en Research Paper Research Paper <div style="text-align: justify;">In this research, Germanium-carbon coatings were deposited on ZnS substrates by plasma enhanced chemical vapor deposition (PECVD) using GeH₄ and CH₄ precursors. Optical parameters of the Ge_1-xC_x coating such as refractive index, Absorption coefficient, extinction coefficient and band gap were measured by the Swanepoel method based on the transmittance spectrum. The results showed that the refractive index of the Ge₁_&minus;xC_x coatings at the band of 2 to 2.2 &micro;m decreased from 3.767 to 3.715 and the optical gap increased from 0.66 to 0.72 eV as CH₄:GeH₄increases from 10:1 to 20:1.</div> Ge1−xCx, PECVD, Optical coatings, Optical properties. 24 30 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-1448-1&slc_lang=en&sid=1 F. Sousani f_sousani@mut-es.ac.ir 180031947532846009632 180031947532846009632 Yes Faculty of Materials Science and Engineering, Malek Ashtar University of Technology, Esfahan, Iran R. Mozafarinia a_1990_bakhshi@yahoo.com 180031947532846009633 180031947532846009633 No Faculty of Materials Science and Engineering, Malek Ashtar University of Technology, Esfahan, Iran A. Eshaghi eshaghi.akbar@gmail.com 180031947532846009634 180031947532846009634 No Faculty of Materials Science and Engineering, Malek Ashtar University of Technology, Esfahan, Iran H. Jamali hossein.j6813@gmail.com 180031947532846009635 180031947532846009635 No Faculty of Materials Science and Engineering, Malek Ashtar University of Technology, Esfahan, Iran