Observation of the amorphous-crystalline phase transition in the Ovonic semiconducting glass Te81Ge15As4 by the Mössbauer effect in Te125 and I129

Mössbauer spectra obtained with absorbers of ${\mathrm{Te}}_{81}^{125}{\mathrm{Ge}}_{15}{\mathrm{As}}_4$ and a ZnTe^125m source indicate that tellurium atoms are in an environment similar to that in tellurium metal. These spectra as well as those obtained with sources of ${\mathrm{Te}}_{81}^{129\mathrm{m}}{\mathrm{Ge}}_{15}{\mathrm{As}}_4$ and a CuI¹²⁹ absorber indicate that the amorphous phase has a higher charge asymmetry than the crystalline phase which is consistent with the concept of ``dangling'' chemical bonds. Because of the great difference in the I¹²⁹ spectra of the amorphous and crystalline phases it appears of interest to investigate Ovonic devices prepared with Te^129m in order to see if voltage‐dependent phenomena can be observed in the I¹²⁹ Mössbauer spectra.