EXAFS Study on Selenium-Tellurium Mixed Chains

Extended X-ray absorption fine structure (EXAFS) has been taken on the Se K-edge for isolated Se-Te mixed chains confined in the mordenite channels, as well as for trigonal and amorphous Se-Te mixtures. The Se-Se and Se-Te bond lengths in the Se-Te chain molecules have been determined by utilizing large difference in the wave vector dependence of backward scattering between Se and Te. The Se-Se and Se-Te bonds in the isolated chains are found to be shorter than those in the trigonal mixtures, which suggests that the intrachain covalent bonds are strengthened by reducing the interchain coupling. The Se-Se bond in the mixed chain molecule elongates with addition of Te, while the Se-Te bond changes little.