Structural and optical properties of phase‐change amorphous and crystalline Ge_{1 − <i>x</i>}Te_<i>x</i> (0 &lt; <i>x</i> &lt; 1) thin films

Abstract

Abstract Ge 1 − x Te x thin films were grown using thermal coevaporation deposition. The dielectric functions and the phonon modes of amorphous (a‐) and crystalline (c‐) Ge 1 − x Te x 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‐Ge 1 − x Te x alloys and the standard critical point (SCP) model, we obtained optical transition energies for the a‐Ge 1 − x Te x 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‐Ge 1 − x Te x . magnified image The second derivative spectra of d 2 ε ( E )/d E 2 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).