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CALCULATION OF OPTICAL PARAMETERS OF a-Ge-Se-Sn THIN FILMS

A. Thakur1, V. Sharma1, G. S. S. Saini1, N. Goyal1, S. K. Tripathi1,*

Affiliation

  1. Centre of Advanced Study in Physics, Panjab University, Chandigarh-160 014, India

Abstract

The present paper reports the effect of Sn impurity on the optical properties of Ge20Se80 glassy alloy. Thin films of Ge20Se80 and (Ge20Se80)90Sn10 alloys have been prepared by thermal evaporation technique. The optical transmission spectra of the substrate with and without of these amorphous thin films have been measured in the spectral range of 400 nm to 2000 nm. Refractive index (n) and thickness (d) of the films have been calculated using an optical characterization method based on creating the upper and lower envelope curves of the spectrum. The value of n increases after the Sn addition. These values of n have been fitted to the single oscillator model. The value of oscillator strength (Ed) increases and average energy gap (E0) decreases after the Sn incorporation. The optical absorption edge is described using the non-direct transition model proposed by Tauc and the optical band gap (Eg opt) is calculated from the absorption coefficient ( ) values by Tauc’s extrapolation procedure. The value of Eg opt and disorder parameter (B1/2) decrease with the Sn addition. The dispersion of the refractive index is explained in terms of the single-oscillator-model. The decrease of the optical gap (Eg opt) has been explained on the basis of difference on the binding energies of different bonds which are arising due to the incorporation of Sn into a-Ge20Se80 thin films..

Keywords

Chalcogenide glasses, Optical properties, Band gap.

Submitted at: July 4, 2005
Accepted at: July 21, 2005

Citation

A. Thakur, V. Sharma, G. S. S. Saini, N. Goyal, S. K. Tripathi, CALCULATION OF OPTICAL PARAMETERS OF a-Ge-Se-Sn THIN FILMS, Journal of Optoelectronics and Advanced Materials Vol. 7, Iss. 4, pp. 2077-2083 (2005)