The document summarizes the fundamentals of atomic force microscopy (AFM). It describes that AFM has very high resolution on the order of fractions of nanometers. It operates by measuring the force between a probe tip and the sample surface. The document outlines the basic theory of AFM, including that it consists of a cantilever with a sharp tip used to scan the sample surface. Forces between the tip and sample lead to deflection of the cantilever. It also describes the different operating modes of AFM including contact, non-contact, and tapping modes.

1. Fundamentals of Atomic Force Microscope
(AFM)
Md Ataul Mamun
BSc. in EEE
Bangladesh University of Engineering and
Technology (BUET), Dhaka, Bangladesh
Instructor: Dr. Nirmal Adhikari

2. Outline
• Introduction
– Background
– Motivation
– Objectives
• Theory
– Working principle
– Operating modes
• Results and Analysis
• Conclusion
• Future Work

3. Introduction
• AFM is one kind of scanning probe microscope
that possesses a very high resolution (on the order
of fractions of nanometers)
• Operates by measuring force between its probe
and the sample
• Can measure local properties, such as height,
friction, magnetism with the probe
• Unlike the electron microscope, AFM provides a
3-D surface profile
Source: https://en.wikipedia.org/wiki/Atomic-force_microscopy

4. Introduction
• In the field of solid state physics, it can be used
for identification of atoms at a surface, and to find
interactions between a specific atom and its
neighboring atoms.
• Besides solid state physics, the AFM is applied in
molecular engineering, polymer engineering,
polymer chemistry etc.
• Due to its versatility, science and research
students should know the working principle and
applications of the AFM.

5. • AFM was invented by IBM Scientists in 1982
• Improved AFM was invented and used by Gerd
Binnig et al. in 1980s which earned them noble
prize in 1986
• The first commercially available AFM was
introduced in 1989.
Background
Source: https://en.wikipedia.org/wiki/Atomic-force_microscopy

6. Objective
• To learn AFM working principle, application, and
study of images
Motivation
• Need to understand how to use AFM to study dye
monolayer on TiO2 surface

7. Theory
• AFM consists of a cantilever with a sharp tip
(probe) at its end that is used to scan the specimen
surface.
• The cantilever is typically silicon with a tip radius
of curvature on the order of nanometers.
• When the tip is brought into proximity of a
sample surface, forces between the tip and the
sample lead to a deflection of the cantilever
according to Hooke’s law
F = -kx

8. Theory
Figure: AFM probe tip (on the order of nanometers) and cantilever
Source: https://en.wikipedia.org/wiki/Atomic-force_microscopy

9. Working principle
Figure: Working principle of AFM

10. Working principle
Feedback loop:

11. AFM Modes of Operation
AFM has 3 modes of operation
• Contact mode
• Non contact mode
• Tapping mode
(Tapping mode provides higher
resolution with minimum sample
damage)

12. AFM Modes of Operation
Contact Mode:
• Measures repulsion between tip and sample
• Force of tip against sample remains constant (With
Feedback)
• Feedback regulation keeps cantilever deflection constant
Non Contact Mode:
• Measures attractive forces between tip and sample
• Tip doesn’t touch sample
• Van der Waals forces between tip and sample detected
• Doesn’t degrade or interfere with sample- better for soft
samples

13. Tapping (Intermittent Contact) Mode:
• Tip vertically oscillates at frequency of 50,000 to
500,000 cycles/sec.
• Oscillation amplitude reduced as probe contacts surface
due to loss of energy caused by tip contacting surface
• Advantages: overcomes problems associated with
friction, adhesion, electrostatic forces
• Tapping mode provides higher resolution with minimum
sample damage
• More effective for larger scan sizes
AFM Modes of Operation

14. Results and Analysis

15. Conclusions
Future Work
• Characterize dye monolayer on TiO2 with AFM
• AFM has diverse applications in research areas
• It is capable to produce 3-D images with high
resolution

16. Acknowledgements
• SDSU EE&CS Dept.
• Dr. Qiquan Qiao
• Dr. Nirmal Adhikari