Microscopic origin of demixing in Ge(20)Se(x)Te(80-x) alloys

László Rátkai1, C Conseil, V Nazabal, B Bureau, I Kaban, J Bednarcik, B Beuneu, P Jovari

1Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, Budapest H-1525, Hungary

The structure of Ge(20)Se(x)Te(80-x) (x = 5, 10, 15, 20) glasses has been investigated by X-ray and neutron diffraction as well as Ge and Se K-edge extended X-ray absorption fine structure (EXAFS) measurements. Experimental datasets have been fitted simultaneously by the reverse Monte Carlo simulation technique. It has been found that all components obey the 8-N rule. Se binds preferentially to Ge. At x = 20, experimental data can be fitted without Se-Te bonding, but Se-Se bonds appear, and the Te-Te coordination number starts to increase. These observations show that though Se and Te are completely miscible in the liquid and in the solid phases the presence of Ge induces nanoscale phase separation. (C) 2011 Elsevier B.V. All rights reserved.