Optical Study of Ge₁Sb₂Te₄ and GeSbTe thin films

Extensive optical study has been carried out on as-deposited and annealed thin films of Ge₁Sb₂Te₄ and GeSbTe chalcogenides prepared through vacuum thermal evaporation on glass substrates. These films are found to be amorphous in nature for as-dep samples. The modifications that manifest in these films upon annealing are thoroughly investigated in view of the optical parameters. UV–vis spectroscopy has been utilized as the major tool for computation of optical constants, optical bandgap energy, urbach energy, skin depth, optical conductivity etc. Theoretical models for optical analysis like Wemple Di-Domenico model and Single Sellmier model have been applied to evaluate the dispersion energy parameters and oscillator parameters. Comparative analysis has been carried out which highlights the phase change characteristics of Ge₁Sb₂Te₄ and non-phase change behavior of GeSbTe. (paper)