Effect of different substrate on optical properties of Se₉₂Te₄Ag₄ films

Abstract

Present work reports the effect of substrate on the optical properties of Se₉₂Te₄Ag₄ thin films. Thin films of thickness 2500 Å were prepared by the thermal evaporation of the bulk samples. Amorphous nature of thin films is confirmed by the X-ray diffraction spectra. The transmittance spectra of Se₉₂Te₄Ag₄ thin films were obtained in the spectral region in the range 300–1100 nm. The optical band gap (E_g) and extinction coefficient (k) has been calculated from the absorbance data. The value of refractive index (n) has been determined from Swanepoel's method. The band gap of the film deposited on mica substrate (1.24 eV) is smallest as compared to the band gap of the films deposited on microscopic glass (1.29 eV) and quartz (1.26 eV). The change in value of optical parameters with change in substrate is explained in terms of disorder and defects, which confirms the dependence of optical parameters on types of substrates.

Keywords:

• amorphous semiconductors
• chalcogenides
• thin films
• Se–Te–Ag system
• optical properties

Acknowledgements

One of the authors (DS) gratefully acknowledges the Council of Scientific and Industrial Research (CSIR), New Delhi [No. 09/254 (0221)/2010 EMR-1], for providing a Senior Research Fellowship.