Optical properties of amorphous Ge20Se80 and Ag6(Ge0.20Se0.80)94 thin films

✍ Scribed by Anup Thakur; G. Singh; G.S.S. Saini; N. Goyal; S.K. Tripathi

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 254 KB
• Volume: 30
• Category: Article
• ISSN: 0925-3467
• DOI: 10.1016/j.optmat.2006.12.013

✦ Synopsis

Thin films of chemical composition Ge 20 Se 80 and Ag 6 (Ge 0.20 Se 0.80 ) 94 are prepared by thermal evaporation technique. The optical properties of these thin films are determined by a method, based only on the transmission spectra at normal incidence, measured over the 400-2000 nm spectral range. This useful optical method takes into consideration the non-uniform thickness of thermally evaporated thin films. The dispersion of refractive index is discussed in terms of the single-oscillator Wemple and DiDomenico model. The optical absorption edge is described using the non-direct transition model proposed by Tauc and the optical band gap ðE opt g Þ is calculated from the absorption coefficient (a) by Tauc's extrapolation procedure. It has been found that the value of refractive index (n) and oscillator strength (E d ) increase while average energy gap (E 0 ) and ðE opt g Þ decrease after Ag incorporation. The decrease of ðE opt g Þ has been explained on the basis of difference on the binding energies of different bonds which are arising due to the incorporation of Ag into a-Ge 20 Se 80 thin films.