Download Cornil Jerome - Lancaster University

Negative Differential Resistance in Conjugated Molecular Wires:
A Quantum-Chemical Insight
Jérôme Cornil
Laboratory for Chemistry of Novel Materials
Center for Research on Molecular Electronics and Photonics
University of Mons-Hainaut (Belgium)
Conjugated molecular wires inserted into nanopores can be used as
active elements for the fabrication of resonant tunneling diodes (RTDs), whose
I/V characteristics reveal a Negative Differential Resistance (NDR) behavior, i.e.,
an initial raise of the current followed by a sharp decrease as the voltage is
amplified [1]. Several mechanisms have been proposed to explain the origin of
the NDR signal and are still hotly debated. In this contribution, we demonstrate
on the basis of quantum-chemical calculations that the incorporation of saturated
spacers [2] or the introduction of ring twists [3] along conjugated backbones can
promote a NDR behavior in molecular wires; this is simply illustrated by analyzing
the evolution of the one-electron structure of the wires as a function of a static
electric field applied along the chain axis (which simulates the driving voltage
applied in the experiments).
[1] M. A. Reed, C. Zhou, C. J. Muller, T. P. Burgin, J. M. Tour, Science 1997,
278, 252; M. A. Reed, IEEE Proc. 1999, 87, 652.
[2] Y. Karzazi, J. Cornil, J.L. Brédas, J. Am. Chem. Soc. 2001, 123, 10076.
[3] J. Cornil, Y. Karzazi, J.L. Brédas, J. Am. Chem. Soc., in press.