Atomic force microscopy system and method for nanoscale measurement

• US 8,726,410 B2
• Filed: 07/29/2011
• Issued: 05/13/2014
• Est. Priority Date: 07/30/2010
• Status: Active Grant

• Current Assignee: US Department of The Air Force (U.S. Department Of Defense)
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Sathish, Shamachary, Nalladega, Vijayaraghava, Jata, Kumar V, Blodgett, Mark P
• Primary Examiner(s): Berman, Jack
• Assistant Examiner(s): Smith, David E
• Application Number:
  US13/194,422
• Publication Number:
  US 20120030846A1
• Time in Patent Office: 1,019 Days
• Field of Search: 850/6, 850/25, 850/33, 850 46- 49, 250306-311
• US Class Current: 850/46
• CPC Class Codes: G01Q 60/08 MFM [Magnetic Force Microscopy] combined with AFM [Atomic Force Microscopy

Abstract

An atomic force microscope (AFM) system capable of imaging multiple physical properties of a sample material at the nanoscale level. The system provides an apparatus and method for imaging physical properties using an electromagnetic coil placed under the sample. Excitation of the coil creates currents in the sample, which may be used to image a topography of the sample, a physical property of the sample, or both.

Claims

1. A method of using an atomic force microscope system to image at least one electrostrictive property of a dielectric sample material the atomic force microscope system comprising:

A cantilever including a non-magnetic reflective surface, a first end and a second end, wherein the first end has a pointed tip and the second end defines a length between the first end and the second end;

A scanner coupled to a scanning controller and the second end of the cantilever, wherein the cantilever is positioned such that the pointed tip is adjacent to the sample upper surface, the scanning controller providing a scanner signal to the scanner to position the scanner and the cantilever such that the pointed tip is able to move across at least a portion of the sample upper surface;

A laser positioned to emit a light;

A photodetector;

A generator to generate a single-coil excitation signal;

An electromagnetic coil coupled to the generator to receive the single coil-excitation signal; and

A single phase sensitive detector;

the method comprising;

placing the dielectric sample material near the electromagnetic coil;

supplying the single coil excitation signal having a predetermined amplitude and a predetermined frequency to the electromagnetic coil such that the single coil-excitation signal creates a single time-varying magnetic field;

positioning the dielectric sample material such that the dielectric sample material intersects the single time-varying magnetic field, whereby the single time-varying magnetic field generates a first amount of electrostrictive strain in the dielectric sample material;

focusing the laser on the reflective surface of the cantilever, wherein the cantilever comprises a magnetic pointed tip;

raster-scanning the dielectric sample material with the magnetic pointed tip of the cantilever such that the magnetic pointed tip is in contact with a sample upper surface, wherein the cantilever is coupled to the scanner, wherein the electrostrictive strain causes the cantilever to deflect toward or away from the sample upper surface;

detecting a portion of the laser that is reflected from the reflective surface using the photodetector;

collecting an output of the photodetector and the amplitude of the single coil-excitation signal using the single phase sensitive detector; and

generating at least one electrostrictive property image by comparing the output of the photodetector and the amplitude of the single coil-excitation signal, wherein the at least one electrostrictive property image is generated independently of the scanner signal.

2. The method of claim 1 wherein the electrostrictive property image and a topography image are obtained simultaneously.

3. The method of claim 1 further comprising varying the second magnetic field by altering at least one of the amplitude and the frequency of the single coil-excitation signal, thereby generating a second amount of electrostrictive strain in the sample material.

4. A method of using an atomic force microscope system to image at least one dielectric polarization property of a dielectric sample material having a first amount of dielectric polarization the atomic force microscope system comprising:

A cantilever including a non-magnetic reflective surface, a first end and a second end, wherein the first end has a pointed tip and the second end defines a length between the first end and the second end;

A scanner coupled to a scanning controller and the second end of the cantilever, wherein the cantilever is positioned such that the pointed tip is adjacent to the sample upper surface, the scanning controller providing a scanner signal to the scanner to position the scanner and the cantilever such that the pointed tip is able to move across at least a portion of the sample upper surface;

A laser positioned to emit a light;

A photodetector;

A generator to generate a single-coil excitation signal;

An electromagnetic coil coupled to the generator to receive the single coil-excitation signal; and

A single phase sensitive detector;

the method comprising;

placing the dielectric sample material near the electromagnetic coil;

supplying the single coil excitation signal having a predetermined amplitude and a predetermined frequency to the electromagnetic coil such that the single coil-excitation signal creates a single time-varying magnetic field;

positioning the dielectric sample material such that the dielectric sample material intersects the single time-varying magnetic field, whereby the single time-varying magnetic field alters the first amount of dielectric polarization in the dielectric sample material to generate a second amount of dielectric polarization;

positioning the cantilever at a predetermined distance above a sample upper surface, wherein the cantilever comprises a magnetic pointed tip;

focusing the laser on the reflective surface of the cantilever;

raster-scanning the dielectric sample material, wherein the cantilever is coupled to the scanner, wherein interactions between dipoles in the dielectric sample material and the single time-varying magnetic field cause the cantilever to deflect toward or away from the sample upper surface;

detecting a portion of the laser that is reflected from the reflective surface using the photodetector;

collecting an output of the photodetector and the amplitude of the single coil-excitation signal using the single phase sensitive detector; and

generating at least one dielectric polarization property image by comparing the output of the photodetector and the amplitude of the single coil-excitation signal, wherein the at least one dielectric polarization property image is generated independently of the scanner signal.

5. The method of claim 4 further comprising obtaining a topography image by raster-scanning the dielectric sample material with the magnetic pointed tip of the cantilever such that the magnetic pointed tip is in contact with the sample upper surface.

6. The method of claim 4 further comprising varying the second magnetic field by altering at least one of the amplitude and the frequency of the single coil-excitation signal, thereby generating a third amount of dielectric polarization in the dielectric sample material.