The antireflection Germanium carbide (Ge1-xCx) coating, deposited using RF reactive sputtering, on both sides of ZnS substrate wafer has been developed. The infrared (IR) transmittance spectra show that the IR transmittance in the wavelength region between 8 and 12 mu m for the designed system Ge1-xCx/ZnS/Ge1-xCx is greatly enhanced compared to that for ZnS substrate. In addition, the double-layer coated ZnS substrate is approximately four times as hard as uncoated ZnS substrate. This investigation indicates that a double-layer Ge1-xCx coating can be used as an effective antireflection and protection coating on ZnS infrared window. (c) 2005 Elsevier B.V. All rights reserved.