Effect of Functional Group on Electrical Switching Behaviour of an Imidazole Derivative in Langmuir‐Blodgett Film

Abstract

AbstractHere we report the design and synthesis of an imidazole derivative namely 1‐benzyl‐2,4,5‐triaryl imidazole (compound 2) and its switching behaviour assembled onto Langmuir‐Blodgett (LB) films. Monolayer characteristic of compound 2 at the air‐ water interface has been studied by surface pressure vs area per molecule (π – A) isotherm, hysteresis analysis and in‐situ Brewster Angle Microscopy (BAM). These studies indicated the formation of stable floating Langmuir film at the water subphase. Atomic Force Microscopy (AFM) investigation confirmed the successful deposition of the Langmuir film onto solid substrate. Device consisted of 60 layers LB films of 2 showed resistive bipolar switching behaviour irrespective of the first applied bias voltage polarity. Observed bipolar switching has been explained in terms of reduction – oxidation process. Due to the presence of strong reducible group (C=N) in the imidazole core, reduction – oxidation process takes place easily during bias. Presence of sharp reduction and oxidation peaks in the Cyclic Voltammetry (CV) measurement of 2 also supported this hypothesis. Presence of benzyl group with the imidazole core played the crucial rule in the reduction – oxidation process and hence the switching behaviour. When benzyl group was replaced by a ‘–H’ then bipolar switching was not observed. In that case oxidizable group N – H opposed the reduction process during bias. This type of bipolar switching is very promising for future technological applications in organic electronics.