The molecule, designed at Columbia, is an oxidised thiophene derivative with molecular resonance in nearly perfect alignment with the Fermi electron energy levels of the gold electrodes, according to Berkeley Labs.
It is a symmetrical molecule in an ionic solution, with asymmetry coming from different sized gold electrodes – see diagram.
“Electron flow at molecular length-scales is dominated by quantum tunnelling,” said Jeff Neaton, director of Berkeley Labs’ Molecular Foundry. “The ionic solution, combined with the asymmetry in electrode areas, allows us to control the junction’s electrostatic environment simply by changing the bias polarity. In addition to breaking symmetry, double layers formed by ionic solution also generate dipole differences at the two electrodes, which is the underlying reason behind the asymmetric shift of molecular resonance.”
Work at Columbia confirmed no rectification happened in non-ionic solution.
“We expect the understanding gained from this work to be applicable to ionic liquid gating in other contexts, and mechanisms to be generalised to devices fabricated from two-dimensional materials,” said Brian Capozzi of Columbia, adding that the molecular circuit is also revealing new routes to charge and energy flow at the nanoscale.
The work is convered by a Nature Nanotechnology paper: ‘Single-molecule diodes with high rectification ratios through environmental control’.
from News http://ift.tt/1PawJed
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