References Atomic force Microscopy by Peter Eaton and Paul West

1. Atomic Force Microscopy
Sonu
1411NT11
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2. Atomic Force Microscopy
AFM works by scanning a probe over the sample surface,
building up a map of the height or topography of the
surface as it goes along.
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3. Background of AFM
 In 1929 Shmalz described Stylus Profiler.
 In 1950 Becker suggested oscillating the probe that
approach contact with surface.
 In 1971 Young described non contact type Stylus Profiler.
 In 1981 Binning and Rohrer described STM.
 AFM Invented in 1986 by Binning.
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4. Different From other Microscopy
 No need of focusing, illumination, Depth of field.
 It also have height information that make it simple to
quickly measure the height, volume, width of any feature
in the sample.
 It physically feels the sample’s surface with a sharp probe,
building up a map of the height of samples surface.
 It provides single atomic level structure so provide high
resolution.
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6. The first AFM instrument built by Binning,
Quate and Gerber
The STM with a lever
made by carefully gluing a
tiny diamond onto the end
of a spring made of a thin
strip of gold. This was the
cantilever of the first AFM.
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7. AFM Instrument
The main components of an AFM are
1.Microscope stage – Moving AFM tip, Sample holder,
Force Sensor
2.Control electronics - Optical Microscope, Vibration
controller
3.Computer - The control electronics usually takes the form
of a large box interfaced to both the microscope stage
and the computer.
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8. Basic concept of AFM Instrumentation
The piezoelectric transducer moves the tip over the
sample surface, the force transducer senses the force
between the tip and the surface, and the feedback
control feeds the signal from the force transducer back in
to the piezoelectric, to maintain a fixed force between the
tip and the sample.
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9. Piezoelectric transducers
Convert electrical potential into mechanical motion.
amorphous lead barium titanate, PdBaTiO3 or lead
zirconate titanate, Pb[ZrxTi1–x]O3,0<x<1
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10. Force transducers
It may be constructed that measure forces as low as 10
piconewtons.
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11. Force Sensor
Optical lever sensor the
End of the cantilever
bends the position of
the laser spot on the
detector changes. As the
cantilever detector
distance is large a small
movement of the
cantilever causes a large
change in the laser spot
position at the detector.
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12. Feedback control
Feedback control is used to maintain a set force between
the probe and the sample.
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14. Challenges of AFM regarding Design
 Requirement of sharp probe for high resolution.
 The force between probe and sample should be 1nN or
less than that.
 The feedback controller should have a rapid control so
adjust topographic film can be formed.
 A high speed computer that can generate the images in
real time.
 Vibration free stage.
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15. Scanning Modes
There are different imaging modes of AFM
 Contact Mode
 Non Contact Mode
 Tapping Mode
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16. Modes of Operation in AFM
Mode of Operation Force of Interaction
 Contact mode strong(repulsive) - constant force or
constant Height
 Non-contact mode weak (attractive) - vibrating probe
 Tapping mode strong (repulsive) - vibrating probe
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17. Contact Mode
 High Resolution Images.
 Tip of the probe always touching the sample.
 Fastest of all the topographic modes.
 Because of repulsive forces tip and sample may damage.
 Sensitive to the nature of sample.
 Not good for soft samples.
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19. Non Contact Mode
 Signal-to-noise benefits associated with modulated
signals.
 Oscillating modes can measure images with a small
probe–sample force.
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20. Tapping Mode
 No Capillary effect.
 Amplitude signals are used in feedback.
 Used for Imaging in Air.
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22. Limitations
 AFM can only image a maximum height on the order of
10-20 micrometers and a maximum scanning area of
about 150×150 micrometers.
 The scanning speed of an AFM is also a limitation.
 Highly Dependent on AFM probes.
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23. Applications
 It can image far more biological processes, such as
imaging of proteins.
 Any sample like ceramic material, human cells or
individual molecules of DNA, Dispersion of metallic
Nanoparticles can be imaged.
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24. References
 Atomic force Microscopy by Peter Eatson and Paul West.
 http://hansmalab.physics.ucsb.edu/afmapp.html
 Quazar Technologies Pvt., LTd. Guide section.
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25. Thank you
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