An Experimental and Analytical Study of an Asymmetric Capacitively Coupled Plasma Used for Plasma Polymerization

Abstract

Plasma processing is widely used to provide novel surface modifications to materials for a variety of applications. Typically, the systems used to carry out these modifications are poorly characterised. Here we describe the basics of a global model for a capacitively coupled asymmetric parallel plate radiofrequency plasma system routinely used to produce plasma polymers. An analytical global model was developed for argon, for which cross-sections are known, at a constant pressure of 1 Pa, and includes an electrical model and a power balance. The main parameters of interest were ion flux and self-bias voltages. The argon modelling results were then compared to experimental results for a range of operating gases (argon, oxygen, amines, acids, alcohols, ethers, siloxanes) including both saturated and unsaturated compounds with molecular weights ranging from 40 to 162 g Á mol À1 , for different inter-electrode separations and from 2 to 50 W using an Impedans OctIV probe. Importantly, it is shown that the RF power transfer efficiency is dependent on the gas. The results show that the argon model results can be used to predict the plasma parameters for other gases when the RF power transfer efficiency is taken into account.

Plasma Parameter Aspects in the Fabrication of Stable Amine Functionalized Plasma Polymer Films

“…The mean ion energy for AA and EDA plasmas was also measured between 2 and 15 W. It is expected that the ion energy should increase with RF power as the electron temperature increases . The results provided in the Supporting Information (Figure S1) show that the ion energy increases with applied plasma power from around 10 eV at 2 W to 20 eV at 15 W. This is in agreement with previous results obtained with this plasma system using Argon as the discharge gas …”

“…[44] The results provided in the Supporting Information ( Figure S1) show that the ion energy increases with applied plasma power from around 10 eV at 2 W to 20 eV at 15 W. This is in agreement with previous results obtained with this plasma system using Argon as the discharge gas. [45]…”

Evolution of Hydrophobicity in Plasma Polymerised 1,7‐Octadiene Films

“…More recently, it has been shown that plasma polymers may be deposited non-continuously in the very early stages of plasma polymerisation. [43] According to ellipsometry analysis, the thickness of the coating deposited for 40 s is 2.8 AE 0.2 nm. Although the ToF-SIMS sampling depth (1-2 nm) is smaller than the measured thickness, some traces of Si þ originating from the silicon substrate were still detected in this sample (Figure 4) via ToF-SIMS.…”

Deposition of Functional Plasma Polymers Influenced by Reactor Geometry in Capacitively Coupled Discharges

“…This approach, however, only considers gas phase processes, while effects as caused by energetic particle bombardment during film growth are neglected. The latter strongly influences, for example, the cross‐linking of plasma polymer films and their functional group density . A round‐robin study initiated by the Mawson Institute in Adelaide, Australia (conducted in 2012/2013) thus revealed a high variability in plasma polymerization processes (both in deposition rate and chemical functionality) using acrylic acid as monomer at nominally fixed plasma parameters within 14 different plasma reactors …”

“…The latter strongly influences, for example, the cross-linking of plasma polymer films and their functional group density. [4,5] A round-robin study initiated by the Mawson Institute in Adelaide, Australia (conducted in 2012/2013) thus revealed a high variability in plasma polymerization processes (both in deposition rate and chemical functionality) using acrylic acid as monomer at nominally fixed plasma parameters within 14 different plasma reactors. [6] As acrylic acid shows a complex chemical reaction pathway revealing different regimes, [7] mixtures ofCO 2 /C 2 H 4 were selected in this work to study the influence of different degrees of asymmetry within the same capacitively coupled plasma (CCP) reactor set-up.CO 2 /C 2 H 4 discharges were found to show three distinct deposition regimes showing one transition influenced by gas phase processes (increased fragmentation) and one by surface processes (ion-induced effects).…”