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4 Toward More Sophisticated Problems
(a)
(b)
(c)
(d)
Fig. 4.4 NBO patterns of a σ lone pair of S, b Au–S bonding orbital, c π lone pair of S, and d Au–
S antibonding orbital in the binding structure in Fig. 4.3b. Reprinted from Fueno et al. (2006).
Copyright 2006, with permission from Elsevier
pairs of the S atom.
4.1.2 Molecular Field-Effect Transistor (FET)
In molecular nanotechnology, it is often required to estimate the current-voltage (I −
V ) characteristics of electrically conductive molecular wire connecting between two
nanoelectrodes. A more sophisticated molecular wire is equipped with a quantum dot
in its middle area separated by energy barriers from the wire portions as illustrated
in Fig. 4.5. This kind of fabrication is of importance to design molecular field-effect
transistor (FET). In this subsection, theoretical examination of electric behavior is to
be described by consideration of design toward molecular wire model with a quantum
dot consisting of single-walled carbon nanotube (SWCNT) of chiral indices (6, 6)
with a finite length as an example, theoretical examination of its electric behavior is
to be described.
Drain
Source
Gate
Quantum
dot
Capacitive coupling
Tunneling junction
as energy barrier
Tunneling junction
as energy barrier
Molecular wire
as conductive part
Molecular wire
as conductive part
10 – 20 nm
Anchor atom
Anchor atom
Fig. 4.5 Schematic drawing of a molecular field-effect transistor (FET) device