Understanding a Bisferrocene Molecular QCA Wire - Field-Coupled Nanocomputing: Paradigms, Progress, and Perspectives - page 304

Understanding a Bisferrocene Molecular
QCA Wire

B

Azzurra Pulimeno, Mariagrazia Graziano (

) , Aleandro Antidormi,
Ruiyu Wang, Ali Zahir, and Gianluca Piccinini

Dipartimento di Elettronica e delle Telecomunicazioni,
Politecnico di Torino, Turin, Italy
[e-mail]

Abstract. Molecular QCA are considered among the most promising
beyond CMOS devices. Frequency as well as self-assembly characteris-
tics are the features that make them most attractive. Several challenges
restrain them for being exploited from a practical point of view in the
near future, not only for the diculties at the technological level, but
for the inappropriateness of the tools used when studying and predicting
their behavior.
In this chapter we describe our methodology to simulate and model
sequences of bisferrocene molecules aimed at understanding the behavior
of a realistic MQCA wire. The simulations consider as variables distances
between successive molecules, as well as different electric field applied (in
terms of input and of clock). The method can be used to simulate and
model also other more complex structures, and perspectives are given on
the exploitation of the achieved results.

1 Introduction on Molecules for QCA

1.1 Molecular Implementation

Molecules, with their moving charges, present well-suited properties to perform
information storage and processing in the ways expressed by the QCA paradigm
[ 1 ]. Molecular charges can localize, under the influence of an external field, in
determined locations of the molecule, resulting in different spatial charge con-
figurations. Thus, molecular systems can be exploited as basic cells for binary
computing: each configuration encodes a binary state and a switch from a state
of the cell to another results from a charge flow through tunneling paths within
the molecule itself. Molecular sites where charge localization occurs are called
redox centers and represent the dots of the QCA device; they are effectively capa-
ble of attracting or releasing an electron thus becoming negatively or positively
charged.
Since a molecule is neutral, a better performance is obtained with the oxidized
and reduced forms of the same molecule; in the oxidized molecule, an electron
is missing and its net charge is positive; in the reduced form, the molecule has
gained an electron picking up a negative net charge.