DISTRIBUTION OF CHALCOGEN ATOMS IN THE WURTZITE CDSXSE1-X SOLID-SOLUTION - EXPERIMENTAL-STUDY BY X-RAY-ABSORPTION

The assumption of a random distribution of chalcogen atoms in the wurt zite structure is usually made to interpret the properties of ternary CdSxSe1-x compounds. However, there has not yet been any experimental evaluation of this distribution. We report here the results of low-tem perature x-ray absorption measurements (4.5 K) at the selenium K edge in CdSxSe1-x compounds for x = 0, 0.2, 0.5 and 0.8. These measurements make a quantitative analysis of the next-nearest neighbours up to the fourth-neighbour shell around selenium atoms possible. The numbers of sulphur and selenium second neighbours of selenium atoms for each ter nary compound are found to be proportional to the respective molar rat io. The analysis can be made with the best accuracy for x = 0.5, and n o clustering is observed. As maximum clustering is expected for this v alue of x, it is concluded that deviation from the random distribution of selenium atoms is very small in CdSxSe1-x.