Electrodeposition of Cu on PEDOT for a Hybrid Solid-State Electronic Device

Martina Vizza,Claudio Fontanesi,Massimo Innocenti,Roberto Giovanardi,Andrea Stefani,Giulio Pappaianni,Walter Giurlani

doi:10.3390/surfaces4020015

Abstract

Conductive polymers are nowadays attracting great attention for their peculiar mechanical, electrical and optical proprieties. In particular, PEDOT can be used in a wide range of innovative applications, from electroluminescent devices to photovoltaics. In this work, the electrochemical deposition of 3,4 ethylenedioxythiophene (EDOT) was performed on various substrates (ITO, thin films of gold and palladium on silicon wafers) by means of both potentiostatic and potentiodynamic techniques. This was intended to further expand the applications of electrochemically deposited PEDOT, particularly regarding the preparation of thin films in tight contact with electrode surfaces. This allows one to obtain systems prone to be used as electrodes in stacked devices. Chronoamperometric experiments were performed to study the nucleation and growth process of PEDOT. SEM, ESEM and AFM analysis allowed the characterization of the morphology of the polymeric films obtained. Raman and visible spectroscopy confirmed the high-quality of the coatings on the different substrates. Then, the PEDOT films were used as the base material for the further electrodeposition of a copper layer. In this way, a hybrid electronic device was obtained, by using electrochemical methods only. The high conductivity and ohmic behavior of the device were confirmed over a wide range of frequencies with electrical impedance spectroscopy analysis.

Highlights

Conductive polymers (CPs) constitute an important class of materials, which combine some mechanical characteristics of plastics with the typical electrical properties of semiconductors; these polymeric species contain conjugated bonds, which give rise to almost continuous valence and conduction bands
The microscopic characterization of PEDOT films was carried out using an environmental scanning electron microscope (ESEM; Quanta-200, Fei Company, Oxford Instruments (High Wycombe, UK)
The scanning electron microscopy analysis and the focused ion beam (FIB) ablation were performed by means of a GAIA 3 instrument equipped with Triglav electron and gallium FIB Cobra Gallium columns manufactured by Tescan (Brno, Czech Republic)

Summary

Introduction

Conductive polymers (CPs) constitute an important class of materials, which combine some mechanical characteristics of plastics with the typical electrical properties of semiconductors; these polymeric species contain conjugated bonds, which give rise to almost continuous valence and conduction bands. Many research groups have focused on PEDOT chemistry in recent years, bringing about an exponential increase in the number of patents and publications This material features a unique combination of properties: high conductivity (≈300 S/cm) [19,30], good transparency in thin films [3,7] and low bandgap (1.6–1.7 eV) [31]. These characteristics make PEDOT films suitable for optoelectronic and hybrid electronics applications, allowing the preparation of organic/inorganic interfaces without the need of high-cost vacuum techniques [32]. The conductivity and the Surfaces 2021, 4 ohmic behavior of the samples were characterized by means of electrochemical impedance spectroscopy (EIS)

Materials and Methods

Potentiodynamic Growth

Copper Electrodeposition

Electrical Impedance Spectroscopy

Conclusions