Presented by:
Dhwani
Varuna

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Atomic force microscopy
 It is also known as scanning force microscopy.
 AFM is a very high resolution type of scanning probe microscopy , with resolution of order of a fraction of nanometer.
 AFM is one of the foremost tools for imaging , measuring and manipulating matter at the nanoscale.
Modes of AFM
There are three modes in which AFM can be operated depending on application:-
1. Static mode (contact).
2. Dynamic mode(non contact).
3. Tapping mode.
Static mode
 Feedback-static tip deflection.
 Attractive forces-strong,causing the tip to ‘snap in’ to the surface.
 Force is repusive.
Dynamic mode
 In the dynamic mode, the cantilever is externally oscillated at or close to its fundamental resonance frequency or a harmonic . The oscillation amplitude, phase and resonance frequency are modified by tip-sample interaction forces.
 Non-contact mode AFM does not suffer from tip or sample degradation effects that are sometimes observed after taking numerous scans with contact AFM. This makes non-contact AFM preferable to contact AFM for measuring soft samples as shown in fig.
Schemes for dynamic mode operation include
 frequency modulation and
 the more common amplitude modulation .
Tapping mode
 In tapping mode, the cantilever is driven to oscillate up and down at near its resonance frequency by a small piezoelectric element mounted in the AFM tip holder similar to non-contact mode.
 Due to the interaction of forces acting on the cantilever when the tip comes close to the surface, Van der Waals force, dipole-dipole interaction, electrostatic forces, etc cause the amplitude of this oscillation to decrease as the tip gets closer to the sample.