Monolayer Rectifiers

Abstract

Molecular-scale electronics has now been enriched by the discovery that molecules, studied singly by scanning tunneling spectroscopy, or a large array of those molecules, studied in parallel as a Langmuir–Blodgett monolayer between metal electrodes, exhibit rectification, i.e., an asymmetric current as a function of applied voltage. This asymmetry can come, first, from work function differences between two dissimilar metals or the metal–molecule interfaces (Schottky barriers), second from an asymmetric placement of the chromophore between the two metal electrodes, and third, from an asymmetry of the molecular orbitals of the molecule. This third, electronic origin of rectification, first proposed by Aviram and Ratner in 1974, and confirmed in the work reported here, gives us hope that, not too many years from now, molecules can form the basis of ultra-small yet ultra-fast electronic devices and integrated circuits.