Annealing effects on the bonding structures, optical and mechanical properties for radio frequency reactive sputtered germanium carbide films |
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Authors: | CQ Hu JQ Zhu JC Han |
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Institution: | a Centre for Composite Materials, Harbin Institute of Technology, Harbin 150001, PR China b Department of Materials Science, Key Laboratory of Superhard Materials and Key Laboratory of Automobile Materials, MOE, Jilin University, Qianjin Street 2699, Changchun 130012, PR China |
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Abstract: | The effects of thermal annealing in vacuum on the bonding structures, optical and mechanical properties for germanium carbide (Ge1−xCx) thin films, deposited by radio frequency (RF) reactive sputtering of pure Ge(1 1 1) target in a CH4/Ar mixture discharge, are investigated. We find that there are no significant changes in the bonding structure of the films annealed below 300 °C. The fraction of Ge-H bonds for the film annealed at temperatures (Ta) above 300 °C decreases, whereas that of C-H bonds show a decrease only when Ta exceeds 400 °C. The out-diffusion of hydrogen promotes the formation of Ge-C bonds at Ta above 400 °C and thus leads to a substantial increase in the compressive stress and hardness for the film. The refractive indices and optical gaps for Ge1−xCx films are almost constant against Ta, which can be ascribed to the unchanged ratios of Ge/C and sp2-C/sp3-C concentrations. Furthermore, we also find that the excellent optical transmission for an antireflection Ge1−xCx double-layer film on ZnS substrate is still maintained after annealing at 700 °C. |
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Keywords: | 78 20 62 20 |
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