Silicon contamination of substrates in fluorocarbon plasmas produced in glass reactors

Abstract

SYNOPSISExtensive research has been carried out in recent years using fluorocarbon plasmas for modification and depositions on polymer substrates. In some cases anomalous results have been obtained that are not explainable based on conventional fluorine chemistry. In this investigation pure polypropylene films were exposed to carbon tetrafluoride plasmas in a Pyrex glass reactor. A t short reaction times (less than 1 min) significant amount of silicon was detected by ESCA on the surface of the films. Analysis of liquid nitrogen trapped fluorocarbon plasma gases and molecular fragments indicated high concentrations of silicon and carbon containing species, the former indicative of ablation and etching reactions of the glass reactor walls. The production of a relatively high quantity of fluorosilicon derivatives was explained by the greater affinity of silicon for fluorine than for carbon, with the tendency to readily form SiF,. These fluorosilicon radical and ionic species generated under cold plasma conditions can easily react with polymeric substrates causing unexpected surface modifications. In addition Si-F bonds could be readily hydrolyzed to SiOH islands on the surface of the substrate to impart anomalous characteristics.

Primary Amine Implantation Onto Polypropylene Surfaces from Melamine and Urea RF Plasmas.

“…Radical species resulted from the plasma-generated dissociation of U will probably lead to the implantation onto substrate surfaces of =NH, -NH2, and -C(NH2)=0 functionalities. MS-electron and plasma-induced molecular fragmentation mechanisms are certainly not identical, however, significant similarities have been found between the two processes [37,2,5,6]. Some similarities between the plasma induced M and U based processes should not be excluded due to the possible synthesis of M from U according to the following reaction:…”

Synthesis and characterisation of macroporous poly(methyl methacrylate) with plasma-polymerised hydrophilic coating

“…The CH 2 and CH 3 stretching vibrations in the region of 2800-3000 cm -1 , the carbonyl (C=O) band at 1720 cm -1 , the ester peaks at 1140 cm -1 to 1450 cm -1 , the α-CH 3 deformation peak at 970 cm -1 and the intense CH 2 rocking modes coupled with C-C stretching at 750 cm -1 can be identify in this spectrum [62]. There is not much information in the literature about poly(2-hydroxyethyl acrylate).…”

“…Figure 1.7) can be identified in this spectrum: the CH 2 and CH 3 stretching vibrations in the region of 2800-3000 cm -1 , the stretching of the carbonyl group at 1724 cm -1 and the absorption bands characteristic of carboxylic acid esters at ~1143 cm -1 [62].…”

“…Therefore, plasma polymers are expected to be essentially different in chemical and mechanical properties than conventional ones, even if the same monomer is used for both plasma and conventional polymerisations. In addition, it is well known that plasma polymers are always cross-linked in some extent [62,51] and for this reason generally exhibit superior stability to chemical, thermal, and mechanical stress than conventional polymers. Their partial or total insolubility has made plasma polymers rather difficult to characterise.…”

“…In this work, the FTIR spectrum of bulk PHEA was also measured for comparison with that of plPHEA. The FTIR spectra of plasma-polymerised PMMA and conventional PMMA were compared in reference [62] and it was found that the PMMA films formed under RF cold plasma conditions were substantially modified and cross-linked in nature and do not retain many of the structural characteristics of conventional PMMA.…”