Structural and optical properties of phase‐change amorphous and crystalline Ge_1 − xTe_x (0 < x < 1) thin films

Abstract

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. magnified imageThe 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).

Functional Monochalcogenides: Raman Evidence Linking Properties, Structure, and Metavalent Bonding

“…Screening from this charge softens phonons [44] and will also contribute to Raman linewidth broadening. Finally, Park et al [50] have shown that local Te rich phases can exhibit a variety of modes with energies ranging between 120 and 170 cm −1 , the range of the background signal in our high temperature Raman spectra. These modes originate in Te-Te bonds (induced by Ge vacancies) and GeTe 4 edge sharing octahedra.…”

Interband transitions in semi-metals, semiconductors, and topological insulators: a new driving force for plasmonics and nanophotonics [Invited]

“…Bulk dielectric functions (1 solid line, 2 dashed line) of some binary compounds of p-block elements, taken from the literature: IV-VI chalcogenide compounds (GeS [56], GeSe [56], GeTe [57], SnSe [58], SnTe [56,59], PbS [43,60], PbSe [56], PbTe [56]); V-VI chalcogenide compounds (Sb2Se3 [56], Sb2Te3 [56], Bi2Se3 [61], Bi2Te3 [62]).…”

Temperature dependent structural evolution and crystallization properties of thin Ge15Te85 film revealed by in situ resistance, x-ray diffraction and scanning electron microscopic studies

“…In order to develop devices with better characteristics, understanding material properties are of vital importance. Therefore, optical properties such as dielectric functions, optical band gap, and phonon modes have been studied using ellipsometry and raman spectroscopy [13]. Moreover, the electronic properties of amorphous as well as crystalline phase have been studied for various Ge 1−x Te x compounds [14].…”