Understanding a Bisferrocene Molecular QCA Wire - Field-Coupled Nanocomputing: Paradigms, Progress, and Perspectives - page 331

Driver-MUT distance = 0.8 nm (Y-displ = -0.20 nm) Driver-MUT distance = 1.0 nm (Y-displ = 0 nm)

Dot1
Dot2

Dot1
Dot2

0.8 0.8

0.6 0.6

0.4 0.4 Driver

@ logic 0

Driver
@ logic 1

Driver
@ logic 0

Driver
@ logic 1

0.2 0.2

0 0

-0.4 -0.2 0 0.2 0.4 -0.4 -0.2 0 0.2 0.4

X-displacement [nm] X-displacement [nm]

Driver-MUT distance = 1.25 nm (Y-displ = +0.25 nm)

Dot1
Dot2

0.8

0.6

Driver
@ logic 0

0.4

Driver
@ logic 1

0.2

0

-0.4 -0.2 0 0.2 0.4

X-displacement [nm]

Fig. 35. MUT dot charges as function of the driver misalignments (X-displ), in three
case of driver-molecule distance (Y-displ).

driver defects are considered: ideal position (no defects), lateral misalignment
and vertical shift at the ideal driver-molecule distance, vertical shift at a lower
driver-molecule distance. The results in case of ideal position of the driver are
showninFig. 36 (A): the positions (the barycenter of the molecule) of the receiver,
in which it could still encode the two logic states, are highlighted. Two red
circles indicate the working dot of the MUT, that was kept fixed. In case of
driver misalignment equal to X - displ =0 . 5 nm, the region where the receiver
could be safely placed (Fig. 36 (B)) is a little bit wider than the previous case,
especially in the Y direction, but the equivalent voltage at the receiver is quite
lower. A vertical shifting of the driver due to the roughness of the substrate
( Z - displ =0 . 2 nm) is reflected at the receiver level with a SOA that includes
a wide range of both misalignments and higher distances from the molecule
(Fig. 36 (C)). In this case, the values of the equivalent voltage at the receiver
are intermediate, confirming again that the gold roughness (0.20 nm

0.1 nm)
obtained at the experimental level does not affect the information propagation.
In case of a bigger vertical shifting of the driver ( Z - displ =0 . 8 nm), the charge
distribution of the molecule is such that the SOA for the receiver is quite limited,
as shown in Fig. 36 (D). Finally, the simultaneous concurrency of a vertical shift
and a variation in the driver-molecule distance ( Z - displ =0 . 4nm and Y - displ =
−

±

0 . 2 nm) is quantified at the receiver level in a very small SOA, depicted in