Understanding a Bisferrocene Molecular QCA Wire - Field-Coupled Nanocomputing: Paradigms, Progress, and Perspectives - page 314

Fig. 12. Model of driver-molecule interaction.
of ab-initio simulations. Then, switching the driver to a logic 0 (as represented
in Fig. 12 (C)) the target molecule is expected to switch, as well, to the
opposite state.
The amount of charge mentioned here is always referred to the elementary
charge ( e ) as unit of measure and hereinafter the e will be omitted for sake of
brevity.
S I-C - Effect of Switching Field. As already demonstrated in [ 21 ], the
electric field generated by the write-in system of the molecular QCA cells is
called switching field and the direction of the switching field is considered to
be parallel to the working dot axis. The electric field should force the charge
to localize in one of the two active dots, thus writing a logic state in a QCA
molecule. By changing the sign of the switching field, the charge localization
could be led in the opposite dot and, as a consequence, the molecule should
change its logic state. The write-in system could be modeled and simulated
applying a uniform electric field to the molecule as shown in Fig. 13 and the
effectiveness of this method could be evaluated computing the charge distribution
of the molecule: considering for example the oxidized bis-ferrocene and applying
a positive switching field (Fig. 13 (A)) the free positive charge should localize on
Dot2; while in case of negative switching field (Fig. 13 (B)) the charge should be
on Dot1.
Fig. 13. Model of write-in system.