A model of clocked electric field inputs for molecular quantum-dot cellular automata.

Quantum-dot cellular automata (QCA) is a low-power, high-speed, beyond- CMOS approach to general-purpose computing [1]. Elementary devices called “cells” are implemented using mixed-valence molecules with redox centers having a few quan- tum dots. These support three distinct localized electronic states labeled “0”, “1”, and “Null”. Cells can be clocked to either the “Null” state or an active (“0” or “1”) state using the vertical component of an applied electric field. Clocking provides power gain for restoring weakened signals and allows synchronous control of QCA circuits. In this paper, clocked molecular QCA circuits are simulated in the presence of an applied input field, using the intercellular Hartree-Fock approximation [2]. In- put circuits and down-stream circuits function in the presence of the input field and unwanted field fringing from electrodes. This emphasizes that widely-available fabri- cation techniques may be used to form electrodes for writing bits to molecular QCA circuits.