IMAGE FROM AN STM Iron atoms on the surface of Cu(111) Image
from an STM
Slide 3
STM schematic "ScanningTunnelingMicroscop e schematic" by
Michael Schmid - Michael Schmid, TU Wien; adapted from the IAP/TU
Wien STM Gallery. Licensed under Creative Commons Attribution-Share
Alike 2.0-at via Wikimedia Commons - http://commons.wikimedia.or
g/wiki/File:ScanningTunneling Microscope_schematic.png#m
ediaviewer/File:ScanningTunn elingMicroscope_schematic.pn g
Slide 4
Slide 5
Theory of STM: tunneling effect
Slide 6
Tunneling current
Slide 7
VIDEO: TUNNELING EFFECT VIDEO: TUNNELING EFFECT thanks to
http://www.toutestquantique.frhttp://www.toutestquantique.fr
Slide 8
Tunneling current with bias
Slide 9
A little more approximation
Slide 10
What STM can really detect STM detect the electronic state, not
the atom itself. STM detect the electronic state, not the atom
itself. We can detect different electronic state or even bonding by
applying different voltage We can detect different electronic state
or even bonding by applying different voltage
Slide 11
The operation of STM Constant current mode Constant current
mode use the feedback to maintain the tip at constant density of
state position. If the material is the same, this can be seen as
constant distance from the sample. Thus we can get the topography
image of the sample surface Constant height mode Constant height
mode disable the feedback and let tip move in the constant height.
The scan in this mode can be much faster, but can only be done in
the flat surface to avoid the crash of the tip
Slide 12
Positioning The STM tip position was controlled by several
piezoelectrical component The STM tip position was controlled by
several piezoelectrical component For the ease of use, it usually
includes coarse positioner and fine positioner (tube scanner with
tip) For the ease of use, it usually includes coarse positioner and
fine positioner (tube scanner with tip)
Slide 13
Conclusion STM and (AFM) make seeing atom and manipulate the
atom not a dream at all. STM and (AFM) make seeing atom and
manipulate the atom not a dream at all. We can control and play the
single atom. Someone even draw a movie by atoms We can control and
play the single atom. Someone even draw a movie by atoms STM gives
us the direct and extremely localized information about electronic
density of state for the materials. Even the spin can be measured
by the spin- polarized STM. STM gives us the direct and extremely
localized information about electronic density of state for the
materials. Even the spin can be measured by the spin- polarized
STM. STM is suitable to study the material with non-empty density
of state, that is metal, semiconductor STM is suitable to study the
material with non-empty density of state, that is metal,
semiconductor With AFM, even the insulator can be studied directly
With AFM, even the insulator can be studied directly