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Proceedings Paper

Optical properties of hydrogenated amorphous carbon determined by ellipsometry
Author(s): Margit Koos; Tivadar Lohner; Said H. Moustafa; Istvan Pocsik
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Paper Abstract

The complex dielectric function [(epsilon) ((omega) ) equals (epsilon) 1((omega) ) + i(epsilon) 2((omega) )] and the complex refractive index [N((omega) ) equals n((omega) ) + ik((omega) )] are presented for diamond-like amorphous carbonlayers as well as for amorphous carbon thin films (a- C:H) exhibiting other properties. By employing spectral ellipsometry the optical constants were determined in the photon energy range of 1.47 - 4.59 eV. Series of thin films were prepared in radio frequency plasma discharge of methane by varying the negative self bias (US.b.) in the range of 200 V < US.b. < 600 V. The a-C:H samples in this series exhibit transition in electrical and optical properties with increasing room temperature conductivity from approximately 4 X 10-10 (Omega) -1 cm-1 to 2 X 10-2 (Omega) -1 cm-1 and with decreasing optical gap from 1.3 eV to 0.5 eV as the deposition voltage changes in the range of 200 - 600 eV. The most pronounced changes in optical constants and in bonding structure occur near 500 V self bias. The (epsilon) 2((omega) ) spectrum exhibits a broad maximum which shifts to lower energies by increasing deposition self bias. The optical properties are discussed in terms of electronic band structure related to sp3 and sp2 hybridized bonding states of carbon atoms and to intermediate range ordering of sp2 bonded sites.

Paper Details

Date Published: 19 August 1998
PDF: 4 pages
Proc. SPIE 3573, OPTIKA '98: 5th Congress on Modern Optics, (19 August 1998); doi: 10.1117/12.320958
Show Author Affiliations
Margit Koos, Research Institute for Solid State Physics (Hungary)
Tivadar Lohner, Institute for Technical Physics and Materials Science (Hungary)
Said H. Moustafa, Research Institute for Solid State Physics (Hungary)
Istvan Pocsik, Research Institute for Solid State Physics (Hungary)

Published in SPIE Proceedings Vol. 3573:
OPTIKA '98: 5th Congress on Modern Optics
Gyorgy Akos; Gabor Lupkovics; Andras Podmaniczky, Editor(s)

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