Structural and optical properties of phase-change amorphous and crystalline Ge1 − xTex (0 < x < 1) thin films



Ge1 − xTex thin films were grown using thermal coevaporation deposition. The dielectric functions and the phonon modes of amorphous (a-) and crystalline (c-) Ge1 − xTex films were measured using spectroscopic ellipsometry and Raman spectroscopy in order to investigate electronic and vibrational properties of these alloys. Using the second derivative spectra of the dielectric functions of a-Ge1 − xTex alloys and the standard critical point (SCP) model, we obtained optical transition energies for the a-Ge1 − xTex alloys. The optical transition energies were not only consistent with the density of states (DOS) reported in the literature, but also provided more detailed structures for the joint density of states (JDOS) of a-Ge1 − xTex.

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The second derivative spectra of d2ε(E)/dE2 for amorphous GeTe. The transition energies were estimated using SCP model (short arrows) and were compared to those of photoemission spectroscopy from literature (long arrows).