The effect of Ge content on the structure and properties of low temperature deposited infrared Ge100-xCx films on As40Se60 chalcogenide glass

Abstract

In this work, amorphous Ge100-xCx films were deposited on As40Se60 chalcogenide glass by radio frequency magnetron co-sputtering (rf MS) with different Ge content. The deposition temperature rise, the structural, mechanical and optical properties of Ge100-xCx films as a function of Ge content was investigated by thermocouple, X-ray photoelectron spectroscopy (XPS), Raman Spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transformed Infrared Spectroscopy, Surface Profiler and Continuous Stiffness Measurement (CSM). The deposition temperature rise of Ge100-xCx films derived from radical ions and neutrals is mild (<140℃) and lower than the transition temperature of As40Se60 chalcogenide glass (185 ± 5℃). The results reveal that both sp3 CC and sp2 CC clusters within Ge100-xCx film are converted to sp3 C-Ge bonds and finally depleted as Ge content increases from 18% to 79%. The conversion of sp2 CC structure to sp3 C-Ge bonds is faster than sp3 CC structure. The olefinic chains and nc-graphite clusters of sp2 CC structure are preferentially consumed to construct the sp3 C-Ge bonds. The nanohardness of Ge100-xCx films increases from 6.86 GPa to 9.87 GPa and elastic modulus of Ge100-xCx films increases from 35.72 GPa to 62.42 GPa as Ge content increases from 18% to 79%. Elastic recovery parameter (ERP) of Ge100-xCx film increases from 33.79% to 35.01% and nanohardness/Elastic modulus (H/E) decreases from 0.192 to 0.158 as Ge content increases from 18% to 79%. Ge100-xCx (66% Ge) /DLC double layer promotes the longwave infrared band (8 μm ∼ 11 μm) mean transmittance of As40Se60 chacogenide glass from 61.3% to 66.4%.