Effects of copper and lead on the properties of As-Ge-X glasses (X = S, Se, Te)

Defect configurations in Ge–S chalcogenide glasses studied by Raman scattering and positron annihilation technique

“…Open volume with larger size will have longer lifetime of trapped positrons because of the lower electron density [7,8]. Secondly, it is well known that the negatively charged CD generally exist in all of the known binary chalcogenide glasses system [15,16]. Furthermore, on the basis of numerous experimental data for the various chalcogenide glass systems, it was assumed that the main types of these CD were characterized by the following lifetimes -0.32 ns (s À 1 ) and 0.42 ns (Ge À 3 ) [16].…”

“…Secondly, it is well known that the negatively charged CD generally exist in all of the known binary chalcogenide glasses system [15,16]. Furthermore, on the basis of numerous experimental data for the various chalcogenide glass systems, it was assumed that the main types of these CD were characterized by the following lifetimes -0.32 ns (s À 1 ) and 0.42 ns (Ge À 3 ) [16]. Consequently, the obtained lifetime values can be considered as a superposition of lifetimes corresponding to the free positron annihilation ($0.2 ns) and to the annihilation within the open volume originated from the CD (s À 1 and Ge À 3 ).…”

Structural analysis of Cu–As–Te glasses: Results from Raman and 65Cu NMR spectroscopy

“…Density measurements 9 Density measurements were carried out using a Micromeritics AccuPyc II gas expansion pycnometer under a helium environment of 6N purity. Approximately 0.5-2.0 g of each sample was loaded into a 1 cm 3 cup.…”

“…In particular, amorphous chalcogenides are known to exhibit semiconducting properties due to their narrow band-gaps with typical E g values of ~2 eV for sulfides and ~1.5 eV for selenides, compared to those characteristic (> 3eV) of oxide glasses [1,6]. On the far end, telluride glasses can reach band-gap energies below 1 eV and can therefore exhibit unusually high electronic conductivities, especially when alloyed with metals such as Cu, Ag, Tl or Pb [7][8][9][10][11][12]. Within these metal-telluride systems the Cu-As-Te ternary shows one of the widest glassformation domain and highest metal solubility [13,14].…”

Modified Positron Annihilation Model for Glassy-Like As2Se3

“…In the 80's of the last century, Shantarovich [2,3] presented a hypothesis that electronegatively charged point-like defects within vitreous lattice (so-called coordination topological defects) are responsible for positron trapping in ChG. A contrary approach was taken by Jensen et al [4] in the mid 90's. The theoretical calculations of positron lifetimes for different kinds of vacancy-type defects in crystalline (orthorhombic) c-As 2 Se 3 were performed on the basis of Puska's positron trapping model [5].…”