Formation and behavior of negative ions in low pressure aniline-containing RF plasmas

Cedric Pattyn,Thomas Strunskus,Johannes Berndt,Eva Kovacevic,Thomas Lecas

doi:10.1038/s41598-019-47425-9

Abstract

This paper is focused on the formation mechanisms and the general behavior of negative ions in low pressure radio-frequency (RF) plasmas operated in a mixture of argon and aniline vapor. This type of plasma is mostly used for the synthesis of polyaniline, one of the most studied conductive polymers. Experiments based on mass spectroscopy measurements reveal the necessity to have a thin layer of plasma synthesized polyaniline on the electrodes to produce negative ions through complex surface reactions. In addition, thin-films deposited using this type of discharge are analyzed by means of Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS). The material analysis gives a first indication about the possible contribution of negative ions to polyaniline deposition.

Highlights

Polyaniline (PANI) is a conductive polymer which has been widely studied for the last decades
X-ray material analysis (Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS), using a synchrotron radiation source) of plasma synthesized polyaniline are presented in correlation to negative ions behavior, in order to give a first indication of their contribution to thin-film growth
Experiments performed in this study indicate that in the present case of a low pressure aniline plasma, surface reactions may play an important role in the production of negative ions

Summary

Introduction

Polyaniline (PANI) is a conductive polymer which has been widely studied for the last decades. The most common one is the chemical oxidative polymerization of aniline which can be used to obtain different types of supramolecular PANI structures such as nanofibers, nanorods, nanoribbons, nanobelts or nanoparticles[17,18,19] Another method involves the use of reactive plasmas (allowing the fast and solvent-free synthesis of this polymer), and is mostly used for the production of PANI thin-films and more recently PANI nanoparticles[20]. The study of negative ions in aniline plasmas is an important point in the understanding of plasma based synthesis of polyaniline This contribution mainly deals with mass spectroscopic measurements of negative ions produced in a low pressure capacitively coupled RF plasma (f = 13.56 MHz) ignited in a mixture of aniline vapor and argon and the influence of these ions on the deposition process. X-ray material analysis (Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS), using a synchrotron radiation source) of plasma synthesized polyaniline (pPANI) are presented in correlation to negative ions behavior, in order to give a first indication of their contribution to thin-film growth

Methods

Results

Conclusion