Ran Liu1,2,Enrique del Barco1,Christian Nijhuis3
University of Central Florida1,University of Georgia2,University of Twente3
Ran Liu1,2,Enrique del Barco1,Christian Nijhuis3
University of Central Florida1,University of Georgia2,University of Twente3
Since the discrete orbitals of molecules can provide multiple distinguishable electrical states, controllable single-molecule devices stand as ideal candidates for ultra-simple circuit elements to perform high-density computations. However, the expansion of the energy levels of molecular orbitals (MOs) by the electrodes and the effect of the external potential on the absolute value of the energy levels make it difficult to build stable multifunctional devices based on the precise manipulation of MOs. Our recent study found that gated Au/S-(CH<sub>2</sub>)<sub>3</sub>-Fc-(CH<sub>2</sub>)<sub>9</sub>-S/Au (Fc=ferrocene) single-electron transistors (~2 nm) not only hold the advantage of controlling MOs via orthogonal bias (<i>Vb</i>) and gate (<i>Vg</i>) voltages, but also exhibit a unique electronic structure with two stable adjacent conductive MOs. With the (CH<sub>2</sub>)<sub>n</sub> (n >= 3) chain effectively isolating the Fc from the gold electrodes, the MOs of the Fc moiety display narrow energy levels, allowing a clear current change as the energy level enters and leaves the bias window. Built upon the diamond-shaped Coulomb blockade response, a prototype single-electron logic calculator was proposed, implementing all universal 1- and 2-input logic gates within a single-molecule device. In addition, the asymmetry of the molecule leads translates into an asymmetric Coulomb blockade response, enabling switching the logic gate function by changing the bias direction.