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Influence of Hydrogen Content and Carbon Hybridizations on Optical Properties of A-C:H Thin Films Obtained by PECVD

Author: E. Tomasella, Laboratoire de Métrologie des Interfaces Techniques; C. Meunier, Laboratoire de Métrologie des Interfaces Techniques; S. Mikhailov, Centre d'Analyse par Faisceau lonique   |   Document Download   |   Product code: ZCP2000SMT449

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Hydrogenated amorphous carbon (a-C:H) have recently received considerable attention because they posses interesting properties like extreme hardness, chemical inertness and optical transparency. In this work, the optical properties of a-C:H thin films prepared by r.f. plasma enhanced vapor deposition from a CH4/Ar or CH4/He gas mixtures are investigated. The optical gap Eg and the Urbach gap parameter Eu have been determined by optical-ultraviolet absorption characteristics. The Urbach disorder parameter and the optical gap are important parameters to characterize a-C:H. These parameters depend on initial disorder, hydrogen content and sp3/sp2 ratio. Elastic Recoil Detection Analysis, Infrared and Raman spectroscopies have been respectively used to quantify hydrogen content, the bonding and sp2 carbon proportion of thin films.

We have found that optical band gap Eg of these films decrease with the loss of hydrogen (bonded and unbonded) and increasing sp2 content with Eu gap increase indicating a structural disorder increase with the loss of hydrogen. Moreover, sp2 clusters sizes obtained from Raman scattering decrease with decreasing hydrogen content.

  • From: Surface Modification Technologies XIV: Proceedings of the Fourteenth International Conference on Surface Modification Technologies 2000 (ASM International)
  • Published: March 01, 2001
  • Pages: 5