Experimental study on thickness-related electrical characteristics in organic/metal-nanocluster/organic systems

Abstract

Organic bistable devices with the trilayer structure, organic/metal-nanocluster/organic, interposed between two electrodes have been systematically studied by varying the thickness of the organic layers and the metal-nanocluster layer. Devices fabricated in this fashion exhibit either electrical bistability or current step, depending on the thickness of the metal-nanocluster layer. Electrical bistable devices have been studied by fixing the metal-nanocluster layer thickness at 20 nm and changing the organic-layer thickness from 20 to 60 nm. Device injection current at the on state shows an exponential decrease with an increasing organic-layer thickness, suggesting that the electron transmission probability of the devices decreases with an increasing thickness of the organic layer. This is in agreement with theoretical calculations based on the single-band Hubbard model. The evolution of the electrical current step is observed for devices fabricated by fixing the organic-layer thickness at 50 nm and changing the metal-nanocluster layer thicknesses (2, 4, and 8 nm). The discontinuous metal-nanocluster layer is believed to lead to the observed current step. When the metal-nanocluster layer is thick enough resonant tunneling occurs between nanoclusters causing positive and negative charges to be stored on the opposite sides of the metal-nanocluster layer inducing electrical bistability. Discussions of the observed phenomena are presented.