Fabrication and investigation of asymmetric current-voltage characteristics of a metal/Langmuir–Blodgett monolayer/metal structure

Abstract

Metal/Langmuir–Blodgett monolayer/metal devices, where the monolayer consists of the dodecyloxyphenylcarbamate of 2-bromo, 5(2′-hydroxyethoxy) tetracyanoquinodimethan, a donor-σ-acceptor molecular system, have been constructed, and dc current-voltage (I-V) characteristics of these devices were recorded at room temperature. For biases of ±20 mV, the I-V characteristics are linear, changing to a nonlinear form for higher voltages. This nonlinear characteristic exhibited a ln(I)∝V1/4 dependence for both positive and negative voltages up to ±1 V. For positive voltages >+2.0 V for as-prepared devices and >+1.5 V for annealed devices, a ln(I)∝V3 dependence was observed, revealing a very large increase in current for small voltage changes. Such behavior was not observed for corresponding negative voltages, indicating rectification across a distance approximated by the length of an individual molecule.