Structure of GeSe₄–In and GeSe₅–In glasses

Abstract

Abstract(Ge 0.2 Se 0.8 ) 100-x In x and (Ge 0.17 Se 0.83 ) 100-x In x (x = 0, 5, 10, 15 at.%) chalcogenide glasses have been studied with high-energy x-ray diffraction, neutron diffraction and extended x-ray absorption spectroscopy at Ge, Se and In K-edges. The experimental data were modelled simultaneously with the reverse Monte-Carlo simulation method. GeSe 4/2 tetrahedra are shown to be the main structural units in the binary and ternary glasses investigated. Indium bonds to the excess Se atoms in the ternary Ge-Se-In glasses. While majority of In atoms have three Se neighbours, some In atoms may be tetrahedrally coordinated by Se.

The Effect of Indium Content on the Atomic Environment and Cluster Stability of GeSe4Inx=10,15 Glasses

“…Two amorphous chalcogenide systems with nominal compositions of GeSe4In10 and GeSe4In15 were studied; both systems were originally synthesized in [13] from elemental Ge, Se and In (all elements were of 99.99% purity), by sealing the required alloy constituents in quartz ampoules under an underpressure of 10 −3 Pa and heating the mixtures up to 1273 K under continuous vibration stirring, at a rate of 2 K/min. The samples were then quenched in a mixture of ice and water and total scattering datasets were obtained by X-Ray (XRD) and Extended X-Ray Absorption Fine Structure (EXAFS) spectroscopy.…”

“…The XRD datasets were recorded by a Ge solid-state detector at the BW5 facility in HASYLAB, DESY at incident beam energy of 100 keV with a cross section equal to 4 mm 2 and appropriate corrections (background, absorption, polarization) were imposed on the resultant data. EXAFS transmission datasets (approximately 1/e) were attained with a step size of 0.5 eV in the vicinity of the absorption edge for Ge, Se and In K-edges at the HASYLAB X beamline [13]. The materials' total structure factors, S(Q), were estimated on the basis of the experimental X-ray and neutron scattering intensities attained; The total S(Q) data were then correlated to the partial structure factors, Sij(Q) via the Faber-Ziman formalism [14].…”

“…In the current work, both the total and partial PDF from the Fourier-transformed structure factors originally obtained were fitted by the RMC method via use of the molecular RMC_POT code [15]. In our simulation we retained the minimum interatomic distances (cut-offs) as established in [13]. Aside from cut-offs, partial distances of furthest approach within the first coordination shell were also defined; both cut-offs and distances of furthest approach are listed in Table 1.…”

“…Hence, number density and its corresponding mass density refer to the exact stoichiometries. Additionally, we note that mass density measurements for the systems at hand are scarce and the principal density estimates are based on the work by Saffarini [16,17], who also provided a phenomenological expression accounting for mass density in respect to content; that work was compiled by Kaban et al [13] to derive the number densities utilized here. The RMC simulation boxes each contained 3000 atoms with a number density of 0.0328 atoms/Å 3 estimated on the basis of GeSe4In10 and 0.0335 atoms/Å 3 estimated on the basis of GeSe4In15 models.…”

“…In a previous contribution, the atomic topology of ternary Ge-Se-In glasses was determined by X-ray Diffraction (XRD), Neutron Diffraction (ND) and Extended X-ray Absorption Fine Structure (EXAFS) experiments in conjunction with Reverse Monte Carlo (RMC) fitting of the total scattering datasets [13]. The simultaneous modeling of the experimental datasets for each composition enabled the determination of partial pair distribution functions and the extraction of the local atomic order in these glasses.…”