Device variability and circuit redundancy in signal processing based on nanoswitches

Abstract

Signal processing based on molecular switches whose conductance can be tuned by anexternal stimulus between two (on and off) states has been proposed recently(Cervera et al 2008 J. Appl. Phys. 104 084317). The basic building block is a metalnanoparticle linked to two electrodes by an organic ligand and a nanoswitch. Thenet charge delivered by this nanostructure exhibits a sharp resonance when thealternating potential applied between the electrodes has the same frequency as theperiodic variation between the on and off conductance states induced on thenanoswitch. This resonance can be used to process an external signal by selectivelyextracting the weight of the different harmonics. However, because of the fabricationprocess at the nanoscale, the nanostructures will show a significant variability inthe physical characteristics. By using a phenomenological model that includesthis variability, the stochastic nature of electron transference, and the thermalnoise, we demonstrate that reliable signal processing can still be achieved byadapting the number of nanoswitches per bit of information (circuit redundancy) tothe nanostructure tolerance (device variability). Extensive kinetic Monte Carlosimulations show that a moderate level of redundancy can compensate for significantnanostructure variability. This result gives support to the concept of ensembles ofredundant switches as reliable components for signal processing at the nanoscale.