A study of ta-C, a-C : H and Si-a : C : H thin films on polymer substrates as a gas barrier

TY - JOUR

T1 - A study of ta-C, a-C : H and Si-a : C : H thin films on polymer substrates as a gas barrier

AU - Abbas, GA

AU - McLaughlin, JAD

AU - Harkin-Jones, E

N1 - 14th European Conference on Diamond, Diamond-like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide, Salzburg, AUSTRIA, SEP 08-12, 2003

PY - 2004/4

Y1 - 2004/4

N2 - Two types of diamond-like carbon (DLC) films were grown on Poly (ethylene terepthalate) (PET) substrates have been investigated for density, internal stress, gas permeability and structural properties by an X-ray reflectometry, surface profilometer, Raman spectroscopy and water vapour permeation analysis system, respectively. The high density tetrahedral amorphous carbon (ta-C) films (3.27 g/cm(3)) prepared by filtered vacuum cathodic arc (FCVA) showed unexpected high water vapour transmission rate (WVTR) (1.3 g/m(2) day) and a surface covered by a network of deep micro-cracks, which is due to intrinsic stress inside the ta-C films (up to 12 GPa). The soft Si doped hydrogenated amorphous carbon (Si-a:C:H) films prepared by plasma enhanced chemical vapour deposition (PECVD) exhibited low transmission rate (0.03 g/m(2) day) with a water vapour reduction factor up to 98% and a surface almost completely free of micro-cracks. Si incorporation in the a-C:H films reduced both the film density from 2.3 g/cm(3) to 1.85 g/cm(3) and the compressive stress to < 0.5 GPa. This could be understood by two possibilities. Firstly, the increasing in the hydrogen content within the films (as indicated by increasing the Raman background slope) developed more polymer-like bonds, which weakens the microstructure. Second, replacing the stronger C-C bonds (3.7 eV) by C-Si (3.21 eV) bonds where the relaxation of residual stress would occur with large strains in the C-Si bonds. (C) 2003 Elsevier B.V. All rights reserved.

AB - Two types of diamond-like carbon (DLC) films were grown on Poly (ethylene terepthalate) (PET) substrates have been investigated for density, internal stress, gas permeability and structural properties by an X-ray reflectometry, surface profilometer, Raman spectroscopy and water vapour permeation analysis system, respectively. The high density tetrahedral amorphous carbon (ta-C) films (3.27 g/cm(3)) prepared by filtered vacuum cathodic arc (FCVA) showed unexpected high water vapour transmission rate (WVTR) (1.3 g/m(2) day) and a surface covered by a network of deep micro-cracks, which is due to intrinsic stress inside the ta-C films (up to 12 GPa). The soft Si doped hydrogenated amorphous carbon (Si-a:C:H) films prepared by plasma enhanced chemical vapour deposition (PECVD) exhibited low transmission rate (0.03 g/m(2) day) with a water vapour reduction factor up to 98% and a surface almost completely free of micro-cracks. Si incorporation in the a-C:H films reduced both the film density from 2.3 g/cm(3) to 1.85 g/cm(3) and the compressive stress to < 0.5 GPa. This could be understood by two possibilities. Firstly, the increasing in the hydrogen content within the films (as indicated by increasing the Raman background slope) developed more polymer-like bonds, which weakens the microstructure. Second, replacing the stronger C-C bonds (3.7 eV) by C-Si (3.21 eV) bonds where the relaxation of residual stress would occur with large strains in the C-Si bonds. (C) 2003 Elsevier B.V. All rights reserved.

KW - DLC

KW - coatings

KW - diffusion

KW - surface characterization

U2 - 10.1016/j.diamond.2003.10.084

DO - 10.1016/j.diamond.2003.10.084

M3 - Article

VL - 13

SP - 1342

EP - 1345

IS - 4-8

ER -