Optical modulation of nano-gap tunnelling junctions comprising self-assembled monolayers of hemicyanine dyes.
Light-driven conductance switching in molecular tunnelling junctions that relies on photoisomerization is constrained by the limitations of kinetic traps and either by the sterics of rearranging atoms in a densely packed monolayer or the small absorbance of individual molecules. Here we demonstrate light-driven conductance gating; devices comprising monolayers of hemicyanine dyes trapped between two metallic nanowires exhibit higher conductance under irradiation than in the dark. The modulation of the tunnelling current occurs faster than the timescale of the measurement (∼1 min). We propose a mechanism in which a fraction of molecules enters an excited state that brings the conjugated portion of the monolayer into resonance with the electrodes. This mechanism is supported by calculations showing the delocalization of molecular orbitals near the Fermi energy in the excited and cationic states, but not the ground state and a reasonable change in conductance with respect to the effective barrier width.
Stratingh Institute for Chemistry, and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Parisa
P
Pourhossein
Molecular Materials and Nanosystems and Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513, Eindhoven 5600 MB, The Netherlands.
Ratheesh K
RK
Vijayaraghavan
Molecular Materials and Nanosystems and Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513, Eindhoven 5600 MB, The Netherlands.
Stefan C J
SC
Meskers
Stratingh Institute for Chemistry, and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Ryan C
RC
Chiechi