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Electrical Conduction through Molecules

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School of Electrical and Computer Engineering. Purdue ... Homo. Eta=0.5. Eta=1. 9/20/09. 8. Two Experimental Results. M.A. Reed et. al., Science 278, 252 (1997) ... – PowerPoint PPT presentation

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Title: Electrical Conduction through Molecules


1
Electrical Conduction through Molecules
  • Geng-Chiau Liang
  • School of Electrical and Computer Engineering
  • Purdue University

Picture from Mark Reeds Group
2
Outline
  • I. Introduction
  • Motivations
  • Fundamental Concepts
  • II. Modeling
  • Calculation Approaches
  • Results and Discussions
  • III. Conclusions

3
Switches (Molecular Junction)
PN Junction
4
Resonant Tunneling Structure
10001 on-off peak-to-valley ration
5
SAMFETs V.S. MOSFETs
SAMFETs
MOSFETs
Ref Schon, et al., nature Vol. 413, pp. 713 2001
Pierret, Semiconductor Device Fundamentals
6
Fundamental Concepts
Lumo
Device (Molecule)
V0 Ef1Ef2Ef
qV
Homo
7
Two-state Toy Model
Eta0.5
Eta1
8
Two Experimental Results
Benzene 1,4-Dithiolate (PDT, BDT)
Schoen, 2002
9
Modeling (Approaches)
E-field
F, S
P. Damle, et al, Phys. Rev. B (2001)
10
Formulas
Ref Datta, S. Electronic Transport in Mesoscopic
System Cambridge University Press, 1997
11
Results and Discussions (I)
Simulation
Experiment Schoen, 2002
12
Results and Discussions (II)
Vg
Vd
13
Results and Discussions (III)
  • Reasons of Bad Results
  • Not real voltage profile in the molecule (Image
    charge effect, Gaussians limitation, and so on)
  • Unknown interactions

I
14
Summary
  • I. Successfully using method of DFT coupling
    with NEGF and Self-energy approach to model
    behavior of molecular devices
  • II. Important topics in future
  • Ef in Molecules?
  • Interaction between Molecules and Surface
  • Correct voltage profile through Molecule

15
Acknowledgement
  • Professor Jorge Rodriguez
  • Group mates
  • Professor Supriyo Datta, A. Ghosh, M. Paulsson,
    P. Damle, T. Rakshit, and F. Zahid.

16
Energy states
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