Atomic force microscopy (AFM) is a scanning probe microscopy technique capable of producing high-resolution topographical images of a sample surface. AFM works by scanning a sharp tip over a surface and measuring the force between the tip and sample using a laser beam and photodetector. This force is characterized by Hooke's law and depends on the tip deflection and spring constant. AFM can operate in contact, non-contact, or tapping mode and is used across many fields due to its ability to image both hard and soft materials with nanoscale resolution.

2. ATOMIC FORCE MICROSCOPY

3. SCANNING PROBE MICROSCOPY
AFM STM

4. • AFM is the common form of scanning probe microscopy
and is used in all fields of science including Chemistry,
Biology, Physics, Materials science, Nanotechnology,
Astronomy, Medicine and more.
• It is suitable for all types of surfaces. Almost any sample
can be imaged either it is hard (ceramic material) or very
soft (human cells, individual molecules of DNA).
• The AFM has three major abilities: force
topographic imaging, and manipulation
DNA AFM image

5. Atomic force microscopy (AFM) is a
powerful imaging technique that, by
scanning a sharp tip (typical end diameter
5–10 nm) over a surface, can produce
topographical images which quantify
surface morphology.
The surface characteristics can be
explored with very accurate resolution in a
range of 100 μm to less than 1 μm.

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7. WORKING PRINCIPLE
•
NATURE OF
INTERATOMIC/
INTERMOLECULAR
FORCES AND
HOOK’S LAW

8. WORKING PRINCIPLE
•
•
•
•
FORCES
HOOKE'S LAW
•
SEM and TEM images of a micromachined
silicon cantilever with an integrated tip

9. F= −𝑘𝑥
Where:
F: The force acting on the probe
(has sometimes not only vertical
but also horizontal components)
K: constant of proportionality
that contains the info
about elastic properties of the
cantilever.
X: tip deflection vector
dependent on the applied force
F
x= 𝐹𝑘−1
• The cantilever can be thought of as a
spring.
• The quantity of the generated force
between the tip and the surface depends
on the spring constant (stiffness) of the
cantilever and the distance x between the
tip and the surface.
• This force can be characterized with
Hooke’s Law.
• As the tip travels across the sample, it
moves up and down according to the
surface properties of the sample (eg.
topography)

10. ATTRACTIVE FORCES REPULSIVE FORCES
Van der Waals Interaction
Electrostatic Force
Chemical Force
Electron–Electron
Coulomb interaction
Pauli-exclusion
Interaction
Hard Sphere Repulsion
SHORT RANGE
FORCES
LONG RANGE
FORCES

11. Schematic view of an AFM tip close to sample.
Chemical short range forces act when tip and sample orbitals overlap. Long range
forces originate from surface of tips are indicated by arrows.

12. UNDERSTANDING THE WORKING PRINCIPLE
THROUGH SOME EXAMPLES
•
• CAPILLARY FORCES,
COVALENT FORCES, ELECTROSTATIC FORCES, COMMON
REPULSIVE INTERACTION FORCES, VAN DER WALLS FORCES
•
CAPILLARY FORCES

13. • COVALENT FORCES
SHORT-
RANGE CHEMICAL FORCES
•
ELECTROSTATIC FORCES
•
SHORT-
RANGE ELECTROSTATIC

14. •
HARD SPHERE REPULSION PAULI
EXCLUSION INTERACTION ELECTRON-ELECTRON
COULOMB INTERACTIONS
•
VAN DER WAALS
FORCES COULOMB INTERACTION
•
POLARIZATION
•
VAN DER
WAALS FORCES ATTRACTIVE
ACTION
Griffiths’ description of
the effects of Pauli
exclusion[47]: We call it
an exchange force but
it is not really a force at
all - no physical agency
is pushing on the
particles; rather it is
purely a geometric
consequence of the
symmetrization
requirement.

15. •
•
•
Contact mode
Non Contact mode

16. INSTRUMENTATION
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•
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17. WORKING METHODOLOGY
•
•

18. •
•

19. OPERATION MODES
Contact Mode Non Contact ModeTapping Mode
It is also called Static mode. Contact
mode, is the original and
simplest mode to operate an AFM. In
this mode, the probe is in
continuous contact with the sample.
Tapping Mode refers to a
collection of AFM modes in
which the cantilever oscillates
at a high frequency at or close
to resonance.
Non contact Mode in
which the cantilever is
moved close to the
surface without any
contact.

20. MODES OF OPERATION
• High Resolution
• Only mode that can obtain “atomic
resolution” images
• Can measure frictional forces
DISADVANTAGES
• Shear forces can distort features in the image.
• The forces normal to the tip-sample interaction can be
high in air due to capillary forces from the adsorbed
fluid layer on the sample surface.
Topography image/Phase image

21. • BETTER RESOLUTION
• LATERAL FORCES ARE VIRTUALLY ELIMINATED
SO THERE IS NO SCRAPING/ DAMAGING OF
THE SAMPLES.
DISADVANTAGES
• SLIGHTLY LOWER SCAN SPEED THAN CONTACT
MODE AFM
Topography image Phase image

22. • NO DAMAGE TO SAMPLE
• NO TIP DAMAGE/CRASH
Magnetic bits
of a disc
Magnetic domain
of MnAs
DISADVANTAGES
• Lower resolution

23. AFM TIPS
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•
(a) normal tip (3 µm tall) (b) supertip (c) Ultralever (also 3 µm tall).
(Electron micrographs by Jean-Paul Revel, Caltech. Tips from Park Scientific
Instruments; supertip made by Jean-Paul Revel)

24. SOME RESULTS OF
AFM
AFM Images Acquired with Two Different Tips
Contact AFM images of the same area of a (001) oriented
TiO2 thin film, acquired with a pyramidal Si3N4 tip (a) and
a conical, etched Si tip (b)
AFM image of human Cornea (tapping mode)

25. AFM image of ZnO thin
film
AFM image of Graphene
by Tapping mode

27. AFM SAMPLE THAT ARE SOLIDS ARE PREPARED VERY
EASILY!
• SOLID SAMPLES MAY REQUIRE NO PREPARATION AT ALL.
• THEY COULD BE IMAGED DIRECTLY UNDER THE MICROSCOPE.

28. WHAT ABOUT THE SAMPLES THAT ARE NOT
SOLIDS?
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*Polydimethylsiloxane (PDMS): a type of silicone
AFM of Cleaved Mica

29. • NANOMANIPULATION: THE AFM CAN BE OPERATED
AS A NANOROBOT FOR MANIPULATION PURPOSES
ALLOWING FOR NANOMETER PRECISION.
• LITHOGRAPHY: AFM IS USED TO “WRITE” WITH
BIOMOLECULES SUCH AS DNA SEQUENCES. THIS
ALLOW FOR THE CREATION OF MICRO DNA CHIPS
WHICH CAN BE USED IN A WIDE VARIETY OF
APPLICATIONS.
• NANOIDENTATION: AFM IS ALSO USED FOR
INDENTATION HARDNESS TESTS THAT ARE APPLIED TO
SMALL VOLUMES. INDENTATION IS PERHAPS THE
COMMONLY APPLIED MEANS OF TESTING THE
MECHANICAL PROPERTIES OF MATERIALS.

30. AFM
Bright-Field
Microscopy
Epifluoresc
ence
Surface
Interferenc
e
Microscopy
Scanning
Confocal
laser
Microscopy
(SCLM)
Raman
Spectrosco
py
Total
Internal
Reflection
Fluorescen
ce
Fluorescen
ce Lifetime
Imaging
Microscopy
Afm Combined With
Optical Or
Spectroscopic
Techniques