Influence of Air-Oxidation on Rectification in Thiol-Based Molecular Monolayers

Abstract

Spontaneous structural degradation processes occurring on metallic surfaces upon exposure to air-self-passivation-are well known for conventional silicon-based electronic materials; however, the effect of the analogous process for organic materials inside molecular electronic devices on their electrical behavior is rarely understood. Here, we show the influence of air-oxidation on molecular rectification in large-area junctions formed from a self-assembled monolayer (SAM) comprising 2,2'-bipyridyl terminated n-alkanethiolate. Upon exposure to air, the rectification ratio decreases as a function of air-exposure time and disappears in similar to 3 h. Structural analyses of the SAM using X-ray photoelectron spectroscopy and wet electrochemistry, as well as several physical-organic studies indicate that the decrease of rectification over time stems from structural degradation, facilitated by light, of the thiolate anchoring group of the SAM. (C) 2016 The Electrochemical Society. All rights reserved.