1. Research Center for Applied Sciences
Electrical Transport and Current-driven Dynamics in Molecular Junctions
Chao-Cheng Kaun (關肇正)
Research Center for Applied Sciences
Academia Sinica
Collaborators:
D. A. Luzhbin (RCAS)
N. L. Yoder, R. Jorn, T. Seideman and M. C. Hersam (Northwestern Univ., USA)
July 3, 2010

2. Outline:
High- and low-conductance in alkanediisothiocyanate single-molecule junctions
Phys. Rev. B 81, (2010)
2. Current-Driven Desorption at the Organic Molecule–Semiconductor Interface: Cyclopentene on Si(100)
Current-Driven Phenomena in Nanoelectronics, in press (Pan Stanford, Singapore, 2010)

3. 1. High- and low-conductance in alkanediisothiocyanate single-molecule junctions:
Bridging up the theory and experiment is one of the key issues involving the progress of molecular electronics.

4. 1. High- and low-conductance in alkanediisothiocyanate single-molecule junctions:
Experimental results
J. Phys. Chem. C 111, (2010)
Is the HC and LC due to atop-hollow and atop-atop contact geometries?

5. Experimental results Nature 395, 780 (1998)
Faraday Discuss. 131, 145 (2006)

6. Our model:
The HC and LC may comes from the geometric configurations of electrodes

7. Sumary:
Our first-principles calculated results are agree with measured data
The HC and LC may comes from the geometric configurations of electrodes

8. Molecular electronic devices + silicon microelectronic technology
2. Current-Driven Desorption at the Organic Molecule–Semiconductor Interface: Cyclopentene on Si(100)
Molecular electronic devices + silicon microelectronic technology
The stability of organic molecules on semiconductors must be established.
Saturated organic/silicon systems offer stability with respect to current-induced failure of silicon-based molecular electronics.
S. N. Patitsas et al., Surf. Sci. 457, L425 (2000).

9. Elevated sample bias (threshold voltage: -2.5 and 3.5)
Desorption of cyclopentene from Si(100)
Experimental results
-2V, nA
Elevated sample bias (threshold voltage: -2.5 and 3.5)
-2V, nA
N. L. Yoder et al., PRL 97, (2006)

10. Previous studies: benzene bound to Si(100) with π-orbital character
Low-lying ionic resonances
S. Alavi, et al., PRL 85, 5372 (2000).
Cyclopentene on Si(100):
A saturated molecule
Why threshold voltages is so small (-2.5 V and 3.5 V)?

11. Yield = N*e/(I*t) Experimental results
The yield is a factor of lower than for benzene/Si(100) or chlorobenzene/Si(111).
A new avenue for desorption dynamics!

12. Our model: Cyclopentene -2.49 6.90 Cyclopentene+Si -2.00 2.95
HOMO LUMO
Cyclopentene Cyclopentene+Si
Hybridization introduces new states into the gap

13. PDOS peaks and the localized orbitals:
The positive ion
lifetime 94 fs
The negative ion
lifetime 257 fs

14. Geometries of cyclopentene on a Si9H12 cluster:
Neutral molecule
Positive molecule
Negative molecule

15. Sumary:
Hybridization introduces new states into the gap leading to lower threshold voltages
New desorption pathways are found in a cyclopentene/silicon system.