Transcript 2011 AFM NANOweek Presentation and Image Library

Notre Dame extended Research Community
The Atomic Force Microscope
Michael Crocker
Valerie Goss
Rebecca Quardokus
Natalie Wasio
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The Braille Game!
Can you feel the surface and identify the features?
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What is nano?
10-9 meters (one billionth of a meter)
Objects between 1-100 nm
1 mm = 1000 μm
μm, micrometer, micron
1 μm = 1000 nm
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Individual fibers are 18 ± 1 μm
How many mm?
How many nm?
Blue mouse
pad 400X
How can we visualize or “see” such small items?
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The first AFM
Invented and built in 1985 by
Calvin F. Quate , Gerd Binnig,
and Christoph Gerber.
This is the first
Atomic Force Microscope.
The AFM works by ‘touching’
objects with the probe and
reading the surface rather
than looking at them.
sciencemuseum.org.uk
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What is the AFM?
An analog!
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AFM Chip, Cantilever + Tip holder
http://www.tedpella.com/prob
es_html/budgetsensors.htm
7/13/11
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AFM cantilever and AFM tips
The tip is roughly 20 µm long, the cantilever is 450 µm in length and
20-50 µm wide, and the thickness is usually 3-4 µm thick.
www.veeco.com, 7/13/11
http://www.tedpella.com/prob
es_html/budgetsensors.htm
7/13/11
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Basic operation of the AFM
AFMs monitors the forces of
attraction and repulsion
between a tip and a sample
surface
The tip is attached to a
cantilever which moves up and
down in response to forces of
attraction or repulsion with the
sample surface
Movement of the cantilever is
detected by a laser and
photodetector
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AFM Schematic
Let’s talk
about
contact
mode
Actuator contains a
piezoelectic crystal
that expands and
contacts as a
voltage is applied
across its crystal
surfaces…a few
hundred volts can be
applied to move the
scanner tens of
microns
Nanosurf AFM acquires an image by scanning a sharp probe
across the surface
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Two common AFM system designs
Sample moves
relative to the tip
Tip moves
relative to the sample
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The powerful, versatile AFM
Resolutions:
X and Y 2 -10 nm
Z
0.05 nm
Microstructure of solids:
CD, glass beads, circuits
Biological samples:
skin cross section, viruses,
bacteria, blood, DNA and RNA
~30 um scan
http://www.nanotech-now.com/Art_Gallery/antonio-siber.htm
July 13, 2011
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Feedback loop and gains
To make a
topographical image
in contact mode, a
feedback loop is
implemented to keep
the deflection of the
cantilever constant
as the Z height
changes to bumps on
the surface.
The topographical
image is created by
recording the Z output
as a function of x and y
position.
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Borrowed image to illustrate scanning
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Limitations on the tip size
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Double effect – tip artifact
Salt crystals imbedded in a polymer matrix
borrowed image
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Gains control
In which image are the gains too high, too low, or
just about right?
borrowed image
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Thank you!
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AFM Image Library
Dan Witt’s AFM images – calibration grid
Mishawaka High School Teacher, July 2010
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Silicon calibration grid, vgoss – AFM
Ram memory chip, vgoss - AFM
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Ram memory chip, vgoss - AFM
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CD, vgoss - AFM
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staphylococcus aureus bacteria on glass
substrate, vgoss -AFM
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staphylococcus aureus bacteria, on
glass substrate, vgoss - AFM
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2 nM DNA origami in air, vgoss -AFM
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2 nm DNA origami in liquid, vgoss - AFM
2.36 nm
1.0µm
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0.00 nm