Download - Force Microscopy
![Page 1: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/1.jpg)
Force Microscopy
Principle of Operation
![Page 2: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/2.jpg)
Force Microscopy
• Basic Principle of Operation: detecting forces between a mass attached to a spring (cantilever), that feels some force when it is brought very close to the surface. Ideally the mass (tip) would not damage the surface.
• Sensor that responds to a force and a detector that measures it.
• The sensor-a cantilever beam with an effective spring constant k, moves in accordance with the forces acting on its tip
![Page 3: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/3.jpg)
Force Microscopy
• Frequency of atoms vibration, , at room temperature ~ 1015 Hz
• The mass, m, of an atom ~ 10-30 kg The effective spring constant, k, between atoms is
k=2m1N/m
![Page 4: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/4.jpg)
Materials Characterization
![Page 5: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/5.jpg)
AFM -PrincipleAFM -Principle
![Page 6: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/6.jpg)
AFM -PrincipleAFM -Principle
![Page 7: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/7.jpg)
Materials Characterization
Courtesy Dr. Z. Barkai
![Page 8: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/8.jpg)
Materials Characterization
![Page 9: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/9.jpg)
AFM Images2. Carbon nanotube
3. Human chromosomes
TappingMode AFM image of single carbon-nanotube molecule on electrodes. These images represent an important breakthrough where we measured electronic transport through a single nanotube molecule for the first time. 530nm x 300nm scan courtesy C. Dekker and Sander Tans, Delft University of Technology, Department of Applied Physics and DIMES, The Netherlands.
![Page 10: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/10.jpg)
Materials Characterization
Courtesy Dr. Z. Barkai
![Page 11: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/11.jpg)
Materials Characterization
![Page 12: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/12.jpg)
AFM Images1. Au (111)
High resolution scan of Au (111) surface, with reconstruction strips (inset)
hexagonal atomic structure. Scan size: 5nm; inset: 20 nm
![Page 13: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/13.jpg)
Contact - Atomic Force Microscopy
All rights reserved @ Norbert
Hooke Law F = kx so x =1
k F = F + F T v c
F
Total Repulsive
Total Atractive
Fv
Fc
Laser
![Page 14: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/14.jpg)
AFM -CantileversAFM -Cantilevers
kEwt
l
w
N
Tip radii A
3
3
4
4,
E - Young Module
width, l - lenght, t - thickness
Comercial cantilivers - SiO and Si
- 300
2 3
![Page 15: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/15.jpg)
AFM -CantileversAFM -Cantilevers
![Page 16: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/16.jpg)
Diamond-coated AFM tip FIB Sharp Tip
AFM -CantileversAFM -Cantilevers
Gold-coated Si3N4 Tip
Pyramidal, tetrahedral, or conical tips are the most
common tip shapes
![Page 17: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/17.jpg)
AFM -CantileversAFM -Cantilevers
Depositing a Si3N4 layer on an etch pit in Si
Tips are broader then Si conical tips, harder, and thinner (stress in the film)
not suitable for non-contact (small thickness, small )
![Page 18: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/18.jpg)
AFM -Resolution
AFM
• STM-single atom interaction
STM
AFM-several atoms on tip interact with
several atoms on surface
In contact, not necessarily a single atom
contact, radius of contact ~(Rd)1/2
(d-penetration depth, R-radius of tip)
![Page 19: Force Microscopy](https://reader036.vdocument.in/reader036/viewer/2022063005/56815a64550346895dc7a994/html5/thumbnails/19.jpg)
AFM -Resolution
• Interaction of atom 1 : t=0 different from interaction of atom 3,2
• Each tip atom produces a signals with offset to each other
• Periodicity reproduced but no true atomic resolution