A topological phase transition in ternary chalcogenide films

Abstract

In thin amorphous chalcogenide films evaporated from the ternary (As2S3)y(Ge2S3)1 - y and (As2Se3)y(Ge2Se3)1 - y glass systems, a structural phase transition takes place at an average coordination number, approximately equal to Z, 2.67. The presence of this topological threshold is established by indirect evidence, such as the peculiarities in the compositional dependence of the optical band gap of as-evaporated and annealed films. These peculiarities are caused by the two- to three-dimensional (2D ⇒ 3D) transition, recently shown to take place in chalcogenide glassy systems at about the same value of Z.