Development of a Schottky barrier diode using molecular network of 1-alkyl-2-(arylazo) imidazole prepared by Langmuir–Blodgett technique

Abstract

In this paper we report the photophysical and electrical characteristics of our synthesized imidazole derivative namely l-alkyl-2-(arylazo) imidazole (AAI) organized in Langmuir-Blodgett (LB) films towards the development of organic Schottky barrier diode (SBD). Presence of long alkyl chain in the molecule make it suitable for LB technology and may favour aggregations of the molecules in LB films under barrier compression. The interfacial properties of the formation of Langmuir monolayer of AAI at air-water interface have been studied by surface pressure versus area per molecule (π-A) isotherm and compressibility modulus. Hysteresis study of the isotherm confirmed the formation of stable monolayer of AAI molecular assemblies at air-water interface. The aggregation of AAI molecules in LB films is confirmed by Ultraviolet–visible (UV–vis) absorption, fluorescence emission spectroscopy and Atomic force microscopic (AFM) methods. AAI molecules also formed network type morphology in LB films due to their closure association and aggregations or cluster of molecules which were evidenced by AFM technique. The compression induced aggregations of AAI is reflected as broadened nature of monomeric absorption band along with the emergence of a new absorption band at longer wavelength side for LB film deposited at surface pressure of 25 mN/m. The optical absorption bands of AAI and the corresponding transitions between different electronic states have been simulated by density functional theoretical (DFT) analysis and is compared with the experimental results. Nonlinear behaviour of the current-voltage characteristics and various relevant electrical parameters of the LB film device at the interface of metal electrode (gold) satisfy the necessary conditions showing the properties of a Schottky barrier diode.