Ab initio quantum mechanical calculations of energy, geometry, vibrational frequencies and IR intensities of tetraphosphorus tetrasulphide, α-P4S4(D2d), and vibrational analysis of As4S4 and As4Se4

Molecular-Network Transformations in Tetra-Arsenic Triselenide Glassy Alloys Tuned within Nanomilling Platform

Polyamorphic transformations driven by high-energy mechanical ball milling (nanomilling) are recognized in a melt-quenched glassy alloy of tetra-arsenic triselenide (As4Se3). We employed XRPD analysis complemented by thermophysical heat-transfer and micro-Raman spectroscopy studies. A straightforward interpretation of the medium-range structural response to milling-driven reamorphization is developed within a modified microcrystalline model by treating diffuse peak-halos in the XRPD patterns of this alloy as a superposition of the Bragg-diffraction contribution from inter-planar correlations, which are supplemented by the Ehrenfest-diffraction contribution from inter-atomic and/or inter-molecular correlations related to derivatives of thioarsenide As4Sen molecules, mainly dimorphite-type As4Se3 ones. These cage molecules are merely destroyed under milling, facilitating the formation of a polymerized network with enhanced calorimetric heat-transfer responses. Disruption of intermediate-range ordering, due to weakening of the FSDP (the first sharp diffraction peak), accompanied by an enhancement of extended-range ordering, due to fragmentation of structural entities responsible for the SSDP (the second sharp diffraction peak), occurs as an interplay between medium-range structural levels in the reamorphized As4Se3 glass alloy. Nanomilling-driven destruction of thioarsenide As4Sen molecules followed by incorporation of their remnants into a glassy network is proved by micro-Raman spectroscopy. Microstructure scenarios of the molecular-to-network polyamorphic transformations caused by the decomposition of the As4Se3 molecules and their direct destruction under grinding are recognized by an ab initio quantum-chemical cluster-modeling algorithm.

Photo-stability of pulsed laser deposited Ge(x)As(y)Se(100-x-y) amorphous thin films

Quest for photo-stable amorphous thin films in ternary Ge(x)As(y)Se(100-x-y) chalcogenide system is reported. Studied layers were fabricated using pulsed laser deposition technique. Scanning electron microscope with energy dispersive X-ray analyzer, Raman scattering spectroscopy, transmittance measurements, variable angle spectroscopic ellipsometry, and non-linear imaging technique with phase object inside the 4f imaging system were employed to characterize prepared thin films. Their photo-stability/photo-induced phenomena in as-deposited and relaxed states were also investigated, respectively. In linear regime, we found intrinsically photo-stable relaxed layers within Ge(20)As(20)Se(60) composition. This composition presents also the highest optical damage threshold under non-linear optical conditions.

Laser desorption ionization time-of-flight mass spectrometric study of binary As-Se glasses

Binary chalcogenide As-Se glasses and their thin films are important for optics, computers, materials science and technological applications. To increase understanding of the properties of thin films fabricated by plasma deposition techniques, more information concerning the physics of plasma plume is needed. In this study the formation of clusters in plasma plume from different As-Se glasses by laser desorption ionization (LDI) or laser ablation (LA) was studied by time-of-flight mass spectrometry (TOF MS) in positive and negative ion modes. Formation of a number of As(p)Se(q) singly charged clusters As(3)Se(q)(+) (q = 1-5), AsSe(q)(-) (q = 1-3), As(2)Se(q)(-) (q = 2-4), and As(3)Se(q)(-) (q = 2-5) was found from As-Se glasses with the molar ratio As:Se in the range from 1:2 to 7:3. The stoichiometry of the As(p)Se(q) clusters was determined via isotopic envelope analysis and computer modeling. The structure of the clusters is proposed and the relationship to the structure of the parent glasses, as also suggested by Raman scattering spectra, is discussed.