Mechanism for Doping in Bi Chalcogenide Glasses

n-type chalcogenides by ion implantation

“…We therefore propose that the implanted Bi preferentially associates with an oxide site that is electrically inactive and generates 700 nm PL; at higher doses, the oxide sites are filled and Bi associates with a sulphide site that is related to electrical doping and generates NIR PL. From extended X-ray absorption fine structure spectroscopy measurements of Ge 20 S 80 À x Bi x (x ¼ 3-10), Elliott et al 25 argued that Bi is only threefold coordinated, asserted that the glasses were homogeneous without Bi 2 Ch 3 clusters and that the mechanism of CTR is due to the presence of charged Bi atoms, which suppress the concentration of positively charged VAPs at the expense of negatively charged VAPs and, as a result, the electron concentration is increased. This is accompanied by a shift from purely covalent to partially ionic bonding between Bi and chalcogen atoms, with the most favourable configuration being Bi Our XPS measurements show that n-type Bi-implanted GeTe and GaLaSO both contain a positively charged Bi species (Bi þ or Bi 2 þ ), and GaLaSO also contains neutral Bi.…”

Thermal and electrical switching studies on Ge20Se80−xBix (1≤x≤13) ternary chalcogenide glassy system

“…However, Bi atoms show a variable coordination number and several possibilities have been proposed involving positively charged Bi ions having three-fold [29] and four-fold [30] coordination, as well as negatively charged Bi ions having the twofold [31] and sixfold [30] coordination. The X-ray Absorption Fine Structure (XAFS) measurements carried out for a series of Ge-Se-Bi glasses by Elliott and Steel [32] indicate that Bi atoms are positively charged and the coordination number is 3. In this study, the coordination number of Bi is taken as 3.…”

Optical and electronic properties of bismuth-implanted glasses

“…A.C. measurements indicate that these clusters may have n-type defects situated at excess S − atoms on cluster surfaces; these defects may be taking part in a single-polaron hopping process [27]. However, on the basis of EXAFS measurements, Elliott et al argued that Bi is only 3-fold coordinated, and that the glasses were homogeneous without Bi2S3 clusters [28], and that the mechanism of CTR is due to the presence of charged Bi atoms which suppress the concentration of positively charged chalcogen defects at the expense of negatively charged defects. In 1989, a p-n junction based on the Ge-Se-Bi glass system was fabricated [29].…”