EXAFS Studies of Zn1-xMnxS Ternary Compounds

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EXAFS Studies of Zn1−x\text{}_{1-x}Mnx\text{}_{x}S Ternary Compounds

We performed extended X-ray absorption fine structure (EXAFS) measurements of Zn$\text{}_{1-x}$Mn$\text{}_{x}$S solid solution for various concentrations x in the range of 0 ≤ x ≤ 0.4. Data were collected on Zn and Mn K-edges with the use of synchrotron radiation from the ADONE storage ring in Frascati utilizing the Si(111) channel-cut monochromator. Applying the usual procedure of data reduction described elsewhere, we found well-defined different nearest-neighbor Zn-S and Mn-S distances, according to the previous results, almost independent on x. For Mn-S distances in the range of 0.1 ≤ x ≤ 1.0 we found, within the limit of experimental error, a constant value equal to 2.430±0.008 Å. For Zn-S distances for concentration changing from x = 0.0 to x = 0.4 we observed a weak, linear increase from 2.343±0.008 Å to 2.354 ± 0.008 Å, respectively

Statistical model analysis of local structure of quaternary sphalerite crystals

At the 2004 Ural International Winter School, we introduced the statistical strained tetrahedron model and discussed ternary tetrahedron structured crystals. The model allows one to interpret x-ray absorption fine structure (EXAFS) data and extract quantitative information on ion site occupation preferences and on the size and shape of each elemental constituent of the configuration tetrahedra. Here we extend the model to cover quaternary sphalerite crystal structures. We discuss the two topologically different quaternary sphalerite systems: the pseudo balanced A₁₋xBxYyZ₁₋y (2:2 cation:anion ratio), and the unbalanced AxBx C₁₋x₋x Z or AXyYy Z₁₋y₋y (3:1 or 1:3 cation:anion ratios) truly quaternary alloy systems. These structural differences cause preference values in pseudo quaternaries to vary with the relative contents, but to remain constant in truly quaternary compounds. We give equations to determine preference coefficient values from EXAFS or phonon spectra and to extract nearest-neighbour inter-ion distances by EXAFS spectroscopy. The procedure is illustrated and tested on CdMnSeTe, GaInAsSb, and ZnCdHgTe quaternary alloys