Molecular Scale Electronics: A Synthetic/Computational Approach to Digital Computing

This paper outlines a design paradigm for molecular scale electronic systems. The contrast between the present bulk devices and potential molecular systems is presented along with the limitations of using bulk design philosophies for molecular-sized components. For example, the overwhelming considerations of heat dissipation on molecular scale electronic architectures are shown which demonstrate the need for dramatically different information transfer methods if these ultradense molecular devices are to be used for computation. The use of changes in electrostatic potential for information coding is suggested. The issue of signal restoration is addressed using a periodic external potential through the underlying substrate. Several convergent synthetic routes are shown to conjugated molecules with various potential digital device applications including a twoterminal molecular wire with a tunnel barrier, a molecular wire with a quantum well to serve as a resonanttunneling diode, three-terminal systems with switch-like possibilities, and four-terminal systems that could serve as logical gates without the use of multiple transistors. Ab initio computational methods are used to show that (i) molecules can be considered active electronic devices able to transfer the information from one molecule to another, (ii) the electrostatic potential can also be used as a tool to perform logical operations, and (iii) the molecules synthesized here could perform the functions for which they were designed.