Optical characterization of phase changing Ge2Sb2Te5 chalcogenide films

The variable angle spectroscopic ellipsometry and spectroscopic reflectometry is used for the optical characterization of the as-deposited and annealed Ge2Sb2Te5 (GST) films. The dispersion model of the GST films is based on the parameterization of the density of electronic states. As a consequence of annealing, roughness of the upper boundaries of the GST films originates. This annealing also causes the evident redistribution of the density of electronic states from the higher energies to lower energies. The roughening and redistribution of the electrons are explained by means of the phase change of the GST films from amorphous to polycrystalline structure. This phase change is accompanied by changing the conductivity of the films that was proved by introducing the terms of the free carriers in the dispersion model of the GST films. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)