Local structure and vibrational spectra of vAs2O3

Induced crystallization and structural aspects of PbO-As2O3 glass system doped with Fe2O3

“…As 2 O 3 is a strong network former with corner sharing AsO 3 pyramidal units. Normal bond lengths of As-O lie in the range 1.72-1.81 Å and O-As-O and As-O-As bond angles lie in the range 90-103 o and 123-135 o , respectively [40][41][42][43]. PbO in general is a glass modifier and enters the glass network by breaking up the As-OAs bonds (normally the oxygens of PbO break the local symmetry while Pb 2+ ions occupy interstitial positions) and introduces coordinate defects known as dangling bonds along with non-bridging oxygen ions.…”

Chemical Bonding Self-Organizations and Percolation Theory Applied to Minimization of Macroscopic Strain: Internal Interfaces in Non-Crystalline and Nano-Crystalline Thin Films

“…This article addresses these issues, providing a simple and elegant way to (i) understand the nature of the CBSOs that minimize macroscopic strain, and thereby (ii) predict the IP window boundaries and widths for a majority of the alloys studied by Boolchand and coworkers, as well as other IPs identified through electronic property studies [7]. The theory, as originally proposed is oversimplified, and requires (i) two modifications to constraint counting that go beyond the valence forces of Phillips in Refs.…”

“…This theory requires modification when the local site symmetries are reduced; this is addressed in Refs. [1], [2], [6], [7] and [10]. For example, if the ideal tetrahedral symmetry of an XY 4 local arrangement is reduced as for XY 3 Z and XY 2 Z 2 , where Y and Z are different terminal atoms, then the respective number of bonding constraints/atom of these groups is reduced by approximately a factor of 2, e.g., from 5 for an XY 4 ideal tetrahedron to 2.5 for the lower symmetry XY 3 Z and XY 2 Z 2 arrangements [1,7].…”

“…There are additional constraints associated with relatively strong repulsive forces between electrons in (i) lonepair orbitals on nearest and second neighbor network As and Se atoms in As-Se and Ge-As-Se alloys [6,7]. These constraints have been addressed specifically in classical inorganic chemistry in the valence shell electron pair repulsion model (VSEPR) [14], and the concept of a bondfree volume as it applies to chalcogenide glasses [15].…”

“…The transitions for entering into, and remaining within the IP window in Ge x Se 1−x alloys involve competition between locally-compliant Se-Se dimer bonding in Ge-SeSe-Ge groups, and locally-rigid monomer bonding in GeSe-Ge groups. Thin film dielectrics and phase change memory materials are also addressed in this article, and compositions with minimal strain, and low defect densities have been identified by electrical measurements and spectroscopic techniques [6,7], rather than the reversible heat flow approach of Boolchand and coworkers [3]. The conceptual framework developed by Lucovsky and Phillips to understand chemical bonding self-organizations (CBSOs) in chalcogenide and oxide glasses that result in macroscopic strain-reduction in IPs in bulk glasses is applied to strain-reduction in a broader range of thin film materials.…”