ZINC SULFIDE ANTI-REFLECTIVE THIN FILM COATING FOR GERMANIUM OPTICAL WINDOWS

Abstract

In this work, Anti-reflective thin film is made on Germanium (Ge) optical window, which is one of the most used materials in thermal imaging systems. ZnS material was used its optical transmittance between 2-14 m and due to the fact that it has a refractive index proportional to the refractive index of Ge. ZnS thin films have been prepared by Radio Frequency (RF) magnetron sputtering on Germanium (Ge) optical windows for anti-reflection coating (ARC). ZnS films were produced at different thicknesses using RF sputtering system working pressures under 3, 20 and 30 mTorr. The other RF systems parameters such as RF power, deposition temperature were kept constant for all depositions. Crystal structures, optical and surface properties of ZnS thin films were characterized with X-ray diffraction (XRD), Atomic force microscopy (AFM), Fourier transform ınfrared (FTIR) and UV-VIS transmission spectrometer. The characterization results of Ge optical windows coated ZnS thin films grown at 3 mTorr pressure show that high optical transmission and good crystallinity in ınfrared wavelength region (2-14 um).