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EP-4741840-A1 - CONDUCTIVE ATOMIC FORCE MICROSCOPE

EP4741840A1EP 4741840 A1EP4741840 A1EP 4741840A1EP-4741840-A1

Abstract

Disclosed is a conductive atomic force microscope capable of measuring the electric capacity of a sample by providing alternating current power to the sample. The conductive atomic force microscope includes: a voltage provision device for providing a voltage to a sample; a current detection device for detecting a current generated by the provided voltage; and a characteristic calculation device for calculating IV characteristics of the sample on the basis of the detected current, wherein the voltage provision device provides an alternating current (AC) voltage to the sample and the characteristic calculation device calculates the electric capacity of the sample on the basis of the detected current.

Inventors

  • JO, AHJIN
  • AHN, BYOUNG-WOON
  • PARK, SANG-IL

Assignees

  • Park Systems Corp.

Dates

Publication Date
20260513
Application Date
20240705

Claims (9)

  1. A conductive atomic force microscope (C-AFM, conductive-AFM) that scans the surface of a sample by measuring the current flowing in the sample through the tip of a cantilever, comprising: a voltage provision device for providing a voltage to the sample; a current detection device for detecting the current generated by the provided voltage; and a characteristic calculation device for calculating IV characteristic of the sample based on the detected current, the voltage provision device provides an alternating current (AC) voltage to the sample, and the characteristic calculation device calculates the capacitance of the sample based on the detected current.
  2. The conductive atomic force microscope of claim 1, the voltage provision device provides the direct current (DC) voltage to the sample.
  3. The conductive atomic force microscope of claim 2, the voltage provision device provides the DC voltage to the sample and then provides the AC voltage.
  4. The conductive atomic force microscope of claim 2, the cantilever and the current detection device are connected to a first line through which a current generated by the provided voltage flows, and a current amplifier for amplifying the generated current is installed in the first line.
  5. The conductive atomic force microscope of claim 4, the current detection device measures the current amplified through the current amplifier.
  6. The conductive atomic force microscope of claim 5, the first line is branched into a second line and a third line, the second line outputs an output signal according to the DC voltage, and the third line outputs an output signal according to the AC voltage.
  7. The conductive atomic force microscope of claim 6, the characteristic calculation device calculates a resistance of the sample based on the output signal according to the DC voltage output through the second line, and calculates a capacitance of the sample based on the output signal according to the AC voltage output through the third line.
  8. The conductive atomic force microscope of claim 7, a low pass filter is installed in the second line.
  9. The conductive atomic force microscope of claim 7, a lock-in amplifier is installed in the third line, and the lock-in amplifier synchronizes a sample bias and a current of the tip to output an output signal according to the AC voltage.

Description

Technical Field The present disclosure relates to a conductive atomic force microscope, and more particularly, to a conductive atomic force microscope that scans the surface of a sample by means of a tip of a cantilever that contacts the surface of the sample. Background Art An atomic force microscope (AFM) obtains surface information of a sample using a tip. The atomic force microscope includes a tip and a cantilever connected to the tip. The cantilever possesses a high degree of flexibility and bends due to the atomic repulsive force-specifically, attractive and repulsive forces-acting between the sharp tip suspended at its end and the sample surface, and by measuring the degree of this bending through changes in the reflection angle of laser light, surface information of the sample can be obtained. The atomic force microscope can be divided into a contact mode and a non-contact mode. The atomic force between the tip and the sample changes from repulsive force to van der Waals attractive force as the distance between the two increases. The contact mode AFM uses repulsive force, and the non-contact mode AFM uses attractive force. The magnitude of the repulsive force used in the contact mode is very small, ranging from 1 to 10 nN, but the cantilever with the tip is also very sensitive, so it is bent by a small change in force. The angular displacement of the cantilever that occurs at this time also bends the angle of the laser beam reflected off the cantilever's upper surface, and by measuring the deflection angle of this laser beam using a PSPD (position sensitive photodiode), it is possible to recognize very small changes in surface elevation. Cantilevers are usually 100µm long, 10µm wide, and 1µm thick, and play a role in amplifying the microscopic interaction between the tip and the sample and transmitting it to the macroscopic world. The tip attached to the end of the cantilever is usually 10µm high and the diameter of the end of the tip is about 10nm. The contact mode AFM has the advantages of relatively easy operation and fast response speed. The contact mode AFM includes a conductive atomic force microscope (C-AFM). The conductive atomic force microscope obtains surface information of a sample by applying a voltage to the sample and/or the tip and measuring the current flowing inside the sample due to the potential difference thereof. A conventional conductive atomic force microscope measured the IV characteristics of the sample by providing a DC voltage to the sample and/or tip. Here, the IV characteristic includes the resistance between the tip and the sample, the threshold voltage, etc. However, the conventional conductive atomic force microscope has a problem in that when the surface of a sample has an insulating structure, the current is not measured from the sample by a DC voltage method, so that the surface information of the sample cannot be obtained. Disclosure of Invention Technical Problem An object of the present disclosure for solving the above-described problems is to provide a conductive atomic force microscope capable of measuring the electric capacity of a sample by providing AC power to the sample. Another object of the present disclosure is to provide a conductive atomic force microscope capable of determining the electrical characteristics of a sample by providing a DC power and an AC power to the sample together. Solution to Problem In order to achieve the above object, a conductive atomic force microscope according to an embodiment of the present disclosure is a conductive atomic force microscope (C-AFM, conductive-AFM) that scans the surface of the sample by measuring the current flowing in the sample through the tip of a cantilever, and the conductive atomic force microscope includes a voltage provision device for providing a voltage to the sample, a current detection device for detecting the current generated by the provided voltage, and a characteristic calculation device for calculating the IV characteristic of the sample based on the detected current, the voltage provision device provides an alternating current (AC) voltage to the sample, and the characteristic calculation device calculates the capacitance of the sample based on the detected current. The voltage provision device provides a direct current (DC) voltage to the sample. The voltage provision device provides the DC voltage to the sample and then provides the AC voltage. The cantilever and the current detection device are connected to a first line through which a current generated by the provided voltage flows, and a current amplifier for amplifying the generated current is installed in the first line. The current detection device measures the current amplified through the current amplifier. The first line is branched into a second line and a third line, the second line outputs an output signal according to the DC voltage, and the third line outputs an output signal according to the AC voltage. The characteristi