Vertical Organic Artificial Synaptic Devices with Electric Field Permeable Pinhole Electrode

Key Words: Artificial synapse, Vertical organic transistor, Neuromorphic electronics , pinhole metal electrode, permeable source electrode<br/><br/>Vertical organic field effect transistors (VOFETs) with the electric field permeable source electrode have great advantages such as low voltage operation and energy consumption due to a nano scale channel length. However, conventional electric field permeable source electrodes like silver nanowires and carbon nano tubes have a network structure which is formed by random self-assembly, hence it’s difficult to control network density and position. Here, we introduced a metal thin film formed by thermal evaporation in the vacuum chamber which has a number of nanoscale pinholes that allow the electric field to pass through from gate dielectric. Also, we controlled the pinhole morphologies, such as density or size, to facilitate the electric field permeability. As a result, VOFETs with the electric field permeable pinhole metal source show high current density at low operating voltage. Moreover, the biological synapse characteristics including short term plasticity (STP), long term plasticity (LTP) and Spike-timing dependent plasticity (STDP) are stimulated by light pulse to trigger charge trapping of the active layer and the light absorbing material. Due to the novel and advanced results, the photonic synapse based on VOFETs are expected to be used as image sensing or optical communication devices.