What Makes a Good Molecular-Scale Computer Device?

Abstract

The lithographically-produced CMOS transistor has been the key technology that has enabled the information revolution. However, in the near future the limitations, both technical and economic, introduced by lithographic fabrication may inhibit further decreases in feature size. Chemically assembled electronic nanotechnology (CAEN) is a promising alternative to CMOS for constructing circuits with device sizes in the tens of nanometers, far smaller than is thought possible using lithography. In this paper we examine and contrast the constraints imposed by lithographic versus CAEN fabrication; the key limitation is that three-terminal devices, such as transistors, will be impractical at the nanoscale. We demonstrate that these constraints can be satisfied by outlining an architecture that uses only two-terminal CAEN devices to compute without transistors. One crucial requirement of this design circuit is that it be able to restore signals to a reference state without transistors. We present preliminary results for a molecular latch, constructed from molecular resonant tunneling diodes (RTDs) that can perform signal restoration, I/O isolation, and voltage buffering without transistors at the nanoscale.

Built-In Self-Test and Defect Tolerance for Molecular Electronics-Based NanoFabrics

“…The nanofabric architecture requires that all connections be made only at the crosspoints between two orthogonal wires. Molecular latches based on resonant tunneling diodes, referred to as RTDs, are also incorporated in this architecture for saving states and for signal restoration [8].…”

“…The molecular latch, constructed entirely from molecularscale devices, is used to perform signal restoration using power from the clock to provide gain. The molecular latch also provides the properties of I/O isolation and noise immunity [8].…”

“…In the FDC-1 configurations, we make the following assumptions based on published papers on nanofabrics: (1) Each output port has an associated inline NDR latch, whose state can be reset to B0^ [8], and (2) Resistors attached to Gnd have much smaller resistance that those attached to V DD [6].…”

Automated design flow for diode-based nanofabrics

“…The self-assembly process does not allow for precise end-to-end connections between nanowires, and hence, all connections are made at crosspoints of orthogonally aligned wires. Molecular latches based, on resonant tunneling diodes, are used for saving states and restoring signals [Goldstein and Rosewater 2002]. A post fabrication configuration step is used to realize circuits on the nanofabric.…”