is further contacted, the cantilever 5 bends in a direction opposite to the previous direction. The piezoelectric driving device 9 is controlled through the control signal generating circuit 8 so as to keep the amount of bending constant.
Scans along the surface of the sample 4 while controlling the piezoelectric body 3 in the Z direction. 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, AF
An M image can be obtained. The amount of deflection of the cantilever 5 is measured by a two-division photodiode 7 which is a displacement measuring unit. For the displacement measurement unit, a method such as optical lever, laser interference, or tunnel current is usually used. The resolution of the AFM depends on the tip radius of curvature and the tip angle of the probe 10, and the smaller these are, the better the resolution is.

[0004]

During scanning of a sample or a probe, friction is caused by an atomic force, an adsorption force, an elastic force, a viscous force, a Coulomb force or a van der Waals force acting between the probe and the sample. The force acts, the cantilever flexes in the direction perpendicular to the longitudinal direction, and the cantilever flexes sharply immediately above the sample having a large friction coefficient. For this reason, there was a problem that it was impossible to control the frictional force between the probe and the sample. Further, it was impossible to measure the absolute value of the shear stress, and there was a problem that the contact area between the probe and the sample was changed depending on the type of the material.

[0005]

To solve this problem, a friction force probe microscope according to the present invention comprises a cantilever with a probe having a magnetic material and a cylindrical position control mechanism for controlling the position of a sample. And a minute 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. During scanning of the probe or the sample, the force acting in the direction perpendicular to the longitudinal direction is controlled by feedback control of the deflection in the direction perpendicular to the longitudinal direction of the cantilever with an external magnetic field generated from the magnetic field control mechanism. It can be detected by a magnetic field.

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

In addition, by directly feedback-controlling the voltage or current required for generating the magnetic field to the magnetic field control mechanism, the magnitude of the vibration in the direction perpendicular to the longitudinal direction is always constant in the direction perpendicular to the longitudinal direction of the cantilever. 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 by performing magnetic field feedback control so that the bending in the direction perpendicular to the longitudinal direction generated in the cantilever during scanning of the sample surface is made zero. A clear image with a 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 that the magnetic field control mechanism does not come into contact with the sample, the sample stage, and the magnetic field generation mechanism.

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

In addition, by applying a static magnetic field from the lateral direction while depositing the magnetic substance on the cantilever, a cantilever with a magnetic substance with the magnetic pole directed in the lateral direction can be manufactured. In this case, the cantilever is a piezoelectric body, a piezoelectric thin film,
The device can be made smaller if it is composed of either a capacitance sensor or a piezoresistor.

Further, if the probe provided at the tip of the cantilever is a conductive probe capable of controlling the potential and allowing a current to flow, a contact current depending on the contact area can be passed.

The present invention is an AFM / STM (scanning tunneling microscope) having an active cantilever that can arbitrarily control the amount of deflection in the direction perpendicular to the longitudinal direction of the cantilever using a magnetic field. It can measure frictional and shearing stresses on the order of meters and micrometers, and can identify atomic species and materials based on a great deal of this information.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
FIG. 1 is a schematic diagram illustrating an embodiment of a force probe microscope. The sample 4 includes the piezoelectric body 1 in three directions of X, Y and Z,
The coil with the iron core, which is the magnetic field control mechanism 12, is installed on the cylindrical fine movement mechanism formed by the steps 2 and 3, and is installed in a range that 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 a 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-division photodiode 7 irradiate the cantilever 5 with laser light and detect reflected light thereof, and constitute an optical lever. Then, the displacement (deflection) of the cantilever 5 is measured by the optical lever, and the force converted from the spring constant of the cantilever 5 is detected, whereby the force acting between the sample 4 and the probe 10 can be detected. it can.

The cantilever 5 is made of titanium and has a triangular shape having a thickness of 600 nm, a length of 200 μm, and a width of 500 μm.
Vapor deposition is performed at a side of 10 μm while supplying a static magnetic field by a sputtering method. In addition, this thin film cantilever 5
The other side of the probe 10 is fixed at a fixed end 14. Also, a magnetic 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 magnetic poles in a direction perpendicular to the longitudinal direction with a static magnetic field before measurement. Alternatively, the measurement may be performed while applying a static magnetic field during measurement (scanning).

The sample 4 is fixed on a conductive sample stage 15.
The contact current flowing between the probe 10 and the sample 4 by applying a voltage from the voltage generator 16 is detected by the current measuring device 17. In FIG. 2, reference numeral 13 denotes a lens for condensing 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 driving device 9. After the contact between the probe and the sample, the sample is scanned and imaged. When a large frictional force is applied to the probe of the cantilever and the sample at that time, the cantilever is largely bent in a direction perpendicular to the longitudinal direction ( FIG.
(See (a) and (b)). Therefore, a current is applied to the magnetic field control mechanism 12 to generate a magnetic field, and the torsion of the probe is returned to its original state, thereby returning the torsion of the cantilever 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 next data. Furthermore, if a material having a large coefficient of friction of the sample is present, the filter is set so that the bending of the cantilever becomes zero.
Apply deflection to undo the deflection. 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 is 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 obtain the difference in the contact area in the case of the same material. Further, since the sample can be rotated in an arc, the characteristics of the sample 4 in all directions can be observed. Further, by scanning while causing the cantilever to vibrate in a direction perpendicular to the longitudinal direction with the generated AC external magnetic field, the material can be identified by utilizing the fact that the degree of attenuation of the vibration of the cantilever differs depending on the material. Further, by feeding back the attenuation of the vibration to the magnetic field control mechanism, the shear stress of the material can be determined from the magnetic field (see FIG. 4).

FIG. 5 shows that a permanent magnet of samarium-cobalt as a static magnetic field generator 20 is 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 included in the cantilever with this static magnetic field, the cantilever can be oscillated by 30 nm with a 10 Gauss magnetic field generated by 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 amount of lateral deflection of the cantilever using a magnetic field, one atom or one atom can be obtained. Friction and shear stress in the order of nanometer to micrometer can be measured, and many kinds of information can be used to identify atomic species and materials.

[Brief description of the 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 one 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 a friction force probe microscope according to an embodiment of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric body of X direction 2 Piezoelectric body of Y direction 3 Piezoelectric body of Z direction 4 Sample 5 Cantilever 6 Semiconductor laser 7 Two-segment photodiode 8 Control signal generation circuit 9 Piezoelectric body driving device 10 Probe 11 Computer 12 Magnetic field control mechanism 13 Lens 14 Fixed end 15 Conductive sample stage 16 Voltage generator 17 Current measuring device 18 Magnetic thin film 19 Magnetic pole direction 20 Static magnetic field generator

Claims (12)

[Claims] 1. A cantilever with a probe having a magnetic material, a cylindrical position control mechanism for controlling a position of a sample, a minute displacement measuring mechanism for measuring a bending amount of the cantilever, and a bending of the cantilever. Or a magnetic field control mechanism for arbitrarily controlling the distance between the sample and the probe, wherein the magnetic poles provided at the tip of the cantilever are aligned in a direction perpendicular to the longitudinal direction. Features a friction force probe microscope. 2. A cantilever with a probe having a magnetic material, a cylindrical position control mechanism for controlling a position of a sample, a minute displacement measuring mechanism for measuring a bending amount of the cantilever, and a bending 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 a direction perpendicular to the longitudinal direction. Friction Force Probe Microscope 3. The friction according to claim 1, wherein the probe provided at the tip of the cantilever is a conductive probe capable of controlling a 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. When the magnetic field control mechanism is installed in the cylindrical position control mechanism, the magnetic field control mechanism is not in direct contact with any of a sample, a 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 method according to claim 1, wherein the cantilever includes one selected from a piezoelectric body, a piezoelectric thin film, a capacitance sensor, and a piezoresistor. The friction force probe microscope according to 1. 7. The apparatus according to claim 1, wherein a static magnetic field generator is installed in a direction perpendicular to said cantilever.
The friction force probe microscope according to any one of 4, 5, and 6. 8. A cantilever with a probe having a magnetic material, a cylindrical position control mechanism for controlling a position of a sample, a minute displacement measuring mechanism for measuring an amount of bending of the cantilever, and bending 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, detecting a force acting in a vertical direction by a magnetic field by performing a feedback control of a deflection in a direction perpendicular to a longitudinal direction of the cantilever with an 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 material, a cylindrical position control mechanism for controlling a position of a sample, a minute displacement measuring mechanism for measuring an amount of bending of the cantilever, and a length 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 oscillated in a direction perpendicular to the longitudinal direction by an AC external magnetic field generated from the magnetic field control mechanism. And measuring the degree of attenuation of the cantilever by using a friction force probe microscope. 10. A cantilever with a probe having a magnetic material, a cylindrical position control mechanism for controlling a position of a sample, a minute displacement measuring mechanism for measuring an amount of bending of the cantilever, and bending 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,
During the scanning of the probe or the sample, the cantilever is vertically oscillated using the magnetic field control mechanism, and the voltage or current required for generating a magnetic field is controlled by the feedback control directly to the magnetic field control mechanism in the lateral direction. Identification of atomic species and materials using a friction force probe microscope, characterized in that the magnitude of vibration in the direction perpendicular to the longitudinal direction of the cantilever is always kept constant to measure shear stress. Method. 11. A cantilever with a probe having a magnetic material, a cylindrical position control mechanism for controlling a position of a sample, a minute displacement measuring mechanism for measuring an amount of bending of the cantilever, and bending of the cantilever. 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 an atomic species or a material using a friction force probe microscope, wherein a magnetic field feedback control is performed so that a bending in a direction perpendicular to a longitudinal direction generated in the cantilever is reduced to zero. 12. A cantilever with a probe having a magnetic material, a cylindrical position control mechanism for controlling a position of a sample, a minute displacement measuring mechanism for measuring a bending amount of the cantilever, and a bending of the cantilever. 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,
The magnetic field feedback control is performed so that the bending in the vertical direction with respect to the longitudinal direction generated in the cantilever becomes zero, and the micro-displacement measuring mechanism for measuring the bending amount of the cantilever is rotated by an arc so that the crystal direction and the crystal axis are changed. A method for identifying an atomic species and a material using a friction force probe microscope, wherein a shear stress is measured for each of the following.