JP2000009624A - Scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning probe microscope capable of accurately controlling the distance between a probe and a sample and capable of measuring the magnetic force of a cooled sample with good reproducibility. SOLUTION: A scanning probe microscope is constituted of a cantilever probe 1 having a probe provided to the tip thereof, a sample temp. varying means 13, an excitation part consisting of an exciting piezoelectric element 3 and an AC voltage generating means 4, a vibration detection part consisting of a quartz vibrator 5 and a current/voltage amplifying circuit 6, a coarse adjustment mechanism 7 allowing the probe to approach a sample, a distance control means consisting of a Z-axis fine adjustment element 8 and a Z servo circuit 9 to control the distance between the sample and the probe, a two-dimensional scanning means consisting of an XY fine adjustment element 10 and an XY scanning circuit 11 and a data processing means 12 performing the three-dimensional imaging of a measuring signal and, further, the cantilever probe for measuring magnetic force is formed from a magnetic body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scanning probe microscope. Furthermore, the present invention relates to a scanning probe microscope for measuring a magnetic force while cooling a sample.

[0002]

2. Description of the Related Art Conventionally, as a scanning probe microscope for measuring a sample while cooling it, for example, Robert D. Glover, Rev. Sci. Instrum. 65 (3), 1994, 62
A low-temperature scanning probe microscope disclosed on pages 6 to 631 is known. FIG. 2 is a schematic diagram of a conventional low-temperature scanning probe microscope. C is a sample and a piezo-electric scanner for scanning the sample, and D is a probe and a piezoelectric element for vibration. The probe is oscillated in parallel with the sample surface using a piezo element for oscillation. A horizontal force from the sample surface, that is, a shear force acts on the tip of the probe, and the vibration state of the probe changes. Laser light is used to measure the vibration of the probe. A is a diode laser, B is a lens, and F is a photodiode detector. The tip of the probe is irradiated with laser light for position control, and the shadow of the probe is detected by a lens and a detector.
The distance between the sample and the tip of the probe is controlled by using a piezo piezoelectric scanner so as to keep the shear force constant, that is, to keep the amplitude change or the phase change constant. The distance between the surface of the sample and the tip of the probe is controlled by utilizing the fact that the shear force is rapidly attenuated according to the distance from the sample. A cryostat is used for cooling the sample. E is the cryostat chamber and optical window.

[0003]

However, such a conventional variable sample temperature scanning probe microscope has the following problems. (1) Laser light is radiated to the sample surface near the tip of the optical probe to detect the shear force, and the probe tip image (shadow) in the reflected light is detected. The measurement of the vibration amplitude is difficult, and the accurate surface shape measurement is difficult.
In addition, alignment of the laser beam is not easy, and there is a problem in reproducibility of data. (2) Since the sample is inside the cryostat and the optical system such as a shear force detection laser is outside the cryostat, the laser light amount is easily attenuated by the optical window, making the measurement difficult. In addition, the fluctuation of the laser light due to the flow of the low-temperature helium gas or liquid helium is apt to occur, making it difficult to control the probe. (3) Since the probe is caused to vibrate horizontally with respect to the sample surface, it has been difficult to apply the probe as a magnetic force microscope utilizing the vertical vibration of a magnetic probe.

Therefore, the present invention has the following problems. (1) A scanning probe microscope capable of accurately controlling the distance between a probe and a sample and obtaining data with good reproducibility is realized. (2) A scanning probe microscope capable of stably measuring a cooled sample is realized. (3) A scanning probe microscope capable of measuring the magnetic force of a cooled sample is realized.

[0005]

A scanning probe microscope according to the present invention comprises a cantilever probe having a probe at the tip, a means for varying the sample temperature, an exciting section comprising an exciting piezoelectric body and an AC voltage generating means, A vibration detector comprising a crystal oscillator and a current-voltage amplifier circuit, a coarse movement mechanism for bringing the probe closer to the sample, a distance control means between the sample and the probe comprising a Z-axis fine movement element and a Z servo circuit, and an XY fine movement element. A scanning probe microscope constituted by two-dimensional scanning means comprising an XY scanning circuit and data processing means for forming a three-dimensional image of a measurement signal. With such a configuration, the distance between the probe and the sample can be accurately controlled while the temperature of the sample is changed, and a scanning probe microscope with high reproducibility of measurement data due to stable device characteristics is provided. Also,
Provided is a scanning probe microscope capable of measuring a magnetic force while changing a sample temperature by using a cantilever probe as a magnetic material.

[0006]

FIG. 1 is a schematic diagram of a scanning probe microscope of the present invention. The scanning probe microscope according to the present invention includes a cantilever probe 1 having a probe at the tip, a sample temperature varying unit 13, an excitation unit including an excitation piezoelectric body 3 and an AC voltage generation unit 4, and a quartz oscillator 5. A vibration detection unit comprising a current / voltage amplifying circuit 6, a coarse movement mechanism 7 for bringing the probe closer to the sample 2, a distance control means between the sample and the probe comprising a Z-axis fine movement element 8 and a Z servo circuit 9, and an XY fine movement element Two-dimensional scanning means 10 comprising an XY scanning circuit 10 and a data processing means 12 for forming a three-dimensional image of a measurement signal
It is composed of Further, the cantilever probe was made of a magnetic material to measure the magnetic force.

When the probe is brought close to the sample while vibrating in the direction perpendicular to the sample surface, a repulsive force acts on the probe from the sample, and the vibration amplitude of the probe decreases. Since the probe and the quartz oscillator are joined and operate integrally, a decrease in the vibration amplitude of the probe results in a decrease in the amplitude of the quartz oscillator. This decrease in amplitude reduces the output current of the crystal resonator. The output current is detected by a current-voltage amplifier. The distance between the sample and the probe is controlled by the Z-axis fine movement element and the Z servo circuit so that the amount of change in the output current of the crystal unit becomes constant. In such a state, the probe is two-dimensionally scanned on the sample surface to measure the shape of the sample. A three-dimensional image is obtained by the data processing means based on the measurement signal. The use of a magnetic probe enabled measurement of magnetic force.

As described above, the use of the quartz oscillator for controlling the distance between the probe and the sample eliminates the need for a position control laser as in a conventional temperature-variable scanning probe microscope. Data inaccuracies due to fluctuations in the amount of light and fluctuations due to fluctuations in helium gas or liquid helium can be avoided. In addition, a scanning probe microscope that can perform stable measurement while changing the temperature of the sample by means of changing the sample temperature, and that can measure magnetic force by vibrating the magnetic probe perpendicular to the sample surface has been developed. can get.

[0009]

Embodiments of the present invention will be described below. [Embodiment 1] FIG. 3 is a schematic view of Embodiment 1 of a scanning probe microscope of the present invention. Parts other than those shown in FIG. 3 are the same as those in FIG.

[0010] The sample 2 is cooled by a cryostat 14.
Was used. The crystal unit 5 and the excitation piezoelectric body 3 were bonded and fixed. A plate-like PZT element was used as the piezoelectric material for excitation. As the crystal resonator, a vibrator having only one vibrating piece without a vibrating piece on one side of a fork-type vibrator was used. When an AC voltage is applied to the PZT element, the PZT element vibrates, and the crystal resonator is excited. When the excitation frequency is set to the resonance frequency of the crystal unit, the crystal unit resonates.
When the crystal oscillator vibrates, electric charges are induced in the electrodes of the crystal oscillator due to the piezoelectric effect, and are detected as a current by the current-voltage amplifier circuit. Since a current proportional to the vibration amplitude of the crystal resonator is generated, the vibration state of the crystal resonator can be measured based on the detected current. In addition to the PZT plate, a cylindrical PZT scanner, a laminated PZT plate, and the like are conceivable as the excitation piezoelectric body, and all of them are included in the present invention. Further, as the quartz oscillator, a flat oscillator or the like may be considered in addition to the above-described fork-type oscillator having only one side, which is included in the invention.

The probe 1 was pressed and fixed to the quartz oscillator 5 using the spring property of the probe 1 itself. As the probe, a magnetic probe in which a magnetic film was coated on the tip of a glass probe was used. In addition to the probe, a cantilever made of silicon or silicon nitride is also included in the present invention. The PZT plate for excitation is provided with an XYZ fine motion element 8 through a substrate.
Fixed to 10. As the fine movement element, a cylindrical piezoelectric element in which an XYZ three-axis scanner was integrated was used. In addition, as the fine movement element, an element using a piezo scanner or an electrostrictive element in which the Z axis and the XY axis are separated is considered, and is included in the present invention. In addition, a piezo stage, a stage using a parallel spring, a one-axis piezo element arranged on three axes of XYZ, a tripod type piezoelectric element integrated, a stacked piezo scanner, and the like are considered, all of which are included in the present invention. .

The magnetic probe is moved closer to the magnetic sample 2 using the coarse movement mechanism 7. As the coarse movement mechanism, a coarse movement mechanism including a stepping motor, a reduction gear, and a coarse screw was used. Other coarse movement mechanisms include a Z stage with a stepping motor added, a stage using a piezoelectric element, such as an inchworm mechanism, and a stage combining a Z stage and a piezoelectric element. Included in the invention.

A sample surface is scanned by using an XY scanning circuit and an XY fine movement element. Simultaneously measure the vibration amplitude or phase of the probe. The data of the XY scanning circuit and the Z servo circuit, and the amplitude or phase data are input to the data processing means and are converted into a three-dimensional image. The surface shape can be measured from Z servo circuit data, and the distribution of magnetic force can be measured from amplitude or phase data. An electronic computer and a CRT display were used as data processing means. In addition to the above, various methods such as a storage oscilloscope or a combination of a computer and a liquid crystal display are considered as data processing means.
Both are included in the present invention.

With this configuration, it is possible to measure the magnetic force on the sample surface at a low temperature.

[0015]

As described above, according to the present invention, a cantilever probe having a probe at the tip, a means for varying a sample temperature, an exciting section comprising an exciting piezoelectric body and an AC voltage generating means, and a quartz oscillator A vibration detection unit comprising a current and voltage amplification circuit; a coarse movement mechanism for bringing the probe closer to the sample;
It is composed of a distance control means between the sample and the probe, which comprises an axis fine movement element and a Z servo circuit, a two-dimensional scanning means comprising an XY fine movement element and an XY scanning circuit, and a data processing means for performing three-dimensional imaging of a measurement signal. Scanning probe microscope. By adopting such a configuration, the distance between the probe and the sample can be accurately controlled while the temperature of the sample is changed, and a scanning probe microscope with high reproducibility of measurement data by stable device characteristics has been realized. . In addition, by using a magnetic material for the cantilever probe, a scanning probe microscope capable of measuring a magnetic force while changing the sample temperature has become possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a scanning probe microscope of the present invention.

FIG. 2 is a schematic diagram of a conventional low-temperature scanning probe microscope.

FIG. 3 is a schematic diagram of Embodiment 1 of the scanning probe microscope of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Probe 2 Sample 3 Excitation piezoelectric body 4 AC voltage generating means 5 Quartz crystal vibrator 6 Current voltage amplifier circuit 7 Coarse movement mechanism 8 Z axis fine movement element 9 Z servo circuit 10 XY fine movement element 11 XY scanning circuit 12 Data processing means 13 sample Variable temperature means 14 cryostat

Claims (5)

[Claims] 1. A cantilever probe having a probe at a tip thereof, a sample temperature varying means, an exciting section comprising a piezoelectric body for excitation and an AC voltage generating means, and a vibration detecting section comprising a quartz oscillator and a current / voltage amplifier circuit. A coarse movement mechanism for bringing the probe closer to the sample; a distance control means between the sample and the probe, comprising a Z-axis fine movement element and a Z servo circuit;
A scanning probe microscope comprising two-dimensional scanning means comprising a scanning circuit and data processing means for producing a three-dimensional image of a measurement signal. 2. The scanning probe microscope according to claim 1, wherein the means for changing the sample temperature is a sample cooling means. 3. The scanning probe microscope according to claim 1, wherein the tip of the cantilever probe is a magnetic material. 4. The method according to claim 1, wherein the bonding of the probe and the quartz oscillator is performed by a spring pressure of an elastic body.
3. The scanning probe microscope according to any one of 3. 5. The scanning probe microscope according to claim 4, wherein the probe itself also functions as an elastic body.