Understanding the complicated crystallization behaviors in Germanium-Tellurides

Abstract

Crystallization behaviors and configurations of germanium-tellurides (GexTe100-x) at a wide compositional range (12.5 ≤ x ≤ 85) have been investigated. It is found GexTe100-x film exhibits one- or two-step crystallization behavior with a complicated competition between GeTe and Te (or Ge) phases. The composition dependences of crystallization temperature and activation energy have been revealed. They exhibit four singularities at x = 20.4 (GeTe4), x = 33 (GeTe2), x = 49 (GeTe), and x = 22 (Ge22Te78). Based on the method of X-ray photoelectron spectroscopy, the structural sketches for the GexTe100-x glasses that is helpful to understand the evolution of crystallization behavior are built up. It is evident that, the presence of homopolar TeTe and heteropolar GeTe bonds is the main reason for the structural and thermal stability of Ge-deficient films, and GeGe bond in GeGe4 tetrahedron appears when x > 50 and effectively enhances the stability of Ge-rich films.