REDSHIFT IN THE OPTICAL BAND GAP OF AMORPHOUS NANOSTRUCTURE Se 80 Te 20-x Sn x FILMS

摘要

Ternary glasses of Se 80 Te 20-x Sn x (x=3 and 9 at.%) are prepared by melt quench technique. Thin films of Se 80 Te 20-x Sn x (x=3 and 9 at.%) of different thicknesses in the range of (25 nm -1450 nm) are prepared by the conventional thermal evaporation technique on glass substrate. X -ray diffraction measurements show that both bulk and thin films of Se 80 Te 20-x Sn x have amorphous natures. Optical transmissio n and reflection spectra of the studied thin films are measured in the wavelength range of 200.2500 nm at room temperature. The absorption coefficient (α) as an optical constant is determined as a function of film thickness. The width of localized states near the mobility edge increases with increasing the film thickness. The optical band gap is redshifted from 1.87 to 1.49 eV and from 1.85 to 1.35 eV with increasing the film thickness for both Se 80 Te 20-x Sn x (x=3 and 9 at.%) thin films respectively, due to quantum size effect.