  Highly efficient information processing in brain is based on processing and
memory components called synapses, whose output is dependent on the history of
the signals passed through them. Here we have developed an artificial synapse
with both electrical and optical memory effects using reactive tunnel junctions
based on plasmonic nanorods. In an electronic realization, the electrons
tunneled into plasmonic nanorods under low bias voltage are harvested to write
information into the tunnel junctions via hot-electron-mediated chemical
reactions with the environment. In an optical realization, the information can
also be written optically by external light illumination to excite hot
electrons in plasmonic nanorods. The stored information is non-volatile and can
be read in both realizations either electrically or optically by measuring the
resistance or inelastic-tunnelling-induced light emission, respectively. These
memristive light-emitting plasmonic tunnel junctions can be used as memory,
logic units or artificial synapses in future optoelectronic or neuromorphic
information systems.
