Distillation with separate condensation of components as a new way to prepare especially pure GexTe100−x glasses with precisely desired composition

Abstract

The study is aimed to develop a method for preparing especially pure GexTe100−x glasses that provides low oxygen impurity content and, at the same time, high accuracy of a given, desired composition. It is shown that the conventional distillation of the Ge20Te80 melt can lead to a deviation in the glass composition from 0.5 to 2.1 at.% depending on the number of stages due to the thermal decomposition of GeTe. Such deviations in the composition have a significant effect on the crystallization of glasses upon heating and the values of the characteristic temperatures. A method for purification of GexTe100−x charge that makes it possible to minimize the deviation of the glass composition from the desired value is developed. The method is based on creating a constant tellurium vapor excess over germanium(II) telluride that suppresses its thermal decomposition. This is achieved by separate condensation of tellurium and GeTe and their subsequent successive evaporation. Two options for practical implementation of the method with the same efficiency, differing in the initial stage of the charge synthesis, are proposed. Using the developed method, Ge20Te80 glass samples with an oxygen impurity content of <10 ppb(wt) and a composition deviation of ≤0.2 at.% are prepared.