Structure of Se–Te glasses by Raman spectroscopy and DFT modeling

Abstract

For the first time, the Raman spectra of bulk SexTe1‐x glasses, 0.5 ≤ x ≤ 1.0, have been measured over the entire glass‐forming range. The spectra exhibit three broad spectral features between 150 and 300 cm−1, attributed to Te–Te, Se–Te, and Se–Se stretching modes according to DFT simulations. The observed weak chemical ordering in the glasses is discussed on the basis of heteropolar and homopolar bond fractions derived from integrated intensity of the Raman modes and DFT cross‐sections. The underlying structural model of the glasses suggests a random distribution of the Se–Se, Se–Te, and Te–Te chemical bonds with some preference for heteropolar bonding within Se–Te–Se structural units.

Intrinsic second‐order nonlinearity in chalcogenide glasses containing HgI2

“…However, the HgI 2 molecules in condensed matter are not isolated, experiencing at least van der Waals or similar interactions. These intermolecular interactions play an important role changing, in particular, vibrational properties, as it was observed for Se–Te glasses …”

“…These intermolecular interactions play an important role changing, in particular, vibrational properties, as it was observed for Se-Te glasses. 19 Taking (HgI 2 ) 2 weakly interacting dimer, we have fully optimized the geometry using Grimme's dispersion corrections D3BJ 24 where r vdW (Hg) and r vdW (I) are the van der Waals radii of mercury and iodine. 35 After DFT optimization, a dimer with slightly bent HgI 2 molecules, separated by 3.48 Å, was obtained, Figure 3C.…”

“…The DFT calculations have been carried out using Gaussian 16 software in parallel environment. Both isolated monomers HgI 2 and weakly interacting dimers (HgI 2 ) 2 were simulated similar to our previous DFT modeling of Se–Te glasses . The initial geometry of these clusters has been relaxed toward the nearest local minimum and then a harmonic frequency analysis has been performed.…”

Investigation of the crystallization behavior of laser‐irradiated EXTREME pattern by Raman spectroscopy

“…Upon heat treatment, the c‐GSST phase transition is accompanied by dissociation of the Se‐Se and Te‐Se bonds at the interfacial double layers . The new peak at ~120 cm −1 can be attributed to the triatomic Se‐Se‐Se clusters bending and inter‐layer stretching modes in the double layers …”

“…Similar to GST, the phase change transition in GSST is related to atomic block movement and local distortion. The broad Raman spectral feature observed in the a‐GSST phase, centered at ~150 cm −1 , is characteristic of Sb‐Sb bonds in (Se 2 )Sb‐Sb(Se 2 ) units at ~143 cm −1 and (Te 2 )Sb‐Sb(Te 2 ) at ~160 cm −1 ; whereas the band at 200 cm −1 is representative of corner‐sharing GeSe 4/2 tetrahedra at ~202 cm −1 , and Se‐Te stretching at 210 cm −1 . Upon heat treatment, the c‐GSST phase transition is accompanied by dissociation of the Se‐Se and Te‐Se bonds at the interfacial double layers .…”