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

We have analysed the effect of silver content on the optical properties of Ag-doped Ge10Sb30S60 chalcogenide glass films; the chalcogenide host layers were prepared by vacuum thermal evaporation. Films of compositions Ag-x(Ge 0.1Sb0.3S0.6)(100-x), With x less than or similar to 8 at.%, were obtained by successively photodissolving thin (around 10 nm) layers of silver. The o ptical constants (n, k) have been determined by a method based on the envel ope curves of the optical transmission spectrum at normal incidence. The di spersion of the refractive index of the Ag-photodoped chalcogenide films is analysed within the single-effective-oscillator approach. The optical-abso rption 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 1.9 7+/-0.01 to 1.67+/-0.01 eV. These results are consistent with the hypothesi s that the photodoped Ag is a structure modifier in the a-Ge10Sb30S60 films . (C) 2000 Elsevier Science B.V. AU rights reserved.