Optical characterization of nanostructured Ge1-xSnxSe2.5 (x=0, 0.3, 0.5) films

The paper reports the optical properties of thin films of nanostructured Ge1-xSnxSe2.5 (x=0, 0.3, 0.5) glassy alloys. The glassy alloys of Ge1-xSnxSe2.5 (x=0, 0.3, 0.5) were prepared using melt quenching method. Thin films of nanostructured Ge1-xSnxSe2.5 (x=0, 0.3, 0.5) glassy alloys were prepared using physical vapor deposition method. The films were characterized using XRD, EDX and TEM, which confirmed the amorphous nature, composition and formation of nanorods in the samples. Absorption and transmission spectra of thin films were recorded in the spectral range 400-2500nm to obtain energy band gap, refractive index, extinction coefficient, dielectric constant etc. Results show that refractive index increases while band gap decreases on increase of Sn content in the Ge-Se system. This is due to the increase in density of defect states within band gap. The values of Urbach energy support the obtained results.