Electric-Field Bit Write-In for Molecular Quantum-Dot Cellular Automata Circuits

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Quantum-dot cellular automata (QCA)was conceptualized to provide low-power, high-speed, general-purpose computing in the post-CMOS era. Here, an elementary device, called a “cell” is a system of quantum dots and a few mobile charges. The configuration of charge on a cell encodes a binary state, and cells are networked locally using the electrostatic field. Layouts of QCA cells on a substrate provide non-von-Neumann circuits in which digital logic, interconnections, and memory are intermingled. QCA supports reversible, adiabatic computing for arbitrarily low levels of dissipation. Here, we focus on a molecular implementation of QCA and describe the promise this holds. This discussion includes an outline of an architecture for clocked molecular QCA circuits and some technical challenges remaining before molecular QCA computation may be realized. This work focuses on the challenge of using macroscopic devices to write-in bits to nanoscale QCA molecules. We use an electric field established between electrodes fabricated using standard, mature lithographic processes, and the field need not feature single-molecule specificity. An intercellular Hartree approximation is used to model the state of an $N-$ molecule circuit. Simulations of a method for providing bit inputs to clocked molecular circuits are shown.