| Abstract
| - Producing reliable electrical contacts of molecular dimensions has been a critical challenge inthe field of molecule-based electronics. Conventional thin film deposition and photolithography techniqueshave been utilized to construct novel nanometer-sized electrodes on the exposed vertical plane on theedge of a thin film multilayer structure (metal/insulator/metal). Via thiol surface attachment to metal leads,an array of paramagnetic, cyanide-bridged octametal complexes, [(pzTp)FeIII(CN)3]4[NiII(L)]4[O3SCF3]4 (1)[(pzTp) = tetra(pyrazol-1-yl)borate; L = 1-S(acetyl)tris(pyrazolyl)decane], were covalently linked onto theelectrodes forming a dominant conduction pathway. A series of molecule-based devices were fabricatedusing Ni, NiFe, Ta, and Au as metal electrodes separated by insulating Al2O3 spacers, followed by treatmentwith 1. A series of control experiments were also performed to demonstrate that the conduction path wasthrough tethered metal clusters. The molecular current was analyzed via the Simmons tunnel model, andcalculations are consistent with electron tunneling through the alkane ethers to the central metal core.With a Ni/Al2O3/Au molecular electrode, the tether binding was found to be reversible to the top Au layer,allowing for a new class of chemical detection based on the steric bulk of coordinating analytes to disconnectthe molecular current path. Simple and economical photolithography/liftoff/self-assembly fabricationtechniques afford robust molecular junctions with high reproducibility (>90%) and long operational lifetimes(>1 year).
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