Optical constants of Sn-doped amorphous Ge-As-Te thin films and their physical characterization

Abstract

The paper presents theoretical estimations of the effects Sn inclusion on the physical parameters including cohesive energy (CEn), lone-pair electrons (LP), coordination number (CN), constraints number (CON) and heats of atomization (HA) for the Ge12As23Te65-xSnx (where 0 ≤ x ≤ 8 at. %) glasses. In addition, Minkov method helped in evaluating the optical constants of the thin films. It is found that CN, CON, HA and CEn increase whereas LP decreases by increasing the Sn content. It is evident that by increasing the Sn content, the rigidity of the glasses (Ge12As23Te65-xSnx) can be increased. The study helped in estimating the chemical bonds occurred within the Ge12As23Te65-xSnx glasses. Furthermore, by the examination of glasses, it was found that the bonds that exist in glasses are Ge-Sn, Ge-As, Te-As and Te-Te with the respective energies of 42.41, 35.61, 32.74 and 33 kcal/mol. According to the two-term Cauchy dispersion equation, the values obtained from evaluating the refractive index (n) of the thin films were values of oscillator (Eo) and dispersion (Ed) energies. Additionally, the absorption coefficient (α) values were obtained by applying all the suggested conditions of Connell and Lewis. The paper also showed that an increase of the Sn content from 0 to 8 at. %, stimulates to reduce the energy gap (Eg) from 1.5 to 1.25 eV.