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EFFECT OF THALLIUM ON THE OPTICAL PROPERTIES AND STRUCTURE OF THIN As-S-Tl FILMS

K. Petkov1,* , R. Todorov1, M. Kincl2, L. Tichy2

Affiliation

  1. Central Laboratory of Photoprocesses, Bulgarian Academy of Sciences, Acad. G. Bonchev St., bl. 109, 1113 Sofia, Bulgaria
  2. Joint Laboratory of Solid State Chemistry of Institute of Macromolecular Chemistry of Czech Academy of Science and University of Pardubice, 84 Studentska, 53009 Pardubice, Czech Republic

Abstract

Thin films from the system (As2S3)100-xTlx (0 x 15) were deposited by thermal evaporation on Si, graphite and optical glass substrates BK-7. From transmission and reflection measurements of the thin films, the refractive index, n, film thickness, d, optical band gap, Egopt, oscillator energy, Eo and dispersion energy, Ed, before and after exposure to light were determined. The results for optical parameters were analyzed using the Wemple - Di Domenico single-oscillator model and Lorenc-Lorenc equation. It was found that Eg decreases, while n, E0 and Ed increase for as deposited films with increasing of Tl concentration passing through a maximum at 6 at. % of Tl. After exposure to light, n, E0 and Ed increase, and Eg decreases for all compositions investigated. The maximum change in n (Dn = 0.16 at l = 632.8 nm) was observed for thin As38S56Tl6 films. From infrared spectroscopy measurements of bulk glasses and thin films we could conclude that when up to 6 at. %of thallium is introduced, As-S-As chains break and a ternary TlAsS2 compound appears at 10 at% Tl..

Keywords

Chalcogenide thin films, Optical properties, Infrared spectroscopy.

Submitted at: Sept. 15, 2005
Accepted at: Sept. 22, 2005

Citation

K. Petkov, R. Todorov, M. Kincl, L. Tichy, EFFECT OF THALLIUM ON THE OPTICAL PROPERTIES AND STRUCTURE OF THIN As-S-Tl FILMS, Journal of Optoelectronics and Advanced Materials Vol. 7, Iss. 5, pp. 2587-2594 (2005)