EXAFS MEASUREMENTS OF LIQUID SE-TE MIXTURES

We have measured EXAFS spectra of liquid (l-) Se, Te, Se-Te mixtures and vapour (v-) Se for the first time. It is clearly observed that the two-fold coordinated chain structure is largely preserved in 1-Se and that the intrachain covalent bond contracts on melting. The EXAFS spectra of 1-Te can be reproduced well by assuming a two-fold coordinated chain structure with shorter and longer bonds within the chain. In order to obtain partial structure-parameters in liquid Se-Te mixtures, spectra are taken on both Se and Te K edges. The Se-Se bond elongates with increasing Te concentration. The number of the longer Te-Te bonds increases with increasing temperature or increasing Te concentration; this may be associated with the semiconductor-to-metal transition.