S. Vasquez-borucki et al., Amorphous hydrogenated carbon films as barrier for gas permeation through polymer films, DIAM RELAT, 9(12), 2000, pp. 1971-1978
The influence of amorphous hydrogenated carbon (a-C:H) coatings on the gas
permeation through polymer films was investigated. a-C:I-S films were depos
ited from a 13.56-MHz RF glow discharge in methane or acetylene atmosphere.
Thin poly(ethylene terephthalate) and polyimide foils were used as substra
tes. The permeation of the gases H-2, N-2, O-2 and CO2 was measured and the
reduction of the permeability coefficient was correlated to composition an
d density of the a-C:H films. The stoichiometry of the layers was analyzed
using ion-beam techniques on films deposited onto silicon samples. The a-C:
H/PET surfaces were analyzed using optical microscopy and atomic force micr
oscopy (AFM). Multilayer structures comprising different types of a-C:H fil
ms were also investigated. A reduction of the permeability coefficient by 8
0% for hard, dense and 94% for soft, polymer-like layers was found. Surpris
ingly, the barrier efficacy of the coating decreases with increasing a-C:H
film density. This unexpected result is attributed to the appearance of a n
etwork of deep cracks spread out over the whole coating. (C) 2000 Elsevier
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