JPH08136552A - Interatomic force microscope and similar scanning probe microscope - Google Patents

Abstract

PURPOSE: To realize accurate origin adjusting and automation by providing a mechanism for applying a voltage to a cantilever or a sample thereby canceling noise caused by electrostatic force or other interaction. CONSTITUTION: A voltage control section 17 applies a voltage to a cantilever 6 or a sample 5 and thereby electrostatic force and other interaction can be offset by an electrostatic force. For example, the electrostatic force or other interaction causing noise is increased as the distance between the sample 5 and the cantilever 6 decreases and the applying voltage is thereby varied effectively as a function of the distance between the sample 5 and the cantilever 6. It is realized by interlocking the control signal at a motor control section 15 for rough motion with the voltage at the voltage control section 17.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to scanning atomic force microscopes and similar scanning probe microscopes.

[0002]

2. Description of the Related Art A conventional scanning probe microscope, for example, a scanning tunneling microscope is shown in U.S. Pat. No. 4,434,393. Generally, a scanning atomic force microscope is designed to detect a cantilever, a sample, a z-direction fine movement part that moves the sample so that the atomic force is constant, an xy fine movement part that scans an xy plane, and a cantilever. Coarse motion part that moves to a region that can be sensed, control system that controls the z direction so as to keep the atomic force constant, scanning system that scans the xy plane, image processing system that displays the obtained three-dimensional data Consists of.

Further, as a measuring device similar to the scanning atomic force microscope, the sample surface information is obtained by scanning the sample surface with a similar configuration so that the interaction between the cantilever and the sample becomes constant. To be For example, there is a scanning magnetic force microscope that utilizes magnetic force. In the following, atomic force microscopes and similar scanning probe microscopes are collectively referred to as scanning probe microscopes.

[0004]

In the prior art, the sample-
When the distance between the cantilevers is approached to a region where interactions such as atomic forces can be detected using the coarse movement part, noise such as electrostatic forces causes the cantilevers to undergo interactions such as electrostatic forces. The origin of the interaction, which is the standard of interaction such as the interatomic force, moves. Therefore, each time the measurer moves a certain distance by the coarse movement part, the origin of the interaction is adjusted so as to make a judgment and cancel the noise. This adjustment requires knowledge from the experience of the measurer, such as how often it should be performed, and it is still not easy to make accurate adjustments.

An object of the present invention is to precisely simplify and automate these adjustments.

[0006]

In order to achieve the above object, the scanning probe microscope of the present invention has a structure capable of applying a voltage to a cantilever or a sample, and the distance between the sample and the cantilever depends on the voltage. Change with the function of.

[0007]

The scanning probe microscope of the present invention is capable of easily and objectively canceling noise due to interactions other than the intended interaction such as atomic force by electrostatic force due to the voltage applied to the sample or the cantilever. Measurements can be performed by extracting only the interactions that occur. Further, even when the noise changes depending on the distance between the sample and the cantilever, the measurement can be easily performed by changing the voltage according to the change.

[0008]

Embodiments of the present invention will be described below.

FIG. 1 is a block diagram showing an embodiment of a scanning probe microscope according to the present invention. As an example, an optical lever type atomic force microscope will be described. In this figure, scanning of the XY plane is performed on the sample side using a tripod type scanner, and the voltage applying mechanism is provided on the cantilever side. Atomic force microscopes other than the optical lever method, eg STM
The same applies to the atomic force microscope of the method, the atomic force microscope that scans the XY plane on the cantilever side, and the atomic force microscope that uses a tube scanner other than the tripod type. The same applies when the voltage applying mechanism is provided on the sample side.

In the conventional atomic force microscope, the laser beam emitted from the laser 11 hits the cantilever 6 and reaches the mirror 14.
It is reflected by and enters the PSD (position sensor) 12. At this time, the interaction between the sample and the cantilever is regarded as the deflection of the cantilever, and the deflection is grasped by the change in the angle of the laser beam, and the change in the angle is grasped by the change in the position of the light spot on the PSD. Further, in order to bring the cantilever closer to the atomic force region, the rotation of the DC motor 10 is converted into the linear movement of the coarse movement drive screw 9, and the cantilever base 7 is used as the fulcrum to support the cantilever as a sample. The method of approaching is generally used. The present invention can be similarly applied to other coarse movement mechanisms, for example, a manual coarse movement mechanism using a micrometer, or a shingling insect type coarse movement mechanism using a piezoelectric element.

In the conventional atomic force microscope, as shown in FIG. 2, when a coarse motion is approached, electrostatic force or other interaction causes
The cantilever receives forces other than the atomic force. Therefore, even if the origin adjustment is performed as a reference of the atomic force to be measured, the origin is shifted, so it is necessary to interrupt the coarse movement several times and perform the origin adjustment again. Case 1 in FIG. 2 shows a case where a repulsive force is received as the distance becomes shorter, and case 2 shows a case where an attractive force is received.

The present invention is provided with a voltage control section 17 for applying a voltage to the cantilever in addition to the configuration of FIG. By applying a voltage to the cantilever, it becomes possible to cancel the electrostatic force and other interactions by the electrostatic force.

Since electrostatic force and other interactions that cause noise generally increase as the distance between the sample and the cantilever decreases, it is necessary to change the applied voltage as a function of the distance between the sample and the cantilever as shown in FIG. It is valid. In that case, in FIG. 1, it is realized by interlocking the control signal of the coarse movement motor control unit and the voltage of the voltage control unit. In FIG. 3, the distance is changed by a linear function, but it may be changed by a quadratic or higher function or a more complicated function.
Incidentally, A and B in FIG. 3 correspond to A and B in FIG. When the voltages shown in FIG. 3 are applied, if they are ideally canceled, the electrostatic force and other interactions are as shown in A and B of FIG.

When the distance function of electrostatic force or other interaction has a complicated shape, it is necessary to input the shape in advance.
Have difficulty. Even in that case, a certain distance is approached without applying a voltage, the electrostatic force and other interactions at that time are automatically calculated as a function of the distance, and the subsequent coarse movement approach is taken as a voltage function as the distance function. Can be set to apply. In that case, the distance function is calculated from the control signal of the coarse movement motor control unit and the signal of the PSD signal processing unit in FIG. 1, and then the voltage according to the distance function is applied to the voltage control unit.

In the above, the electrostatic force and other interactions are regarded as a function of distance. However, when the coarse movement approach is a constant velocity, time can be used as a variable instead of distance, and can be regarded as a time function. .

[0016]

The scanning probe microscope of the present invention is provided with a mechanism for applying a voltage to the cantilever or the sample, so that electrostatic noise and other interaction noise can be canceled. This makes it possible to accurately perform the origin adjustment performed by the measurer and to simplify and automate the origin adjustment.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a scanning probe microscope according to the present invention.

FIG. 2 is an explanatory diagram of the operation of the present invention.

FIG. 3 is an explanatory diagram of the operation of the present invention.

FIG. 4 is an explanatory diagram of the operation of the present invention.

[Explanation of symbols]

1 ... Scanner base, 2 ... Z-axis piezoelectric element, 3 ... X-axis piezoelectric element, 4 ... Sample holder, 5 ... Sample, 6 ... Cantilever,
7 ... cantilever base, 8 ... fulcrum, 9 ... coarse drive screw, 10 ... DC motor, 11 ... laser, 12 ... PSD,
13 ... Optical path of laser light, 14 ... Mirror, 15 ... Coarse movement motor control section, 16 ... PSD signal processing section, 17 ... Voltage control section.

Claims (3)

[Claims] 1. A mechanism for applying a voltage to the cantilever and / or the sample in order to cancel an interaction such as an electrostatic force that causes noise other than the interaction for the purpose of measurement that acts between the sample and the cantilever. Characteristic atomic force microscope and similar scanning probe microscope. 2. An atomic force microscope and similar scanning probe microscope according to claim 1, wherein the voltage applied to the cantilever or the sample is changed as a function of the distance between the sample and the cantilever. 3. An atomic force microscope and a similar scanning probe microscope according to claim 2, wherein the distance function of the voltage applied to the cantilever or the sample is automatically set by preliminary coarse approach.