Investigation of the Atomic Structure of Ge-Sb-Se Chalcogenide Glasses

Abstract

at. %) have been synthesized. Neutron and X-ray diffraction techniques were used to study the atomic glassy structure, and Reverse Monte Carlo (RMC) simulations were applied to model the 3-dimensional atomic configurations and thorough mapping of the atomic parameters, such as first and second neighbour distances, coordination numbers, and bond-angle distributions. The results are explained with formation of GeSe 4 and SbSe 3 structural units, which correlate with the Ge/Sb ratio. For all the studied compositions, the Ge-Se, Sb-Se, Ge-Ge, and Se-Se bonds are significant. RMC simulations reveal the presence of Ge-Sb and Sb-Sb bonds, being dependent on Ge/Sb ratio. All atomic compositions satisfy formal valence requirements, i.e., Ge is fourfold coordinated, Sb is threefold coordinated, and Se is twofold coordinated. By increasing the Sb content, both the Se-Ge-Se bonds angle of 107±3 ∘ and Se-Sb-Se bonds angle of 118±3 ∘ decrease, respectively, indicating distortion of the structural units. Far infrared Fourier Transform spectroscopic measurements conducted in the range of 50-450 cm -1 at oblique (75 ∘ ) incidence radiation have revealed clear dependences of the IR band's shift and intensity on the glassy composition, showing features around x=27 at.% supporting the topological phase transition to a stable rigid network consisting mainly of SbSe 3 pyramidal and GeSe 4 tetrahedral clusters. These results are in agreement with the Reverse Monte Carlo models, which define the Ge and Sb environment.

Ge–Sb–S–Se–Te amorphous chalcogenide thin films towards on-chip nonlinear photonic devices

“…This has been clearly evidenced for composition tie-lines crossing the stoichiometric GeSe 2 /Sb 2 Se 3 pseudo-binary tie-line as Ge 40-x Sb x Se 60 51 , Ge x Sb 10 Se 90-x 52 , 53 Ge x Sb 15 Se 85-x or Ge x Sb 20 Se 80-x 53 glasses. These compositions are again those with the smallest amount of homopolar bonds and corresponding to a limit of topological phase transition as reported in Ge 40-x Sb x Se 60 glasses 54 , 55 . Besides, in bulk glasses as well as in thin films, the decrease of the GeSe 2 /Sb 2 Se 3 ratio was shown to result in an increase of the refractive index and a decrease of the band gap energy since electronic polarizability of Sb–Se bonds is much higher than that of Ge-Se bonds 24 , 56 , 57 .…”

On the optical nonlinearity in the GeSbSe chalcogenide glasses

“…Figure 3 indicates the value of the absorption coefficient, the increase/decrease of the Ge/Sb content upon photon energy incident for all the samples of Refractive index can be obtained using the normal incidence reflectance according to Fresnel's equations [12,13] computed by relation (4): Figure 5 shows the results obtained by the refractive index according to (4). The value of the refractive index and extinction coefficient decrease/ increase with Ge / Sb content [14][15][16][17]. The optical band gap E g was derived assuming indirect transitions between the edge of the valence and conduction band.…”

“…where A is the absorptance, α, the absorption coefficient,Ã,ã are constants and E u is the Urbach energy. The Wemple-DiDomenico (WD) model is using to calculate various dispersion parameters such as band-gap energy (E g ) oscillator energy (E 0 ) and dispersion energy (E d ) [16,19,20]. Accordingly, a graph (figure 5) is constructed with ( ) -n 1 2 1 against ( ) u h .…”

“…The GeSbSe, like all chalcogenides in general, are characterized by important fluctuations of the atomic distances in material as suggested in figure 13(a). The peaks in interatomic distances for Ge-Sb, Ge-Ge, Sb-Sb, and Se-Se atoms appear to be 3.80±0.05 Å, 3.85±0.05 Å, 3.80±0.05 Å, and 3.80±0.05 Å, respectively [16]. The atomic structure of GeSbSe is presented in figure 13(b).…”

AC CONDUCTIVITY AND DIELECTRIC PROPERTIES OF AMORPHOUS Se69Sn10Ge21-xSbx (6≤ x ≤14) GLASSY SYSTEM

“…In the recent years the study of amorphous semiconductor glasses has become one of the interesting areas of research due to their technical applications such as memory switching devices, optical switching, electro-photography, solar cells and IR transmission devices [1][2][3][4]. Dielectric properties such as dielectric constant and dielectric loss are important in explaining the defect states and structure of glassy network [5].…”