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Optical characterization of Ag/As-S-Se thin films

J. TASSEVA1, V. LOZANOVA1, R. TODOROV1, K. PETKOV1,*

Affiliation

  1. Central Laboratory of Photoprocesses, Bulgarian Academy of Sciences, Acad. G. Bonchev St., b.l 109, 1113 Sofia, Bulgaria

Abstract

Results of investigations of optically uniform thin As33S67-xSex (0≤x≤67) films deposited by thermal evaporation on BK-7 optical glass substrates are presented. Bulk samples were prepared by melting pure elements As, S and Se in a quartz ampoule at 760°C for 12 hours. The changes in transmittance, reflectance, refractive index and optical band gap in the visible and NIR region of thin films (700 nm thick) depending on composition and exposure to light have been studied. The photo-induced diffusion of Ag into As-S-Se thin films was studied using glass substrates with initially deposited by RF sputtering Ag films with different thickness. It was shown that the refractive index increases with the increase in the Se and Ag content from 2.24 for As33S67 to 2.80 for As33Se67 and from 2.40 for Ag/As33S67 to 3.65 for Ag/As33Se67 at λ=1060 nm, while Eg decreases from 2.58 to 1.78 and from 2.25 to 1.5, respectively (the Ag thickness was 70 nm). Thus, the dispersion energy, Ed, single-oscillator energy, E0 and the effective coordination number per cation, Nc, have been calculated. In agreement with other authors, we have observed Ed and Nc increasing with the Se-content in the films. The dependence of the surface microstructure and optical parameters of the quaternary system on the Ag concentration was demonstrated. Some conclusions about the mechanism of the photoinduced structural changes of the studied system were drawn..

Keywords

Chalcogenide glasses, Thin films, Optical properties.

Submitted at: July 3, 2007
Accepted at: Oct. 15, 2007

Citation

J. TASSEVA, V. LOZANOVA, R. TODOROV, K. PETKOV, Optical characterization of Ag/As-S-Se thin films, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 10, pp. 3119-3124 (2007)