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A study of optical parameters of amorphous Se90InxGe10-x thin films before and after heat treatment

V. PANDEY1, S. K. TRIPATHI2, A. KUMAR1,*

Affiliation

  1. Department of Physics, Harcourt Butler Technological institute, Kanpur-208 002, India
  2. Department of Physics, Panjab University, Chandigrah-160 014, India

Abstract

Amorphous thin film of Se90InxGe10-x (x = 2 and 4) were thermally evaporated onto chemically cleaned glass substrates. Some optical parameters of these films were studied before and after thermal annealing above glass transition temperature of the respective alloys. The optical transmission spectra were measured in thin films of the above glasses in the wavelength range 400-2000 nm using spectrophotometer. The straight forward analysis proposed by Swanepoel has been successfully employed to determine the optical constants. It is observed from the measurements that the values of refractive index (n) and real dielectric constant (ε`) decrease with increase in wavelength while extinction coefficient (k) and imaginary dielectric constant (ε”) increase with increase in wavelength. The absorption coefficient (α) measured at strong absorption region also increases with photon energy (hν). Optical band gap (Eg) decreases with In concentration and also after thermal annealing of the films above glass transition temperature. This decrease in band gap could be accounted for by the generation of excess electronic delocalized states on incorporation of Indium as well as on thermal annealing in binary Se-Ge system..

Keywords

Chalcogenide glasses, Amorphous semiconductors, Optical properties, Optical band gap.

Submitted at: April 9, 2007
Accepted at: July 15, 2007

Citation

V. PANDEY, S. K. TRIPATHI, A. KUMAR, A study of optical parameters of amorphous Se90InxGe10-x thin films before and after heat treatment, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 7, pp. 2010-2015 (2007)