PowerPointPrsentation

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Scanning probe microscopies, courtesy Prof. M.
Hietschold, Technical University Chemnitz

• Nature of Resolution Limits
• Near-Field Principle
• Scanning Tunneling Microscopy / Spectroscopy /
  Manipulation
• Scanning Force Microscopy
• Other Near-Field Microscopies
• Multi-Tip Devices

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• Nature of Resolution Limits
• Near-Field Principle

Restriction of resolution of (conventional)
optical microscope Abbe-Raleigh criterion ?x
0.65 ? / n sin a ? ? / 2 ( ½ ... ¼
µm) diffraction limits resolution
?x
?x
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Near-Field Principle
No diffraction limit Geometrical restrictions
via s, d.
Probing tip
s
Sample
any probing interaction (forces, currents,
light, temperature, ...)
d
Synge 1928
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II. Scanning Tunneling Microscopy /
Spectroscopy / Manipulation
Gerd Binnig, Heini Rohrer Nobel Price in Physics
1986
http//www.chembio.uoguelph.ca/educmat/chm729/STMp
age/stmdet.htm
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Quantum mechanical tunneling
V(x)
V0
E
s
www.rufy.com/STM.ppt
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Tunneling probability
Wave function within the wall (classically
forbidden) fin wall exp (- ? s)
? v2m(V0-E)/h2   Transmission
probability T f(s)2 exp (- 2 ? s)
For V0-E 2 eV and s 1 nm, there causes a
ds of 0.1 s a change dT by a factor of 10 !!!
? Tunneling is highly sensitive to changes
of the barrier width !
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Scanning-Tunneling-Microscopy (STM)
Mesoscopic Topography   including
abberations (Tip artefacts) !     Microscopically
  Profiles of constant LDOS (local
den- sity of states)      STS IT(UT) local
measure- ment dIT/dUT ? LDOS

   
Constant Current Mode
G.Binnig, H.Rohrer 1981
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Coarse movements louse
Fine movements tripode
First operating STM by Binnig and Rohrer
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Piezoelectric tube scanner allows sub-nm
controlled motion with 3 independent degrees of
freedom
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What are we seeing on the atomic scale
? Standard model (Tersoff, Hamann)
Constant current mode probes profiles of
constant local density of states
(LDOS) LDOS(r0, Eµ) ? f?(r0)2 d(E?-Eµ)
?
r0
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UHV Scanning Tunneling Microscope
VT STM
LEED
Preparation chamber
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First atomic-resolution STM image Si(111)7x7 by
Binnig et al. 1983
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Si (111)7x7 Cu (100)
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Tunneling Spectroscopic Imaging
CDW on TaS2 Electronic structure superimposed
to atomic topography
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Inelastic tunneling with emission of photons from
a C60 thin film (mapping of light emission)
(Website of Richard Berndt, Univ. Kiel)
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• Scanning Tunneling Lithography
• Possible mechanisms
• - mechanical impact by tip crashing
• local heating/melting (metglasses)
• local (electron induced) chemical reaction
• (PMMA)
• modification of electronic structure (layered
• materials)
• local electrical force (single atoms)

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Atomic manipulation using the STM
Ag atoms on the surface of a silver crystal
(S.W.Hla et al. PRL 2003)
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Man-made atomic structures
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Quantum stadium and corral
Fe atoms on a Ni surface at 4 K
M.Crommie (Univ. Boston)
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III. Scanning Force Microscopies
Atomic-Force microscope (AFM) G.Binnig, C.F.Quate
1986
http//stm2.nrl.navy.mil/how-afm/how-afm.htmlSPM
20concept
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Atomic-Force Microscopy
Contact modus
Universal interaction
Force-Distance Spectroscopy F(s)
Nanoindenter local mech. surface parameters
as bulk modulus, hardness, ...
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Control circuit for contact mode AFM
http//stm2.nrl.navy.mil/how-afm/how-afm.htmlSPM
20concept
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Vertical and lateral force measurement
http//stm2.nrl.navy.mil/how-afm/how-afm.htmlSPM
20concept
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Nanoscope IIIa
http//www.che.utoledo.edu/nadarajah/webpages/what
safm.html
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Dynamical Scanning Force Microscopy
Non-Contact Modus Dynamical Modus
m d2x/dt2 - k ?x - mg - Fext(x)
Fext(x) Fext(x0) ?Fext(x)/?xx0 ?x
... k ? k k - ?Fext(x)/?xx0
Driven oscillator m d2x/dt2 - k ?x -
m? dx/dt - F0 ei?t x x0(?) ei?t x0(?)
F0 / ?2 - i?? - ?02 ?02 k/m
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Application True 3-dimensional surface
topography
Nucleosomal DNA Storage disc
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Imaging artefacts by tip-induced abberations
Especially important on the nm- and µm-scale !!!
http//spm.phy.bris.ac.uk/techniques/AFM/
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Surface lithography by local anodic oxidation
http//www.rhk-tech.com/briefs/AFMoxidation/
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Force spectroscopy
Interaction force between two complementary
strands of DNA, measured by AFM. "Relative
surface displacement" is the distance between the
tip and sample relative to the position at which
1000 piconewtons (pN) of force is reached.
Measurements are recorded both as the tip and
sample are brought together (thin trace) and as
they are separated (thick trace) (D.R. Baselt, et
al., to appear in Proc. IEEE 85, 1997).
http//www.aip.org/png/html/afm.htm
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IV. Other Near-Field MicroscopiesNear-field
scanning optical microscopy (NSOM)
http//physics.nist.gov/Divisions/Div844/facilitie
s/nsom/nsom.html
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http//physics.nist.gov/Divisions/Div844/facilitie
s/nsom/nsom.html
Shear force (topography), transmission NSOM, and
fluorescence NSOM images of a phase separated
polymer blend sample.
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Scanning thermal microscope (SThM)
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V. Multi-Tip Devices
Despite of all revolutionary advantages there
remains a basic problem working with only one
slowly moving tip restricts efficiency e.g. in
lithography dramatically Way-out many
independently parallel operating tips !
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The First Ideas of Miniaturization
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The Millipede
1024 Cantilever-Array for Mass-Storage Application
Website of IBM Zurich Research Laboratory
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Final Conclusions

• SPM made possible nanaoanalysis and
  nanomanipulation
• SPM is still in developing state
• SPM is a challenge for young, flexible and
  intelligent
• girls and boys
• There is (still) plenty of room on the bottom !