Michael Deilmann, Mirko Grabowski, Sebastian Theiss, Nikita Bibinov, Peter Awakowicz

Permeation mechanisms of pulsed microwave plasma deposited silicon oxide films for food packaging applications

Journal of Physics D 41 (2008) 111

Silicon oxide barrier layers are deposited on polyethylene terephthalate as permeation barriers for food packaging applications by means of a low pressure microwave plasma. Hexamethyldisiloxane (HMDSO) and oxygen are used as process gases to deposit SiO(x) coatings via pulsed low pressure plasmas. The layer composition of the coating is investigated by Fourier transform infrared spectroscopy and energy dispersive x-ray spectroscopy to show correlations with barrier properties of the films. The oxygen permeation barrier is determined by the carrier gas method using an electrochemical detector. The transition from low to high barrier films is mapped by the transition from organic SiO(x)C(y)H(z) layers to quartz-like SiO(1.7) films containing silanol bound hydrogen. A residual permeation as low as J = 1 +/- 0.3 cm(3) m(-2) day(-1) bar(-1) is achieved, which is a good value for food packaging applications. Additionally, the activation energy E(p) of oxygen permeation is analysed and a strong increase from E(p) = 31.5 kJ mol(-1) for SiO(x)C(y)H(z)-like coatings to E(p) = 53.7 kJ mol(-1) for SiO(1.7) films is observed by increasing the oxygen dilution of HMDSO : O(2) plasma. The reason for the residual permeation of high barrier films is discussed and coating defects are visualized by capacitively coupled atomic oxygen plasma etching of coated substrates. A defect density of 3000 mm(-2) is revealed.

This article may also be available to you online

Cited Articles

1. Zajíčková L., Rudakowski S., Becker H.-W., Meyer D., Valtr M., Wiesemann K.,
   Study of Plasma Polymerization from Acetylene in Pulsed RF Discharges,
   Thin Solid Films 425 (2003) 72–84