Microscopic origin of demixing in Ge20SexTe80−x alloys

The structure of Ge20SexTe80−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.

Research highlights
► At around 20% Se content Se–Se bonds appear and Se–Te bonding disappears
► It has been found that Se binds preferentially to Ge.
► The separation of Se and Te is due to their different affinity to Ge.