e xploring the n anolandscape scanning probe microscopy
DESCRIPTION
E XPLORING THE N ANOLANDSCAPE Scanning Probe Microscopy. I MAGE G ALLERY. The Nanoscale. Atomic diameter ~ 0.3 nm = 3 Å Microelectronics interconnect ~ 0.25 µm http://www.intel.com/technology//itj/q31998/articles/art_1.htm Red blood cell (5µm). Proximal Probes. History. Topografiner - PowerPoint PPT PresentationTRANSCRIPT
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EXPLORING THE NANOLANDSCAPEScanning Probe Microscopy
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IMAGE GALLERY
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The Nanoscale
• Atomic diameter ~ 0.3 nm = 3 Å
• Microelectronics interconnect ~ 0.25 µm– http://www.intel.com/technology//itj/q31998/articles/art_1.htm
• Red blood cell (5µm)
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Proximal Probes
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History
• Topografiner
• Tunneling through a controllable vacuum gap
• Scanning Tunneling Microscope
• Atomic Force Microscope (Scanning Force Microscope)
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Operation of a Scanning Probe Microscope
• Scanning with sub-Angstrom precision• Probe detection (e.g., current, force, position, …)• Electronics processing• Computer control• Image processing• Vibration isolation• Environmental control (e.g., vacuum, atmosphere,
fluid; temperature)
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Scanning Tunneling Microscope
Omicron
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Scanning Force Microscope
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Tunneling
• One-dimensional tunneling
• Density of electronic statesof sample and tip
2m1/ 2
2
I So 2
To 2
e 2d
So
= sample wavefunction
To
= tip wavefunction
= workfunction
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Forces
non-contact Distance
tip to sample separation
repulsive force
attractive force
contact
Force
Trace
Retrace
F k x
Typical:
k 0.3N / m
x = 10nm
F = 3nN
Contact vs. non-contact modes ...Forces to atto-newton (10-18 N) range ...
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Themes
• IMAGING
• INTERROGATING
• MANIPULATING
atoms and nanoscale objects
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IMAGING
ATOMS AND NANOSCALE OBJECTSATOMS AND NANOSCALE OBJECTS
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Large-scale Atomic-scale
Graphite4.2 nm 4.2 nm
STM
Gold Grating30 µm 30 µm
STMDiNardo
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Semiconductor Surfaces - Si(100)
Tilted dimer
SymmetricDimer
Unreconstructed
L) OccupiedR) Unoccupied
Hamers, 1986
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Temperature-dependent Reconstructions
• Low-temperature Si(100)-c(42) vs. (2 1)– Domain boundaries, p(2 2) regions
Wolkow, 1992
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Homoepitaxial Growth - Si(100)
Mo, 1988
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Fractional Images
• Probing atomic orbitals– Frequency-modulated
Atomic Force Microscopy
– Si tip / Si(111)-77
Si atom
Giessibl, 2000
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Metal Surfaces
Wahlström, 1998
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0.4 ML Ag/Cu(110)
c(102) model
a, b) 230230 nm2
c) 5.45.4 nm2
d) 3.83.8 nm2Sprunger, 1996
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Interfaces - Cross-sectional Imaging
Ohmori, 1999
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Molecular Adsorption - CO/Pt(111)
Pederson, 1996
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Coatings - Colloidal Latex Particles
VacancyRecoveryFaulted LayerInterstitial DefectLine DefectOrientation ChangeBrennan, 2000
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Coatings - Latexes
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Carbon Nanotubes
Odom, 1998
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Overlapping Nanotubes
Avouris, 1999
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Nanotube Shapes and Forces
Avouris, 1999
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Biological Macromolecules - Collagen
Brennan, 2000
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Biological Macromolecules - Fibronectin
Brennan, 1999
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INTERROGATING
ATOMS AND NANOSCALE OBJECTSATOMS AND NANOSCALE OBJECTS
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Visualizing the Tunnel JunctionSTM-TEM
Naitoh, 1996
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Scanning
Ohnishi, 1998
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Bias-dependent imaging ~ Graphite
DiNardo
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Bias-dependent imaging ~ GaAs(110)
• GaAs(110) (cleaved) surface
Feenstra, 1987
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Spectroscopy ~ on the Nanoscale
• Beam techniques average over surface species• SPM techniques measure density of states related
to the atom (or molecule) under the tip– electronic spectrum - measure dI/dV [or (dI/dV)/(I/V)]
Hamers, 1986
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Electronic SpectroscopyAtom by Atom
• Reconstructed Si(100)-21 surface– Dimers– Occupied electronic states of dimers (between atoms)
– Unoccupied electronic states of dimers (away from atoms)
Hamers, 1986
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Defects
• Atomic-sized defects– Al/Si(111)-√3√3 structure
– different electronic states
Hamers, 1988
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Chemical Reactivity
NH3 reacted with the Si(111)-77 surface
Wolkow, 1988
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Vibrational SpectroscopyMolecule by Molecule
Lauhon, 2000
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Chemical Reactions
Lauhon, 2000
Electron-induced dissociation product -pyridine on Cu(100) at 8K
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Surface DiffusionChasing Atoms with the Atom Tracker
Swartzentruber, 1996
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H-enhanced diffusion of Pt atoms
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Horch, 1999
an STM movie ...
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Electrostatic Force Microscopy (EFM)
• Application– Topography of integrated circuit
– Monitoring an active integrated circuit
Digital Instruments, www.di.com
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Scanning Capacitance Microscopy
Nakakura, 1999
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Magnetic Force Microscopy (MFM)
• Magnetic tip interaction with surface• Application: Disk drive
– Morphology
– Magnetic structure
Digital Instruments, www.di.com
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Scanning Chemical Microscopy
• Measure chemical interaction between the tip and sample
• Functionalize the tip with hydrophobic or hydrophilic species
• Scan over surface and measure adhesion force or friction force
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Carbon Nanotube Tips- Functionalization -
Wong, 1998
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Scanning Chemical Microscopy
Frisbee, 1994 / Wong, 1998
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Adhesion Forces
Wong, 1998
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Friction Force Microscopy
• Macroscopic friction forces
• Microscopic friction forces
Ffr N
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Polymer Thin Films
Nie, 1999
Polypropylene film(a) AFM + (b) FFM, (c) non-contact AFM
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nN Bond ForcesStrength of a Covalent Bond
Grandbois, 1999
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Ballistic Electron Emission Microscopy - BEEM
• Three-terminal setup• Probe potential barrier at interface between metal
and semiconductor• Electrons are forward-focused without scattering
(ballistic)
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BEEM
Bell, 2000
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MANIPULATING
ATOMS AND NANOSCALE OBJECTSATOMS AND NANOSCALE OBJECTS
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Moving Atoms
• Xe– Physisorbed noble gas - (low temperature)
• Fe– Quantum “Corrals”
Eigler, 1991 / Crommie, 1993
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Confined Electrons
• Reflections of free electron (waves) at boundaries
• Standing waves solutions
• One-dimensional free electron solution (infinite barrier)
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Quantum Corral
Crommie, 1993
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Forming Nanowires
Ohnishi, 1998
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Nanowire modeling
Okamoto, 1999
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Measuring Currents through One- and Two-atomic-row Nanowires
Ohnishi, 1998
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Nanoelectronics
• Nanoscale channels
• Nanoscale objects
• Currents - description based on quantum-mechanical transport
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Nanoscale patterning
• Desorption– H-terminated Si(100)
• Deposition– Fe(CO)5
Adams, 1996
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Nanotube Circuits
Avouris, 1999
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Nanotube FET
Martel, 1998 / Avouris, 1999
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Diamond-like Carbon Films
STM AFM
Mercer, 1996
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Protein-folding Forces
Rief, 1999
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Comparison of Force Curves
Rief, 1999
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Related Techniques
• Scanning Near-field Optical Microscopy
• Scanning Thermal Microscopy
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Some Acronyms ...
• STM• STS• AFM• TM-AFM• FFM, LFM• CFM