Transcript STM/AFM Images - Purdue University

STM / AFM
Images
Explanations from
www.iap.tuwien.ac.at/www/surface/STM_Gallery/stm_schematic.html
www.almaden.ibm.com/vis/stm/lobby.html
www.nanoscience.com/education/STM.html
Scanning Tunneling Microscopy
In 1981, the Scanning Tunneling microscope
was developed by Gerd Binnig and Heinrich
Rohrer – IBM Zurich Research Laboratories in
Switzerland (Nobel prize in physics in 1986).
This instrument works by scanning a very sharp
metal wire tip over a sample very close to the
surface. By applying an electric current to the tip
or sample, we can image the surface at an
extremely small scale – down to resolving
individual atoms.
Tunneling
Quantum mechanics tells us that
electrons have both wave and
particle like properties.
Tunneling is an effect of the
wavelike nature. The top image
shows us that when an electron
(the wave) hits a barrier, the
wave doesn't abruptly end, but
tapers off very quickly. For a
thick barrier, the wave doesn't
get past.
The bottom image shows the
scenario if the barrier is quite
thin (about a nanometer). Part of
the wave does get through, and
therefore some electrons may
appear on the other side of the
barrier.
The number of electrons that will actually tunnel is
very dependent upon the thickness of the barrier.
The actual current through the barrier drops off
exponentially with the barrier thickness.
To extend this description to the STM: The barrier
is the gap (air, vacuum, liquid) between the
sample and the tip. By monitoring the current
through the gap, we have very good control of the
tip-sample distance.
Computer software is used to add color
and analyze the captured data.
SCAN IMAGE
DEMONSTRATE ANALYSIS
Use images from Science Express laptop.
Diffraction Grating
3-D View: Diffraction Grating
Diffraction Grating - Analysis
Red Blood Cells
Red Blood Cells – Analysis
Graphite
3-D View : Graphite
Graphite - Analysis
Graphite - magnified
Graphite - magnified
Graphite - magnified
Graphite – magnified – AGAIN!
Graphite – magnified – AGAIN!
Graphite – magnified – AGAIN!
Purdue University
Physics Department
http://www.physics.purdue.edu/nanophys/stm.html
Atomically flat
gold film.
Atoms of Highly
Oriented Pyrolytic
Graphite (HOPG).
Atomic Force Microscopy
In principle, the AFM works like the
stylus on an old record player.
There is actual contact between the
probe tip and the sample.
The following explanation taken from
www.chembio.uoguelph.ca/educmat/chm729/afm/general.htm
Atomic Force Microscopy
1. Laser
2. Mirror
3. Photodetector
4. Amplifier
5. Register
6. Sample
7. Probe
8. Cantilever
Atomic Force Microscopy
www.wikipedia.com
AFM IMAGES
http://jpk.com/spm/gallery1.htm
JPK INSTRUMENTS
GERMANY
DIC (Differential Interference
DIC (Differential Interference Contrast) image
ofimage
human
Contrast)
of human lymphocyte
lymphocyte metaphase
metaphase chromosomes on microscopy
slide
chromosomes on microscopy
slide
dimensions 83 µm * 83 µm
dimensions 83 µm * 83 µm
height image (left, 3D plot) and
corresponding optical
microscope image (above, bright
field) of a
moth wing scale
height image (left, 3Dintermittent
plot)contact
andmode
field 10 µm * 10 µm
corresponding optical scan
microscope
z-range 0 - 1.7 µm
image (above, bright field) of a
moth wing scale
intermittent contact mode
scan field 10 µm * 10 µm
z-range 0 - 1.7 µm
Height image (left, 3D plot) and corresponding
optical microscope image (above, phase
contrast)
of a moth's eye - region of three adjacent
facets.
intermittent contact mode
scan field 10 µm * 10 µm
z-range 0 - 6.0 µm
Atomic force microscope topographical scan of a glass surface. The micro and nano-scale features of
the glass can be observed, portraying the roughness of the material.
Constructed at the Nanorobotics Laboratory at Carnegie Mellon University (http://nanolab.me.cmu.edu).
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