Title: Electrical Conduction through Molecules
1Electrical Conduction through Molecules
- Geng-Chiau Liang
- School of Electrical and Computer Engineering
- Purdue University
Picture from Mark Reeds Group
2Outline
- I. Introduction
- Motivations
- Fundamental Concepts
- II. Modeling
- Calculation Approaches
- Results and Discussions
- III. Conclusions
3Switches (Molecular Junction)
PN Junction
4Resonant Tunneling Structure
10001 on-off peak-to-valley ration
5SAMFETs V.S. MOSFETs
SAMFETs
MOSFETs
Ref Schon, et al., nature Vol. 413, pp. 713 2001
Pierret, Semiconductor Device Fundamentals
6Fundamental Concepts
Lumo
Device (Molecule)
V0 Ef1Ef2Ef
qV
Homo
7Two-state Toy Model
Eta0.5
Eta1
8Two Experimental Results
Benzene 1,4-Dithiolate (PDT, BDT)
Schoen, 2002
9Modeling (Approaches)
E-field
F, S
P. Damle, et al, Phys. Rev. B (2001)
10Formulas
Ref Datta, S. Electronic Transport in Mesoscopic
System Cambridge University Press, 1997
11Results and Discussions (I)
Simulation
Experiment Schoen, 2002
12Results and Discussions (II)
Vg
Vd
13Results 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
14Summary
- 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
15Acknowledgement
- Professor Jorge Rodriguez
- Group mates
- Professor Supriyo Datta, A. Ghosh, M. Paulsson,
P. Damle, T. Rakshit, and F. Zahid.
16Energy states