An optical study of amorphous (Se80Te20)100-xGex thin films using their transmission spectra

Optical constants (refractive index and extinction coefficient) have been studied for a-(Se80Te20)(100-x)Ge-x (x = 0, 2, 4, 6) thin films using transmission spectra in the wavelength range 500-2500 nm. It is observed from optical transmission measurements that the optical energy gap (E-g) increases while the refractive index (n) and the extinction coefficient (k) decrease with the incorporation of Ge in the Se-Te system. The increase in the optical energy gap is interpreted by correlating the optical energy gap with the decrease in electronegativity and increase in the heat of atomization (H-s). The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple-DiDomenico model.