Local structure ofAsxTe100−

Qing Ma

¹

,

D. Raoux

²

,

S. Bénazeth

³

Abstract

The local structure of As Te&00 glassy semiconductors has been studied using x-ray anomalous scattering and x-ray-absorption spectroscopy as a function of the composition. Two important findings are (a) tellurium (Te) atoms are twofold coordinated in arsenic (As) rich alloys (x )40), while the Te coordination suddenly increases to 2.4 at the stoichiometric As40Te«composition, which indicates a large fraction (about 50%) of threefold Te sites in this glass. This percentage of occupancy of the threefold Te sites remains almost constant with increasing further the Te concentration; (b) a significant level of chemical disorder, marked by the existence of homopolar As-As and Te-Te pairs in the first coordination shell, is observed for all the investigated glasses. At the As4OTe«composition, nearly about the same amount of As-As and Te-Te pairs do exist in the first coordination shell. Thus the stoichiometric As4OTe«composition is not a chemical threshold as it is the case for the Seor S-based glasses. Based on these results, a number of peculiar and unique features in the physical properties of these glasses, such as the glass transition temperature (Tg) the microhardness, the glass forming ability, and the electrical conductivity, can be understood.

Extended X-ray Absorption Fine Structure Investigation of Arsenic in HgCdTe: the Effect of the Activation Anneal

“…17,18 The arsenic-arsenic and arsenic-tellurium distances deduced from the fit perfectly matched those found in the As x Te 100Àx glassy compound. These distances were too far away from those of the crystalline As 2 Te 3 structure (distances), thus enabling us to state unambiguously that arsenic and tellurium are involved in the glassy form of As 2 Te 3 .…”

Interpretation of Differential Anomalous X-Ray Scattering Data for Amorphous Cd-As

“…Recently, the synchrotron radiation technique of differential anomalous X-ray scattering (DAXS) has proved to be a very effective tool for the structural studies of two-component noncrystalline semiconduction as amorphous Ga-As [3,4] and glassy As-Te [8]. This technique yields the structural information which is qualitatively similar to that obtained from EXAFS but includes long-range correlations [9].…”

As2Te3 glass under high hydrostatic pressure: Polyamorphism, relaxation, and metallization

“…4), which likely indicates that the structure of the short-range order in these glasses is the same at increasing and decreasing pressure [28]. It is interesting that the density dependences of the effective bulk moduli at increasing and decreasing pressure are joined in the density range of 6.55-6.7 g/cm 3 (see the lower plot in Fig. 4).…”

“…Of particular interest are the As x Te 100−x glasses that serve as model systems, but an atomistic understanding of the structure−property relations in it remains obscure due to controversies [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. The As 2 Te 3 melt, similar to the Te melt, is a metal at small overheating above the melting temperature [16,17], as a result, cooling-induced crystallization can be avoided only at quenching rates above 100 K/s.…”

“…However, it was established more recently that stoichiometric glassy g-As 2 Te 3 strongly differs in structure of the short-range order from the crystalline phase and is characterized by a chemical disorder of 30 to 60% (chemical disorder is defined as the number of homopolar As-As bonds to the total number of As-Te and As-As bonds) [3][4][5][6][7][8][9][10][11][12]. Furthermore, the analysis of the structure of g-As 2 Te 3 is also complicated because of a strong dependence on the fabrication procedure [8,15].…”