Controlling the optical constants of thermally-evaporated Ge10Sb30S60 chalcogenide glass films by photodoping with silver

Abstract We have analysed the effect of silver content on the optical properties of Ag-doped Ge 10 Sb 30 S 60 chalcogenide glass films; the chalcogenide host layers were prepared by vacuum thermal evaporation. Films of compositions Ag x (Ge 0.1 Sb 0.3 S 0.6 ) 100− x , with x ≲8 at.%, were obtained by successively photodissolving thin (around 10 nm) layers of silver. The optical constants ( n , k ) have been determined by a method based on the envelope curves of the optical transmission spectrum at normal incidence. The dispersion of the refractive index of the Ag-photodoped chalcogenide films is analysed within the single-effective-oscillator approach. The optical-absorption data indicate that the absorption mechanism is non-direct transition. We found that the refractive index of the Ag-doped samples increases with the Ag content, whereas the optical band gap, E g opt , decreases from 1.97 ± 0.01 to 1.67 ± 0.01 eV. These results are consistent with the hypothesis that the photodoped Ag is a structure modifier in the a -Ge 10 Sb 30 S 60 films.

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