Making Contact to Molecules: Interfacing to the Nanoworld

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Making Contact to Molecules Interfacing to the
Nanoworld

• Peter Grutter
• Physics Department
• McGill University
• NSERC, FCAR, CIAR, McGill, IBM, CIHR,
  GenomeQuebec, CFI, NanoQuebec

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What is Nanoelectronics?
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What is Electronics?

• By electronics we mean the handling of
  complicated electrical wave forms for
  communicating information, probing (such as in
  radar) and data processing.
• Data processing is the result of one complex
  stream of information interacting with another.
• This requires non-linear behavior, otherwise
  information just gets passed on from one place to
  the other.
• (Landauer, Science 1968)

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Molecular electronics the issues

• Contacts
• Structure-function relationship between transport
  process and molecular structure
• Dissipation

• Crosstalk (interconnects)
• Architecture
• I-O with a trillion processors
• Fault tolerance
• Manufacturing costs

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Does atomic structure of the contact matter?

• YES !

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Does atomic structure of the contact matter?
Mehrez, Wlasenko, et al., Phys. Rev. B 65,
195419 (2002)
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Comparison of Experimental and Modeling Results

• Mehrez, Wlasenko, et al., Phys. Rev. B 65,
  195419 (2002)

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Calculating Conductance

• Traditional infinite, structureless leads -gt
  periodic boundary conditions.
• but
• - result depends on lead size!
• - bias not possible due to periodic boundary
  condition!

Jellium lead
Jellium lead
molecule
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Calculation of electrical transport
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ab-initio modelling of electronic transport
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DFT plus non-equilibrium Greens Functions

• J. Taylor, H. Guo , J. Wang, PRB 63, R121104
  (2001)
• 1. Calculate long, perfect lead.
• Apply external potential V by shifting energy
  levels
• -gt create electrode data base and get potential ?
  right

lead
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2. Solve Poisson equation for middle part
(device plus a bit of leads) match
wavefunctions ? and potential as a function of V
to leads (use data base) in real space.
3. ? calculated with non-equilibrium Greens
functions (necessary as this is an open system).
This automatically takes care of bound states
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Molecular electronics the issues

• Contacts
• Structure-function relationship between transport
  process and molecular structure
• Dissipation

• Crosstalk (interconnects)
• Architecture
• I-O with a trillion processors
• Fault tolerance
• Manufacturing costs

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Reliable, chemically well defined contacts

• Cui et al. Nanotechnology 13, 5 (2002), Science
  294, 571 (2001)

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Low-T UHV STM/AFM/FIM

• 140K,
• 10-11mbar
• quick change between
• FIM - AFM/STM mode
• Stalder, Ph.D. Thesis 1995
• Cross et al. PRL 80, 4685 (1998)
• Schirmeisen et al. NJP 2, 29.1 (2000)

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Field Ion Microscopy (FIM)
E. Muller, 1950s
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FIM of W(111) tip
Imaging at 5.0 kV
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FIM of W(111) tip

• Imaging at 5.0 kV
• Manipulating at 6.0 kV

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FIM of W(111) tip
Imaging at 5.0 kV Manipulating at 6.0 kV
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FIM of W(111) tip

• Imaging at 5.0 kV
• Manipulating at 6.0 kV

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Single Au atom on W(111) tip

• Imaged at 2.1 KV

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W(111) tip on Au(111)

• Cross et al.
• PRL 80, 4685 (1998)
• Schirmeisen et al,
• NJP 2, 29.1 (2000)

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Molecular Dynamics Simulations

• U. Landman et al, Science 248, 454 (1990)

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W(111) trimer tip on Au(111)

• Ead 21 eV
• l 0.2 nm

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Tip relaxation effects
W tip on Au(111) surface
Hofer, Fisher, Wolkow and Grutter Phys. Rev.
Lett. 87, 236104 (2001)
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Tip relaxation effects
W tip on Au(111) surface
Hofer, Fisher, Wolkow and Grutter Phys. Rev.
Lett. 87, 236104 (2001)
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F(z) and I(z) of W(111) trimer on Au(111)

• Schirmeisen et al,
• NJP 2, 29.1 (2000)

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Yan Sun, Anne-Sophie Lucier Henrik Mortensen
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The samples (measurements in progress)

• A) Au(111)
• 170 nm170 nm,
• B) mixture of C6 and C8 thiol (ratio 61) on
  Au(111) 450nm450nm
• C) C8 thiol, 6nm6nm
• D) C8/C8 dithiol
• 36nm36 nm.

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Stimulation of Single Ligand-Gated Ion Channels
Goal To study channel gating kinetics and
binding forces, while maintaining precise
control of agonist location.
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Tethering Scheme GABA v.s. GABOB

• Is it possible to tether a molecule of GABA
  without destroying its functionality?

N. Cameron, B. Lennox (McGill)
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Tethering Scheme Polymer Linker
Au -S-(CH2)12-(O-CH2-CH2)23-O-GABOB
alkanethiol PEO
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Planar Patch-Clamp Chips
Fertig et. al. Phys Rev E Stat Phys Plasmas
Fluids Relat Interdiscip Topics 2001
Oct64(4-1)040901.
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Loading Rate Dependent Unbinding
Good review Evans, E. Annu. Rev. Biophys.
Biomol. Struct. 2001. 30105-28.
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F(z) as a function of pulling speed
Allows the determination of energy barriers and
thus is a direct measure of the energy
landscape in conformational space.
Clausen-Schaumann et al., Current Opinions in
Chem. Biol. 4, 524 (2000)
Merkel et al., Nature 397, (1999)
Evans, Annu. Rev. Biophys. Biomol. Struct., 30,
105 (2001)
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Summary

• Tools, both experimental and theoretical, drive
  our capabilities to understand the nanoworld!
• We develop and apply SPM techniques to interface
  to
• molecules and neurons
• in order to understand
• structure - property relationships

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14 graduate students, 6 post doctoral fellows
Supported by NSERC, FCAR, CIAR, NanoQuebec CFI,
IBM, GenomeQuebec, CIHR McGill Dawson Scholarship