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Fig. 3.40 Scheme of the
formation of molecular
layers using the Langmuir-
Blodgett method: (a)
amphiphilic molecules on
the water surface, (b)
compression of the film of
amphiphilic molecules, (c)
transfer of the film to the
substrate
The electrical characteristics of monomolecular films of [2] rotaxane R, mea-
sured in the course of experiments, showed that the chosen molecule switches from
one state to another due to a voltage in the range between 2 V and +2 V applied to
the film (Fig. 3.41 ). To fabricate a memory device based on the molecules of
[2] rotaxane R, a unique technique was used employing the technological principle
“bottom-up.” The main characteristic features of this technique are:
- The so-called crossbar architecture of the memory device
- Imprint lithography which allows to form nanometer-size elements on the
substrate surface
- The Langmuir-Blodgett method for fabricating monomolecular films of ori-
ented [2] rotaxane R molecules
The crossbar architecture (Fig. 3.42 ) comprises two sets of linear electrodes
placed perpendicular to each other, with rotaxane molecules situated between them.
Thus, the i , j th memory element is the entire population of molecules between the i th
and the j th electrodes. A set of electrodes is transferred onto the substrate surface by
imprint lithography (Fig. 3.43 ). To this end a thin polymer layer, with a system of
grooves for the electrodes imprinted by a solid stamp, is applied to the substrate.
After removing the stamp and polymer residues, metal is sprayed into the grooves
to fill them. In a final step the polymer layer is removed from the substrate.
To assemble a storage device monomolecular rotaxane film was applied to the
substrate with the generated set of electrodes, and on top of it a second substrate was
placed with the electrodes perpendicular to the electrodes of the first electrode set
(Fig. 3.44 ).
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